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Dr. Kennedy's Vocabulary Course: -D-
(View Course for 11/18/2013)
(A B C D E F G H I J K L M)
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Ron Kennedy, M.D.
Vocabulary Search:Phrase  Any Words

- D -
(A B C D E F G H I J K L M)
D & C (D and C):  Dilatation and curettage, a minor operation in which the cervix is expanded enough (dilatation) to permit the cervical canal and uterine lining to be scraped with a spoon-shaped instrument called a curette (curettage).
Dacryoadenitis:  Inflammation of a lacrimal gland (the gland that produces tears). (Dacryo-: A combining form denoting tears)
Dacryocyst:  The lacrimal sac; tear sac. The dilated (widened) upper end of the nasolacrimal duct, the passageway that permits tears to drain into the nasal cavity.
Dacryocystorhinostomy:  The surgical creation of a passage between the lacrimal sac (tear sac) and the nasal cavity to permit the drainage of tears. Dacryocystorhinostomy may be done to remedy an obstructed nasolacrimal duct.
Dactyledema: Swelling of the fingers or toes. (Dactyl-, -dactyl:  Prefix or suffix denoting involvement of the digits (fingers or toes)
Dactylitis:  Inflammation of a digit (either a finger or a toe).
Daily Value:  DV, a term on food labels based on the RDA (Recommended Dietary Allowance) designed to help consumers use food label information to plan a healthy diet. The Daily Value serves as a basis for declaring on the label the percent of the DV for each nutrient that a serving of the food provides. For example, the Daily Value for fat, based on a 2,000-calorie diet, is 65 grams (g). A food that has 13 g of fat per serving would state on the label that the "percent Daily Value" for fat is 20 percent. The DV also provides a basis for thresholds that define descriptive words for nutrient content, called descriptors, such as "high fiber" and "low fat." For example, the descriptor "high fiber" can be used if a serving of food provides 20 percent or more of the Daily Value for fiber - that is, 5 g or more.
Daltonism:  Colorblindness of the red-green type (also known as deuteranopia or deuteranomaly). The term "Daltonism" is derived from the name of the chemist and physicist, John Dalton (1766-1844). Dalton described his and his brother's affliction of colorblindness with defective perception of red and green in the first scientific paper he published. It was entitled "Extraordinary facts relating to the vision of colours, with observation" (Mem Literary Philos Soc Manchester 5: 28-45, 1798). It is the first recognized account of red-green colorblindness.
Dancing mania of Maracaibo (Huntington disease) (Saint Vitus Dance):  Beginning in the 1950s Dr. Americo Negrette observed a number of people with a dancing mania in villages along Lake Maracaibo, Venezuela. The syndrome was then called el mal (the bad meaning in context the sickness) or el mal de San Vito (the sickness of Saint Vitus). Dr. Negrette diagnosed and reclassified the dancing mania as Huntington disease. In 1981, a field trip to Lake Maracaibo led to the collection of blood samples and the creation of an Huntington disease pedigree and in time to the discovery of the causative gene.
Dander:  Tiny scales shed from human or animal skin or hair. Dander floats in the air, settles on surfaces and makes up much household dust. Cat dander is a classic cause of allergic reactions.
Dandruff:  A mild skin condition that produces white flakes that may be shed and fall from the hair. Dandruff is due to the sebaceous glands overworking. (The sebaceous glands keep the skin properly oiled.) Another cause of dandruff is fungus, especially one called Pitrosporum ovale. (Most people have this fungus, but people with dandruff have more.)
Dandy fever:  An acute mosquito-borne viral illness of sudden onset that usually follows a benign course with headache, fever, prostration, severe joint and muscle pain, swollen glands (lymphadenopathy) and rash. The presence (the "dengue triad") of fever, rash, and headache (and other pains) is particularly characteristic. Better known as dengue, the disease is endemic throughout the tropics and subtropics. It goes by other names including breakbone fever. Victims of dengue often have contortions due to the intense joint and muscle pain. Hence, the name "breakbone fever." Slaves in the West Indies who contracted dengue were said to have "dandy fever" because of their postures and gait.
Danlos syndrome:  Better known today as Ehlers-Danlos syndrome (EDS), this is an inherited disorder with easy bruising, joint hypermobility (loose joints), skin laxity, and weakness of tissues.
Danon disease:  A genetic disorder characterized by heart problems, mental retardation and muscle weakness that affects males who usually die of cardiac arrhythmia or heart failure at around the age of 30. The disease is due to a deficiency of LAMP-2 (which stands for lysosome-associated membrane protein 2.)
Darier disease:  A genetic skin disease characterized by slowly progressive hardening of the skin (keratoses) around the hair follicles. This disorder is inherited in an autosomal dominant manner and is due to mutation in a gene called ATP2A2 on chromosome 12. Also known as keratosis follicularis.
Dark adaptometry:  A type of electrophysiologic retinal testing done to measure the period of time which passes before the retina regains its maximal sensitivity to low amounts of light when going from conditions of bright light to darkness.
DASH diet:  An eating plan designed to lower the blood pressure. DASH is an acronym for Dietary Approaches to Stop Hypertension. The DASH "combination diet" has been shown to decrease the blood pressure and so helps prevent and control high blood pressure. The DASH "combination diet" is rich in fruits, vegetables, and low fat dairy foods, and low in saturated and total fat. It also is low in cholesterol, high in dietary fiber, potassium, calcium, and magnesium, and moderately high in protein. The DASH eating plan is recommended by the NIH's National Heart, Lung, and Blood Institute (NHLBI) which states: "Use the Dietary Approaches to Stop Hypertension (DASH) eating plan as a guide. DASH encourages you to eat more fresh fruits, vegetables and low fat dairy products, and to limit saturated fat and salt. The DASH eating plan can help you lose weight and maintain a healthier body. In fact, according to the report, sticking to the DASH eating plan can be as effective as some medications in lowering your blood pressure."
Day sight (Night blindness):  Listed in medical dictionaries under "Nyctalopia" from the Greek "nyct' (night) + "aloas" (obscure or blind) + "opsis" (vision), the condition involves impaired vision in dim light and in the dark (but normal sight in bright light), due to impaired function of specific vision cells (the "rods") in the retina. Day sight (night blindness) is a classic symptom resulting from deficiency of vitamin A.
DCIS (Ductal carcinoma in situ):  A precancerous condition characterized by the clonal proliferation of malignant-looking cells in the lining of a breast duct without evidence of spread outside the duct to other tissues in the breast or outside the breast. DCIS is clearly the precursor (forerunner) of invasive breast cancer. This is evident from the sharing of clonal chromosome changes by DCIS and adjacent invasive cancers. In other words, invasive breast cancer evolves from DCIS. Also called intraductal carcinoma. The incidence of DCIS has increased greatly, thanks to the widespread use of screening mammography. DCIS now accounts for nearly 20% of all breast cancers detected on screening mammograms. Risk factors for DCIS include older age, benign breast disease, an older age at the time of the first term pregnancy or nulliparity (not having children), and a family history of breast cancer.
DDH (developmental dislocation of the hip):  The abnormal formation of the hip joint in which the ball at the top of the thighbone (the femoral head) is not stable within the socket (the acetabulum). The ligaments of the hip joint may also be loose and stretched. The degree of instability or looseness varies. A baby born with this condition may have the ball of the hip loosely in the socket (subluxed) or the ball of the hip may be completely dislocated at birth. Untreated, the condition may cause legs of different lengths and a "duck-like" walk and lead to pain on walking and early osteoarthritis. There is a familial tendency. It usually affects the left hip and is more common in girls than boys, in first-born children and in babies born in the breech position. It is more common in Native Americans than in whites and is rarely seen in African-American children. One of the early signs that a baby has been born with a dislocated hip may be a clicking sound when the baby's legs are moved apart.
de Lange syndrome:  A relatively common birth defect syndrome with multiple malformations and mental retardation of unknown origin. de Lange syndrome is recognized by the presence of:
  • Prenatal and postnatal growth retardation
  • Delayed development and mental retardation
  • Abnormally small head (microcephaly)
  • Hair low on the nape of the neck
  • Characteristic facial appearance with
  • Low-set ears,
  • Hair well down onto the forehead
  • Bushy eyebrows
  • Eyebrows that meet in the middle (synophrys)
  • Unusually long eyelashes
  • Depressed bridge of the nose
  • Uptilted tip of the nose
  • Forward-directed nostrils
  • Protuberance of the upper jaw (maxillary prognathism)
  • "Carp-shaped" mouth
  • Small, widely spaced teeth
  • Upper limb anomalies with flat spadelike hands with a "simian" (single transverse) palmar crease and short tapering fingers

    The majority of children with de Lange syndrome have no known family history of the disorder. There are, however, some reports of familial cases. These reports suggest autosomal dominant transmission with a mildly affected parent having a more seriously affected child. The chance is from 2 to 5% that a child whose sib has de Lange syndrome will also have the syndrome. In familial de Lange syndrome, a gene on chromosome 5 is mutated.

de Musset sign:  Rhythmic nodding or bobbing of the head in synchrony with the heart beat, a sign of aortic insufficiency - incompetence of the aortic valve with aortic regurgitation. The causes include syphilitic aortitis, rheumatic fever, and aortic aneurysm. Named after the French Romantic poet and playwright Alfred de Musset (1810-1857).
De Quervain's tenosynovitis:  Inflammation of the extensor pollicus longus tendon on the side of the wrist at the base of the thumb. De Quervain's tenosynovitis typically is associated with pain when the thumb is folded across the palm and the fingers are flexed over the thumb as the hand is pulled away from the involved wrist area. (This is referred to as the Finklestein sign.) Treatment of De Quervain's tenosynovitis includes any combination of rest, splinting, ice, anti-inflammation medication, and/or cortisone injection. Surgery is only rarely necessary.
Deafness:  Deafness is defined by partial or complete hearing loss. Levels of hearing impairment vary from a mild but important loss of sensitivity to a total loss of hearing. Older adults suffer most often from hearing loss. Age-related hearing loss affects 30 to 35 percent of the population between the ages of 65 and 75 years, and 40 percent of the population over the age of 75. The most common cause of hearing loss in children is otitis media, a disorder that affects predominantly infants and young children. A substantial number of hearing impairments are caused by environmental factors such as noise, drugs, and toxins. A major cause in older people is arteriosclerosis which blocks circulation of blood through the auditory artery which feeds the auditory nerve. This kind of hearing loss usually improves with intravenous EDTA chelation therapy.
Death:  1. The end of life. The cessation of life. (These common definitions of death ultimately depend upon the definition of life, upon which there is no consensus.) 2. The permanent cessation of all vital bodily functions. (This definition depends upon the definition of "vital bodily functions.") See: Vital bodily functions. 3. The common law standard for determining death is the cessation of all vital functions, traditionally demonstrated by "an absence of spontaneous respiratory and cardiac functions." 4. The uniform determination of death. The National Conference of Commissioners on Uniform State Laws in 1980 formulated the Uniform Determination of Death Act. It states that: "An individual who has sustained either (1) irreversible cessation of circulatory and respiratory functions, or (2) irreversible cessation of all functions of the entire brain, including the brain stem is dead. A determination of death must be made in accordance with accepted medical standards." This definition was approved by the American Medical Association in 1980 and by the American Bar Association in 1981.
Death rate:  The number of deaths in the population divided by the average population (or the population at midyear) is the crude death rate. In 1994, for example, the crude death rate per 1,000 population was 8.8 in the United States, 7.1 in Australia, etc. A death rate can also be tabulated according to age or cause.
Death rate, infant:  The number of children dying under a year of age divided by the number of live births that year. The infant death rate is also called the infant mortality rate. The infant mortality rate is an important measure of the well-being of infants, children, and pregnant women because it is associated with a variety of factors, such as maternal health, quality and access to medical care, socioeconomic conditions, and public health practices. In the United States, about two-thirds of infant deaths occur in the first month after birth and are due mostly to health problems of the infant or the pregnancy, such as preterm delivery or birth defects. About one-third of infant deaths occur after the first month and are influenced greatly by social or environmental factors, such as exposure to cigarette smoke or problems with access to health care. The infant mortality rate in the US, which was 12.5 per 1,000 live births in 1980, fell to 9.2 per 1,000 live births in 1990. However, in 1999 it was reported that "Over the past 8 years, the death rate among black infants has remained nearly 2.5 times that among white infants." (Pediatrics 104: 1229-1246, 1999.)
Debilitate:  To impair the strength or to enfeeble. A chronic progressive disease may debilitate a patient. So may, temporarily, a major surgical procedure. In both cases the weakness is pervasive. Weakness in an arm or leg following the removal of a cast is not debility. The word "debilitate" comes from the Latin word "debilis" for "weak."
Debride:  To remove dead, contaminated or adherent tissue or foreign material. The purpose of wound debridement is to remove all materials that may promote infection and impede healing. This may be done by enzymatic debridement (as with proteolytic enzymes), mechanical nonselective debridement (as in a whirlpool), or sharp debridement (by surgery). Debride comes from the French débrider, to remove the bridle (as from a horse).
Debridement:  The act of debriding (removing dead, contaminated or adherent tissue or foreign material). Debridement encompasses enzymatic debridement (as with proteolytic enzymes), mechanical nonselective debridement (as in a whirlpool), and sharp debridement (by surgery). See: Debride.
Debris flow injury:  Also known as mudslide injury.
Debulk:  To remove part of the bulk, usually of a tumor or dead tissue. Debulking may be done by surgery, irradiation, laser or chemotherapy.
Decease:  To depart from life; to die.
Decompress:  1. In general, to remove pressure physically or emotionally. 2. In surgery, to remove pressure on a structure such as the spinal cord. 3. To lessen atmospheric pressure on deep-sea divers returning to the surface, or on persons ascending to great heights.
Decompression:  1. In general, the removal of pressure. 2. In surgery, a procedure to remove pressure on a structure, as in decompression of the spinal cord. 3. The lessening of atmospheric pressure on deep-sea divers returning to the surface, or on persons ascending to great heights.
Decongestant:  A drug that shrinks the swollen membranes in the nose and makes it easier to breath. Decongestants can be taken orally or by nasal spray. Decongestant nasal sprays should not be used for more than five days without the doctor's advice, and if so, usually only when accompanied by a nasal steroid. Many decongestant nasal sprays often cause a rebound effect if taken too long. A rebound effect is the worsening of symptoms when a drug is discontinued. This is a result of a tissue dependence on the medication. Decongestants should not be used by patients with high blood pressure (hypertension) unless under doctor's supervision.
Decortication:  Removal of part or all of the outer surface of an organ such as the lung, kidney, or brain.
Decubitus:  Lying down. The Latin "decubitus" (meaning lying down) is related to "cubitum" (the elbow) reflecting the fact the Romans habitually rested on their elbows when they reclined.
Decubitus ulcer:  A bed sore, a skin ulcer that comes from lying in one position too long so that the circulation in the skin is compromised by the pressure, particularly over a bony prominence such as the sacrum (sacral decubitus).
Deep:  In anatomy, away from the surface or further into the body. As opposed to superficial. The bones are deep to the skin.
Deep vein thrombosis:  A blood clot (thrombus) in a deep vein in the thigh or leg. The clot can break off as an embolus and make its way to the lung, where it can cause respiratory distress and respiratory failure. Deep vein thrombosis is sometimes called the "economy-class syndrome." Even in young, healthy travelers, long stretches of time spent immobilized in the cramped seat of an aircraft with very low humidity sets the stage for formation of a blood clot in the leg. Abbreviated as DVT.
Defecation syncope:  The temporary loss of consciousness (syncope) upon defecating (having a bowel movement). Syncope is the temporary loss of consciousness or, in plain English, fainting. The situations that trigger this reaction are diverse and include having blood drawn, straining while urinating (micturition syncope) or defecating, coughing or swallowing. The reaction also can be due to the emotional stress of fear or pain. Under these conditions, people often become pale and feel nauseated, sweaty, and weak just before they lose consciousness.
Defensin:  A family of potent antibodies made within the body by neutrophils (a type of white blood cell) and macrophages (cells that can engulf foreign particles). The defensins play important roles against invading microbes. They act against bacteria, fungi and viruses by binding to their membranes and increasing membrane permeability. On a chemical level, the defensins are small peptides unusually rich in the amino acid cysteine (Cys).The human defensins are classified into the alpha-defensins and beta-defensins on the basis of their sequence homology and their Cys residues. From the Latin defendo, to repel. Defensin is also called human neutrophil peptide (HNP).
Defibrillation:  The use of a carefully controlled electric shock, administered either through a device on the exterior of the chest wall or directly to the exposed heart muscle, to restart or normalize heart rhythms.
Defibrillator:  A device used to correct a dangerously abnormal heart rhythm, usually ventricular fibrillation, or to restart the heart by depolarizing its electrical conduction system and delivering brief measured electrical shocks to the chest wall or the heart muscle itself.
Defibrillator storm:  A condition that arises when a defibrillator implanted in the chest to right an arrhythmia (an abnormal heart rhythm) fires off frequently --sometimes several times a day or even more often -- each time with a jolt like a boxer's punch to the chest, because of far advanced heart disease. Defibrillator storm is an uncommon but grave complication with an implantable defibrillator. a device that can profitably prolong a patient's life but can also make a patient's life painful.
Deformation:  A change from the normal size or shape of an anatomic structure due to mechanical forces that distort an otherwise normal structure. Deformations occur most often late in pregnancy or during delivery. A twin pregnancy can cause deformations due to crowding of the twins late in pregnancy. A well-known example of a deformation is molding of the head of a baby born by vaginal delivery. There are usually no significant lasting effects of a deformation. The effects are typically temporary. A deformation is different from a malformation in timing and impact. In a malformation, the development of a structure is arrested, delayed, or misdirected early in embryonic life and the effect is permanent.
Degenerative arthritis:  Also known as osteoarthritis, this type of arthritis is caused by inflammation, breakdown and eventual loss of the cartilage of the joints. Among the over 100 different types of arthritis conditions, osteoarthritis is the most common, affecting usually the hands, feet, spine, and large weight-bearing joints, such as the hips and knees. Also called degenerative joint disease.
Degenerative joint disease:  Also known as osteoarthritis, this type of arthritis is caused by inflammation, breakdown and eventual loss of the cartilage of the joints. Among the over 100 different types of arthritis conditions, osteoarthritis is the most common, affecting usually the hands, feet, spine, and large weight-bearing joints, such as the hips and knees. Also called degenerative arthritis.
Deglutition:  The act of swallowing, particularly the swallowing of food. The muscles of deglutition are the muscles employed in the act of swallowing.
Dehisce:  To burst open or gape. A surgical wound may partially or completely dehisce after surgery, depending upon whether some or all of the layers of tissue come open. The noun is dehiscence.
DEHP [di(2-ethylhexyl)phthalate]:  A softener for polyvinyl chloride (PVC), a plastic polymer used in a wide array of products. Unplasticized PVC is hard and brittle at room temperature. A plasticizer (softener) is typically added to increase the flexibility of the polymer. DEHP is the plasticizer for most PVC medical devices. Devices that may contain DEHP-plasticized PVC include: intravenous (IV) bags and tubing, umbilical artery catheters, blood bags and infusion tubing, enteral nutrition feeding bags, nasogastric tubes, peritoneal dialysis bags and tubing, tubing used in cardiopulmonary bypass (CPB) procedures, tubing used in extracorporeal membrane oxygenation (ECMO), and tubing used during hemodialysis. Everyone is exposed to small levels of DEHP in everyday life. However, some individuals can be exposed to high levels of DEHP through certain medical procedures. DEHP can leach out of plastic medical devices into solutions that come in contact with the plastic. The amount of DEHP that will leach out depends on the temperature, the lipid content of the liquid, and the duration of contact with the plastic. Seriously ill individuals often require more than one of these procedures, thus exposing them to even higher levels of DEHP. Exposure to DEHP has produced a range of adverse effects in laboratory animals. Of greatest concern are the effects on the development of the male reproductive system and the production of normal sperm in young animals.
Dehydration:  Excessive loss of body water. Diseases of the gastrointestinal tract that cause vomiting or diarrhea may, for example, lead to dehydration. There are a number of other causes of dehydration including heat exposure, prolonged vigorous exercise (e.g., in a marathon), kidney disease, and medications (diuretics). One clue to dehydration is a rapid drop in weight. A loss of over 10% (15 pounds in a person weighing 150 pounds) is considered severe. Symptoms and signs of dehydration include increasing thirst, dry mouth, weakness or lightheadedness (particularly if worse on standing), and a darkening of the urine or a decrease in urination. Severe dehydration can lead to changes in the body's chemistry, kidney failure, and become life-threatening. Dehydration due to diarrhea is a major cause of morbidity (disease) and mortality (death) in children. The young child has a more rapid turnover of body fluids than an adult. In rehydrating a child, there is less margin for error than for an adult. The younger the child, the more careful the rehydration must be. Cases that demand particular attention to detail are those in which organ function (especially skin, heart, brain, or kidney) is critically compromised. Overhydration may be as serious as severe dehydration in children; the rehydration should therefore be done under medical supervision.
Dehydroepiandrosterone (DHEA):  A steroid hormone made by the adrenal glands that acts on the body much like testosterone and is converted into testosterone and estrogen. DHEA and its sulfate (DHEAS) are abundant in the body, but their normal roles are not fully understood. The blood levels of DHEA and DHEAS decline with age. DHEA is sold in the US without a prescription as a "nutritional supplement." It has been claimed to improve mood, boost the immune system, sharpen memory, and combat aging.
Deinococcus radiodurans:  A bacterium that can survives extremely high levels of radiation and therefore has high potential for radioactive waste cleanup. The genome of Deinococcus radiodurans has been sequenced. It is composed of two chromosomes, a megaplasmid, and a small plasmid. The total genome contains 3,284, 156 base pairs. Deinococcus radiodurans is an organism in which all systems for DNA repair - DNA damage export, desiccation and starvation recovery, and genetic redundancy - are all present in one cell.
Deja vu:  (In French, déjà vu means "already seen." and the word déjà has an acute accent on the é and a grave accent on the à but we have omitted the accents from the entry term for the sake of the English-speaking search engine.) Déjà vu is a disquieting feeling of having been somewhere or done something before, even though one has not. Although most people have experienced this feeling at some time or another, in certain people such sensations of déja vu are part of a seizure or migraine aura; while in others they are the seizure phenomenon itself. (Jamais vu, meaning "never seen" is the illusion that the familiar does not seem familiar and is the opposite of the feeling of "déjà vu.")
Delirium:  A sudden state of severe confusion and rapid changes in brain function, sometimes associated with hallucinations and hyperactivity, in which the patient is inaccessible to normal contact. Symptoms may include inability to concentrate and disorganized thinking evidenced by rambling, irrelevant, or incoherent speech. There may be a reduced level of consciousness, sensory misperceptions and illusions, disturbances of sleep, drowsiness, disorientation to time, place, or person, and problems with memory. Delirium can be due to a number of conditions that derange brain metabolism, including infection, brain tumor, poisoning, drug toxicity or withdrawal, seizures, head trauma, and metabolic disturbances such as fluid, electrolyte, or acid-base imbalance, hypoxia, hypoglycemia, or hepatic or renal failure.
Delirium tremens:  A neurological symptom of alcohol withdrawal seen in chronic alcoholism, with includes symptoms of psychosis. These may include uncontrollable trembling, hallucinations, severe anxiety, sweating, and sudden feelings of terror. Delirium tremens can be both frightening and, in severe cases, deadly. Treatment includes observation, comfort care, and in some cases medication. Intramuscular or intravenous magnesium is a mainstay of treatment.
Delta cell, pancreatic:  A type of cell in the pancreas (the organ of the digestive system located behind the stomach). Within the pancreas, the delta cells are located in areas called the islets of Langerhans. The delta cells make somatostatin, a hormone that inhibits the release of numerous hormones in the body.
Delta storage pool disease (Hermansky-Pudlak syndrome):  Abbreviated HPS, a genetic disorder characterized by albinism (lack of pigment in the skin or eye), bruising and prolonged bleeding (due to defective blood platelets), and fibrosis of the lungs. There is occasionally also inflammatory bowel disease and impaired kidney function. All HPS patients suffer from varying degrees of albinism. The lack of pigment in the eye impairs their vision and often leads to involuntary rhythmic eye movements called nystagmus. The most serious health problems in HPS are the tendency to bruise easily and bleed and the progressive deterioration in lung function.
Deltoid muscle:  The large muscle, roughly triangular in shape, that stretches from the clavicle (collarbone) to the humerus (the long bone in the upper arm) and so covers the shoulder. When the deltoid is contracted (flexed), it moves the arm away from the side of the body.
Delusion:  A false personal belief that is not subject to reason or contradictory evidence and is not explained by a person's usual cultural and religious concepts (so that, for example, it is not an article of faith). A delusion may be firmly maintained in the face of incontrovertible evidence that it is false. Delusions are a frequent feature of schizophrenia.
Delusional jealousy (Othello syndrome):  The delusion of infidelity of a spouse or partner. The Othello syndrome affects males and, less often, females. It is characterized by recurrent accusations of infidelity, searches for evidence, repeated interrogation of the partner, tests of their partner's fidelity, and sometime stalking. The syndrome may appear by itself or in the course of paranoid schizophrenia, alcoholism, or cocaine addiction. As in Othello, the play by Shakespeare, the syndrome can be highly dangerous and result in disruption of a marriage, homicide and suicide.
Delusional parasitosis:  A mistaken belief that one is infested by parasites such as mites, lice, fleas, spiders, worms, or other organisms.
Dementia:  Significant loss of intellectual abilities such as memory capacity, severe enough to interfere with social or occupational functioning. Criteria for the diagnosis of dementia include impairment of attention, orientation, memory, judgment, language, motor and spatial skills, and function. By definition, dementia is not due to major depression or schizophrenia. Dementia is reported in as many as 1% of adults 60 years of age. It has been estimated that the frequency of dementia doubles every five years after 60 years of age. Alzheimer's disease is the most common cause of dementia. There are many other causes of dementia, including (in alphabetical order): AIDS (due to HIV infection), alcoholism (the dementia is due to thiamine deficiency), brain injury, brain tumors, Creutzfeldt-Jakob disease, dementia with Lewy bodies (tiny round structures made of proteins that develop within nerve cells in the brain), drug toxicity, encephalitis, meningitis, Pick disease (a slowly progressive deterioration of social skills and changes in personality leading to impairment of intellect, memory, and language), syphilis, thyroid disease (hypothyroidism) and vascular dementia (damage to the blood vessels leading to the brain).
Demonophobia:  An abnormal and persistent fear of evil supernatural beings in persons who believe such beings exist and roam freely to cause harm. Those who suffer from this phobia realize their fear is excessive or irrational. Nevertheless, they become unduly anxious when discussing demons, when venturing alone into woods or a dark house, or when watching films about demonic possession and exorcism.
Demulcent:  Soothing. The word "demulcent" comes from the Latin verb, "demulcere" meaning "to caress." Something that is demulcent is caressing. The term "demulcent" refers to an agent, such as an oil, that forms a soothing film when administered onto the surface of a mucous membrane. A demulcent is meant to relieve the irritation of the inflamed mucous membrane. For example, a cough syrup may claim to be "a gentle demulcent medicine that will relieve the pain of sore throat."
Demyelination:  A degenerative process that erodes away the myelin sheath that normally protects nerve fibers. Demyelination exposes these fibers and appears to cause problems in nerve impulse conduction that may affect many physical systems. Demyelinization is seen in a number of diseases, particularly multiple sclerosis.
Dendrite:  A short arm-like protuberance from a nerve cell (a neuron). Dendrites from neurons next to one another are tipped by synapses (tiny transmitters and receivers for chemical messages between the cells). The word "dendrite" means "branched like a tree." It comes from the Greek "dendron" (tree).
Dendritic:  Referring to a dendrite, a short arm-like protuberance from a nerve cell (a neuron). Dendrites from neurons next to one another are tipped by synapses (tiny transmitters and receivers for chemical messages between the cells).
Dendritic cell:  A special type of cell that is a key regulator of the immune system, acting as a antigen-presenting cell (APC) capable of activating naïve T cells and stimulating the growth and differentiation of B cells.
Denervate:  To deprive of the nerve supply. Denervate is the opposite of innervate.
Desmoplastic Fibroma:  A rare type of primary bone tumor characteristically composed of well-differentiated cells that produce collagen. Desmoplastic fibromas are discovered most often in the first three decades of life, in the mandible (the femur and pelvis are also favored sites). Although benign, these tumors are locally infiltrative and may cause pain and swelling or an effusion (if near a joint). Treatment is surgical removal but the tumor may recur.
Diabetes, type 1:  An autoimmune disease that occurs when T cells attack and destroy some or all of the beta cells in the pancreas that are needed to produce insulin, so that the pancreas makes too little insulin (or no insulin). Without the capacity to make adequate amounts of insulin, the body is not able to metabolize blood glucose (sugar), to use it efficiently for energy, and toxic acids (called ketoacids) build up in the body as a result of burning fats for energy in place of glucose. There is a genetic predisposition to type 1 diabetes. The disease tends to occur in childhood, adolescence or early adulthood (before age 30) but it may have its clinical onset at any age. The symptoms and signs of type 1 diabetes characteristically appear abruptly, although the damage to the beta cells may begin much earlier and progress slowly and silently. The symptoms and signs include a great thirst, hunger, a need to urinate often, and loss of weight. Among the risks of the disease are serious complications, among them blindness, kidney failure, extensive nerve damage, and accelerated atherosclerosis. The long-term aim with treatment is to avoid these complications or, at the least, to slow their progression. There is no known cure. To treat the disease, the person must inject insulin, follow a diet plan, exercise adequately (ideally, daily), and test their blood glucose several times a day. This type of diabetes used to be known as "juvenile diabetes," "juvenile-onset diabetes," and "ketosis-prone diabetes." It is now called type 1 diabetes mellitus or insulin-dependent diabetes.
Diabetes, type 2:  One of the two major types of diabetes, the type in which the beta cells of the pancreas produce insulin but the body is unable to use it effectively because the cells of the body are resistant to the action of insulin. Although this type of diabetes may not carry the same risk of death from ketoacidosis, it otherwise involves many of the same risks of complications as does type 1 diabetes (in which there is a lack of insulin). The aim of treatment is to normalize the blood glucose in an attempt to prevent or minimize complications. People with type 2 diabetes may experience marked hyperglycemia, but most do not require insulin injections. In fact, 80% of all people with type 2 diabetes can be treated with diet, exercise, and, if need be, oral hypoglycemic agents (drugs taken by mouth to lower the blood sugar). Type 2 diabetes requires good dietary control including the restriction of calories, lowered consumption of simple carbohydrates and fat with increased consumption of complex carbohydrates and fiber. Regular aerobic exercise is also an important method for treating both type 2 diabetes since it decreases insulin resistance and helps burn excessive glucose. Regular exercise also may help lower blood lipids and reduce some effects of stress, both important factors in treating diabetes and peventing complications. Intravenous chelation therapy with EDTA helps restore insulin sensitivity to the cells suggesting that Type 2 diabetes is related to metal toxicity. Type 2 diabetes is also known as insulin-resistant diabetes, non-insulin dependent diabetes, and adult-onset diabetes, although in recent years many children and adolescents have developed this kind of diabetes, probably thanks to the high refined and simple carbohydrate dietary patterns of western civilization.
Diabetes, unstable:  A term used when a diabetic person's blood glucose (sugar) level often swings quickly and widely from high to low and from low to high. Also called brittle and labile diabetes.
Diabetic coma:  Coma in a diabetic due to the buildup of ketones in the bloodstream. Ketones are a product of metabolizing (using) fats rather than the sugar glucose for energy. The best approach to diabetic coma is prevention. Careful diet, medication, and insulin dosing as needed should prevent ketone build-up. Patients with diabetes and their family members should be aware of the early signs of ketone build-up. These include weight loss, nausea, confusion, gasping for breath, and a characteristically sweet, chemical odor similar to that of acetone or alcohol ("acetone breath") to the patient's breath and sometimes sweat. Diabetic coma may be presaged (heralded) by confusion and convulsions. Immediate emergency medical treatment is needed in a hospital setting for patients who show the early signs of incipient diabetic coma.
Diabetic dermopathy:  A skin condition characteristic of diabetes involving light brown or reddish oval or round scaly patches, most often on the shins or front of the thighs and less often on the scalp, forearm and trunk. The cause of diabetic dermopathy is thought to be a type of angiitis (vascular inflammation) affecting small blood vessels in the skin. There is no known effective treatment. The patches tend to go away after a few years. The patches are also called shin spots. They appear sometimes in nondiabetics after trauma.
Diabetic eye disease:  1. A disease of the small blood vessels of the retina of the eye in people with diabetes. The vessels swell and leak liquid into the retina, blurring the vision and sometimes leading to blindness. Also called diabetic retinopathy. 2. Any eye disease to which diabetes predisposes including not only diabetic retinopathy but also cataracts (clouding of the lens) and glaucoma (increased fluid pressure inside the eye that can lead to optic nerve damage and loss of vision). It is recommended that all diabetics have a dilated eye examination at least once a year.
Diabetic macular edema:  Swelling of the retina in diabetes mellitus due to leaking of fluid from blood vessels within the macula. The macula is the central portion of the retina, a small area rich in cones, the specialized nerve endings that detect color and upon which daytime vision depends. As macular edema develops, blurring occurs in the middle or just to the side of the central visual field. Visual loss from diabetic macular edema can progress over a period of months and make it impossible to focus clearly. Macular edema in common in diabetes. The lifetime risk for diabetics to develop macular edema is about 10%. The condition is closely associated with the degree of diabetic retinopathy (retinal disease). Hypertension (high blood pressure) and fluid retention also increase the hydrostatic pressure within capillaries which drives fluid from within the vessels into the retina. A common cause of fluid retention in diabetes is kidney disease with loss of protein in the urine (proteinuria).
Diabetic musculoskeletal disorder:  A musculoskeletal problem associated with diabetes mellitus. These include: Diabetic syndrome of limited joint mobility (cheiroarthropathy) -- a syndrome characterized by thickening of the skin over the joints. Diabetic stiff hand syndrome -- thickening of the skin of the palm that results in loss of ability to hold the hands straight. Adhesive capsulitis -- severe limitation of the range of motion of the shoulder due to scarring around the shoulder joint. Also called a "frozen shoulder." Neuropathic joints (below the knee) -- destruction, increased density, dislocation, debris, distension, and disorganization of joints due to diabetic neuropathy, nerve damage caused by diabetes. Diffuse idiopathic skeletal hyperostosis -- general overgrowth of bone of unknown cause. Carpal tunnel syndrome and other nerve entrapment syndromes. Flexor tenosynovitis -- inflammation of the extensor pollicis longus tendon on the side of the wrist at the base of the thumb, typically associated with pain when the thumb is folded across the palm and the fingers are flexed over the thumb. Dupuytren contracture -- formation of scar tissue in the palm over the tendons that pull the fingers. Diabetic amyotrophy -- acute neuropathy of a large proximal nerve.
Diabetic nephropathy:  The kidney disease associated with long-standing diabetes. Diabetic nephropathy is also called Kimmelstiel-Wilson disease (or Kimmelstiel-Wilson syndrome) or intercapillary glomerulonephritis. Diabetic nephropathy typically affects the network of tiny blood vessels (the microvasculature) in the glomerulus, a key structure in the kidney composed of capillary blood vessels. The glomerulus is critically necessary for the filtration of the blood. Features of diabetic nephropathy include the nephrotic syndrome with excessive filtration of protein into the urine (proteinuria), high blood pressure (hypertension), and progressively impaired kidney function. When it is severe, diabetic nephropathy leads to kidney failure, end-stage renal disease, and the need for chronic dialysis or a kidney transplant.
Diabetic neuropathy:  A family of nerve disorders caused by diabetes. Diabetic neuropathies cause numbness and sometimes pain and weakness in the hands, arms, feet, and legs. Neurologic problems in diabetes may occur in every organ system, including the digestive tract, heart, and genitalia. People with diabetes can develop nerve problems at any time, but the longer a person has diabetes, the greater is the risk. About half of diabetics have some form of neuropathy, but not all with neuropathy have symptoms. The highest rates of neuropathy are among people who have had the disease for at least 25 years. Diabetic neuropathy is more common in people who have had problems controlling their blood glucose levels, in those with high levels of blood fat and blood pressure, in overweight people, and in people over the age of 40.
Diabetic retinopathy:  A common complication of diabetes affecting the blood vessels in the retina (the thin light-sensitive membrane that covers the back of the eye). If untreated, it may lead to blindness. If diagnosed and treated promptly, blindness is usually preventable. Diabetic retinopathy begins without any noticeable change in vision. But even then there often are extensive changes in the retina visible to an ophthalmologist (eye doctor). It is therefore important for a diabetic to have an eye examination at least once (ideally twice) a year.
Diabetic shock:  Hypoglycemia (low blood sugar) associated with diabetes. Symptoms include a sweet, chemical odor on the patient's breath that is similar to that of acetone or alcohol ("acetone breath"), fatigue, light-headedness or fainting, and often reddening of the skin if the patient is Caucasian. Immediate treatment is administration of glucose in a prescription sub-lingual form, or even in the form of hard candy if nothing else is available. Patients with diabetes and their families should learn the early warning signs of hypoglycemia and carry glucose tablets for emergency use. Patients in a state of diabetic shock should also be evaluated medically immediately after emergency treatment. Changes in diet, medication, or insulin administration can then be used to prevent future episodes.
Diabetic skin disease:  A skin disorder that is caused by diabetes or affected by diabetes. Skin disorders are common in diabetes. Some of these disorders are conditions that anyone can have but to which people with diabetes are particularly prone, such as atherosclerotic skin changes, bacterial and fungal infections of the skin, and itching. Other diabetic skin diseases are seen mainly or exclusively in people with diabetes as is the case, for example, with diabetic dermopathy, necrobiosis lipoidica diabeticorum (NLD), diabetic blisters (bullosis diabeticorum), and eruptive xanthomatosis.
Diabetic spinal cord disease:  Involvement of the spinal cord in diabetes. Most of the neurologic attention in diabetes mellitus has focused on distal symmetric polyneuropathy (DSP) -- abnormalities of the peripheral nerves, in particular, the nerves to the feet and hands. However, the nerve damage in diabetes can be more generalized and involve the spinal cord. The spinal cord is significantly smaller in diabetic patients with DSP compared to normal, whereas the spinal cord in diabetic patients without DSP is normal. Whether spinal-cord involvement in diabetes is a primary or secondary event in DSP is uncertain, but it is now clear that the spinal cord can be an important target in diabetes.
Diabetic xanthoma (eruptive xanthoma):  The sudden eruption on the skin of crops of pink papules (firm pea-sized bumps) with a creamy center. They may appear on the hands, feet, arms, legs and buttocks. The papules may be pruritic (itchy). It is due to high concentrations of plasma triglycerides, as occurs with uncontrolled diabetes. The xanthomas usually disappear when the underlying condition is treated, as when the diabetes comes under control.
Diachronic study:  A study done over the course of time. For example, such a study of children with Down syndrome (trisomy 21) might involve the study of 100 children with this condition from birth to 10 years of age. Also called a longitudinal study. The opposite of a synchronic (cross-sectional) study.
Diagnosis:  The outcome of the effort to identify a disease as distinct from other diseases.
Diagnosis, differential:  The process of weighing the probability of one disease versus that of other diseases possibly accounting for a patient's illness.
Dialectical behavioral therapy:  A mode of treatment designed for people with borderline personality disorder (BPD), particularly those with suicidal behavior. Dialectical behavioral therapy (DBT) aims to help people with BPD to validate their emotions and behaviors, examine those behaviors and emotions that have a negative impact on their lives, and make a conscious effort to bring about positive changes. In validation the therapist helps the patient see that their behavior and responses are understandable in relation to their current life situation. In BPD however these behaviors and responses often create a great deal of stress, suffering, and instability in the patient's life. With training in problem solving the patient works on building social and personal skills to deal effectively with the problems in life. Studies have indicated that people with BPD who have had DBT make fewer suicide attempts and enter the hospital less often. DBT may have applications outside BPD. It is being tested as a therapy for other kinds of patients such as suicidal adolescents, older adults with depression, and women with eating disorders.
Dialysis:  The process of cleansing the blood by passing it through a special machine. Dialysis is necessary when the kidneys are not able to filter the blood. Dialysis allows patients with kidney failure a chance to live productive lives. There are two types of dialysis: hemodialysis (dialysis of the blood) and peritoneal dialysis (see below). Each type of dialysis has advantages and disadvantages. Patients can often choose the type of long term dialysis that best matches their needs.
Dialysis machine:  A machine that filters a patient's blood to remove excess water and waste products when the kidneys are damaged, dysfunctional, or missing. Blood is drawn through a specially created vein in the forearm, which is called an arterio-venous (AV) fistula. From the AV fistula, blood is taken to the dialysis machine through plastic tubing. The dialysis machine itself can be thought of as an artificial kidney. Inside, it consists of more plastic tubing that carries the removed blood to the dialyser, a bundle of hollow fibers that forms a semipermeable membrane for filtering out impurities. In the dialyser, blood is diffused with a saline solution called dialysate, and the dialysate is in turn diffused with blood. Once the filtration process is complete, the cleansed blood is returned to the patient. Most patients using dialysis due to kidney impairment or failure use a dialysis machine at a special dialysis clinic. Most sessions take about four hours, and typically patients visit the clinic one to three times per week.
Dialysis, peritoneal:  Technique that uses the patient's own body tissues inside of the belly (abdominal cavity) to act as a filter. The intestines lie in the abdominal cavity, the space between the abdominal wall and the spine. A plastic tube called a "dialysis catheter" is placed through the abdominal wall into the abdominal cavity. A special fluid is then flushed into the abdominal cavity and washes around the intestines. The intestinal walls act as a filter between this fluid and the blood stream. By using different types of solutions, waste products and excess water can be removed from the body through this process.
Diaper rash:  Also called "diaper dermatitis," a diaper rash is a skin inflammatory reaction localized to the area usually covered by the diaper. It can have many causes including infections (yeast, bacterial or viral), friction irritation, chemical allergies (perfumes, soaps), sweat and plugging of sweat glands.
Diaper rash, yeast:  Infection in the diaper area caused by a yeast formerly called Monilia and now called Candida. These organisms are part of the germs normally found in various parts of the body and ordinarily do not cause any symptoms. Certain conditions, such as antibiotic use or excessive moisture, may upset the balance of microbes and allow an overgrowth of Candida. Candida may exacerbate diaper rash and make it much worse, as this yeast grows very readily on damaged skin. The infected skin is usually fiery red with areas that may have a raised red border.
Diaphragm (contraceptive):  A barrier method of contraception that is available by prescription only and must be sized by a health professional to achieve a proper fit. The diaphragm has a dual mechanism to prevent a pregnancy. A dome-shaped rubber disk with a flexible rim covers the cervix so sperm cannot reach the uterus and a spermicide applied within the diaphragm before insertion kills sperm. A diaphragm protects against conception for six hours. For intercourse after the six-hour period, or for repeated intercourse within this period, fresh spermicide should be placed in the vagina with the diaphragm still in place. The diaphragm should be left in place for at least six hours after the last intercourse. A diaphragm should not be left in place for more than a total of 24 hours because of the risk of toxic shock syndrome (TSS), a rare but potentially fatal condition. Symptoms of TSS include sudden fever, stomach upset, a sunburn-like rash, and a drop in blood pressure.
Diaphragm (muscle):  The muscle that separates the chest (thoracic) cavity from the abdomen. The diaphragm is the main muscle of respiration. Contraction of the diaphragm muscle expands the lungs during inspiration when one is breathing air in. We rely heavily on the diaphragm for our respiratory function so that when the diaphragm is impaired, it can compromise our breathing. The nerve that controls the diaphragm is the phrenic nerve, which originates much higher in the embryo than its is found in full development. During embryological development the diaphragm moves down and drags the phrenic nerve with it. The phrenic nerve innervates the diaphragm and comes from the 2nd and 3rd cervical levels of the spinal cord.
Diaphragm pacing:  A procedure to help patients with spinal cord injuries to breathe. Their breathing is helped by setting the respiratory rate by electrical stimulation (pacing) of the phrenic nerve. The pacing is accomplished via electrodes surgically implanted into the diaphragm, which is innervated by the phrenic nerve. This procedure is currently experimental. It is being tested in patients with injuries that cut across (transect) the cervical spinal cord high in the neck and result in paralysis of all four limbs (tetraplegia or quadriplegia) and respiratory failure requiring chronic mechanical ventilatory support. For the procedure to work, the function of the phrenic nerve must be normal. Diaphragm pacing originally required surgery opening the chest cavity (thoracotomy) to implant the electrodes. It is now done by laparoscopy through small openings in the chest.
Diaphragmatic hernia:  Passage of a loop of bowel through the diaphragm muscle. This type of hernia occurs as the bowel from the abdomen "herniates" upward through the diaphragm into the chest (thoracic) cavity. Diaphragmatic hernias may be congenital or acquired. Congenital diaphragmatic hernias are present at birth. They occur because of abnormal development of the embryo. Acquired diaphragmatic hernias are usually caused by traumatic injury.
Diarrhea:  A familiar phenomenon with unusually frequent or unusually liquid bowel movements, excessive watery evacuations of fecal material. The opposite of constipation. There are myriad infectious and noninfectious causes of diarrhea. Persistent diarrhea is both uncomfortable and dangerous to the health, as it can indicate an underlying infection. It may also mean that the body is not able to absorb some nutrients due to a problem in the bowels. Treatment includes drinking plenty of fluids to prevent dehydration, over-the-counter remedies in most cases, and medical examination if diarrhea persists for more than a couple of days, particularly in small children or elderly people.
Diarrhea and dermatitis, zinc deficiency:  Among the consequences of zinc deficiency, dermatitis (skin inflammation) and diarrhea are particularly prominent features.
Diarrhea, antibiotic-induced:  A bacterium called Clostridium difficile (C.difficile), one of the most common causes of infection of the large bowel (colon). Patients taking antibiotics are at particular risk of becoming infected with C. difficile. Antibiotics disrupt the normal bacteria of the bowel, allowing C. difficile bacteria (and other bacteria) to become established and overgrow the colon. Many persons infected with C. difficile bacteria have no symptoms but can become carriers of the bacteria and infect others. In other people, a toxin produced by C. difficile causes diarrhea, abdominal pain, severe inflammation of the colon (colitis), fever, an elevated white blood count, vomiting and dehydration. In severely affected patients, the inner lining of the colon becomes severely inflamed (a condition called pseudomembranous colitis). Rarely, the walls of the colon wear away and holes develop (colon perforation), which can lead to a life-threatening infection of the abdomen.
Diarrhea, Brainerd:  A syndrome characterized by the acute onset of watery nonbloody diarrhea (3 or more loose stools per day), lasting 4 weeks or more, and resolving spontaneously. The disease is of unknown causation and appears in outbreaks or as sporadic cases. It is named after Brainerd, Minnesota, USA the town where the first outbreak was recognized in 1983. Don't you feel cheated that a diarrhea has not been named for your town? People with Brainerd diarrhea typically have 10-20 episodes per day of explosive, watery nonbloody diarrhea with urgency and, often, fecal incontinence. Accompanying symptoms include gas, mild abdominal cramping, and fatigue. Nausea, vomiting, and systemic symptoms such as fever are rare, although many patients experience slight weight loss. Despite much research, the cause of Brainerd diarrhea has not yet been identified. Although it is thought to be an infectious agent, intensive searches for bacterial, parasitic, and viral pathogens (agents of disease) have been unsuccessful. The remote possibility remains that Brainerd diarrhea is caused by a chemical toxin. There is no laboratory test that can confirm the diagnosis. Brainerd diarrhea should be suspected in any patient who presents with the acute onset of nonbloody diarrhea lasting for more than 4 weeks, and for whom stool cultures and examinations for O&P (ova and parasites) have been negative. On colonoscopy, petechiae, aphthous ulcers and erythema may be observed. Microscopic examination of colonic tissue biopsy specimens often reveals mild inflammation, with an increased number of lymphocytes, particularly in the ascending and transverse colon. The stomach and small intestine generally appear normal. There is no known cure for Brainerd diarrhea. A variety of antimicrobial agents have been tried without success, including trimethoprim-sulfamethoxazole, ciprofloxacin, doxycycline, ampicillin, metronidazole, and paromomycin. Neither has there been any response to steroids or antiinflammatory agents. Approximately 50% of patients report some relief in symptoms with high doses of opioid antimotility drugs, such as loperamide, diphenoxylate, and paregoric. Brainerd diarrhea is a self-limited disease. Symptoms may last a year or more, and typically have a waxing and waning course. Long-term follow-up studies have shown complete resolution in essentially all patients by the end of 3 years. There have been no known cases of sequelae or relapse once the illness has completely resolved.
Diarrhea, E. coli hemorrhagic:  Bloody colitis (inflammation of the bowel) caused by E. coli, usually by the strain E. coli 0157:H7. The diarrhea is severe with painful abdominal cramps, gross blood in the stool, and lasts for 6 to 8 days. Most commonly, E. coli 01257:H7 comes from eating raw or undercooked ground beef (hamburger) or from drinking raw milk or contaminated water. Less commonly, E coli O157:H7 can be transmitted from one person to another. With the recent outbreaks this disorder is in danger of being named for Taco Bell.
Diarrhea, rotavirus:  A leading cause of severe winter diarrhea in infants and young children. Each year, rotavirus (RV) causes an estimated 500,000 doctor visits and 50,000 hospital admissions in the United States. Almost every child catches RV before entering school but, with rehydration (and good nutrition), nearly all recover fully. However, in poor countries RV is estimated to be responsible for at least 600,000 deaths of children under 5 years from RV diarrhea and dehydration yearly. Aside from causing acute infantile gastroenteritis and diarrhea in young children, RV infection is typically accompanied by low-grade fever.
Diarrhea, traveler's:  Diarrhea illness associated with travel to a foreign country. Among the causes of traveler's diarrhea are viruses and enterotoxigenic E. coli (ETEC). E.coli is a particular type of bacteria that normally lives in the intestines of people (and animals). Most strains of E coli are quite harmless. They are simply part of the normal intestinal flora. However, there are some kinds of E. coli that are capable of causing disease. Not all E. coli bacteria that cause disease are alike. There are multiple classes of "bad" E.coli. The enterotoxigenic E.coli (ETEC) constitute a class of "bad" E.coli. They produce toxins (poisons). The ETEC toxins do not injure or kill the cells lining the intestines. They alter the metabolism of these cells, disturbing the regulation of fluid and electrolytes (like sodium and potassium) absorbed from the intestines. Instead of absorbing fluid, the intestinal cells permit fluid to be secreted into the intestine. This causes diarrhea. ETEC causes diarrhea in infants and traveler's diarrhea. ETEC is a cause of food poisoning. The cornerstone of ETEC therapy is replacement of fluids and electrolytes (sodium and other ions) lost in the diarrhea. The ideal approach to ETEC is to avoid exposure to it.
Diastole:  The time period when the heart is in a state of relaxation and dilatation (expansion).
Diastrophic dysplasia:  An inherited skeletal disorder involving significantly short stature (dwarfism). Characteristic features at birth include short birth length with short limbs (short-limbed dwarfism), "hitchhiker thumb", and clubfeet. Palatal malformations such as cleft palate or submucous cleft of the palate are present in 50% of patients. There is swelling of the ears in the first days to weeks of life in 80% of children; the swelling then spontaneously subsides but later the ears have a "cauliflower" appearance. Fingers are short and broad and show ulnar deviation (are inclined away from the thumb). The thumb itself has a hitch-hiker-type appearance. There is increased death rate in infancy due to problems breathing, but thereafter people with diastrophic dysplasia have a normal life span. Orthopedic problems are common. The joints can be dislocated, especially the shoulder, elbows, hips, and patellae (knee caps). Flexion contractures of the knees and shoulders are common.
Diathermy:  The use of heat to destroy abnormal cells. Also called cauterization or electrodiathermy.
Diathesis:  In medicine, an elegant term for a predisposition or tendency. Thus, a hemorrhagic diathesis is nothing more than a bleeding tendency.
Dicysteine:  Cystine (an amino acid)
Dieldrin:  A chlorinated hydrocarbon insecticide.
Dieldrix:  Trade name of the insecticide dieldrin.
Diesel exhaust:  The exhaust generated by diesel engines. This exhaust is a complex mixture of combustion products of diesel fuel. The exact composition depends on the type of engine, the speed and load at which it is run, and the composition of the fuel used. In the year 2000 the US government classified diesel exhaust particulates as "reasonably anticipated to be a human carcinogen" -- an agent that causes cancer. There are findings now available of elevated lung cancer rates in occupational groups exposed to diesel exhaust. These groups include railroad workers, mine workers, bus garage workers, and trucking company workers.
Diesel exhaust particle:  A respirable particle produced during the compression ignition of diesel fuel. Diesel particles are composed of elemental and organic carbon compounds as well as trace amount of other elements with toxic properties including transition metals.
Diethylstilbestrol:  The earliest synthetic (man-made) form of the hormone estrogen. Diethylstilbestrol (DES) was once widely prescribed to prevent miscarriages and premature births. Its usage was standard practice in the 1950s and 1960s. Millions of women received the drug. Girls whose mothers were given DES during pregnancy ("DES daughters") were discovered to be at increased risk for being born with malformations of the reproductive organs and to face elevated rates of infertility and miscarriages themselves. DES daughters were also found to be at increased risk for cancer of the cervix and vagina, specifically for developing clear-cell adenocarcinoma of the vagina and cervix, a relatively uncommon type of cancer, at an early age. In 2000, DES daughters were reported to be 3-5 times more likely to have the more common forms of cervical cancer than women whose mothers did not take DES. DES sons are predisposed to testicular abnormalities, such as abnormally small testes and failure of the testes to descend into the scrotum, which increases the risk of testicular cancer. All women and men who believe they may have been exposed to DES before birth should inform their doctor of their exposure so that they may be appropriately examined and monitored. DES is still available for prescription in the US. According to the package insert, DES "is indicated for the treatment of" (and I quote): "Breast cancer (palliation only) in appropriately selected women and men with metastatic disease" and "Prostatic cancer -- palliative therapy of advanced disease."
Differential diagnosis:  The process of weighing the probability of one disease versus that of other diseases possibly accounting for a patient's illness. The differential diagnosis of rhinitis (a runny nose) includes allergic rhinitis (hayfever), the abuse of nasal decongestants and, of course, the common cold.
Differential white cell count:  The proportions of the different types of white cells in the blood, usually split into the different types of granulocytes, lymphocytes, monocytes, eosinophils, and basophils. The differential white cell count was originally done by visual inspection of the blood and is now often machine-generated. Normal values are: 24-62% neutrophils, 19-53% lymphocytes, 2-12% monocytes, 0-7% eosinophils, and 0-2% basophils.
Differentiated cancer:  A cancer in which the cells are mature and look like cells in the tissue from it arose. Differentiated cancers tend to be decidedly less aggressive than undifferentiated cancers composed of immature cells.
Differentiation:  1 The process by which cells become progressively more specialized; a normal process through which cells mature. This process of specialization for the cell comes at the expense of its breadth of potential. Stem cells can, for example, differentiate into secretory cells in the intestine. 2 In cancer, differentiation refers to how mature (developed) the cancer cells are in a tumor. Differentiated tumor cells resemble normal cells and tend to grow and spread at a slower rate than undifferentiated or poorly differentiated tumor cells, which lack the structure and function of normal cells and grow uncontrollably.
Differentiation therapy:  An approach to the treatment of advanced or aggressive malignancies in which the malignant cells are treated so that they can resume the process of maturation and differentiation into mature cells. Differentiation therapy is based on the concept that cancer cells are normal cells that have been arrested at an immature or less differentiated state, lack the ability to control their own growth, and so multiply at an abnormally fast rate. Differentiation therapy aims to force the cancer cell to resume the process of maturation. Although differentiation therapy does not destroy the cancer cells, it restrains their growth and allows the application of more conventional therapies (such as chemotherapy) to eradicate the malignant cells. Differentiation agents tend to have less toxicity than conventional cancer treatments. An outstanding example of this concept in action is the product called Curaderm which cures skin cancers by this very mechanism. Not surpisingly, the active ingredient is derived from nature. It is present in Devil's apple and in eggplant.
Diffuse degeneration of cerebral gray matter with hepatic cirrhosis, Alper's disease:  A progressive disease of the nervous system characterized by spasticity (tightness), myoclonus and dementia and by liver problems with jaundice and cirrhosis. This disorder, first described by Alpers in 1931 as "Diffuse progressive degeneration of gray matter of cerebrum", usually begins early in life with convulsions. A continuous seizure (status epilepticus) is often the final event. Alpers diffuse degeneration of gray matter with hepatic cirrhosis is due to more than one cause. Some cases are inherited as autosomal recessive traits with both parents appearing normal but carrying one Alpers gene and each of their children, boys and girls alike, running a 1 in 4 risk of receiving both of the parental Alpers genes and suffering from this dread disease. Other cases of Alpers disease are due to disorders of oxidative phosphorylation, including mitochondrial DNA depletion syndromes.
Diffuse idiopathic skeletal hyperostosis:  Abbreviated as DISH. Diffuse idiopathic skeletal hyperostosis is a form of degenerative arthritis characteristically associated with flowing calcification along the sides of the vertebrae of the spine and commonly associated with inflammation (tendonitis) and calcification of the tendons at their attachments points to bone. Because areas of the spine and tendons can become inflamed, antiinflammatory medications (NSAIDs) such ibuprofen can be helpful in both relieving pain and inflammation. Also called Forestier's disease.
Diffuse mastocytosis:  A form of mastocytosis in which the entire skin is thickened and leathery with generalized reddening and intense pruritus (itching) due to widespread infiltration of the skin with mast cells. Treatment may include antihistamines, drugs to reduce stomach acid, migraine headache drugs for headache, and cromolyn for bowel symptoms.
Diffuse toxic goiter:  Graves disease, the most common cause of hyperthyroidism (overactivity of the thyroid gland), with generalized diffuse overactivity ("toxicity") of the entire thyroid gland which becomes enlarged into a goiter. There are three clinical components to Graves disease:
1. Hyperthyroidism (the presence of too much thyroid hormone),
2. Ophthalmopathy specifically involving exophthalmos (protrusion of the eyeballs),
3. Dermopathy with skin lesions.
The ophthalmopathy can cause sensitivity to light and a feeling of "sand in the eyes." With further protrusion of the eyes, double vision and vision loss may occur. The ophthalmopathy tends to worsen with smoking. The dermopathy of Graves disease is a rare, painless, reddish lumpy skin rash that of Graves disease is an autoimmune process. It is caused by thyroid-stimulating antibodies which bind to and activate the thyrotropin receptor on thyroid cells. Graves disease can run in families. The rate of concordance for Graves disease is about 20% among monozygotic (identical) twins, and the rate is much lower among dizygotic (nonidentical) twins, indicating that genes make only a moderate contribution to the susceptibility to Graves disease. No single gene is known to cause the disease or to be necessary for its development. Factors that can trigger the onset of Graves disease include stress, smoking, radiation to the neck, medications (such as interleukin-2 and interferon-alpha), and infectious organisms such as viruses. The diagnosis of Graves disease is made by a characteristic thyroid scan (showing diffusely increase uptake), the characteristic triad of ophthalmopathy, dermopathy, and hyperthyroidism, or blood testing for TSI (thyroid stimulating immunoglobulin) the level of which is abnormally high. Current treatments for the hyperthyroidism of Graves disease consist of antithyroid drugs, radioactive iodine, and surgery. There is regional variation in which of these measures tends to be used -- for example, radioactive iodine is favored in North America and antithyroid drugs nearly everywhere else. The surgery, subtotal thyroidectomy, is designed to remove the majority of the overactive thyroid gland. The disease is named for Robert Graves who in 1835 first identified the association of goiter, palpitations, and exophthalmos.
Digestive system:  The organs that are responsible for getting food into and out of the body and for making use of it. These organs include the salivary glands, the mouth, esophagus, stomach, small intestine, liver, gallbladder, pancreas, colon, rectum, and anus. The digestive system has a series of hollow organs joined in a long, twisting tube from the mouth to the anus. Inside this tube is a lining called the mucosa. In the mouth, stomach, and small intestine, the mucosa contains tiny glands that produce juices to help digest food. Two solid organs, the liver and the pancreas (both of which are embryologically derived from the digestive tract), produce digestive juices that reach the intestine through small tubes known as ducts. In addition, parts of other organ systems (for instance, nerves and blood) play a major role in the digestive system.
Digit:  A finger or toe.
Digit, supernumerary:  An extra finger or toe.
Digital subtraction angiogram (DSA):  A type of fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment. Images are produced using contrast medium by subtracting a 'pre-contrast image' (aka the "mask") from later images, once the contrast medium has been introduced into a structure. Hence the term 'digital subtraction angiography'.
Dihydroorotate dehydrogenase:  An enzyme necessary to pyrimidine synthesis and therefore essential to the production of DNA and RNA.
Dihydrotestosterone:  Dihydrotestosterone (DHT) is a byproduct of the breakdown of the male hormone testosterone. Dihydrotestosterone is considered the essential androgenic hormone. DHT is responsible for the formation of male primary sex characteristics during embryonic life and responsible for the development of most secondary sex characteristics in males at puberty, and it continues to be important to male sexual function throughout adult life. In older men the level of DHT increases and is responsible for male pattern hair loss and for benign prostate hypertrophy. Inhibition by the drugs Proscar (for prostate) and Propecia (for hair loss) and certain herbal therapies are designed to combat these conditions.
Dihydroxyacetone:  Also known as DHA, the active ingredient in most sunless tanning lotions.
Dilatate:  To enlarge or expand. For example, to dilatate the eye is to enlarge the pupil temporarily with special (mydriatic) eye drops. This procedure allows the eye care specialist to better view the inside of the eye. The word "dilate" means the same thing as "dilatate". Both come from the Latin "dilatare" meaning "to enlarge or expand."
Dilatation:  The process of enlargement or expansion.
Dilatation and curettage:  A minor operation in which the cervix is expanded enough (dilatation) to permit the cervical canal and uterine lining to be scraped with a curet (or curette), an instrument shaped like a spoon. This procedure also is called D and C.
Dilate:  To stretch or enlarge. It comes from the Latin verb "dilatare" meaning "to enlarge or expand."
Dilated cardiomyopathy:  A disorder in which the chambers of the heart are dilated (enlarged) because the heart muscle is weakened and cannot pump effectively. There are many causes, the most common being myocardial ischemia (not enough oxygen supplied to the heart muscle) due to coronary artery disease.
Dilator:  A device used to stretch or enlarge an opening. Patients with scarring of the muscular tube through which food passes from the throat to the stomach (esophagus) can require a dilator procedure in order to open the esophagus for adequate passage of food and fluids.
Dioxin:  One of a number of poisonous petroleum-derived chemicals which are produced when herbicides (substances used for killing plants) are made or when plastics are burned. Dioxins are chemically dibenzo-p-dioxins. One of the best known is TCDD (2, 3, 7, 8-TCDD). Dioxins cause skin disease (chloracne). In animal tests, dioxins are teratogens (agents that cause birth defects and miscarriages), mutagens (agents that cause mutations) and carcinogens (agents that cause cancer). In 2001 the US government added the TCDD to the list of substances that are known carcinogens based on "sufficient evidence of carcinogenicity from studies in humans." The National Institutes of Health (NIH) concluded that: "It is now clear that there is a causal relationship between exposure to TCDD and human cancer." A factory explosion in northern Italy in 1976 polluted the town of Seveso with dioxin. Some defoliants such as Agent Orange, which was used in the Vietnam war, contain dioxin.
Dipeptide:  A peptide consisting of two amino acids.
Diphtheria:  An acute infectious disease that typically strikes the upper respiratory tract including the throat. It is caused by infection with the bacteria Corynebacterium diphtheriae. Symptoms include sore throat and mild fever at first. As the disease progresses, a membranous substance forms in the throat that makes it difficult to breathe and swallow. Diphtheria can be deadly.
Diploe:  The soft spongy material between the inside table and outside table (the interior and exterior bony plates) of the skull. The diploe contains bone marrow.
Diploid number:  The number of chromosomes in most cells of the body. This number is 46 in humans. It is naturally twice the haploid number of 23 chromosomes contained in human eggs (ova) and sperm.
Diplopia:  The condition in which a single object appears as two objects. Also called "double vision."
Diplopia, binocular:  Double vision (diplopia) that is only evident when looking through both eyes and disappears if one eye is closed or covered. The condition is caused by misalignment of the eyes by the extraocular muscles (the muscles around the eyeball that control gaze). This may be due to strabismus (misalignment of the eyes from birth), neurologic damage to the extraocular muscles (as from a brain abscess, stroke, head trauma or brain tumor), diabetes, myasthenia gravis, Graves disease, or trauma to the eye muscles, as from a fracture of the orbit.
Diplopia, monocular:  Double vision (diplopia) in only one eye. The double vision persists when the other eye is covered. Monocular diplopia can be caused by astigmatism (abnormal curvature of the front of the cornea), keratoconus (cone-shaped cornea), pterygium (thickening of the conjunctiva over the cornea), a cataract, dislocation of the lens, a mass in the eyelid pressing on the front of the eye, xerophthalmia (dry eye), and certain retinal problems. Treatment depends upon the specific cause.
Dipper:  A person in whom there is the normal nocturnal fall (dip) in blood pressure.
Diprosopus:  Two-faced conjoined twins (incompletely separated identical twins). The twins have almost complete fusion of their bodies with one set of limbs. Part or all of the face is duplicated. The condition usually results in stillbirth. The ancient two-faced Mexican figurines known as the "pretty ladies of Tlatilco" are now thought to represent diprosopus. It is believed these early Mesoamerican figurines may, in fact, be "the oldest scientifically medical images in world history." Sculpted over a period of 500 years beginning in 1200 BC, these little statues show diprosopus with two faces side by side. This degree of accuracy in documenting the anatomical and pathological features of a human head does not appear for another two millennia until the 16th-century studies of Hans Baldung Grien and Andreas Vesalius who did anatomical drawings based on dissected cadavers. The term "diprosopus" comes from the Greek "di-," two + "prosopon," face = two-faced.
Dipsophobia:  An abnormal and persistent fear of drinking alcohol. Sufferers of dipsophobia experience undue anxiety about addiction to alcohol and the effect this addiction can have on their body.
Dipsosis:  Excessive thirst; overwhelming desire for water or another liquid. Dipsosis may occur when the amount of water in the body falls below normal.
Directives, advance:  Known also as advance medical directives, these are documents that pertain to treatment preferences and the designation of a surrogate decision-maker in the event that a person should become unable to make medical decisions on their own behalf. Advance directives generally fall into three categories: living will, power of attorney and health care proxy. LIVING WILL: This is a written document that specifies what types of medical treatment are desired. A living will can be very specific or very general. The most common statement in a living will is to the effect that: If I suffer an incurable, irreversible illness, disease, or condition and my attending physician determines that my condition is terminal, I direct that life-sustaining measures that would serve only to prolong my dying be withheld or discontinued. More specific living wills may include information regarding an individual's desire for such services such as analgesia (pain relief), antibiotics, hydration, feeding, and the use of ventilators or cardiopulmonary resuscitation. HEALTH CARE PROXY: This is a legal document in which an individual designates another person to make health care decisions if he or she is rendered incapable of making their wishes known. The health care proxy has, in essence, the same rights to request or refuse treatment that the individual would have if capable of making and communicating decisions. DURABLE POWER OF ATTORNEY: This is the third type of advance directive. Individuals may draft legal documents providing power of attorney to others in the case of incapacitating medical condition. The durable power of attorney allows an individual to make bank transactions, sign Social Security checks, apply for disability, or simply write checks to pay the utility bill while an individual is medically incapacitated.
Disc:  Shortened terminology for an intervertebral disc, a disk-shaped piece of specialized tissue that separates the bones of the spinal column. The center of a disc, called the nucleus, is soft, springy and receives the shock of standing, walking, running, etc. The outer ring of the disc, called the annulus (Latin for ring), provides structure and strength to the disc. The annulus consists of a complex series of interwoven layers of fibrous tissue that hold the nucleus in place. A disc can herniate. A herniated disc is often referred to as a slipped disc. This term came from the action of the nuclear tissue when it is forced from the center of the disc. The nuclear tissue located in the center of the disc can be placed under so much pressure that it can cause the annulus to rupture. When the disc has herniated or ruptured, it may create pressure against one or more of the spinal nerves which can cause pain, weakness or numbness. The terms slipped disc, herniated disc, prolapsed disc, and ruptured disc are synonymous.
Disc, optic:  The circular area in the back of the inside of the eye where the optic nerve connects to the retina. Also called the optic nerve head.
Discharge:  1.The flow of fluid from part of the body, such as from the nose or vagina. 2. The passing of an action potential, such as through a nerve or muscle fiber. 3. The release of a patient from a course of care. The doctor may then dictate a discharge summary.
Discoid lupus:  A chronic inflammatory condition limited to the skin, caused by an autoimmune disease. An autoimmune disease occurs when the body's tissues are attacked by its own immune system. Patients with lupus have unusual antibodies in their blood that are targeted against their own body tissues. Lupus can cause disease of the skin, heart, lungs, kidneys, joints, and nervous system. When only the skin is involved, as mentioned, the condition is called discoid lupus. When internal organs are involved, the condition is called systemic lupus erythematosus (SLE). Up to 10% of persons with discoid lupus eventually develop the systemic form of lupus (SLE). SLE is eight times more common in women than men. The causes of SLE are unknown. However, heredity, viruses, ultraviolet light, and drugs may all play a role. Eleven criteria have been established for the diagnosis of SLE:

Malar (over the cheeks of the face) "butterfly" rash
Discoid skin rash: patchy redness that can cause scarring
Photosensitivity: skin rash in reaction to sunlight exposure
Mucus membrane ulcers: ulceration of the lining of the mouth, nose or throat
Arthritis: 2 or more swollen, tender joints of the extremities
Pleuritis/pericarditis: inflammation of the lining tissue around the heart or lungs, usually associated with chest pain with breathing
Kidney abnormalities: abnormal amounts of urine protein or cellular elements
Brain irritation: manifested by seizures (convulsions) and/or psychosis
Blood count abnormalities: low counts of white or red blood cells, or platelets
Immunologic disorder: abnormal immune tests include anti-DNA or anti-Sm (Smith) antibodies, falsely positive blood test for syphilis, anticardiolipin antibodies, lupus anticoagulant, or positive LE prep test
Antinuclear antibody: positive ANA antibody testing

The treatment of SLE is directed toward decreasing inflammation and/or the level of autoimmune activity. Persons with SLE can help prevent "flares" of disease by avoiding sun exposure and by not abruptly discontinuing medications. Treatments for discoid lupus include avoiding sun exposure, antimalarial medications (hydroxychloroquine/PLAQUINIL and others), local cortisone injections, dapsone, and immune suppression medications.
Discordance:  1. The presence of any given condition such as HIV in only one member of a couple. 2. In genetics, the presence of a phenotype such as asthma in only one members of a twin pair. 3. In clinical care, lack of agreement between physician and patient. In all sense, disconcordance is as opposed to concordance. From dis- + the Latin concordare, to agree = not to agree.
Disinsection:  Spraying aircraft for insects, a procedure called disinsection. Some countries in Africa, Latin America, the Caribbean, Australia and the South Pacific require the spraying of the aircraft passenger compartment with insecticide while passengers are present. This is done to prevent the importation of insects such as mosquitos. Disinsection procedures have been determined to be safe by the World Health Organization (WHO). However, they may aggravate allergies. And, they surely are NOT safe. (Trust WHO at your own risk.)
Disruption sequence:  The events that occur when a fetus that is developing normally is subjected to a destructive agent such as the rubella (German measles) virus.
Dissect:  To cut apart or separate tissue as, for example, for anatomical study or in surgery. Also, an artery is said to dissect when its wall is torn, as in a dissecting aneurysm.
Dissecting aneurysm:  A localized widening (dilatation) of an artery (an aneurysm) in which the wall of an artery rips (dissects) longitudinally. This occurs because bleeding into the weakened wall splits the wall. Dissecting aneurysms tend to affect the thoracic aorta. They are particularly a major danger in Marfan's disease. Albert Einstein, for example, died ot a dissecting aneurysm.
Dissection:  The process of cutting apart or separating tissue as, for example, in the study of anatomy or in the course of a surgical procedure.
Disseminated sclerosis:  synonym for multiple sclerosis.
Dissociation:  In psychology and psychiatry, a perceived detachment of the mind from the emotional state or even from the body. Dissociation is characterized by a sense of the world as a dreamlike or unreal place and may be accompanied by poor memory of the specific events, which in severe form is known as dissociative amnesia. The term dissociation refers to the act of separating or the state of being separated.
Distal:  The more (or most) distant of two (or more) things. For example, the distal end of the femur (the thigh bone) is the end down by the knee; the end more distant from the torso. The distal bile duct is the far end of the cystic duct, the end away from the gallbladder. And the distal lymph node in a chain of nodes is the most distant one. The opposite of distal is proximal.
Distance healing:  Healing in which people seek to help patients simply with the power of the mind. Distance healing can include anything from therapeutic touch -- in which practitioners, without touching their patients, try to alter their energy fields -- to praying for people who are ill.
Distention:  The state of being distended, enlarged, swollen from internal pressure. For example, on inhalation there is distention of the lungs due to the increased air pressure within the lungs.
Distichiasis:  Double rows of eyelashes. The extra eyelashes grow from glands called the Meibomian glands and may protrude into the cornea, producing severe corneal abrasions.
Diuresis:  The increased formation of urine by the kidney.
Diuretic:  Anything that promotes the formation of urine by the kidney. Diuresis may be due to a huge number of causes including metabolic conditions such as diabetes mellitus (in which the increased glucose level in the blood causes water to be lost in the urine); substances in food and drink (such as coffee, tea, and alcoholic beverages); and specific diuretic drugs. All diuretic drugs -- which are usually called, more simply, diuretics -- cause a person to "lose water" but they do so by diverse means, including: Inhibiting the kidney's ability to reabsorb sodium, thus enhancing the loss of sodium in the urine. And when sodium is lost in the urine, water goes with it. (This type of diuretic is called a high-ceiling diuretic or a loop diuretic). Enhancing the excretion of both sodium and chloride in the urine so that water is excreted with them. This is how the thiazide diuretics work. Blocking the exchange of sodium for potassium, resulting in excretion of sodium and potassium but relatively little loss of potassium. These diuretics are therefore termed potassium sparing diuretics. Some diuretics work by still other mechanisms. And some diuretics have other effects and uses such as in treating hypertension.
Diurnal:  Occurring in the daytime. A patient may have a diurnal fever rather than a nocturnal one. Diurnal also can refer to recurring every day.
Diverticula:  The plural of diverticulum. As a person ages, pressure within the large intestine (colon) causes pockets of tissue (sacs) that push out from the colon walls. A small bulging sac pushing outward from the colon wall is a diverticulum. Diverticula can occur throughout the colon but are most common near the end of the left side of the colon, the sigmoid colon.
Diverticulitis:  Inflammation of the diverticula (small outpouchings) along the wall of the colon, the large intestine. (One outpouching is a diverticulum; two or more are diverticula). For diverticulitis to occur, there must be diverticulosis, the presence of diverticula. Diverticulosis can occur anywhere in the colon but it is most typical in the sigmoid colon, the S-shaped segment of the colon the left lower part of the abdomen. (Sides are from the patient's perspective so the left lower part of your abdomen is nearest your left hand). The incidence of diverticulosis increases with age. Age causes a weakening of the walls of the colon and this weakening permits the formation of diverticula. By age 80, most people have diverticulosis. A key factor promoting the formation of diverticulosis is elevated pressure within the colon. The pressure within the colon is raised when a person is constipated and has to push down to pass small, hard bits of stool. Most patients with diverticulosis have few or no symptoms although some have mild symptoms including abdominal cramping and bloating. Diverticulosis sets the stage for inflammation and infection of the outpouching, that is for diverticulitis. (The "-itis" refers to inflammation.) It is potentially serious and can result in pain in the left lower abdomen, fever, nausea, vomiting, constipation and, paradoxically, diarrhea and frequent urination. Even graver consequences such as perforation of the colon and peritonitis are well known from diverticulitis. The best way to avoid developing diverticulosis in the first place (aside from the impossibility of staying young) is by eating a proper healthy diet with plenty of fiber. A diet high in fiber keeps the bowels moving, keeps the pressure within the colon within normal limits, and slows or stops the formation of diverticuli. Diverticulitis can be diagnosed with barium x-rays of the colon or with sigmoidoscopy or colonoscopy. Treatment of diverticulitis is designed to combat the inflammation and infection.
Diverticulosis:  The condition of having diverticula, small outpouchings from the large intestine, the colon. (One outpouching is a diverticulum; two or more are diverticula). See above and below for more information.
Diverticulum:  A small bulging sac pushing outward from the colon wall is a diverticulum. Plural is diverticula.
Diving injury:  An injury incurred from diving into water that is too shallow or has hidden hazards. These injuries may be to the head, neck, or spinal cord. Many diving injuries result when persons --predominantly males aged 15-25 years -- plunge into swimming pools or natural bodies of water such as rivers, streams, lakes, and oceans. In one study, 15 cases of quadriplegia were reported. One resulted from a dive into a swimming pool; the other 14 cases resulted from dives into rivers, streams, lakes, or oceans. Only three of these injured persons had objective evidence of the depth of the water at the time of injury, Most of the divers had underestimated it. Droughts resulting in low water levels in rivers, lakes, and streams increase the risk of spinal cord injuries from diving, even in natural bodies of water previously considered safe. Because of extremely low water levels, no one should dive -- even into a familiar body of water --until the depth of the water has been objectively measured. Several strategies to prevent diving injuries have been suggested. The authorities can closely monitor water levels in natural bodies of water during periods of low rainfall and can post warning signs to alert potential divers of hazards. In some localities, public education and poster campaigns have been used, and areas that are too shallow for diving have been posted as being hazardous. Other strategies urge divers to determine the depth of the water by wading into it before diving or by first jumping feet first into the water.
Dizygotic twins:  Twins who have shared a common uterine environment with its twin but is due to a different fertilized ovum. Also called fraternal twins.
Dizziness:  Painless head discomfort with many possible causes including disturbances of vision, the brain, balance (vestibular) system of the inner ear, and gastrointestinal system. Dizziness is a medically indistinct term which laypersons use to describe a variety of conditions ranging from lightheadedness, unsteadiness to vertigo.
DNA:  Deoxyribonucleic acid. One of two types of molecules that encode genetic information. (The other is RNA. In humans DNA is the genetic material; RNA is transcribed from it. In some other organisms, RNA is the genetic material and, in reverse fashion, the DNA is transcribed from it.) DNA is a double-stranded molecule held together by weak hydrogen bonds between base pairs of nucleotides. The molecule forms a double helix in which two strands of DNA spiral about one other. The double helix looks something like an immensely long ladder twisted into a helix, or coil. The sides of the "ladder" are formed by a backbone of sugar and phosphate molecules, and the "rungs" consist of nucleotide bases joined weakly in the middle by the hydrogen bonds. There are four nucleotides in DNA. Each nucleotide contains a base: adenine (A), guanine (G), cytosine (C), or thymine (T). Base pairs form naturally only between A and T and between G and C so the base sequence of each single strand of DNA can be simply deduced from that of its partner strand. The genetic code in DNA is in triplets such as ATG. The base sequence of that triplet in the partner strand is therefore TAC. The first proof that DNA was the hereditary material was provided in 1944 by Oswald Avery, Maclyn McCarty and Colin MacLoed. The double helical structure of DNA was discovered in 1953 by James D. Watson and Francis H.C. Crick with the invaluable collaboration of the X-ray crystallographer Rosalind Franklin. Watson and Crick shared the 1962 Nobel Prize in Physiology or Medicine with Maurice H.F. Wilkins.
DNA amplification:  The production of multiple copies of a sequence of DNA. Repeated copying of a piece of DNA. DNA amplification plays a role in cancer cells. A tumor cell amplifies, or copies, DNA segments as a result of cell signals and sometimes environmental events. Amplification can occur in vivo (in the living individual) or in vitro (literally "in glass", or in a plastic vessel in the laboratory).
DNA assembly:  The process of putting fragments of DNA that have been sequenced into their correct chromosomal positions. The pieces of DNA are assembled to reconstitute the sequence of the chromosome from which they came.
DNA cloning:  The use of DNA manipulation procedures to produce multiple copies of a single gene or segment of DNA.
DNA coding:  A sequence of DNA that codes for protein. Coding DNA sequences are separated by long regions of DNA called introns that have no apparent function. Coded DNA is also known as an exon.
DNA forensics:  The application of DNA technology and the knowledge of DNA genetics to the practice of forensic medicine and to the power of legal medicine. Crime scene investigation has been markedly changed -- some would say revolutionized -- by the advent of DNA forensics. This has led to the invention of devices for DNA forensics. One is a plate of glass about the size of a hand is etched with very thin channels and reservoirs. A minute sample of DNA is moved between reservoir and channel through timed electric pulses. These thin channels then act like capillary tubes and can resolve the constituents of this minute sample of DNA. At the crime scene, the forensic technician can perform the PCR reactions for DNA fingerprinting and immediately resolve the samples on the glass plate. What normally would take more than a day, once the sample is taken to the laboratory, now takes only a few hours at the crime scene.
DNA molecules, recombinant:  A combination of DNA molecules of different origin that are joined using recombinant DNA technology.
DNA polymerase:  Enzyme that catalyzes (speeds) the polymerization of DNA. DNA polymerase uses preexisting nucleic acid templates and assembles the DNA from deoxyribonucleotides.
DNA repair:  The body has a series of special enzymes to repair mutations (changes) in the DNA and restore the DNA to its original state. The DNA in genes is constantly mutating and being repaired. This repair process is controlled by special genes. A mutation in a DNA repair gene can cripple the repair process and cause a cascade of unrepaired mutations in the genome that lead to cancer.
DNA repair gene:  A gene engaged in DNA repair. When a DNA repair gene is impaired, mutations pile up throughout the DNA. The DNA in genes is constantly mutating and being repaired.
DNA repair pathway:  The sequence of steps in the repair of DNA. Each step is governed by an enzyme.
DNA replication:  A wondrous complex process whereby the "parent" strands of DNA in the double helix are separated and each one is copied to produce a new "daughter" strand. This process is said to be "semi-conservative" since one of each parent strand is conserved and remains intact after replication has taken place.
DNA sequence:  The precise ordering of the bases (A,T,G,C) from which the DNA is composed. DNA sequencing involves determining the exact order of the base pairs in a segment of DNA.
DNA sequence, draft:  Sequence of a DNA with less accuracy than a finished sequence. In a draft sequence, some segments are missing or are in the wrong order or are oriented incorrectly. A draft sequence is as opposed to a finished DNA sequence.
DNA sequence, finished:  A DNA sequence in which the bases are identified to an accuracy of no more than 1 error in 10,000 and are placed in the right order and orientation along a chromosome with almost no gaps. A finished sequence is as opposed to a draft DNA sequence.
DNA technology, recombinant:  A series of procedures used to join together (recombine) DNA segments. A recombinant DNA molecule is constructed (recombined) from segments from 2 or more different DNA molecules. Under certain conditions, a recombinant DNA molecule can enter a cell and replicate there, autonomously (on its own) or after it has become integrated into a chromosome. This technology is used to create, for example, bacteria which have human genes which then produce products for human use such as human growth hormone.
DNA virus:  A virus in which the genetic material is DNA rather than the usual RNA. The DNA may be either double- or single-stranded. Major groups of double-stranded DNA viruses (class I viruses) include the adenoviruses, the herpes viruses, and the poxviruses. Major groups of single-stranded DNA viruses (class II viruses) include the parvoviruses and coliphages.
DNA, Junk:  Noncoding regions of DNA that have no apparent function. The term "junk DNA" is a disparaging one, expressing some of the disappointment felt by geneticists when they first gazed upon sizable segments of the genetic code and, instead of seeing one wonderful gene after another, they saw a few exons surrounded by vast stretches of "junk DNA." Exons are the regions of DNA that contain the code for producing the polypeptide molecules that make up protein. Each exon codes for a specific portion of the complete protein. In humans and some other species, the exons are separated by long regions of junk DNA. However, junk DNA has been found to be even more conserved than protein-coding regions of the DNA in humans and other mammalian species. The extent of conservation indicates that there is some function for junk DNA that remains to be determined. Junk DNA may prove not to be junk.
DNA, mitochondrial:  Mitochondrial DNA (mtDNA) is the DNA of the mitochondrion, a structure situated in the cytoplasm of the cell rather than in the nucleus (where all the other chromosomes are located). All mtDNA is inherited from the mother. There are 2 to 10 copies of the mtDNA genome in each mitochondrion. mtDNA is a double-stranded, circular molecule. It is very small relative to the chromosomes in the nucleus and so contains only a limited number of genes. It is specialized in the information it carries and encodes a number of the subunits in the mitochondrial respiratory-chain complex that the cell needs to respire. (It also contains genes for some ribosomal RNAs and transfer RNAs). Mutations (changes) in mtDNA can cause disease. The mutations often impair the function of oxidative-phosphorylation enzymes in the respiratory chain. This is especially manifest in tissues with a high energy expenditure such as brain and muscle.
DNA, repetitive:  DNA sequences that are repeated in the genome. These sequences do not code for protein. One class termed highly repetitive DNA consists of short sequences, 5-100 nucleotides, repeated thousands of times in a single stretch and makes up satellite DNA. Another class termed moderately repetitive DNA consists of longer sequences, about 150-300 nucleotides, dispersed evenly throughout the genome, and includes what are called Alu sequences and transposons.
DNA, satellite:  DNA that contains many tandem (not inverted) repeats of a short basic repeating unit. Satellite DNA is located at very specific spots in the genome (on chromosomes 1, 9, 16 and the Y chromosome, the tiny short arms of chromosomes 13-15 and 21 and 22, and near the centromeres of chromosomes).
DNR:  Do not resuscitate.
DNS:  On a prescription, Do Not Substitute. If a physician orders a particular drug and writes DNS on the prescription, that tells the pharmacist not to substitute a generic version or any other drug for the prescribed drug.
DOA:  Dead on Arrival.
DOB:  Date of birth.
Dobelle, William H.:  (1941-2004) Pioneer designer of an experimental system of artificial vision for the blind involving the transmission of electrical signals to electrodes implanted in the brain. The system used a tiny camera mounted in glasses worn by the blind person. The camera images were relayed to a portable computer and transmitted to surgically implanted electrodes attached to the brain's visual cortex.
DOC:  1. Acronym for "daily on call." 2. Deoxycorticosterone.
Docosahexaenoic acid:  DHA. An essential fatty acid, thought to be important to the development of infants, particularly as regards their eyes and brain. DHA is present in breast milk and has been added to some infant formulas. Postnatal DHA may improve vision and some cognitive functions in infants and toddlers. DHA is an omega-3, polyunsaturated, 22-carbon fatty acid. It is present in abundance in certain fish (such as tuna and bluefish) and marine animal oils.
Doctor:  In a medical context, any medical professional with an MD, a PhD, or any other doctoral degree. The term doctor is quite nonspecific. A doctor may, for example, be a physician, psychologist, biomedical scientist, dentist, or veterinarian. In a nonmedical context, a professor of history might be addressed as doctor, an eminent theologian might be named a doctor of a church, and a person awarded an honorary doctorate by a college or university might also be called a doctor. The word "doctor" comes from the Latin "docere" meaning to teach. A doctor was a teacher, especially a learned or authoritative one.
Doctor-assisted suicide:  The term in the UK for physician-assisted suicide.
Doctors Without Borders:  A group which sends physicians and other health workers to some of the most destitute and dangerous parts of the world and encourages them not only to care for people, but also to condemn the injustices they encounter. The 1999 Nobel Peace Prize was awarded to Doctors Without Borders (in French, Medicins Sans Frontieres). The Nobel Committee cited the organization's rapid intervention in and reaction to natural and humanitarian disasters. "By intervening so rapidly, Doctors Without Borders calls public attention to humanitarian catastrophes, and by pointing to the causes of such catastrophes, the organization helps to form bodies of public opinion opposed to violations and abuses of power. As of 1999, Doctors Without Borders had 23 offices worldwide and more than 2,000 volunteers. The organization was working in roughly 80 countries. Its efforts have included intervention following the Nicaragua earthquake, starting a feeding program in Ethiopia in 1984, health programs in Eastern Europe following the fall of the Communist bloc and responses to the earthquake and Turkey and the violence in East Timor. Doctors Without Borders was formed in 1971 by a group of French physicians, most of whom had worked for the International Red Cross in Biafra in 1968 and 1970. According to the group, they aimed to overcome two shortcomings of international aid, "that it offers too little medical assistance and that aid agencies are overly reticent in the face of the many legal and administrative obstacles to the provision of effective humanitarian relief."
Doctors' symbol:  A staff or rod, with a snake curled around it. It is the staff or rod of Aesculapius (also called Asklepios), the ancient mythical god of medicine. His Greek name was Asklepios and his Roman name Aesculapius. In reality, Asklepios may have been a real person who was renowned for his gentle, humane remedies and his humane treatment of the mentally ill. His followers established temples called asclepions, temples of Asklepios, temples of healing. The greatest asklepion was in a grove of trees south of Corinth, Greece where the sick had to spend a night while the proper remedies were revealed during a dream to the priests of the temple and the cured had to make a suitable sacrifice (usually a rooster) to the god. According to mythology, Asculapius had a number of children including Hygieia, the goddess of health (from whose name comes the word "hygiene") and Panaceia, the goddess of healing (from whose name comes the word "panacea" for a universal remedy). Today, the staff of Aesculapius is a commonly used symbol of medicine. It is the symbol of the American Medical Association (AMA) and many other medical societies.
Dol:  A unit of measurement of pain. The term dol was invented by James Hardy and his research colleagues Herbert Wolff and Helen Goodell at Cornell University where from 1950 to 1959, they carried out pioneering experiments on pain. Hasrdy, Wolff and Goodell used precisely calibrated radiant heat directed to the foreheads or hands of trained experimental subjects. They asked the subjects to report each "just noticeable difference" in the intensity of pain they experienced, and graphed their responses on the "dol" scale, in which one dol equals two "just noticeable differences." The graphs showed the effectiveness of different analgesics in relieving the pain, and the physiologic responses with different intensities of pain. From the Latin word for pain, dolor.
Dolor:  1. Pain, one of the four classic signs of inflammation (together with calor, rubor and tumor). 2. By extension, grief or sorrow. From Latin dolor, pain. See also: Calor; Rubor; Tumor.
Domagk, Gerhard:  German physician and chemist (1895-1946) who discovered the first sulfa drug, prontosil, which ushered in the era of antibacterial medicine.
Dominant:  A genetic trait is considered dominant if it is expressed in a person who has only one copy of that gene. (In genetic terms, a dominant trait is one that is phenotypically expressed in heterozygotes). A dominant trait is opposed to a recessive trait which is expressed only when two copies of the gene are present. (In genetic terms, a recessive trait is one that is phenotypically expressed only in homozygotes). Examples of dominant disorders include: Achondroplasia (a common form of dwarfism with short arms and legs), Familial hypercholesterolemia (high blood cholesterol leading to premature coronary artery disease), Huntington disease (a form of progressive dementia from which the folk singer Woody Guthrie suffered), Neurofibromatosis (NF1)(a neurologic disorder with an increased risk of malignant tumors), and Polycystic kidney disease (of adult onset). Most dominant trait are due to genes located on the autosomes (the non-sex chromosomes). An autosomal dominant trait typically affects males and females with equal likelihood and with similar severity. The gene responsible for it can be transmitted from generation to generation and each child born to someone with the gene has a 50:50 chance of receiving the gene and manifesting the disease.
Donor:  The giver of a tissue or organ, for example, of blood or a kidney.
Donor insemination:  A procedure in which a fine catheter (tube) is ; INSERTed through the cervix (the natural opening of the uterus) into the uterus (the womb) to deposit a sperm sample from a man other than the woman's mate directly into the uterus. The purpose of this procedure is to achieve fertilization and pregnancy. Donor insemination is also called artificial insemination by donor (AID) or heterologous insemination. It is to be distinguished from artificial insemination by husband (AIH) which is homologous insemination.
Donor lymphocyte infusion:  (DLI) A cancer treatment in which lymphocytes from a bone marrow donor are infused into the person who received the original bone marrow transplant. The goal of donor lymphocyte infusion is to induce a remission of the cancer by a process called the graft-versus-tumor (GVT) effect. Donor lymphocyte infusion is basically meant to boost the GVT effect. The donor lymphocytes, which are T cells, attack and kill residual cancer cells. That is the strategy. Donor lymphocyte infusion has mainly been used to treat relapsed chronic myelogenous leukemia (CML). Patients with relapsed acute leukemia, chronic lymphocytic leukemia (CLL), myelodysplasia (MDS), Hodgkin disease, non-Hodgkin lymphoma (NHL), and multiple myeloma have also been treated by donor leukocyte infusion.
Donor, universal:  A person who is type O in the ABO blood group system and can donate blood to all recipients.
Dopa:  A precursor (forerunner) of dopamine, a key neurotransmitter (messenger) in the brain. Dopa is used in the treatment of Parkinson disease. Parkinson disease is believed to be related to low levels of dopamine in certain parts of the brain. When dopa is taken by mouth, it crosses through the blood-brain barrier. Once it has crossed from the bloodstream into the brain, it is converted to dopamine. The resulting increase in dopamine concentrations in the brain is thought to improve nerve conduction and to assist in lessening the movement disorders in Parkinson disease. In 1970 the FDA (Food and Drug Administration) approved dopa in the form of L-Dopa, or levodopa, for use in the US. The drug revolutionized the treatment of Parkinson disease.
Dopa-responsive dystonia (DRD):  A condition that typically begins in childhood or adolescence with progressive difficulty in walking and, in some cases, spasticity and can be successfully treated with drugs. Segawa dystonia is an important variant of DRD. In Segawa dystonia, the symptoms fluctuate during the day from relative mobility in the morning to increasing disability in the afternoon and evening and after exercise. DRD may not only be rare but also rarely diagnosed since it mimics some forms of cerebral palsy.
Dopamine:  An important neurotransmitter (messenger) in the brain. Dopamine is classified as a catecholamine (a class of molecules that serve as neurotransmitters and hormones). It is a monoamine (a compound containing nitrogen formed from ammonia by replacement of one or more of the hydrogen atoms by hydrocarbon radicals). Dopamine is a precursor (forerunner) of adrenaline and a closely related molecule, noradrenaline. Dopamine is formed by the decarboxylation (removal of a carboxyl group) from dopa.
Doppler ultrasound:  A form of ultrasound that can detect and measure blood flow. Doppler ultrasound depends on the Doppler effect, a change in the frequency of a wave resulting here from the motion of a reflector, the red blood cell. Doppler ultrasound has many applications including, for example, the detection and measurement of decreased or obstructed blood flow to the legs. Color Doppler ultrasound is done first to evaluate vessels rapidly for abnormalities and to guide placement of the pulsed Doppler to gain sample volume for detailed analysis of velocities. Named for Christian Johann Doppler (1803-1853), the Austrian physicist, who discovered the effect that now bears his name. This is the same technology used by astronomers to gauge the speed with which distant galaxies are moving away from Earth. When they found that that speed increases with the distance of a galaxy from Earth, manifested by a "red shift," Doppler technology became a means for estimating the distance to galaxies and it also led to the notion that the universe is expanding from some central point in the past which has been named the "Big Bang."
Doraphobia:  An abnormal and persistent fear of fur. Sufferers of this fear avoid fur-bearing animals such as dogs, cats, foxes, beavers and rabbits because fur is repulsive to them. Perhaps some of these phobics associate fur with childhood stories about "the big bad wolf" and other fur-bearing predators. Their fear is not always unfounded for some of these animals can be dangerous. The word "doraphobia" is from Greek roots, namely "dora" (the hide or skin) + "phobos" (fear) = fear of the skin or hide (the fur of an animal).
Dorian Gray effect:  Sudden aging, an abrupt change from seeming youthfulness to the reality and ravages of age, as can occur naturally or when the effects of plastic surgery and Botox treatments wear off. Named after "The Picture of Dorian Gray" (1890), the novel by Oscar Wilde, in which Dorian gives his soul to remain young while the painting of him grows old. Despite a life of dissipation and worse, Gray stays youthful in appearance. Instead, his portrait records his dissolute deeds, becoming a hideous mask. When Gray destroys the painting, his face turns into a replica of the portrait.
Dormant Tuberculosis:  The presence of evidence for tuberculosis infection from a positive TB skin test in a person with a normal chest X-ray and no symptoms. Treatment is not mandatory for dormant tuberculosis (TB), as it is with active TB, but it is a good idea because the TB can become active later. Treatment is with the antibiotic isoniazid (INH) and vitamin B6 for 6 to 12 months, which will prevent the TB from becoming active in the future. If a person with a positive skin test does not take INH, there is a 5 to 10% lifelong risk that the TB will become active.
Dorothy Hodgkin:  British crystallographer and Nobel Prize winner (1910-1994). Dorothy Crowfoot, as she was born, was educated at Somerville College, Oxford. After a brief period as a postgraduate student at Cambridge University, she returned to Oxford in 1934 and spent her entire academic career there. After various appointments within the university, she became the first Royal Society Wolfson Research Professor at Oxford in 1960. Hodgkin had the good fortune to fall under the influence of the inspiring and scientifically imaginative physicist J. D. Bernal at Cambridge, who opened the way to investigate complex organic molecules with the technique of X-ray diffraction analysis. Hodgkin's first major result came in 1949 when, with Charles Bunn, she published the three dimensional structure of penicillin. This was followed by the structure of vitamin B12 in 1956 and that of insulin in 1969. For her work on vitamin B12, Hodgkin was awarded the Nobel Prize in Chemistry in 1964.
Dorsal:  Relating to the back or postterior of a structure. As opposed to the ventral, or front, of the structure. Some of the dorsal surfaces of the body are the back, buttocks, calves, and the knuckle side of the hand.
Dorsum:  The back or posterior side of a structure. Dorsum is the Latin word for the back. Something pertaining to the dorsum is dorsal. The dorsal surface of the hand is the back of the hand, the side opposite the palm. The dorsal surface of the foot is the back of the foot, the side opposite the sole. The dorsal vertebrae are the thoracic vertebrae; they form part of the back. The dorsal roots of the spinal nerves are the back roots, the posterior roots. The opposite of dorsum is ventrum which comes from the Latin venter meaning belly. Something that is ventral is oriented toward the belly, toward the front of the body.
Double contrast barium enema:  A series of x-rays of the colon and rectum taken after the patient is given an enema, followed by an injection of air. The barium outlines the intestines on the x-rays, allowing many abnormal growths to be visible.
Double helix:  The structure of DNA with the two strands of DNA spiraling about one other. The double helix looks something like an immensely long ladder twisted into a helix, or coil. The sides of the "ladder" are formed by a backbone of sugar and phosphate molecules, and the "rungs" consist of nucleotide bases joined weakly in the middle by hydrogen bonds.
Double pneumonia:  Inflammation of both lungs. Medically called bilateral pneumonia.
Double-blind:  Term used to described a study in which both the investigator or the participant are blind to (unaware of) the nature of the treatment the participant is receiving. Double-blind trials are thought to produce objective results, since the expectations of the researcher and the participant about the experimental treatment such as a drug do not affect the outcome. Also called double-masked.
Double-blinded study:  A study in which at least two separate groups receive the experimental medication or procedure at different times, with one group to be given the treatment and the other a placebo with neither group being made aware of whwhich is being given. Also, the person administering the placebo and treatment is not aware of which is which. Double-blinded studies are often chosen when a treatment shows particular promise and the illness involved is serious. It can be hard to recruit human subjects for a blinded study of a promising treatment when one group will receive only a placebo or an existing medicine and if the treated group has a good result the study can be stopped to allow actual treatment of the placebo group.
Double-jointed:  Popular term to describe a joint that is unusually flexible. Medically, the joint is said to be hyperflexible, hyperextensible, or hypermobile. People whose fingers are hypermobile have lower rates of arthritis in the hands.
Douche:  A stream of water directed at any part of the body or any body cavity, often into the vagina, for cleansing or medicinal purposes. A douche can be with a simple solution of vinegar in water. Some commercial douche solutions have somewhat more romantic names than vinegar (names such as Country Flowers, Fresh Baby Powder, Fresh Mountain Breeze, Spring Rain Freshness, etc.). Vaginal douching has been done for many, many years. However, there is currently concern that it may sometimes cause problems. It may mask, or even worsen, conditions such as bacterial or yeast infection of the vagina. Even more seriously, douching is associated with an increased risk of pelvic inflammatory disease (PID). It is also associated with an increased risk of an ectopic pregnancy (probably due to PID). The American College of Obstetricians and Gynecologists (ACOG) recommends against douching. "Douche" is the French word for "shower." French, being a Latin language, took the word from the Latin -- from ducere, ductum, meaning to lead or conduct (water).
Doula:  1. A non-medical assistant in childbirth. A doula is not the father but is usually a woman who is experienced in childbirth. The role of the doula is to provide the mother with physical and emotional assistance before, during, or after childbirth. Also known as a birth assistant, birth companion, childbirth assistant, or labor support professional. 2. A non-professional assistant in dying, someone who is not a doctor, nurse, social worker or minister or a person like that, but is a volunteer. A doula has been somewhat enlightened in the particulars of death and nutures someone through their final days. The term doula was first used in this context by Phyllis Farley, a proponent of natural childbirth in New York, about 2000. From the Greek doule referring to a woman who was a slave or servant.
Dowager's hump:  An abnormal outward curvature of the vertebrae of upper back. Compression of the front (anterior) portion of the involved vertebrae leads to forward bending of the spine (kyphosis) and creates a hump at the upper back. Dowager's hump is due to osteoporosis changes in the thoracic spine. It may affect men or women. Like most osteoporotic changes, it is preventable.
Down syndrome:  A common chromosome disorder due to an extra chromosome number 21 (threfore also called trisomy 21). Down syndrome causes mental retardation, a characteristic face, and multiple malformations. Down syndrome is a relatively common birth defect. The chromosome abnormality affects both the physical and intellectual development of the individual. Down syndrome causes mental retardation, a characteristic facial appearance, and multiple malformations. It is associated with a major risk for heart malformations, a lesser risk of duodenal atresia (part of the small intestines is not developed), and a minor but still significant risk of acute leukemia. The chromosome abnormality that causes Down syndrome is trisomy 21, a extra copy of chromosome number 21. This means that instead of having the normal 2 copies of chromosome number 21, the person with Down syndrome has 3 copies of chromosome number 21. Confirmation of such a condition requires a chromosome study (analysis under the microscope of the chromosomes). A chromosome study is also valuable to rule in or out a translocation (a type of rearrangement) of chromosome 21 that can be heritable in which case it can give rise to more cases of Down syndrome in the family. The evaluation of the Down syndrome baby and the family by a medical geneticist is often useful. In Down syndrome there are certain characteristic features in the appearance which may individually be quite subtle but together permit a clinical diagnosis of Down syndrome to be made at birth. These signs of Down syndrome include slight flattening of the face, minimal squaring off of the top of the ear, a low bridge of the nose (lower than the usually flat nasal bridge of the normal newborn), an epicanthal fold (a fold of skin over top of the inner corner of the eye, which can also be seen less frequently in normal babies), a ring of tiny harmless white spots around the iris, and a little narrowing of the palate. There are many, many more minor malformations in Down syndrome. Down syndrome is also associated with a number of major malformations. For example, approximately a half of Down syndrome children are born with a heart defect, most often a hole between the two sides of the heart. For another example, Hirschprung's disease (congenital aganglionic megacolon) which can cause intestinal obstruction occurs more frequently in children with Down syndrome than in other children. The intellectual handicaps in Down syndrome are often the most important problem. These handicaps may not be evident in early infancy. However, they tend to become increasingly noticeable later in infancy and during childhood as developmental delay. In adults with Down syndrome, the intellectual handicap is manifest as mental retardation. Very few adults with Down syndrome can lead independent lives because of their mental retardation. It was once thought that nearly all adults with Down syndrome developed Alzheimer's disease (dementia) so that on top of their mental handicap most people with Down syndrome were slated for premature senility. However, it now appears that a much lower proportion, perhaps 20 to 25%, of Down's adults develop dementia. The majority of adults with Down syndrome may thus be spared this fate. The name Down syndrome refers to a 19th century English physician Langdon Down. Ironically, he was not the first person to describe the condition, he added little to our knowledge of it and, in great error, he attributed the condition to a "reversion" to the mongoloid race. The disorder was also once called mongolism, a term now considered obsolete.
Downregulation:  An decrease in the number of receptors on the surface of target cells, making the cells less sensitive to a hormone or another agent. Some receptors can be rapidly down regulated.
Doxorubicin cardiomyopathy:  Heart disease due to the drug doxorubicin (brand name: Adriamycin), a potent broad-spectrum antitumor agent effective in treating a variety of cancers including solid tumors and leukemia. Unfortunately, its clinical use is limited by dose-dependent cardiac side effects that lead to degenerative cardiomyopathy, congestive heart failure, and death. In addition, some adult patients treated with the drug when they were children later develop dilated cardiomyopathy. Endocardial biopsies from patients undergoing doxorubicin therapy reveal a disruption of myofibrils, impairment of microtubule assembly, and a swelling of the endoplasmic reticulum. Doxorubicin cardiotoxicity is also characterized by a dose-dependent decline in mitochondrial oxidative phosphorylation and a decrease in high-energy phosphate pools.
Doxycycline:  Brand name: Vibramycin. A synthetic broad-spectrum antibiotic derived from tetracycline. Doxycycline is used for many different types of infections, including respiratory tract infections due to Hemophilus influenzae, Lyme disease, Streptococcus pneumoniae, or Mycoplasma pneumoniae. It is also used for the treatment of nongonococcal urethritis (due to Ureaplasma), Rocky Mountain spotted fever, typhus, chancroid, cholera, brucellosis, syphilis, and acne. Doxycycline is also of relevance to bioterrorism since the CDC (US Centers for Disease Control & Prevention) recommends it as "the drug of choice" for anyone who may have been exposed to anthrax. Doxycycline has fewer side effects, costs less and is more available than Cipro.
Doyle, Sir Arthur Conan:  (1859–1930) British physician, better known as the writer who created Sherlock Holmes and Dr. Watson. Educated at the Royal Infirmary in Edinburgh, Scotland, Conan Doyle received a medical degree in 1881, served as a physician in the Boer War (1899-1902), and practiced medicine in Southsea, England. The character of Holmes was based on one of his medical school professors in Edinburgh, Dr. Joseph Bell, who had remarkable powers of observation and deduction, through which he was able to diagnose diseases with almost unerring accuracy. It was these same abilities, turned to crime, that later produced Sherlock Holmes. Conan Doyle left his medical practice in 1890 and devoted his time to writing.
Doyne honeycomb retinal dystrophy:  Abbreviated DHRD. An eye disease also known as malattia leventinese. An hereditary form of macular degeneration that results in progressive and irreversible visual loss. This disease is characterized by the appearance in early adulthood of small round white spots (drusen), particularly in the macula of the retina, which progress to form a honeycomb pattern. Malattia leventinese is inherited in an autosomal dominant manner. The condition was clinically first recognized and reported in 1899 by Robert Walter Doyne (1857-1916), an ophthalmologist in Oxford, England. It is also known as Doyne honeycomb retinal dystrophy (DHRD) and as autosomal dominant radial drusen.
DPT:  Diphtheria-Pertussis-Tetanus vaccine.
DPT immunization:  Immunization to protect against diphtheria, pertussis (whooping cough), and tetanus. DPT immunizations are given in a series of 5 shots at 2, 4, 6, 18 months of age and 4-6 years of age. The worth of these vaccinations is an area of debate in medicine. The predominant mainstream medical opinion is that they have helped make these illnesses rare, however many doctors and scientists believe vaccinations came along just as sanitation of municipal water supplies and other changes occurred and took the full credit for an improvement in public health which they did not fully deserve. Most states allow parents to refuse vaccinations for their children, however most parents are unaware of the controversy and also unaware of the fact that they have a choice. It is surely a fact that most of the population does not question the authority and rightness of the medical system in Western countries.
Dracunculiasis:  A parasitic disease caused by the largest parasite that plagues people and bores into their tissues -- the guinea worm Dracunculus medinensis. Dracunculiasis is also called guinea worm disease and end-of-the-road disease because it is not seen in the big cities. Once it infects a person, the guinea worm migrates through their body. It eventually emerges from the body (through the feet in 90% of cases) causing intensely painful edema (swelling), a blister and then an ulcer. Perforation of the skin by the guinea worm, which can be 6 feet long, is accompanied by fever and nausea and vomiting. Infected persons may remain sick for some months. The disease is gotten by drinking water contaminated with the infected intermediate hosts of the parasite, called cyclops. The full-grown guinea worm begins to migrate throughout the infected person's body within about a year after ingestion. In areas where the disease is endemic (pervasive), it typically reappears every year during the agricultural season, with farmers in particular being affected. There are no drugs to treat the disease. Prevention of the disease is based on effective surveillance systems; the provision of safe water including appropriate water supply systems, filtering devices and the chemical treatment of water to eliminate the vector; and health education. Dracunculiasis is the only parasitic disease that may be eradicated from the globe in the near future. Although widely distributed at the beginning of the 20th century, it is now confined to sub-Saharan Africa. The countries known to harbor the guinea worm are Benin, Burkina Faso, Central African Republic, Ethiopia, Ghana, Ivory Coast, Mali, Mauritania, Niger, Nigeria, Sudan, Togo and Uganda. Two-thirds of the world's estimated 100,000 annual cases of dracunculiasis occur in war-torn Sudan, where peace is needed before aid workers can reach affected areas, mainly in the south.
Drain:  In surgical parlance, a device for removing fluid from a cavity or wound. A drain is typically a tube or wick.
Dream, pre-sleep:  Also called a hypnagogic hallucination, this type of dream is characteristically vivid and occurs as one is falling asleep or awakening.
Dreams:  Thoughts, visions, and other sensations that occupy the mind in sleep. Dreams occur during that part of sleep when there are rapid eye movements (REMs). We have 3 to 5 periods of REM sleep per night. They usually come at intervals of 1-2 hours and are quite variable in length. An episode of REM sleep may be brief and last but 5 minutes. Or it may be much longer and go for over an hour. About 80% of sleep is NREM sleep. If you sleep 7-8 hours a night, all but maybe an hour and a half is spent in dreamless NREM sleep. Dreams are penetrable; it has been found experimentally that one can communicate with a person who is dreaming. The content of dreams is sometimes the topic of psychoanalysis. While this method of therapy is less common than it once was, some doctors still look at dreams as a diagnostic clue to medical disorders. For example, children with bipolar disorders have been found to frequently have a particular type of nightmares, and especially lucid dreams are a side-effect of certain medications. These clues indicate that chemicals in the brain, as well as life events and our own preoccupations, influence our dreams. Dreaming is not uniquely human. Cats and dogs dream, judging from the physiologic features. So apparently do many other animals. The word "dream" is traditionally traced back to an Anglo-Saxon word meaning joy, gladness, or mirth. However, "dream" more likely came from another word (from Sanskrit) meaning deception.
Dressler syndrome:  Pericarditis (inflammation of the pericardium, the sac-like covering of the heart) after a heart attack. Named for the Polish-born American physician William Dressler (1890-1969).
Drinox:  Trade name of the insecticide aldrin.
Drip:  In medical usage, a "drip" is a device for administering a fluid drop-by-drop into a vein. It is an intravenous (IV) fluid dripping into a vein, an intravenous fluid drip, a solution (usually a balanced electrolyte solution) administered directly into the venous circulation. It is, for short, an IV.
Drop atttack (aka drop seizure and atonic seizure):  A seizure in which the person suddenly loses muscle tone and strength and, unless supported, falls down. Also called drop attack or drop seizure. Atonic means a lack of muscle tone and strength.
Dropsy:  An old term for the swelling of soft tissues due to the accumulation of excess water. In years gone by, a person might have been said to have dropsy. Today one would be more descriptive and specify the cause. Thus, the person might have edema due to congestive heart failure. Edema is often more prominent in the lower legs and feet toward the end of the day as a result of pooling of fluid from the upright position usually maintained during the day. Upon awakening from sleeping, people can have swelling around the eyes referred to as periorbital edema.
Drosophila:  The fruit fly. One species, Drosophila melanogaster, is a favorite model organism in genetics and developmental biology.
Drug Enforcement Administration (DEA):  Every prescription written in the United States bears a DEA number, that of the prescribing doctor, the DEA being the Drug Enforcement Administration of the U.S. Department of Justice. Historically, the DEA's roots go back to the founding in 1930 of the Federal Bureau of Narcotics. During World War II, international drug trafficking was effectively suppressed in the U.S. and many addicts sought paregoric, an anti-diarrheal containing powdered opium. The heroin shortage resulted in a rise of thefts from pharmacies, hospitals, and other sources of legitimate drugs. And for the first time, barbiturates became recognizable as a potential drug abuse problem. The U.S. Congress in 1970 passed the comprehensive Drug Abuse Prevention and Control Act, which replaced more than 50 pieces of drug legislation. Title II of the Act, known as the Controlled Substances Act (CSA), gave Congress the authority to regulate interstate commerce for drugs. It also established five schedules that classify controlled substances according to their potential for abuse. Drugs were placed into categories according to how dangerous they were, how great their potential for abuse, and whether they have any legitimate medical value. Under the CSA the DEA licenses individual physicians to prescribe drugs for medical purposes.
Drug resistance:  The ability of bacteria and other microorganisms to withstand a drug to which they were once sensitive and were once slowed in growth or killed outright.
Drusen:  Tiny yellow or white deposits in the retina of the eye or on the optic nerve head. The presence of drusen is one of the most common early signs of age-related macular degeneration (AMD). The eye care specialist can see drusen during an eye examination. Their presence alone does not indicate disease, but it may mean that the eye is at risk for developing more severe AMD.
Dry eye syndrome:  A deficiency of tears. The main symptom is usually a scratchy or sandy feeling as if something is in the eye. Other symptoms may include stinging or burning of the eye; episodes of excess tearing that follow periods of very dry sensation; a stringy discharge from the eye; and pain and redness of the eye. Sometimes people with dry eye experience heaviness of the eyelids or blurred, changing, or decreased vision, although loss of vision is uncommon. Dry eye is more common in women, especially after menopause. Surprisingly, some people with dry eyes may have tears that run down their cheeks. This is because the eye may be producing less of the lipid and mucin layers of the tear film, which help keep tears in the eye. When this happens, tears do not stay in the eye long enough to thoroughly moisten it. Dry eye can occur in climates with dry air, as well as with the use of some drugs, including antihistamines, nasal decongestants, tranquilizers, and anti-depressant drugs. People with connective tissue diseases, such as rheumatoid arthritis, can also develop dry eye. It is important to note that dry eye is sometimes a symptom of Sjögren's syndrome, a disease that attacks the body's lubricating glands, such as the tear and salivary glands. Artificial tears, which lubricate the eye, are the principal treatment for dry eye. They are available over-the-counter as eye drops. Sterile ointments are sometimes used at night to help prevent the eye from drying. Using humidifiers, wearing wrap-around glasses when outside, and avoiding outside windy and dry conditions may bring relief. For people with severe cases of dry eye, temporary or permanent closure of the tear drain (small openings at the inner corner of the eyelids where tears drain from the eye) may be helpful.
Dry mouth:  The condition of not having enough saliva to keep the mouth wet. This is due to inadequate function of the salivary glands. Everyone has dry mouth once in a while when they are nervous, upset or under stress. But if someone has a dry mouth most all of the time, it can be uncomfortable and lead to serious health problems. Dry mouth can cause difficulties in tasting, chewing, swallowing, and speaking. If it goes untreated, severe dry mouth can also lead to increased levels of tooth decay and infections of the mouth such as thrush. Severe dry mouth is not a normal part of aging. It can be a clue to systemic diseases such as Sjogren syndrome, systemic lupus erythematosus, rheumatoid arthritis, scleroderma, sarcoidosis, amyloidosis, and hypothyroidism. Some medications can also cause dry mouth. Dry mouth is medically termed xerostomia. From the Greek "xeros" (dry) + "stoma" (mouth).
Dry skin:  Abnormally dry skin. Can be caused by a dry climate, winter weather, deficiency of vitamin A, systemic illness, overexposure to sunlight, or medication. The skin loses moisture. It may crack and peel. Or it may become irritated, inflamed, and itch. Bathing frequently, especially with soaps, can contribute to dry skin. With dry skin, it can help to keep baths or showers short in warm water with as little soap as possible, drying the skin gently -- pat without rub. Dry skin can also usually be addressed by the use of over-the-counter (OTC) topical preparations for dry skin. If these products do not relieve the condition, see a dermatologist for more specific remedies. Medically, dry skin is called xeroderma. From the Greek "xeros" meaning "dry" + the Greek "derma" meaning "skin" = dry skin.
DSM:  Abbreviation for the "Diagnostic and Statistical Manual of Mental Disorders," a comprehensive classification of officially recognized psychiatric disorders, published by the American Psychiatric Association , for use by mental health professionals to ensure uniformity of diagnosis. DSM describes symptoms and does not discuss the causes of the disorders. DSM-IV designates the 4th edition. Issued in 1993, DSM-IV is currently the latest edition (as of 2001).
DSS1 or Dss1:  A small protein important to the process of error-free DNA repair by recombination.
DT:  Diphtheria-Tetanus vaccine.
DT immunization:  DT (diphtheria and tetanus) vaccine does not protect from pertussis and is usually reserved for individuals who have had a significant adverse reaction to a DPT shot or who have a personal or family history of a seizure disorder or brain disease.
DTaP:  Diphtheria-Tetanus-acellular Pertussis vaccine.
DTaP immunization:  Like DPT, DTaP protects from diphtheria, pertussis (whooping cough) and tetanus. DTaP is the same as DTP, except that it contains only acellular pertussis vaccine which is thought to cause fewer of the minor reactions associated with immunization and is also probably less likely to cause the more severe reactions occasionally seen following pertussis vaccination. DTaP is currently recommended only for the shots given at 18 months and 4-6 years of age.
DTP:  Diphtheria-Tetanus-Pertussis vaccine.
DTs:  delirium tremens, a stage of chronic alcohol intoxications inwhich all rationality is lost and severe tremors occur.
Duchenne muscular dystrophy (DMD):  The best-known form of muscular dystrophy, due to mutation in a gene on the X chromosome that prevents the production of dystrophin, a normal protein in muscle. DMD affects boys and, very rarely, girls. DMD typically appears between the ages of two and three with weakness in the pelvis and upper limbs, resulting in clumsiness, frequent falling, an unusual gait and general weakness. Some patients also have mild mental retardation. As DMD progresses, a wheelchair may be needed. Most patients with Duchenne MD die in their early twenties because of muscle-based breathing and heart problems. There is no cure for DMD. Current treatment is directed toward symptoms, such as assisting with mobility, preventing scoliosis, and providing pulmonary therapy (respiratory toilet). Gene replacement with dystrophin minigenes is being investigated but no cure appears around the corner. The DMD gene: The muscular dystrophies associated with defects in dystrophin range greatly from the very severe Duchenne muscular dystrophy (DMD) to the far milder Becker muscular dystrophy (BMD). DMD and BMD result from different mutations in the gigantic gene that encodes dystrophin. The DMD gene contains 79 exons spanning at least 2,300 kb. Deletions cause deficiencies in 1 or more of these, which may explain why mental retardation and cardiomyopathy sometimes accompany DMD, for there are clearcut differences in clinical presentation depending on what the deletions remove from the dystrophin gene. The DMD gene encodes a 3,685-amino acid protein product. From its amino acid sequence, dystrophin is similar to spectrin and other cytoskeletal proteins. It is rather like an I-beam with globular domains at each end, joined by a rod-like segment in the middle. The disease is named for the pioneering 19th century French neurologist Guillaume Benjamin Amand Duchenne.
Duct:  A passage or a tube with well-defined walls suitable for the conveyance of air or liquids, as the bile duct and the pancreatic duct. Duct is a contraction of the New Latin word ductus.
Duct of Bellini:  A continuation of the collecting tubules in the kidney.
Ductal carcinoma in situ (DCIS):  A precancerous condition characterized by the clonal proliferation of malignant-looking cells in the lining of a breast duct without evidence of spread outside the duct to other tissues in the breast or outside the breast. DCIS is clearly the precursor (forerunner) of invasive breast cancer. This is evident from the sharing of clonal chromosome changes by DCIS and adjacent invasive cancers. In other words, invasive breast cancer evolves from DCIS. Also called intraductal carcinoma. The incidence of DCIS has increased greatly, thanks to the widespread use of screening mammography. DCIS now accounts for nearly 20% of all breast cancers detected on screening mammograms. Risk factors for DCIS include older age, benign breast disease, an older age at the time of the first term pregnancy or nulliparity (not having children), and a family history of breast cancer. One in 20 women with DCIS has a mutation in the BRCA1 or BRCA2 hereditary breast cancer genes. The crucial decision for the pathologist is to distinguish DCIS from invasive cancer. DCIS originates in a single glandular structure but may spread within the breast through the ductal system. Many patients with DCIS have discontinuous disease with gaps between the tumor foci whereas high-grade DCIS tends to be continuous. The goal in treating DCIS is to prevent local recurrence and, in particular, invasive breast cancer. The options for surgical treatment include simple mastectomy or breast-conserving surgery (lumpectomy). Most women now have breast-conserving surgery in keeping with the detection of smaller DCIS lesions on mammography. However, after breast-conserving surgery, there is a risk for recurrence of DCIS within the breast, arising at or near the original site of the tumor. The drug tamoxifen may be taken after surgery and radiation treatment of DCIS. Tamoxifen, a selective estrogen-receptor modulator, reduces the risk of recurrence. There is no role for chemotherapy in the treatment of DCIS.
Ductal carcinoma of the breast, infiltrating:  Infiltrating ductal carcinoma is one of several recognized specific patterns of cancer of the breast. It is so named because it begins in the cells forming the ducts of the breast. It is the most common form of breast cancer, comprising 65-85% of all cases. On a mammogram, invasive ductal carcinoma is usually visualized as a mass with fine spikes radiating from the edges (spiculation). It may also appear as a smooth edged lump in the breast. On physical examination, this lump usually feels much harder or firmer than benign causes of lumps in the breast. On microscopic examination, the cancerous cells invade and replace the normal breast tissue.
Ductular hypoplasia, syndromatic hepatic:  Also called Alagille syndrome or arteriohepatic dysplasia, this is a genetic disorder characterized by jaundice in the newborn period, liver disease with cholestasis, peripheral pulmonic stenosis and unusual face. Children with Alagille syndrome usually present with jaundice (yellowing of the skin and whites of the eyes) in the newborn period. Cholestasis (stagnant flow of bile from the liver) then develops with puritis (itching), stools without the usual yellowing brown color, and enlargement of the liver and spleen. Peripheral pulmonic stenosis is a form of congenital heart disease (CHD). Other types of CHD also occur. The face has deep-set eyes, broad forehead, long nose with flat tip, prominence of the chin, and low-set or malformed ears. The outlook depends upon the degree of severity of the CHD and the liver disease (it can cause liver failure). The condition is an autosomal dominant trait meaning that the gene for it is on a non-sex chromosome (an autosome) and a single edition of the Alagille gene is sufficient to produce the disease. The gene has been discovered on chromosome 20 in band 20p12. The syndrome was first described by D. Alagille in the French medical literature in 1969.
Ductus:  A duct or walled passageway suitable for the conveyance of air or, more often in the body, liquids. The term "ductus" also refers a key arterial shunt (ductus) in fetal life. Before birth, blood pumped from the heart through the pulmonary artery toward the lungs is shunted into the aorta. This arterial shunt, a short vessel, is the ductus arteriosus. When the shunt is open, it is said to be patent. The ductus arteriosus usually closes at or shortly after birth, permitting blood from that moment on to course from the heart directly to the lungs. However, if the ductus arteriosus remains open (patent), flow reverses and blood from the aorta is shunted into the pulmonary artery and recirculated through the lungs. A patent ductus may close later spontaneously (on its own) or need to be ligated (tied off) surgically.
Due date:  The estimated calendar date when a baby will be born, the date the baby is due to be born. It is also called the estimated date of confinement or expecrted date of confinement (EDC).
Dumdum fever:  Also called kala-azar, a chronic, potentially fatal parasitic disease of the viscera (the internal organs) due to infection by an agent called Leishmania donovani. Leishmania donovani is transmitted by sandfly bites in parts of Asia (primarily India), Africa (primarily Sudan) and South America (primarily Brazil) where all together there are an estimated half million cases per year. There are also several hundred cases yearly in Europe (primarily in the Mediterranean region) and a few in North America. The infection can cause no or few symptoms but typically it is associated with fever, loss of appetite (anorexia), fatigue, enlargement of the liver, spleen and nodes and suppression of the bone marrow. The disease also increases the risk of other secondary infections. The first oral drug found to be effective for treating it is miltefosine. The term "kala-azar" comes from India where it is the Hindi for black fever. The disease is also known as Indian leishmaniasis, visceral leishmaniasis, leishmania infection, black sickness, and black fever. The name "Leishmania donovani" honors two men: the British pathologist William Boog Leishman who in 1903 wrote about the protozoa that causes kala-azar and the researcher C. Donovan, who made the same discovery independently the same year.
Dummy:  In science experiments, a substance without any active ingredient, a placebo. In the UK the word refers to what Americans call a pacifier: an artificial nipple, usually made of plastic, upon which an infant can suck to gain some solace and quiet down. Dummies have been claimed to cause early weaning. However, a study (JAMA, July 18, 2001) was done of women who were planned to breastfeed for at least 3 months. All of the women were told how to soothe a crying or fussy child, but one group of women was told to avoid giving their baby a dummy. Advising women not to give their baby a dummy had no effect. The rate of early weaning was the same in both groups. The use of a dummy does not cause early weaning.
Dumping syndrome:  A group of symptoms that occur when food or liquid enters the small intestine too rapidly. These symptoms include cramps, nausea, diarrhea, and dizziness.
Duodenal:  Pertaining to the duodenum, part of the small intestine, as in duodenal ulcer or duodenal biliary drainage.
Duodenal biliary drainage:  A procedure used to diagnose gallstones when suspicion is high but other tests are negative. A thin tube is passed through a nostril down the throat, through the esophagus and stomach, into the duodenum. Once the tube is in place, a synthetic hormone related to cholecystokinin is injected IV. It causes the gallbladder to contract and squeeze out bile into the duodenum. The bile then is sucked up through the tube and examined for the presence of cholesterol and pigment particles under a microscope. A modification of duodenal biliary drainage involves collection of bile through an endoscope at the time of EGD (esophagogastroduodenoscopy) or ERCP (endoscopic retrograde cholangio-pancreatography).
Duodenal ulcer:  An ulcer (a hole in the lining) of the duodenum (the first portion of the small intestine). Ulcers can affect the stomach, duodenum, or esophagus. Their formation is related to Heliobacter pylori bacteria in the stomach, anti-inflammatory medications, and smoking cigarettes. Ulcer pain may not correlate with the presence or severity of ulceration. Diagnosis is made with barium x-ray or endoscopy. Complications of ulcers include bleeding, perforation, and blockage of the stomach (gastric obstruction). Treatment involves antibiotics to eradicate H. pylori, eliminating risk factors, and preventing complications. Alternative medicine doctors first warned that H. pylori was a significant cause of duodenal ulcers in the early 1980s. Mainstream medicine, dragging its feet as usual, was forced to acknowledge this truth around 1990.
Duodenitis:  Inflammation of the duodenum. (The duodenum is the first part of the small intestine.)
Duodenum:  The first part of the small intestine. The duodenum extends from the pylorus at the bottom of the stomach to the jejunum, the second part of the small intestine. The duodenum is a common site for the formation of peptic ulcers. The term duodenum derives from "dodeka-daktulon," meaning twelve fingers in Greek. The duodenum is about 12 finger-breadths long. In German, the popular term for duodenum is Zwölffingerdarm, meaning 12-finger intestine.
Duplication:  Part of a chromosome in duplicate, a particular kind of mutation (change) involving the production of one or more copies of any piece of DNA, including a gene or even an entire chromosome.
Dupuytren's contracture:  A localized formation of scar tissue in the palm of the hand. The scarring accumulates in a tissue called the fascia beneath the skin of the palm that normally covers the tendons that pull the fingers grip. As Dupuytren contracture progresses, more of the fascia becomes thickened and shortened. Dimpling and puckering of the skin over the area eventually occur. The precise cause of Dupuytren contracture is not known. However, it is known that it occurs more frequently in males than females and in people of Northern European extraction. Risk factors include a history of hand trauma (such as from a jackhammer), diabetes mellitus, seizure disorders (epilepsy), smoking, alcoholism, and HIV infection. Dupuytren contracture also can be inherited in an autosomal dominant manner, affecting males and females in succeeding generations in a family. Most patients with Dupuytren contracture only require reassurance and stretching exercises with heat application. When the palm is persistently sore with grasping, ultrasound treatments can be helpful. Sometimes local inflammation is best relieved with cortisone injection. For patients with significant fixed flexed posture (contracture) of the fingers from Dupuytren contracture, surgical procedures can remove the scarred tissue to free the fingers. These procedures can return function to a disabled hand. Minor nodule formation and/or skin thickening of the palm is not a reason to operate. Sometimes the surgeon can release the scarred tissue by carefully cutting it with a needle. This procedure is referred to as a needle aponeurotomy. Named for Guillaume Dupuytren (1777-1835) the leading French surgeon of the early part of the 19th century. Dupuytren reported the condition in 1832. He was not the first to describe the condition but he was the first to recognize that this form of finger contracture was due to scarring of the fascia tissue in the palm.
Dura mater (or "dura"):  (from the Latin for hard mother). The outermost, toughest, and most fibrous of the three membranes (meninges) covering the brain and the spinal cord. Also called the pachymeninx (singular) or pachymeniges (plural). Epidural means outside the dura. An accumulation of blood outside the dura is an epidural hematoma. Subdural means under the dura. A bleed under the dura may result in a subdural hematoma.
Dural sac:  The membranous sac that encases the spinal cord within the bony structure of the vertebral column. Dural refers to the dura, the name of the membrane around the spinal cord (and brain, too).
Dursban:  An insecticide that has adverse neurological effects. Known alternatively as chlorpyrifos. Dursban causes weakness, vomiting, diarrhea and other ill effects in children. It can also cause blurred vision and memory loss. Anyone can be exposed when the chemical is applied in a backyard or a building and through residue on fruits or other foods. Dursban was in hundreds of products including some of Raid sprays, Hartz yard and kennel flea spray, and Black Flag liquid roach and ant killer. The US Environmental Protection Agency (EPA) banned chlorpyrifos from domestic use. The manufacture of chlorpyrifos for most residential uses and all uses where children could be exposed was to halt by December 2000 and its use for termite control was to be phased out by December 2001 in all buildings used by children.
Dust mite:  A tiny microscopic organism that is the primary cause of allergies related to house dust. The term "dust mite allergy" is a misnomer because it is the excretion of these mites to which people are allergic. Dust mites can therefore trigger allergic reactions even when dead.
DVT (deep vein thrombosis):  Blood clotting in the veins of the inner thigh or leg. In air travel, DVT is the "economy-class syndrome." Even in young, health travelers the long stretches immobilized in cramped seats in cabins with very low humidity set the stage for the formation of a thrombus (blood clot) in the lower leg. Blood clots can break off (as emboli) and makes their way to the lung where they have the potential of causing respiratory distress and respiratory failure. DVT is a serious complication of surgery when, in the recovery period, clots tend to form in the legs. For this reason patients are encouraged to be up and around as soon as possible after surgery and are sometimes anticoagulated in the postsurgical period.
Dwarf:  Someone with dwarfism, which is now more correctly called "short stature." People with dwarfism (short stature) also call themselves "little people."
Dwarfism:  Abnormally short stature. Some forms are hereditary. The Little People of America (LPA) define dwarfism as an adult height of 148 cm (4 feet 10 inches) or less. Also known as nanism. Dwarfism is now more (plolitically) correctly called short stature.
Dwarfism, achondroplastic:  A genetic disorder of bone growth, achondroplasia is the most common cause of short stature with disproportionately short limbs -- dwarfism with short arms and legs. There is a typically large head with prominence of the forehead (frontal bossing), underdevelopment (hypoplasia) of the midface with cheekbones that lack prominence, and a low nasal bridge with narrow nasal passages. The fingers are short and the ring and middle fingers diverge giving the hand a trident (three-pronged) appearance. The brain is normal and intelligence is entirely normal in achondroplasia. However, the complications of achondroplasia can impinge on the brain and the spinal cord. Achondroplasia is inherited as an autosomal dominant trait affecting boys and girls equally. The parents of children with achondroplasia are more often than not normal. Most cases of achondroplasia are due to new mutations that appear for the first time in the affected children. Achondroplasia can be diagnosed before birth by molecular means with amniocentesis. The limited number of DNA changes responsible for achondroplasia and the ease with which they can be detected provide the basis for a simple method for prenatal diagnosis.
Dwarfism, pituitary:  Dwarfism caused by a lack of growth hormone, usually due to malfunction of the pituitary gland. Children with growth hormone deficiency may grow normally for the first two to three years of life but they then fall behind their peers in height. They are normally proportioned. This is a key point. Treatment is with human growth hormone given in childhood. Also known as hypopituitary dwarfism, hypopituitarism, panhypopituitarism, and growth hormone deficiency.
Dwarfism, thanatophoric:  A form of short-limbed (micromelic) dwarfism that usually causes death within the first few hours after birth. Thanatophoric dysplasia is due to a lethal mutation (change) in the same gene that produces achondroplasia, a familiar and far more common form of short-limbed dwarfism that is compatible with life.
Dx:  Abbreviation standing for diagnosis, the determination of the nature of a disease. Dx may alternatively be written DX or dx.
DXA:  Dual X-ray absorptometry. A technique for scanning bone and measuring bone mineral density (BMD). A DXA scanner is a large machine that produces 2 X-ray beams, each with different energy levels. One beam is high energy while the other is low energy. The amount of x-rays that pass through the bone is measured for each beam. This will vary depending on the thickness of the bone. Based on the difference between the 2 beams, the bone density can be measured. DXA is relatively easy to perform and the amount of radiation exposure is considered low. DXA is also called dual energy X-ray absorptometry or DEXA.
DXM:  Dextromethorphan, a cough suppressant, sometimes misused as a recreational drug.
Dyad:  The word "dyad" comes from the Greek "dyas" meaning the number two. In psychology, a dyad refers to a pair of persons in an interactional situation. For example, a patient and therapist, a woman and her husband, a girl and her stepfather, etc. In chemistry, a dyad is a bivalent element. And in biology, a dyad is a double chromosome resulting from the splitting of a tetrad (a quadruple chromosome) during meiosis (germ cell formation).
Dynacin:  Brand name for minocycline. Minocycline is tetracycline antibiotic used to treat many different bacteria in urinary tract infections, acne, gonorrhea, and chlamydia, and other injections. Otther brand names for minocycline include Minocin, and Vectrin.
Dynein:  A family of microtubule motor proteins that derive energy from ATP (adenosine triphosphatase) activity. The dyneins also form arms on the outer tubules of cilia and flagella. The dynein motor, a cellular complex believed to be composed of 12 distinct protein parts, performs fundamental transportation tasks critical to the cell. Defects in its structure can prove fatal for the cell. This machine converts chemical energy stored in an ATP molecule into mechanical energy that moves material though the cell along slender filaments called microtubules. One of the dynein motor's most important functions occurs during cell division, when it helps move chromosomes into proper position.
DYS:  Symbol for familial dysautonomia, a genetic disorder of the autonomic nervous system, affecting especially Ashkenazi Jewish children. Familial dysautonomia is inherited in an autosomal recessive manner and is due to mutation in the IKBKAP gene on chromosome 9q31. Dysautonomia refers to the dysfunction of the autonomic nervous system. The features of familial dysautonomia include lack of tears, emotional lability, relative indifference to pain, increased sweating, cold hands and feet, red blotching of the skin, corneal anesthesia and corneal ulcers, paroxysmal hypertension, taste deficiency and lack of the fungiform papillae. Scoliosis may be severe. The disease may be manifest in first days of life. Two-thirds of patients die before age 20.
Dysarthria:  Speech that is characteristically slurred, slow, and difficult to produce (difficult to understand). The person with dysarthria may also have problems controlling the pitch, loudness, rhythm, and voice qualities of their speech. Dysarthria is a disorder caused by paralysis, weakness, or inability to coordinate the muscles of the mouth. Dysarthria can occur as a developmental disability. It may be a sign of a neuromuscular disorder such cerebral palsy or Parkinson disease. It may also be caused by a stroke, brain injury, or brain tumor. Treatment of dysarthria is by intensive speech therapy with the focus on oral-motor skill development.
Dyscalculia:  A specific developmental disability affecting a person's ability to conceptualize and perform mathematics. Mild cases can often be compensated for with use of a calculator, but those with severe dyscalculia will need special education services.
Dyscrasia:  Any disease condition, especially in hematology, as in "blood dyscrasias." The term "dyscrasia" was borrowed from the Greek meaning "a bad mixture."
Dysentery:  Inflammation of the intestine, often with pain, diarrhea, bloody stools, etc. It is usually caused by infestation of the bowel by an ameba. Dysentery can be fatal, usually due to severe dehydration. Treatment includes rapid rehydration, sometimes via IV, and medication.
Dysentery, amebic::  Dysentery (inflammation of the intestine) with ulcers in the colon due to infection with an ameba (Entamoeba histolytica). This single-celled parasite is transmitted to humans via contaminated water and food. Amebic dysentery can be accompanied by amebic infection of the liver and other organs.
Dysfunction:  Difficult function or abnormal function.
Dysfunction, erectile:  A consistent inability to sustain an erection sufficient for sexual intercourse. Also commonly known as "impotence." Medically, the term "erectile dysfunction" is used to differentiate impotence from other problems that interfere with sexual intercourse (such as lack of sexual desire and problems with ejaculation and orgasm). Impotence usually has a physical cause, such as disease, injury, drug side-effects, or a disorder that impairs blood flow in the penis. Impotence is treatable in all age groups.
Dysfunction, orgasmic (anorgasmia):  Failure to achieve orgasm (climax) during sexual intercourse. Anorgasmia can result from many causes including stress, anxiety, depression, fatigue, worry, guilt, fear of painful intercourse, fear of pregnancy, the undesirability of a partner, the undesirability of a setting, and the use of alcohol, prescription or illicit drugs. In women, this problem is also referred to as "frigidity," or female orgasmic dysfunction.
Dysgraphia:  A specific developmental disability that affects the person's ability to write. Problems may include fine-motor muscle control of the hands and/or processing difficulties. Sometimes occupational therapy is helpful. Most successful students with dysgraphia that does not respond to occupational therapy or extra writing help choose to use a typewriter, computer, or verbal communication.
Dyslipidemia:  A disorder of lipoprotein metabolism, including lipoprotein overproduction or deficiency. Dyslipidemias may be manifested by elevation of the total cholesterol, the "bad" low-density lipoprotein (LDL) cholesterol and the triglyceride concentrations, and a decrease in the "good" high-density lipoprotein (HDL) cholesterol concentration in the blood.
Dysmetabolic syndrome X:  A constellation of metabolic abnormalities in serum or plasma insulin/glucose level ratios, lipids (triglycerides, LDL cholesterol subtypes and/or HDL cholesterol), uric acid levels, coagulation factor imbalances and vascular physiology. (This is the official definition by the American Association of Clinical Endocrinologists of this condition which is also known as the metabolic syndrome and syndrome X.)
Dysmorphia, psychological:  the condition of an individual who perceives the aappearance of his or her body radically different from reality.
Dysmorphic feature:  A body characteristic that is abnormally formed. A malformed ear, for example, is a dysmorphic feature.
Dysmorphology:  The study of human congenital malformations (birth defects), particularly those affecting the morphology (the anatomy) of the individual. Dysmorphology literally means "the study of abnormal form."
Dysmorphophobia:  Excessive dislike of a part of ones body.
Dysmotility syndrome:  A vague, descriptive term used to describe diseases of the muscles of the gastrointestinal tract (esophagus, stomach, small and large intestines) in which the muscles do not work normally (hence the term dysmotility). Other terms that are sometimes used for dysmotility problems are gastroparesis when the stomach is involved, and chronic intestinal pseudo-obstruction when the intestines and stomach are involved. In patients with dysmotility syndrome, food does not move normally through the stomach and intestines, there often is distention of the stomach and intestines as fluid collects, and there frequently is pain. The disease may involve any part of the gastrointestinal tract and is due to abnormalities in the muscles of the intestines or the nerves controlling the muscles. The dysmotility problem can be mild or severe. There are medications that can be used for treating these diseases, for example metoclopramide or cisapride, but these usually are of benefit in the milder cases.
Dysostosis, cleidocranial:  A genetic (inherited) disorder of bone development characterized by: Absent or incompletely formed collar bones (the "cleido-" part refers to the clavicles, the collar bones) The child with this disorder can bring its shoulders together or nearly so; and typical cranial and facial abnormalities with square skull, late closure of the sutures of the skull, late closure of the fontanels (the soft spots), low nasal bridge, delayed eruption of the teeth, abnormal permanent teeth, etc. The disorder is transmitted in an autosomal dominant manner. A parent with the condition has a 50:50 chance that each of their children will have the condition. Boys and girls stand an equal chance of being affected.
Dyspareunia:  The medical term for pain during sexual intercourse.
Dyspepsia:  Dyspepsia refers to a condition (disease) in which there are upper abdominal symptoms which may include upper abdominal pain, bloating (a feeling of abdominal fullness without objective abdominal distention), early satiety (a feeling of unusual fullness with very little intake of food), nausea, or belching. The symptoms often are provoked by eating. Dyspepsia is considered a functional disease. (Another functional disease is irritable bowel syndrome or IBS.) Functional diseases are diseases in which no abnormalities can be seen anatomically, for example, on x-rays, or histologically under the microscope. The abnormalities are believed to be due to altered function, primarily of the muscles and nerves of the gastrointestinal tract. Attempts have been made to subcategorize dyspepsia into ulcer-like, dysmotility-like, reflux-like, and unspecified; however, the utility of this categorization is unclear. A French writer (1862) called dyspepsia "the remorse of a guilty stomach." The word "dyspepsia" came into English usage in 1706. It was contrived by cementing "dys-" to the Greek "pepsis" (digestion) = dysdigestion = indigestion. Contrary to the implication of this derivation, there is little evidence that digestion is affected in dyspepsia.
Dysphagia:  Difficulty in swallowing, swallowing problems. Dysphagia is due to problems in nerve or muscle control. It is common, for example, after a stroke. Dysphagia compromises nutrition and hydration and may lead to aspiration pneumonia and dehydration.
Dysphasia:  One in a group of speech disorders in which there is impairment of the power of expression by speech, writing, or signs, or impairment of the power of comprehension of spoken or written language. More severe forms of dysphasia are called aphasia.
Dysphonia:  An impairment of the voice. Difficulty in speaking. Hoarseness is a common sort of dysphonia.
Dysphoria:  Anxiety.
Dysphoric mania:  The concurrent presence of symptoms of depression and mania together. Also called Mixed bipolar state.
Dysplasia:  The process of abnormal formation of an organ.
Dysplastic nevi:  Atypical moles whose appearance is different from that of a common ordinary mole. Dysplastic nevi tend to be larger than ordinary moles, have more irregular borders, are often mixed in color and present in large numbers. A dysplastic nevus can give rise to malignant melanoma. A single instance is called a dysplastic nevus.
Dyspnea:  Difficult or labored breathing; shortness of breath. Dyspnea is a sign of serious disease of the airway, lungs, or heart. The onset of dyspnea should not be ignored but is reason to seek medical attention.
Dyspraxia:  Impaired or painful function of any organ of the body.
Dyspraxia of speech:  A developmental disability characterized by difficulty in muscle control, specifically of the muscles involved in producing speech. It is caused by a neurological difference that has not yet been pinpointed. Treatment is via intensive speech therapy concentrating on oral-motor skills.
Dyspraxia, developmental:  A pattern of delayed, uneven, or aberrant development of physical abilities during childhood development. The physical abilities affected may be gross or fine motor skills. Developmental dyspraxia may be seen alone or in combination with other developmental problems, particularly apraxia or dyspraxia of speech. Treatment is via early intervention, using physical therapy to improve gross motor skills and occupational therapy to assist in fine motor development and sensory integration.
Dysthymia:  A type of depression involving long-term, chronic symptoms that are not disabling, but keep a person from functioning at "full steam" or from feeling good. Dysthymia is a less severe type of depression than what is accorded the diagnosis of major depression. However, people with dysthymia may also sometimes experience major depressive episodes, suggesting that there is a continuum between dysthymia and major depression.
Dystocia:  Difficult or abnormal labor or delivery.
Dystonia:  Involuntary movements and prolonged muscle contraction, resulting in twisting body motions, tremor, and abnormal posture. These movements may involve the entire body, or only an isolated area. Symptoms may even be "task specific," such as writer's cramp. Dystonia can be inherited, occur sporadically without any genetic pattern, or be associated with medications or diseases (for example, a specific form of lung cancer). The gene responsible for at least one form of dystonia has recently been identified. Some types of dystonia respond to dopamine, or can be controlled with sedative-type medications, or surgery.
Dystonia musculorum deformans (DMD):  Also called torsion dystonia, this is a fortunately rare, generalized dystonia (a state of abnormal -- either excessive of inadequate -- muscle tone) that can be inherited, usually begins in childhood, and becomes progressively worse. It can leave individuals seriously disabled and confined to a wheelchair.
Dysuria:  Painful or difficult urination. This includes burning on urination. Dysuria is most commonly due to bacterial infection of the urinary tract causing inflammation of the bladder (cystitis) or kidney (pyelonephritis). In women, dysuria may also reflect inflammation of the vagina (vaginitis) or vulva (vulvitis). And in men, dysuria may be due to inflammation of the prostate (prostatitis) or the urethra (urethritis) from gonorrhea or chlamydia. There are many other causes of dysuria including irritation from chemicals in soaps, bubble baths, spermicides, and douches.

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