Brainerd diarrhea is a syndrome characterized by the acute onset of watery non-bloody 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, 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? Oh, you live in Brainerd; excuse me! People with Brainerd diarrhea typically have 10-20 episodes per day of explosive, watery non-bloody 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 which can confirm the diagnosis. Brainerd diarrhea should be suspected in any patient who presents with the acute onset of non-bloody diarrhea lasting for more than 4 weeks, and for whom stool cultures and examinations for 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-limiting 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 three years. There have been no known cases of sequelae or relapse once the illness has completely resolved.