Pathophysiology of potassium absorption and secretion by the human intestine.

When normal people ingest 90 mEq/day of K+ in their diet, they absorb about 90% of intake (81 mEq) and excrete an equivalent amount of K+ in the urine. Normal fecal K+ excretion averages about 9 mEq/day. The vast majority of intestinal K+ absorption occurs in the small intestine; the contribution of the normal colon to net K+ absorption and secretion is trivial.

The self-limited nature of chronic idiopathic diarrhea.

Background: Little is known about the clinical presentation and natural history of previously healthy patients in whom chronic idiopathic diarrhea develops.

Methods: We reviewed the case records of 152 patients with chronic diarrhea who had no history of gastrointestinal surgery and who were evaluated in detail as part of a chronic-diarrhea protocol from 1985 to 1990. Patients were considered to have chronic idiopathic diarrhea if they had persistently loose stools for more than four weeks, no systemic illness, and no identifiable cause of diarrhea.