Bile Acid malabsorption.

Patients with bile acid malabsorption typically present with chronic, watery diarrhea. Bile acids recirculate between the liver and small intestine in the enterohepatic circulation. They are reabsorbed in the distal small intestine, and normally only a small fraction of the bile acid pool is lost to the colon during each cycle. In patients with bile acid malabsorption, a larger amount of bile acids is spilled into the colon, where the acids stimulate electrolyte and water secretion, which results in loose to watery stools. The common causes of bile acid malabsorption are ileal resection and diseases of the terminal ileum (Crohn's disease and radiation enteritis), which result in a loss of bile acid transporters and, consequently, diminished reabsorption. Bile acid malabsorption also has been documented in a small group of patients with chronic, watery diarrhea who have no demonstrable ileal disease (idiopathic bile acid malabsorption). The amount of bile acid loss to the colon determines the clinical presentation. Patients with mild to moderate bile acid malabsorption present with watery diarrhea and generally respond very well to treatment (with abolishment of diarrhea) with bile acid binders such as cholestyramine. Patients with more severe bile acid malabsorption have both diarrhea and steatorrhea. Treatment with cholestyramine is of no benefit in this group of patients and may, in fact, worsen steatorrhea. These patients are best treated with a low-fat diet supplemented with medium-chain triglycerides.