Microscopic colitis.

Microscopic colitis is a common cause of chronic watery diarrhea, especially among older persons. Diagnosis requires histologic analysis of colon biopsy samples in the appropriate clinical setting. Recent studies have shown an increase in the incidence of microscopic colitis, and several have addressed potential mechanisms. We review recent findings about the clinical features, diagnosis, epidemiology, pathophysiology, and treatment of microscopic colitis.