Microscopic colitis

Microscopic colitis is a relatively common cause of chronic diarrhea. The colonic mucosa appears normal or nearly normal at endoscopy, and the diagnosis is made when there is intraepithelial lymphocytosis and a mixed inflammatory infiltrate in the lamina propria in the appropriate clinical setting. The two subtypes of colitis, collagenous and lymphocytic colitis, are simi-lar clinically and histologically and are differentiated primarily by the presence or absence of a thickened subepithelial collagen band. The possibility of drug-induced microscopic colitis and/or concomitant celiac sprue must be considered when evaluating these patients. Although there have been few controlled treatment trials in microscopic colitis, a systematic approach to therapy often leads to satisfactory control of symptoms.