Microscopic colitis: an update.

Microscopic colitis (MC) causes chronic diarrhea, abdominal cramping, nausea, and weight loss. Colonic mucosa appears normal on endoscopy; however, biopsies show abnormalities such as intraepithelial lymphocytosis in lymphocytic colitis, and a thickened subepithelial collagen band in collagenous colitis. Epidemiologic data demonstrates that MC is a more common cause of diarrhea than previously shown. Although the etiology of this condition is unclear, certain well-defined risk factors exist. Recently there has been more research on the pathophysiology of MC, and studies on treatment have demonstrated budesonide to be most effective, although other treatments also hold promise.