Microscopic colitis

Microscopic colitis is a common cause of chronic watery diarrhea, especially in the elderly. The incidence of this condition is increasing, perhaps due to an association with several commonly used medications. The two subtypes, lymphocytic and collagenous colitis, are only distinguishable histologically. The diagnosis relies on colon biopsies, which show an intraepithelial lymphocytosis and mixed lamina propria infl ammation. In collagenous colitis, the subepithelial collagen band is thickened. The main differential diagnosis is irritable bowel syndrome, and histology is required to distinguish these entities. Several treatment options have been reported, but bismuth subsalicylate and budesonide seem to be the most effective. Many patients require maintenance therapy, but the prognosis is good, with most patients responding to treatment, and no known increased risk of colon cancer or death.