Microscopic Colitis and Clostridium difficile-Associated Disease

The term “microscopic colitis” was used originally in 1980 to describe a condition of chronic watery diarrhea and normal findings on barium enema and colonoscopy but colon biopsy specimens with microscopic inflammation. Collagenous colitis is a closely related condition, with similar clinical and histologic features, but in addition the subepithelial collagen band is thickened. It is unclear whether these conditions represent separate disease entities or are part of the spectrum of a single disease process. Therefore, “microscopic colitis” currently is used as an umbrella term, covering two major subsets: collagenous colitis, with a thickened subepithelial collagen band, and lymphocytic colitis, without collagen thickening.