Collagenous and lymphocytic colitis: systematic review and update of the literature.

Collagenous and lymphocytic colitis are well-described conditions causing chronic watery diarrhoea. A peak incidence from 60 to 70 years of age with a female predominance mainly in collagenous colitis is observed. Both conditions are characterised by a (near) normal colonoscopy, but with specific histologic findings on colonic biopsies. Histopathologically, both conditions are characterised by distinct epithelial abnormalities and a dense lymphoplasmocytic infiltrate. Distinct features consist of a characteristic collagen band deposition in the subepithelial layer in collagenous colitis and a markedly increased number of intra-epithelial lymphocytes in lymphocytic colitis. Although most cases are idiopathic, certain drugs can induce microscopic colitis. In addition, either condition can be associated with coeliac disease. For a long time patients with microscopic colitis were treated with non-specific anti-diarrhoeal agents, anti-inflammatory agents such as mesalazine, or systemic steroids, but with disappointing results. Bismuth subsalicylate was reported to be effective in a small controlled series of patients with collagenous colitis. Now, randomised controlled trials have shown the effectiveness of budesonide over placebo in collagenous colitis and more recently in lymphocytic colitis. The histologic response is variable, but a decrease in the subepithelial collagen layer and a decrease in the lymphoplasmocytic infiltrate in the lamina propria is observed in about half of the patients. In general, patients respond within 2 weeks with no major side effects. However, relapse is common (63-80% of patients) when budesonide is stopped. Longer-term treatment is effective but does not seem to reduce relapse rates upon discontinuation.