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.