Guidelines of the French Society for Digestive Endoscopy (SFED)

Definition and Main Characteristics of Microscopic Colitis

Microscopic colitis is defined as a combination of chronic diarrhea, normal mucosa at colonoscopy, and chronic inflammation of the mucosa at histology 1. Two main histological types of microscopic colitis 2 3 are described: lymphocytic colitis and collagenous colitis. The following histological abnormalities are common to both types of microscopic colitis:- Loss of integrity of the superficial epithelium- Increased numbers of intraepithelial lymphocytes- Infiltration of the lamina propria with inflammatory cells and predominantly mononuclear cells An increase in the thickness of the subepithelial collagen band (> 10 µm when measured) is the hallmark of collagenous colitis. The main characteristics of the two types of microscopic colitis (patient’s general status, possible causes, natural history, response to treatment) are similar. The incidence of both types of microscopic colitis is similar to that of ulcerative colitis and Crohn’s disease 4. In up to 40 % of cases, microscopic colitis starts acutely, like gastroenteritis. Microscopic colitis tends to affect women over 50 years of age, and is often associated with autoimmune disorders (such as celiac disease) or inflammatory disorders (such as rheumatoid polyarthritis). Microscopic colitis is usually idiopathic. Nevertheless, a number of drugs taken on a long-term basis, the list of which is growing steadily, may be responsible for microscopic colitis. In this setting, colitis is reversible when the treatment is discontinued 5. The possible relevance of all long-term treatments taken in patients diagnosed with microscopic colitis must therefore be considered. In addition, it now seems likely that microscopic colitis may be triggered by a bacterial infection, in particular by Yersinia spp. Microscopic colitis is responsible for chronic diarrhea, often of variable intensity, over the whole day, which may not respond to the usual antidiarrheic agents. The patient’s general condition is maintained, but weight loss is possible. The blood hydrosodium balance may be deficient, and hypokalemia is possible. The anatomical and clinical activity of microscopic colitis tends to diminish spontaneously with time. Most cases of lymphocytic colitis and a large number of cases of collagenous colitis tend to have disappeared before the third anniversary of the disorder. Budesonide is the only agent that has been evaluated in placebo-controlled randomized studies for use during the chronic diarrhea phase, when symptomatic treatments are ineffective 6. In more severe and refractory cases, the use of azathioprine 1 or even proctocolectomy with ileoanal anastomosis may be considered.

References

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