Incidence of collagenous and lymphocytic colitis: A 5-year population-based study

Objective: The incidence of collagenous and lymphocytic colitis is not well known. We sought to assess the incidence of collagenous and lymphocytic co litis in a well-defined population during a 5-yr study period, Methods: Fro m January 1, 1993, to December 31, 1997, all new patients diagnosed with co llagenous or lymphocytic colitis living in the catchment area of the Hospit al Mutua de Terrassa (Barcelona, Spain) were identified. Since 1993 all pat ients with chronic diarrhea were referred for a diagnostic colonoscopy. Mul tiple biopsy sampling of the entire colon was performed when appearance of the colonic mucosa was grossly normal. Results: Twenty-three cases of colla genous colitis and 37 of lymphocytic colitis were diagnosed. The female:mal e ratios were 4.75:1 and 2.7:1 for collagenous and lymphocytic colitis, res pectively. The mean age at onset of symptoms was 53.4 +/- 3.2 (range, 29-82 ) yr for collagenous colitis, and 64.3 +/- 2.7 (range, 28-87) yr for lympho cytic colitis (p = 0.012). The mean annual incidence per 100,000 inhabitant s based on the year of onset of symptoms was 1.1 (95% confidence interval [ CI], 0.4-1.7) for collagenous colitis, and 3.1 (95% CI, 2.0-4.2) for lympho cytic colitis. A peak incidence was observed in older women in both disease s. A rate of microscopic colitis of 9.5 per 100 normal-looking colonoscopie s performed in patients with chronic watery diarrhea was observed. Normal r ectal biopsies were found in 43% and 8% of patients with collagenous and ly mphocytic colitis, respectively. Conclusions: The incidence of lymphocytic colitis is three times higher than that of collagenous colitis. Microscopic colitis should be considered as a major possibility in the work-up of chro nic diarrhea in older women. (Am J Gastroenterol 1999;94:418-423. (C) 1999 by Am. Cell, of Gastroenterology).