Distribution of dysplasia in ulcerative colitis.

Epithelial dysplasia was found in the large intestine of 8 of 15 patients with ulcerative colitis operated on between 1980 and 1982. In six of eight patients, dysplasia was found in the cecum and ascending colon, in one of eight in the descending or sigmoid colon, and in four of eight in the rectum. None of the five carcinomas in three patients were located in the sigmoid colon or rectum. The age of onset was much lower, 19 +/- 7 years, and the duration of colitis longer, 15 +/- 7 years, for the group with dysplasia compared with that without dysplasia, 37 +/- 18 and 4 +/- 3 years, respectively. Our study indicates that malignant transformation may frequently occur in the proximal colon and emphasizes the need for total colonoscopy with multiple biopsies in the evaluation of patients with long-standing ulcerative colitis.