Dysplasia and ulcerative colitis--a colonoscopic study.

Cancer will be found on colonoscopic biopsy in 11% of patients with chronic ulcerative colitis for over eight years' duration. Sixteen percent of patients with dysplasia will subsequently be found to have carcinoma of the colon. A total of 3% of patients in the high-risk group will have cancer of the colon. Endoscopic biopsies should be separated into those performed for diagnostic or surveillance purposes, so that meaningful and reproducible results will be obtained. Annual total colonoscopy and biopsies are recommended for surveillance purposes.