Screening by colonoscopy for colonic epithelial dysplasia in inflammatory bowel disease.

We report the results of a prospective study of screening for colorectal epithelial dysplasia by regular colonoscopy in patients with longstanding, extensive colitis (DET group: 112 patients, 366 colonoscopies) together with the findings in all other patients with colitis who have undergone colonoscopy in our unit (non-DET group: 77 patients, 196 colonoscopies). Thirty six DET patients had dysplasia on at least one examination: two patients with high grade dysplasia (HGD) were colonoscoped on suspicion of carcinoma, one asymptomatic patient had HGD at first colonoscopy and one patient had HGD on his sixth colonoscopy, all having carcinomas resected at surgery; the remainder had low grade dysplasia (LGD). Of the DET patients, 100 constituted an ongoing surveillance group (354 colonoscopies) in which LGD was common, being seen on at least one occasion in 33% of patients (16.4% of examinations), but HGD was noted only once with a Dukes A cancer found at surgery. Six non-DET patients had dysplasia diagnosed, this being LGD in all. Even in a carefully selected group of colitics the incidence of HGD is low, but its detection may enable the removal of a colorectal carcinoma at an early and curable stage.