Is sigmoidoscopy sufficient for evaluating inflammatory status of ulcerative colitis patients?

Background and Aims: An adequate range of colonic observations for precise evaluation of inflammation in ulcerative colitis (UC) patients has not been reported. Methods: Retrospective analysis of 545 colonoscopic examinations of UC patients was carried out. Severity of mucosal inflammation was evaluated using the Mayo score of endoscopic index at each location (rectum, sigmoid colon, descending colon, and the oral side of the splenic flexure) in each patient. The colonic site with maximum inflammation was determined for each patient. Results: Of 545 patients, 319 (59%) had maximum inflammation in the rectum, 79 (14%) in the sigmoid colon, 70 (13%) in the descending colon, and 77 (14%) on the oral side of the splenic flexure. Severe inflammatory activity (Mayo 3) was observed more frequently in patients who had maximum activity in the descending colon or the more proximal portion than those who had this in the rectum or sigmoid colon (42% vs 25%, P<0.0001). The first-attack patients were significantly more frequently found in patients with maximum severity in the descending colon or the oral side of splenic flexure than those with maximum severity in the rectum or sigmoid colon (P=0.016). Moreover, among 134 patients with no inflammation in the rectum and sigmoid colon, 54 (40%) had inflamed mucosa in the descending colon or the more proximal portion. Conclusions: Sigmoidoscopy is not sufficient for evaluating inflammation in UC patients. In particular, colonoscopy is necessary for first-attack patients and patients who have a discrepancy between rectosigmoid observation and symptoms.