Efficacy of sigmoidoscopy for evaluating disease activity in patients with ulcerative colitis

BACKGROUND: Endoscopic assessment of disease activity is a key parameter in the management of ulcerative colitis. Whether sigmoidoscopy alone is sufficient to evaluate the disease activity in ulcerative colitis lacks studies. METHODS: We retrospectively analyzed the medical records and endoscopic results of patients with ulcerative colitis followed by colonoscopy in seven tertiary hospitals between January 2012 and December 2018. Endoscopic disease activity was scored using the Mayo endoscopic subscore (MES) and Ulcerative Colitis Endoscopic Index of Severity (UCEIS) for each segment from the colonoscopy images. Concordance was evaluated by comparing the highest MES and UCEIS in the rectosigmoid and proximal regions to confirm the usefulness of sigmoidoscopy. RESULTS: A total of 500 colonoscopic examinations from 333 patients were enrolled. Only in 7.6% [k(kappa): 0.893, r(Spearman): 0.906, p < 0.001] and 8.6% [k(kappa): 0.890, r(Spearman): 0.914; p < 0.001] of cases, MES and UCEIS scored more severely in the proximal colon. Comparison of active disease (MES ≥ 2) in the rectosigmoid area and the entire colon showed a high concordance rate [k(kappa): 0.899, r(Spearman): 0.904, p < 0.001]. Endoscopic healing (MES = 0) also showed a high concordance rate [k(kappa): 0.882, r(Spearman): 0.887, p < 0.001]. In 38 cases (7.6%) of patients with a higher MES in the proximal area, it was significantly higher in patients with previous extensive colitis. CONCLUSIONS: Sigmoidoscopy and colonoscopy showed a high concordance rate. Therefore, sigmoidoscopy is considered a sufficient substitute for colonoscopy. However, colonoscopy should be considered in patients with previous extensive colitis. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12876-022-02178-0.