Association between serum bilirubin and mucosal healing among Japanese patients with ulcerative colitis: a cross-sectional study

PURPOSE Bilirubin is known to have antioxidant effects. Several pieces of evidence regarding association between serum bilirubin and UC exist. Three studies found that serum bilirubin was inversely associated with severity of ulcerative colitis (UC), but no evidence regarding an association between serum bilirubin and mucosal healing (MH) has yet been shown. Thus, we evaluated this issue among Japanese patients with UC. METHODS The study subjects consisted of 304 Japanese patients with UC. Serum total bilirubin and indirect bilirubin were divided into quartiles on the basis of the distribution of all study subjects (low, moderate, high, and very high). Several endoscope specialists were responsible for evaluating MH, which was defined as a Mayo endoscopic subscore of 0. The information on clinical remission was collected using medical records. RESULTS The mean age was 49.9 years, the percentage of male patients was 59.2%, and the percentage of MH was 29.3%. High serum total bilirubin was independently positively associated with MH (OR 2.26 [95%CI 1.13-4.61]. However, after adjustment for confounding factors, the association between total bilirubin and MH disappeared. Very high serum indirect bilirubin was independently positively associated with MH (OR 2.31 [95%CI 1.10-5.00], p for trend = 0.026). No association between bilirubin and clinical remission was found. CONCLUSIONS Among Japanese patients with UC, serum indirect bilirubin, but not total bilirubin, was significantly positively associated with MH but not clinical remission.