Risk factors and long-term outcome of disease extent progression in Asian patients with ulcerative colitis: a retrospective cohort study

The incidence of Ulcerative colitis (UC) in Asia is increasing but reports on its long-term course are few. The aim of this study was to identify risk factors predictive of extent progression in Asian patients with UC and to evaluate the clinical outcome by longitudinal follow-up. We retrospectively analyzed 518 UC patients without ascending colon involvement at diagnosis who were regularly followed and underwent colonoscopy between 2003 and 2016 in an Asian tertiary referral center. Proximal disease extension and associated risk factors were analyzed. A total of 91 (17.6%) patients experienced proximal disease extension followed for a median period of 7.5 years. The median time for extent extension was 16.1 months (interquartile range (IQR) 8.3-42.2). The cumulative rate of disease extension was 9.9, 14.9, 19.6, 24.6 and 30.5% at 1,2,3,4 and 5 years after diagnosis. 43 (12.0%) patients with E1/E2 progressed to E3, and 40 (21.9%) with E1 progressed to E2. Of patients diagnosed with E3 involvement limited to the hepatic flexure distally, 8 (13.3%) progressed to pancolitis. Cox regression analysis found that disease extent at diagnosis was the sole predictor of disease extension (odds ratio (OR),1.74, 95% confidence interval (CI) 1.18-2.57, p = 0.01). Proximal disease extension was associated with disease relapse (p = 0.03) and increased use of steroids and immunosuppressive agents (p