Background and AimsWhether the natural course of ulcerative colitis (UC) in mainland China is similar or different from that in Western countries is unknown, and data on it is limited. We aimed to provide a comprehensive description of the natural course of UC in China and compare it with Western UC patients.MethodsBased on a prospective Chinese nationwide registry of consecutive patients with inflammatory bowel diseases, the medical treatments and natural history of UC were described in detail, including disease extension, surgery, and neoplasia. The Cox regression model was used to identify factors associated with poor outcomes.ResultsA total of 1081 UC patients were included with a median follow-up duration of 5.3 years. The overall cumulative exposure was 99.1% to 5-aminosalicylic acids, 52.1% to corticosteroids, 25.6% to immunomodulators, and 15.4% to biologics. Disease extent at diagnosis was proctitis in 26.9%, left-sided colitis in 34.8%, and extensive colitis in 38.3%. Of 667 patients with proctitis and left-sided colitis, 380 (57.0%) experienced disease extent progression. A total of 58 (5.4%) UC patients underwent colectomy, demonstrating cumulative proportions of surgery at 1, 5, and 10 years after diagnosis of 0.6%, 3.4%, and 8.2%, respectively. In addition, 23 (2.1%) UC patients were diagnosed with neoplasia, demonstrating cumulative proportions of neoplasia at 1, 5, and 10 years after diagnosis of 0.5%, 1.0%, and 3.5%, respectively.ConclusionsChinese UC patients had similar cumulative proportions of exposure to IBD-specific treatments but a lower surgical rate than patients in Western countries, indicating a different natural course, and close monitoring needs for UC in China. However, these results must be confirmed in population-based studies because the hospital-based cohort in our study might lead to selection bias. image