Inflammatory bowel diseases (IBD), including ulcerative colitis and Crohn's disease, are currently of unknown etiology and incurable. In recent years, the incidence of IBD has increased dramatically in China, and it will become a common disease of digestive system in China. Mesenteric adipose tissue hyperplasia indicates disease activity in IBD patients, and abnormal lipid metabolism plays an important role in the pathogenesis of IBD. In addition to intestinal symptoms, nonalcoholic fatty liver disease (NAFLD), also known as metabolic dysfunction associated fatty liver disease (MASLD), has become the most common extraintinal manifestation in IBD patients. What are the similarities and differences between IBD patients with and without MASLD? Does the occurrence and severity of MASLD affect the clinical efficacy of IBD and increase the adverse outcome of IBD? There are no relevant studies to date. We have previously completed the construction of a cohort of 290 IBD patients using the IBD patient database and biobank of Dongfang Hospital, based on which we completed a cohort study on the effect of small intestinal bacterial overgrowth on IBD disease activity. Based on this cohort, multi-center cooperation was carried out to establish an IBD research cohort by collecting basic clinical information and biological samples such as peripheral blood and intestinal mucosa. The clinical characteristics of IBD patients with MASLD were analyzed. logistic regression, COX regression, Kaplan-Meier survival curve and other methods were used. To investigate the effect of MASLD on the clinical efficacy and prognosis of inflammatory bowel disease (IBD). This project will provide efficient, full and reliable research-grade data with Chinese characteristics for IBD clinical research, and improve the level of regional diagnosis and treatment.