We designed a randomized double blinded study to evaluate the efficiency of UDCA in the treatment of duodenal adenomas. One hundred patients are planned to be included. Fifty will receive UDCA and fifty a placebo. Three duodenoscopies are planned: one before inclusion, one at the end of the first year of follow-up and one after two years of follow-up at the end of the protocol. These duodenoscopies are associated to endoscopies of the ileal reservoir performed at the time of restorative proctocolectomy and are recorded numerically. Severity of the duodenal adenomas are evaluated according to the SPIGELMAN score. Patients are seen every 6 months. Before each endoscopy, blood samples are collected for biliary acid profile analysis. Moreover, during endoscopies, duodenal fluid and ileal fluid are collected for biliary acid profile analysis, also.