Abstract: ponding Abstract： Objective To evaluate the diagnostic value of endoscopic ultrasonography (EUS) for unexplained bile duct expansion in patients before retrograde cholangiopancreatography (ERCP). Methods Sixty patients with unknown causes of bile duct dilatation were included in this study. Patients were examined by abdominal ultrasound (TUS), CT and (or) magnetic resonance imaging (MRCP) suggesting the dilatation of common bile duct, suspecting biliary pancreatic disease with unknown cause. EUS diagnosis was performed before ERCP surgery. The final diagnosis was confirmed by ERCP, pathology and follow-up diagnosis. Results Thirty-nine patients were diagnosed as distal bile duct stone by ERCP, 38 were diagnosed by EUS, and one case was diagnosed as common bile duct bottom tumors by EUS. There were 10 cases were diagnosed as common bile duct bottom tumors by ERCP and surgical pathology, 2 cases were diagnosed as biliary papillomatosis, 2 cases were diagnosed as periampullary carcinoma. There were 11, 0 and 3 cases were diagnosed by EUS. One case was diagnosed as distal bile duct stone, which was diagnosed as common bile duct bottom tumor by EUS. Two cases were diagnosed as papillary tumor of the bile duct, one of which was diagnosed as inflammatory stenosis, another one was diagnosed as periampullary carcinoma by EUS. Results of postoperative follow- up confirmed that 7 cases were duodenal papilla inflammatory stenosis. Eight cases were diagnosed by EUS, one of them was followed up and pathologically diagnosed as biliary papillomatosis by ERCP. The diagnostic accuray was 95% (57/60). Conclusion EUS has higher value in the diagnosis of unexplained bile duct expansion, which especially can improve the diagnostic rate of distal bile duct stone compared with that of MRCP detection, and can guide selectively ERCP, improve the therapeutic effect, and reduce its risk．

Key words: cholangiopancreatography, endoscopic retrograde, endoscopic ultrasonography, common bile duct expansion