Abstract: Objective To investigate the impact of different doses of contrast agent iohexol in undergoing endoscopic retrograde cholangiopancreatography（ERCP） on liver function index and prognosis in patients with malignant biliary obstruction. Methods 134 patients with malignant biliary obstruction（including 50 with cholangiocarcinoma，34 with pancreatic carcinoma and 50 with gallbladder caicinoma） underwent ERCP in our hospital between August 2013 and August 2016 were recruited in this study，and the patients were divided into low-dose of contrast agent group （n=67） and large-dose of contrast agent group（n=67）. Serum levels of ALT，AST，ALP，GGT and TBIL were determined preoperatively and postoperatively in these patients. Complications and overall survival were observed and compared between them. Results At 7 d，14 d，21 d and 28 d after ERCP，serum alanine aminotransferase levels in low-dose of iohexol were（131.3±16.9 U/L），（111.1±17.2 U/L），（104.3±13.5 U/L） and （88.1±12.9 U/L），much lower than （151.3±26.4 U/L） before ERCP （P＜0.05），while in large-dose iohexol were （150.3±16.2 U/L），（148.3±17.2 U/L），（146.3±13.4 U/L）and（146.1±12.2 U/L），no significant change as compared to （153.3±26.4 U/L） before ERCP （P>0.05）；serum ALP levels in low-dose group were（143.3 ±16.5 U/L），（121.1±17.2 U/L），（104.3±13.7 U/L） and（90.3±12.2 U/L），much lower than（163.1±31.4 U/L） before ERCP（P＜0.05），while in large-dose group were （161.1±16.5 U/L），（160.1±17.2 U/L），（158.3±13.7 u/L） and （157.1±12.2 U/L），no significant change as compared to（162.3±31.4 U/L）before ERCP （P>0.05）；the infection of biliary tract in low-dose of contrast agent group were 4.5%，significantly lower than in high-dose of contrast agent group（14.9%，P＜0.05）；the overall survival in large-dose group were（19.96±9.39） months，significantly lower than（31.2±11.4） months in low-dose of contrast agent group（P＜0.05）；multivariate analysis showed than the dose of contrast agent was an independent factor for poor prognosis （HR=2.383，95% CI 1.262～4.503，P=0.003） in patients with malignant biliary obstruction. Conclusion Low-dose of contrast agent iohexol underwent ERCP does not affect liver function tests，while large-dose of contrast agent might lead to liver dysfunction and poor prognosis.

Key words: Malignant biliary obstruction, Iohexol, Endoscopic retrograde cholangiopancreatography, Liver injury, Prognosis