Objective To analyze the imaging features of hepatocellular carcinoma(HCC)with bile duct tumor thrombi.Methods Thirteen patients with bile duct tumor thrombi proved pathologically underwent imaging examination.MR and CT were performed in 3 cases,and 2 cases had CT only and 8 cases had MRI only.Uhrasonography(US)was performed in all 13 patients.The accuracy of bile duct tumor thrombi detection was compared between US.CT and MRI with Fisher tost.Results Liver tumors and bile duet tumor thrombi were demonstrated in all patients on CT or MRL Presence of intraluminal soft tissue mass was found in four of five cases on CT.and mild enhancement of the intraluminal mass in the arterial phase was noted.dilated bile duct distal to tumor thrombi was detected in all five patients.Eleven Tumor thrombi showed slight low signal intensity on T1 WI,slight high signal intensity on T2 WI,and mild to moderate contrast enhancement on the contrast-enhanced MR images.The MRCP findings of tumor thrombi were as follows:interruption,stricture of the bile ducts or irregular filling defect in the bile ducts with dilated intrahepatic ducts.bile duct was abruptly interrupted or showed a"rat-tail"stricture(n=5);the common bile duct was filled with tumor thrombi.intrahepatic bile duct dilatation and missing common bile duct was noted on MRCP(n=2).Bile duct tumor thrombi were toltecfly diagnosed in 7 cases on US,and 12 cases on CT or MRI.Six cases were misdiagnosed or miss-diagnosed on US,and 4 cases were misdiagnosed on CT or MRI.There was no significant difference between US and CT/MRI in diagnosis of bile duct tumor thrombi(P=0.270).Conclusion CT or MR imaging is useful for the diagnosis of HCC with biliary tumor thrombi and for evaluating the extension of thrombi.