Pseudo-obstruction of the extrahepatic bile duct due to artifact from arterial pulsatile compression: a diagnostic pitfall of MR cholangiopancreatography

PURPOSE: To evaluate the frequency of artifact from arterial pulsatile compression as the cause of pseudo-obstruction of the extrahepatic bile duct at magnetic resonance (MR) cholangiopancreatography (MRCP) and specify the causative vessels. MATERIALS AND METHODS: In 234 patients (102 men, 132 women; age range, 25-80 years), MRCP images obtained by using a single-shot turbo spin-echo sequence were reviewed to assess pseudo-obstruction of the extrahepatic bile duct caused by vascular compression. Dual-phase spiral computed tomography, contrast material-enhanced three-dimensional MR angiography, and/or digital subtraction angiography also were performed to determine the vessel that caused the pseudo-obstruction. RESULTS: Thirty-six pseudo-obstructions due to vascular compression were found in 33 (14%) patients. The common hepatic duct (27 75%] sites) was the most common pseudo-obstruction site, followed by the left hepatic duct (four 11%] sites), proximal common bile duct (three 8%] sites), and right hepatic duct (two 6%] sites). The causative vessels were identified as the right hepatic artery at 24 (67%) sites; gastroduodenal artery, two (6%) sites; cystic artery, two (6%) sites; proper hepatic artery, one (3%) site; and an unspecified branch of the common hepatic artery, seven (19%) sites. CONCLUSION: At MRCP, pseudo-obstruction of the extrahepatic bile duct can be caused by pulsatile vascular compression of the hepatic and gastroduodenal arteries, and it should not be misdiagnosed as a bile duct tumor or biliary stone.