CT imaging comparison between intraductal papillary neoplasms of the bile duct and papillary cholangiocarcinomas

The histology review identified 19 IPNBs and 48 PCCs, representing an estimated prevalence of IPNBs among biliary neoplasms of 4%. Approximately one half of IPNBs were incidentally found on imaging conducted for other purposes. In terms of tumor location, 15/19 IPNBs (79%) developed in intrahepatic bile ducts, and 41/48 PCCs (85%) in the distal bile duct. Cystic appearance was highly suggestive for IPNBs (p < 0.001). Using these two parameters, 78% of papillary bile duct neoplasms could be classified into IPNBs or PCCs. Other imaging findings favoring IPNBs included frond-like mural nodule, downstream bile duct dilatation, and the lack of abnormal enhancement in the adjacent bile duct. Interestingly, two patients with non-invasive or microinvasive IPNB had undergone abdominal imaging studies > 3 years before, and a retrospective review of the previous images identified small nodular or cystic lesions, suggesting a less progressive nature of IPNBs than currently thought.

• Intrahepatic location and cystic dilatation of the affected bile duct are the strong discriminators between IPNBs and PCCs.

• The shape of the mural nodule and appearance of the neighboring bile duct are helpful for distinguishing IPNBs and PCCs.

• The less aggressive behavior of IPNBs compared with PCCs may facilitate less invasive management in patients with IPNB.