Villous adenoma of extrahepatic bile duct: contrast-enhanced sonography findings.

We report a case of villous adenoma in the extrahepatic bile duct that was successfully diagnosed with contrast-enhanced sonography (CEUS) before surgical resection. On baseline sonography, the mass appeared as a homogeneously isoechoic mass filling the bile duct from the confluence of the right and left hepatic ducts to the distal common bile duct. No intralesional flow signal was found on color Doppler imaging and power Doppler imaging. On CEUS, the mass showed homogeneous enhancement during arterial phase, thus confirming the neoplastic nature of the lesion. The enhancement decreased gradually so that the mass became hypoenhanced during portal and late phases. Surgical resection was performed, and pathologic examination confirmed a villous adenoma of the bile duct epithelium with mild dysplasia.