Diffuse intrahepatic bile duct dilation caused by a very small hepatic cyst.

A 72-year-old woman presented to our hospital with diffuse dilation of the intrahepatic bile ducts. Imaging studies revealed a solitary hepatic cyst, 3 cm in diameter, in segment 4 of Couinaud's category of the liver, riding on the hilar hepatic duct. Deroofing of the hepatic cyst was performed, and the dilation of the intrahepatic bile ducts was attenuated. We concluded that even a very small solitary hepatic cyst might cause stenosis of the common hepatic duct, if it is located just above the hepatic hilum.