Intrahepatic biliary dilatation caused by a small simple hepatic cyst: report of a case.

Biliary obstruction caused by small simple cysts is very rare. We present a case of biliary dilatation caused by a simple cyst with a 4-cm diameter. The patient was a 75-year-old woman referred to our hospital for evaluation of a cystic tumor associated with peripheral biliary duct dilatation in the left segment of the liver. Computed tomography and magnetic resonance imaging showed that the cyst probably communicated with the intrahepatic bile duct. Malignant tumors, including intrahepatic papillary neoplasms of the bile duct, could not be ruled out; therefore, we performed surgery with the patient's consent. Histopathologic examination of the resected liver showed that the cystic lesion was a simple cyst. The finding that even small simple cysts can obstruct the biliary tract is important for the management of cystic lesions of the liver.