Asymptomatic adenomyoma of the common hepatic duct discovered during a medical checkup: report of a case.

Although adenomyoma of the gallbladder is not so rare, adenomyoma arising in the bile duct is extremely rare. We herein report a case of partial biliary obstruction due to adenomyoma of the common hepatic duct. A 64-year-old woman was referred to the 1st Department of Surgery, Niigata University School of Medicine for surgical intervention, in whom a biliary stricture in the common hepatic duct was discovered incidentally during a medical check-up for hyperamylasemia in an affiliated hospital. She was asymptomatic without jaundice. Based on her past history of abdominal contusion, the insidious presentation and the smooth biliary stricture on cholangiography, a diagnosis of benign biliary stricture secondary to blunt abdominal trauma was made. A suspicion of malignancy, however, could not be ruled out. Subsequently, she underwent a resection of the extrahepatic bile duct with lymph node dissection in the hepatoduodenal ligament. The patient's postoperative course was uneventful. She was discharged 18 days after the operation. Histology of the resected specimen confirmed the diagnosis of adenomyoma in the common hepatic duct. Clinicians should note to avoid overlooking or misdiagnosing that adenomyoma is a cause of biliary obstruction, although extremely rare.