Fig. 1

Preoperative imaging. a, b Arterial phase and delayed phase of abdominal dynamic contrast-enhanced computed tomography. These images show a tumor (arrowhead) in the middle portion of the common bile duct and dilatation of the common bile duct and the intrahepatic bile ducts bilaterally; the dilatation is diagnosed as Todani type IV-A. The tumor has enhanced iso-density at the arterial phase, and contrast effect was prolonged to the delayed phase. c Endoscopic ultrasonography shows a tumor (arrowhead) in the cystic dilated common bile duct. d Contrast-enhanced endoscopic ultrasonography shows the uptake of the contrast agent into the tumor. e, f Magnetic resonance cholangiopancreatography and endoscopic ultrasonography show one centimeter of the common channel (arrowhead), which continued from the duodenal papilla