CBD: common bile duct, CCRT: concurrent chemoradiation therapy, CHD: common hepatic duct, CMT: chemotherapy, GEM: gemcitabine, IHD: intrahepatic duct, LHD: left hepatic duct, LIHD: left intrahepatic duct, NA: not available, PD: pancreatic duct, and RHD: right hepatic duct.