In some patients, bile ducts of segments 2 and 3 (B2 and B3) run caudally to the umbilical portion of the left portal vein (UP)--an infraportal course. We aimed to evaluate the frequency and clinical implications of this variation. Between January 1992 and October 2000, 108 patients underwent resection for hilar cholangiocarcinoma. The records of the 6 patients with infraportal left hepatic ducts were evaluated. An infraportal B3 was diagnosed in 6 patients (6%). No patient had an infraportal B2. An infraportal B3 could be demonstrated by computed tomography (CT) before biliary drainage, percutaneous transhepatic or endoscopic cholangiography, portography after percutaneous transhepatic biliary drainage (PTBD) via B3 and CT after PTBD via B3. Four patients (4/6) had a liver bridge covering Rex's recess (B3 not in the bridge). The incidence of the bridge in 75 comparable patients was 9/75. In conclusion, common radiologic methods are sufficient for diagnosis of abnormal biliary anatomy. The presence of a liver bridge over Rex's recess is suggestive of this variation. Separate biliary reconstruction for an infraportal branch is mandatory in an extended right hepatectomy for biliary tract cancer and may be necessary in liver transplantation with segments 2+3 grafting.