Anatomic dissociation between the intrahepatic bile duct and portal vein: risk factors for left hepatectomy.

The anatomic variations of the intrahepatic portal vein and bile duct were analyzed to evaluate the potential risk of left hepatectomy. A total of 210 cholangiograms and hepatic arterioportograms were performed in which the ramifications of the intrahepatic portal vein and bile duct were investigated. The orientation of the intrahepatic duct and portal vein were classified into five types. In 175 patients (83.33%), the intrahepatic portal vein and bile duct had the same anatomic classification. In 24 patients (11.43%), the right anterior or posterior intrahepatic duct drained into the left hepatic duct at the umbilical portion (type IV); there were only 15 patients (7.14%) whose portal veins fell into this category. All patients with type IV portal veins had type IV hepatic ducts, but there were 9/49 patients (18.36%) whose hepatic duct distribution belonged to type IV but their portal veins belonged to type II (6 cases) or III (3 cases). Without complete knowledge of the intrahepatic portal and biliary anatomy, insufficient portal perfusion and bile duct complications may result from the left hepatectomy operation. Preoperative portal vein evaluation or left portal vein clamping can provide significant information, but there are still 18.36% of patients where type IV biliary ducts were not detected in those with type II and III portal veins. Cholangiography is of paramount importance in these two groups of patients, as it can prevent inadvertent injury to the right intrahepatic ducts, which drain into the left intrahepatic duct. On the other hand, intraoperative ultrasonography is recommended to identify or exclude an aberrant portal vein if type VI biliary anatomy is detected during intraoperative cholangiography.