Interhepatic duct: a new biliary anomaly.

True accessory bile ducts occur in only 1% of patients. An accessory bile duct connecting the right and left hepatic ducts at the porta hepatis is described. This anomaly has never been reported previously, and was clinically significant in the presence of partial obstruction of an anomalous right hepatic duct by stones. The embryologic origin of this duct, which we term an "interhepatic duct," is uncertain.