Intrahepatic portal venous system: variations demonstrated with duplex and color Doppler US.

Seventeen cases of variations of the intrahepatic portal venous system were investigated with use of duplex and color Doppler ultrasound (US). Seven cases involved absence of the horizontal segment of the left portal vein, with portal supply to the left lobe arising from the right lobe. The 10 remaining cases involved variations of intrahepatic portal branching resulting from absence of the right portal vein, taking four patterns. It is thought that these findings represent variants of normal. These variants are important in two settings: in planning hepatic surgery and in the differential diagnosis of chronic portal vein thrombosis.