The paracaval segments of the liver

Abstract

Two segments constitute thedorsal sector: I to the left and in front of the inferior vena cava, and IX in front and to the right of the cava; they are united inferiorly by the caudate process. Segment I includes the caudate lobe, and segment IX is incorporated in the posterior surface of the right liver. Small dorsal pedicles, which are quite numerous, arise from the posterior margin of the main portal elements, and ascend upward. Segment I receives twigs from the left or right livers, many from the right lateral pedicle (67 biliary branches enter the right lateral duct, the unique duct in three cases). Segment IX consists of three subsegments. IXb lies under the interval between the middle and right superior hepatic veins, in 40% of the cases examined the veins come from the left portal vein or the bifurcation, in 6 cases the ducts enter the left hepatic duct, in 40 cases the branches extend higher than the plane of the main hepatic veins, in 18 cases reaching the upper surface of the liver. IXc is under the right hepatic vein, and IXd is to the right of a vertical plane passing by the right superior vein. Hepatic veins, enter the cava directly, sometimes the middle or the left hepatic veins.