Location of the ventral margin of the paracaval portion of the caudate lobe of the human liver with special reference to the configuration of hepatic portal vein branches.

The topographic anatomy of the ventral margin of the paracaval portion of the caudate lobe of the human liver has not been clearly described to date. To this end we hypothesize the existence of a precaudate plane, a flat or slightly curved plane defined by the ventral margins of the ligamentum venosum and the hilar plate. Using 76 cadaveric livers, we investigated whether the paracaval portion of the caudate lobe extended ventral to this plane and whether the paracaval caudate branch of the portal vein (PC) ran through this plane to its ventral side. In 28 of the specimens (36.8%), the PC extended over the plane to a variable depth: less than 10 mm in 10 specimens, 10-20 mm in 10, and more than 20 mm in eight specimens. This ventral extension of the PC consistently included its penetration into the dome-like area under the terminals of the three major hepatic veins; therefore, the ventrally extended PC often interdigitated with these veins and their tributaries (in practice, the ventral margin of the paracaval portion of the caudate lobe could generally be considered to run alongside the middle hepatic vein). Moreover, the ventral extension of the PC often reached the upper, diaphragmatic surface or the dorsal surface of the liver immediately to the right of the inferior vena cava. Several branches (termed border branches) in the ventral extension were difficult to identify as belonging to the PC. We discuss both the marginal configuration of the paracaval portion of the caudate lobe and how to identify and operate on the ventrally extended PC and related border branches during liver surgery.