Main accessory sulcus of the liver.

It has been proposed that the superficial part of the portal fissures weakens the surface hepatic parenchyma, allowing the development of accessory sulci caused by diaphragmatic pressure. To evaluate the relationship of the sulci in the antero-superior surface of the right liver with the right portal fissure, macroscopic post mortem examination of 85 livers was carried out and radio-opaque resins were injected into the portal and hepatic venous systems to obtain vascular casts. After formalin fixation, the 85 livers also underwent CT and MR scans and 3D image elaboration. Diaphragmatic sulci were found in 32 cases. We studied the sulci located in the right liver, i.e., those that lay to the right of the line of Cantlie. They were found in 28 instances and in 16 cases they were multiple. In the livers with a single sulcus, it extended between the anterior and right surfaces of the right liver and showed a curved course downward and forward, toward the inferior margin. In the cases with multiple sulci, one sulcus always showed a course similar to that of the single sulci. The 28 sulci, with similar position and course, showed variable characteristics (mean length=7.6 +/- 2.7 cm, mean width=0.8 +/- 0.7 cm, mean depth=1.4 +/- 0.8 cm). Both radiological images and corrosion casts showed a correspondence between these sulci and the right hepatic vein and the right portal fissure in 71% of cases. These sulci may represent the variable expression (cranial, intermediate, or caudal portions) of a potential sulcus, the main accessory sulcus (MAS), that develops along a theoretically predictable course corresponding to the superficial part of the right portal fissure. The high prevalence of location of the MAS at the level of the upper part of the right portal fissure can be ascribed to the presence at this level of the watershed between the roots of the tributaries of the hepatic veins coming from segments VIII and VII, draining respectively into the middle and right hepatic veins. Thus, the coexistence of the two portal and hepatic venous boundaries may represent a further predisposition to the effects of diaphragmatic pressure. The MAS may represent a marking for the right portal fissure, and hence a superficial reference for the deep course of the right hepatic vein.