Study on the segmentation of the right anterior sector of the liver

The segmentation of the right anterior sector of the liver still is debatable due to the lack of an anatomic landmark of the boundary between Couinaud segments V and VIII (cranio-caudal segmentation). Some authors have proposed the concept of a ventro-dorsal segmentation. The aim of this study was to evaluate which concept of segmentation better reflects the anatomy.

Using 3-dimensional computed tomography software, the ramification pattern of the right anterior portal vein was examined in 100 patients. A thick, hepatic, venous branch that passes through Couinaud segment VIII was termed V8, and its course was investigated using a virtual hepatectomy.

Regarding the anatomy of the portal vein in the right anterior sector, the cranio-caudal type was found in 53 patients, the ventro-dorsal type in 23 patients, and the trifurcation type in 13 patients. The remaining 11 patients had miscellaneous patterns of ramification. In the cranio-caudal type, the volume of the cranial segment was greater (P < .001) than that of the caudal segment. In the ventro-dorsal type, the volume of the ventral segment was greater (P = .007) than that of the dorsal segment. The V8 was identified in 81 of the 89 (91%) patients analyzed. The proportion of cases in which the V8 functioned as a landmark of the border between the ventral and dorsal segments was 63% (56/89 patients).

Regarding the segmentation of the right anterior sector of the liver, the cranio-caudal segmentation introduced by Couinaud is dominant (53%), while ventro-dorsal segmentation is less common (23%). Therefore, universalization of the concept of the ventro-dorsal segmentation is unrealistic.