Surgical Implications of Portal Vein Variations and Liver Segmentations: A Recent Update

Abstract

The Couinaud's liver segmentation is based on the identification of portal vein bifurcation and origin of hepatic veins. It is widely used clinically, because it is better suited for surgery and is more accurate in localizing and monitoring various intra parenchymal lesions. According to standard anatomy, the portal vein bifurcates into right and left branches; the left vein drains segment II, III and IV and the right vein divides into two secondary branches - the anterior portal vein drains segments V and VIII, and the posterior drains segments VI and VII. The portal vein variants such as portal trifurcation, with division of the main portal vein into the left, right anterior, and posterior branches, and the early origin of the right posterior branch directly from the main portal vein were found to be more frequent and was seen in about 20 - 35% of the population. Accurate knowledge of the portal variants and consequent variations in vascular segments are essential for intervention radiologists and transplant surgeons in the proper diagnosis during radiological investigations and in therapeutic applications such as preparation for biopsy, Portal Vein Embolization (PVE), Transjugular Intrahepatic Porto-Systemic Shunt (TIPS), tumour resection and partial hepatectomy for split or living donor transplantations. The advances in the knowledge will reduce intra and postoperative complications and avoid major catastrophic events. The purpose of the present review is to update the normal and variant portal venous anatomy and their implications in the liver segmentations, complex liver surgeries and various radiological intervention procedures.

Keywords: Couinaud’s segments; Hepatectomy; Liver transplantation; Portal vein embolization.

[Table/Fig-1]:

(a) Drawing showing the standard portal vein anatomy (Type 1); (b) Drawing showing the Portal trifurcation (Type 2); (c) Right posterior portal vein as the first branch of main portal vein (Type 3); (d) Segment VII branch as the separate branch of the right portal vein (Type 4); (e) Segment VI branch as the separate branch of the right portal vein (Type 5);

Table/Fig-2]:

Drawing showing the Couinaud’s liver segmentation RHV - Right hepatic vein; LHV - Left hepatic vein; MHV - Middle hepatic vein; RPV - Right portal vein; LPV - Left portal vein; MPV - Main portal vein; RAPV - Right anterior portal vein; RPPV - Right posterior portal vein; IVC - Inferior venae cava