The remainder of the segments (2 to 8) are numbered in a clockwise fashion starting superiorly in the left hepatic lobe: is drained directly into the IVC by one or more small hepatic veins, explaining why it might undergo hypertrophy in certain pathologies.may receive its supply from both the right and the left portal vein.its inferior portion is subdivided into a lateral caudate process and a medial papillary process 6.bounded posterolaterally by the fossa for the inferior vena cava, anteriorly by the ligamentum venosum, and inferiorly by the porta hepatis.right posterior (or lateral) section: segment 7 above and segment 6 below the portal plane.right anterior (or medial) section: segment 8 above and segment 5 below the portal plane.left medial section: segment 4a above and segment 4b below the portal plane.left lateral section: segment 2 above and segment 3 below the portal plane.left hepatic vein located in the left intersegmental fissure, divides the left lobe into left medial and left lateral sections.Ī horizontal plane further divides the liver, known as the portal plane where the portal vein bifurcates and becomes horizontal, dividing each section (or sector) of the liver into superior and inferior segments:.To the right is the right medial section and to the left is the left medial section. middle hepatic vein lies in the main lobar fissure, divides the liver into right and left lobes (or right and left hemiliver): this vertical plane runs from the inferior vena cava to the gallbladder fossa and is known as Cantlie's line.right hepatic vein located in the right intersegmental fissure divides the right lobe into right lateral (posterior) and right medial (anterior) sections.These veins run in 3 vertical planes radiating from the intrahepatic IVC that separate 4 sections of the liver (a section is two segments on top of each other): Along the boundaries of each segment there is venous outflow through the hepatic veins so that a hepatic vein drains two adjacent segments and each segment has multiple draining hepatic veins. Generally, each segment can be conceptualised as wedge-shaped with the apex pointing towards the hepatic hilum ( porta hepatis) where a single segmental branch of the portal vein, hepatic artery and bile duct enter (the portal triad). The delineation of the segments is based on the fact that each segment has its own dual vascular inflow, biliary drainage and lymphatic drainage. NB: the hepatic segments were originally numbered by Roman numerals I to VIII, but the Arabic numerals 1 to 8 are now preferred 7. It is the preferred anatomy classification system as it divides the liver into eight independent functional units (termed segments) rather than relying on the traditional morphological description based on the external appearance of the liver. The Couinaud classification (pronounced kwee-NO) is currently the most widely used system to describe functional liver anatomy.