Anatomical division of liver

“Is Life worth Living? It all depends on the Liver.” William James

1. Anatomical Divisions Of Liver Dr Mohsin Khan

2. Liver Liver is the largest organ in the body, weighting 1.5 kg in the average 70-kg man. The liver parenchyma is entirely covered by a thin capsule and by visceral peritoneum on all except the posterior surface of the liver termed the “Bare Area”. Liver is divided into a large right lobe, which constitutes three-quarters of the liver parenchyma, a quadrate lobe (present undersurface of right lobe), a caudate lobe (present on the postero-superior surface of right lobe) and a left lobe.

3. Segmental Anatomy Of The Liver Understanding the internal anatomy of the liver has greatly facilitated safe liver surgery. Couinaud, a French anatomist, described the liver as being divided into eight segments. Each of these segments can be considered as a functional unit with a branch of the hepatic artery, portal vein and bile duct, and drained by a branch of the hepatic vein.

4. Couinaud Classification Right Hepatic Vein divides the right lobe into anterior (V,Vlll) and posterior (VI,VII) segments. Middle Hepatic Vein divides the liver into right and left lobes ( right and left hemilivers ). This plane runs from the IVC to the gallbladder fossa & known as Cantlie’s line. Left Hepatic Vein divides the left lobe into medial (IV) and lateral (II,lll) segments.

5. Couinaud Classification A horizontal plane, known as the portal plane where portal vein bifurcates and becomes horizontal, divides each section of liver into the superior and inferior segments. Left Lateral Section: Segment Il above and segment lll below the portal plane Left Medial Section: Segment IVA above and segment IVB below the portal plane Right Anterior Section: Segment Vlll above and segment V below the portal plane Right Posterior Section: Segment Vll above and segment VI below the portal plane

6. Numbering Of Liver Segments Segment l is the Caudate Lobe Bounded posterolaterally by the fossa for the IVC, anteriorly by the ligamentum venosum and inferiorly by the porta hepatis May receive its supply from both the right and left portal veins Is drained directly into the IVC by one or more small hepatic veins The remainder of the Segments (ll-Vlll) are numbered in a clockwise fashion starting superiorly in the left hemiliver.

7. Numbering Of Liver Segments Segment ll and lll are to the left of left hepatic vein and falciform ligament with ll superior and lll inferior to the portal plane Segment IV lies between the left and middle hepatic veins, it is subdivided into IV-A (superior) and IV-B (inferior) segments. Segment IV also includes the quadrate lobe. Segments V-Vlll make up the right hemiliver and describe as Segment V is located between the right and middle hepatic veins below the portal plane Segment VI is located to the right of right hepatic vein below the portal plane Segment Vll is located to the right of right hepatic vein above the portal plane Segment Vlll is located between the right and middle hepatic veins above the portal plane

8. Couinaud Classification System

9. Segmental Anatomy Of The Liver The overall anatomy of the liver is divided into a functional right and left ‘units along the line between the gall bladder fossa and the middle hepatic vein (Cantlie’s line). Liver segments(V- Vlll ) to the the right of this line are supplied by the right hepatic artery and the right branch of the portal vein, and drain bile via the right hepatic duct. Liver segments(II-IV ) to the left of this line are supplied by the left hepatic artery and the left branch of the portal vein, and drains bile via the left hepatic duct.

10. Importance Of Segmental division Of Liver The division of liver into self-contained units allow the surgical resection of individual segments and sections (two or more adjacent segments) without damaging remaining segments. Hence, for the liver to remain viable, resection occurs along the hepatic veins and portal veins in the planes that define the boundaries of these segments.

11. “Is Life worth Living? It all depends on the Liver.” William James Thank You