SURGICAL ANATOMY OF THE LIVER

7. How many anatomic lobes are present in the liver? What is their topographic boundary?

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The liver is divided into two anatomic lobes, the right and the left. Their boundary lies in an oblique plane extending from the gallbladder fossa anteriorly to the inferior vena cava posteriorly. The three hepatic veins define the division between the lobar segments and the planes of surgical resection. Lobar segments are numbered I-VIII, according to Couinaud’s nomenclature. (See Figure 25-1.)

Figure 25-1 The functional division of the liver and the segments according to Couinaud’s nomenclature. (From Bismuth H: Surgical anatomy and anatomical surgery of the liver. World J Surg 6:6, 1982, with permission.)

8. What is the blood supply to the liver and the relative contribution of each structure to hepatic oxygenation?

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The hepatic artery supplies approximately 30% of the blood flow to the liver and 50% of its oxygen supply. The portal vein provides 70% of the liver’s blood flow and 50% of its oxygen. The relative significance of arterial flow in cirrhotic patients is greater; therefore, hepatic artery ligation is not recommended in patients with cirrhosis.

9. What are the most common variations in hepatic arterial supply to the right and left lobes of the liver?

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In most people, the common hepatic artery originates from the celiac axis and divides into right and left hepatic arterial branches within the porta hepatis. Approximately 15% of people have a replaced right hepatic artery (sole arterial supply to the right lobe) that originates from the superior mesenteric artery (SMA). A replaced right hepatic artery always supplies a cystic artery; thus, ligation should be followed by cholecystectomy. A replaced left hepatic artery (approximately 15% of people) arises from the left gastric artery; it may be the sole blood supply to the left lobe or may contribute to blood supply in conjunction with a normal left hepatic artery. In 5% of people, the hepatic arterial supply does not arise from the celiac axis. In these people, either the right and left hepatic arteries are replaced or a single main hepatic trunk derives from the SMA.

10. What is the venous drainage of the liver?

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The right, middle, and left hepatic veins are the major venous tributaries and enter the inferior vena cava below the right hemidiaphragm.

KEY POINTS: BLOOD SUPPLY AND DRAINAGE OF THE LIVER