Surgical Anatomy

The liver has a dual blood supply, which enters it as a single portal "cable." The portal vein normally supplies approx 80% of the blood flow to the hepatocytes. The hepatic artery supplies a smaller percentage, but is an important source of blood flow to the biliary tree. Venous drainage occurs via the hepatic veins, which empty into the inferior

From: Clinical Gastroenterology: An Internist's Illustrated Guide to Gastrointestinal Surgery Edited by: George Y. Wu, Khalid Aziz, and Giles F. Whalen © Humana Press Inc., Totowa, NJ

Left medial Umbilical fissure segment ducts /

Umbilical Fissure

Fig. 1. Hepatobiliary anatomy and nomenclature. Note the relatively longer and extrahepatic course of the left hepatic duct, and its entry into the hepatic substance at the umbilical fissure. The common duct is named the common hepatic duct above the junction of the cystic duct, and the common bile duct below this junction. The common bile duct passes beneath the first portion of the duodenum to run in the pancreas and duodenal wall until it empties into the second portion of the duodenum at the ampulla of Vater.

Left medial Umbilical fissure segment ducts /

Extrahepatic portion of left hepatic duct

. Common hepatic (cholehepatic) duct

Fig. 1. Hepatobiliary anatomy and nomenclature. Note the relatively longer and extrahepatic course of the left hepatic duct, and its entry into the hepatic substance at the umbilical fissure. The common duct is named the common hepatic duct above the junction of the cystic duct, and the common bile duct below this junction. The common bile duct passes beneath the first portion of the duodenum to run in the pancreas and duodenal wall until it empties into the second portion of the duodenum at the ampulla of Vater.

vena cava (IVC) just below the heart at the top of the liver. The human liver is divided into right and left lobes based on the bifurcation of the portal structures (bile ducts, portal vein, and hepatic artery all within a sheath of Glisson's capsule) at the hepatic hilum, rather than on external appearances. Although the anatomy of the portal structures in hepatic hilum may be quite variable, the main right portal branch typically bifurcates again quickly into anterior and posterior segments within the substance of the liver. The main left portal branch is longer and runs outside the liver before it dives in at the falciform ligament; then it branches to the medial and lateral segments of the left lobe (Fig. 1). The falciform ligament is a fatty structure that runs from the umbilicus to the umbilical fissure in the liver and is a conspicuous feature both on inspection of the external surface of the liver and on computed tomography (CT) scan. Consequently, the falciform is often misapprehended as dividing the larger right lobe from a smaller left lobe. In fact, the two main lobes are roughly equivalent in size and the falciform marks a division between the medial and lateral segments of the left lobe. A line (Cantlie's line) between the gallbladder and the IVC marks the parenchymal plane separating the left and right lobes of the liver. It is also known as the main portal fissure. This plane is also inhabited by the main trunk of the middle hepatic vein . The main trunk of the right hepatic vein runs in a plane between the anterior and posterior segments of the right lobe of the liver, and the left hepatic vein runs in the plane between the medial and lateral segments of the left lobe. The caudate lobe, which is also called segment 1 in the Hepp-Couinad classification, sits underneath the portal structures and on top of the IVC. Using this classification, eight segments are identified. The left lobe contains segments 2, 3, and 4. The right lobe contains segments 5, 6, 7, and 8 (Fig. 2).

Couinad Segment Liver Scan

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