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Sectors and Segments

The liver develops as an embryologic outpouching from the duodenum. The liver is one of the largest organs in the body, representing up to 2% of the total body weight. The relationship of the liver to the other abdominal organs is shown in Figure 24–1. In classic descriptions, the liver was characterized as having four lobes: right, left, caudate, and quadrate; however, this is an overly simplistic view that fails to consider the more complex segmental anatomy, which is depicted in Figure 24–2.

Figure 24–1.

Relationships of the liver to adjacent abdominal organs. The liver is invested with peritoneum except on the posterior surface, where the peritoneum reflects onto the diaphragm forming the right and left triangular ligaments.

Figure 24–2.

Segmental anatomy of the liver. Each of the eight segments numbered. Segment I (caudate) is not shown but indicated at the back of the liver, posterior to the middle hepatic vein. Segments I–IV comprise the anatomical left liver, and segments V–VIII, the right. The most common major hepatic resections performed and the segments removed with each are indicated. LT, ligamentum teres; LPV, left portal vein; RHV, right hepatic vein; M&LHV, middle and left hepatic veins originating from a common trunk; RPV, right portal vein.

The anatomical right and left hemilivers are separated by an imaginary line running from the medial aspect of the gallbladder fossa to the inferior vena cava, running parallel with the fissure of the round ligament (Figure 24–3). This division is known as the Cantlie line or the principal plane and marks the course of the middle hepatic vein. The liver is divided into four sectors and eight segments based on the branching of the portal triads and hepatic veins. The structures of the portal triad (hepatic artery, portal vein, and biliary duct) are separate in their extrahepatic course but enter the hepatic hilum ensheathed within a thickened layer of the Glisson capsule.

Figure 24–3.

Anatomy of the veins of the liver. The major lobar fissure, also referred to as the principal plane or Cantlie line, is represented by the dashed line and divides the anatomical right and left liver. Branches of the hepatic artery and biliary ducts follow those of the portal vein. The darker vessels represent the hepatic veins and vena cava; the lighter system represents the portal vein and its branches.

The three main hepatic veins divide the liver into four sectors, each of which is supplied by a portal pedicle: the right posterior sector (segments VI and VII), the right anterior sector (segments V and VIII), the left medial sector (segment IV), ...

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