dividing loose areolar tissue (Fig. 57-2). Neoplastic or inflammatory conditions may obliterate these

planes. Superiorly and anteriorly, the diaphragm or abdominal wall and liver may jointly be involved in

a pathologic process. Posteriorly, the right adrenal gland or upper pole of the right kidney may involve

or be involved by the liver. Inferiorly, the gallbladder, colon, duodenum, or periportal lymphatics may

be involved. Cancers of the stomach or gastroesophageal junction may involve the left liver or vice

versa.

MORPHOLOGIC AND FUNCTIONAL ANATOMY

The description and definition of the anatomic divisions of the liver have been revised and written

about numerous times in the past 100 years.1–8 At present, there is still confusion between the various

hepatic anatomic nomenclatures in the English and French literature. Based only on morphologic criteria

and surface anatomy, the liver can be divided into right and left halves by forming a plane through the

gallbladder fossa (Cantlie line) and inferior vena cava (IVC) (Fig. 57-3). As will be shown later, this

plane approximates the true division between the right and left halves using the more strict definition of

a plane through the middle hepatic vein and IVC, but the middle hepatic vein is not obvious based

solely on morphology and without ultrasound. Further subdivisions of the right half of the liver into a

right anterior sector and a right posterior sector are not possible based only on surface anatomy. The

left half of the liver can be further subdivided into a left medial section and left lateral section based on

the umbilical fissure and falciform ligament. The caudate (tail-shaped) process of the liver is identified

as lying posterior to the gastrohepatic ligament and emanating from a process of liver situated posterior

to the main portal pedicle and anterior to the IVC.

Figure 57-1. Posterior view of the liver, showing the level of peritoneal reflections.

Figure 57-2. Posterior view of the liver, showing organs that produce impressions on its inferior surface.

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Figure 57-3. Anatomic division of the liver into right and left halves by a plane extending from the gallbladder fossa posteriorly to

the inferior vena cava.

Figure 57-4. Functional divisions of the liver and liver segments according to Couinaud nomenclature with the liver in the natural

position (A) and after it is mobilized (B).

1 The most widely accepted nomenclature is based on Couinaud’s description of the discrete anatomic

segments of the liver (Fig. 57-4).6 The eight segments of a liver can be determined using surface

anatomy and location of the three main hepatic veins, the portal pedicle bifurcation into right and left,

and the umbilical fissure and falciform ligament. As described, the right and left halves of the liver are

delineated by a plane through the middle hepatic vein and IVC. Segments II, III, and IV lie to the left of

this plane and form the left half of the liver. Segments V, VI, VII, and VIII lie to the right of this plane

and form the right half of the liver. Segment I, or the caudate process, is morphologically distinct from

the two halves of the liver and emanates from a process of liver lying posterior to the portal pedicle and

anterior to the IVC. Whereas the right and left halves of the liver derive blood supply from the

corresponding right and left portal veins and hepatic arteries, segment I derives blood supply from both.

Additionally, the right half of the liver has venous drainage primarily through the right and middle

hepatic veins, and the left half of the liver primarily through the left and middle hepatic veins. Segment

I, however, drains directly via small branches into the IVC. The left liver and especially the right liver

usually have small accessory hepatic venous branches draining directly into the IVC. Occasionally on the

right, the accessory branch is significant in size.

The right half of the liver can be further subdivided using a plane through the right hepatic vein and

the IVC. Liver anterior to this plane forms the right anterior sector, and liver posterior to this plane

forms the right posterior sector. The right anterior sector of the liver is composed of segment V

(inferior to the portal bifurcation) and segment VIII (superior to the portal bifurcation). The right

posterior sector of the liver is composed of segment VI (inferior to the portal bifurcation) and segment

VII (superior to the portal bifurcation).

The left half of the liver can be further subdivided using a plane through the umbilical fissure and

falciform ligament. Liver medial to this plane forms the left medial section of the liver or segment IV,

and liver lateral to this plane forms the left lateral section of the liver. The left medial section of the

liver is sometimes divided into two halves, with IVa closer to the IVC and IVb farther. The left lateral

section of the liver is further subdivided into segment II (which is superior) and segment III (which is

inferior).

Hepatic Veins

2 Three major hepatic veins carry blood from the liver to the IVC. Most patients have a right hepatic

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vein that joins the right anterior wall of the IVC and middle and left hepatic veins that converge into a

common trunk about 1 cm from the IVC that enters the left anterior wall of the IVC (Fig. 57-5). In some

patients, the three main hepatic veins join the IVC via three distinct trunks. These hepatic veins usually

lie within the hepatic parenchyma. Usually, a definable extraparenchymal segment of the hepatic veins,

especially the right, can be dissected out before it empties into the IVC, which makes outflow control

safer and easier. Usually, multiple accessory right hepatic veins empty from the right half of the liver

directly into the IVC as it courses posterior to the liver (Fig. 57-6). On occasion, these accessory right

hepatic veins are sizable and may even support venous outflow should the native right hepatic vein

need to be taken. Additionally, sometimes an umbilical vein can be appreciated running to the falciform

ligament between the middle and left hepatic veins and emptying into the terminal portion of the left

hepatic vein.

Portal Veins

The superior mesenteric and splenic veins join posterior to the neck of the pancreas to form the main

portal vein. It receives pyloric and coronary vein branches as it courses cephalad and obliquely to the

right to form the most posterior structure within the hepatoduodenal ligament (portal triad). In the

hilus of the liver, the main portal vein bifurcates into a short oblique right portal vein and a longer,

more transverse, and more superficial left portal vein (Fig. 57-7). These branches then enter the

parenchyma and become invested along with the other components of the portal triad by extensions of

the Glisson capsule. Both the right and left portal veins give off small branches to dually supply segment

I. The right portal vein usually enters the hepatic parenchyma immediately and is quick to divide into a

right anterior portal vein supplying segments V and VIII and a right posterior portal vein supplying

segments VI and VII. The left portal vein may remain near the surface of the left half of the liver in the

hilar plate for a significant distance as it courses to the umbilical fissure to give off medial branches to

segment IV and lateral branches to segments II and III.

Figure 57-5. Three major hepatic veins drain the liver. The caudate segment of the liver usually drains directly into the inferior

vena cava.

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Figure 57-6. Retraction of right liver medially exposes small venous tributaries that drain the right liver directly into the

retrohepatic vena cava. Several branches are ligated.

Figure 57-7. Intrahepatic divisions of the portal vein.

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