Figure 57-8. Variations in hepatic arterial anatomy.

Hepatic Arteries

3 There is much variability in the hepatic arterial supply to the liver. The most common anatomy is a

common hepatic artery that arises from the celiac trunk and courses near the superior border of the

neck of the pancreas. After the origins of the gastroduodenal, supraduodenal, and right gastric arteries,

the proper hepatic artery courses in the left anterior aspect of the hepatoduodenal ligament in front of

the portal vein and to the left of the common hepatic duct. The proper hepatic artery usually bifurcates

into right and left hepatic arteries outside the liver. The anatomy of the hepatic artery is variable and

should be familiar to surgeons operating in this area (Fig. 57-8). Approximately 45% of people have

variant hepatic arterial anatomy.9 The right hepatic artery usually courses posterior to the common

hepatic duct but anterior to the right portal vein to supply the right liver. The left hepatic artery usually

remains extrahepatic until near the base of the umbilical fissure, where it enters the liver to give off

branches to segments II, III, and IV. Small branches from near the bifurcation of the proper hepatic

artery also supply segment I. A middle hepatic artery branch may arise from either the right or left

hepatic arteries after bifurcation. Although this anatomy is described as normal, it is found only in

approximately 50% to 60% of patients. A replaced or accessory right hepatic artery may arise off of the

superior mesenteric artery near its origin and course posteriorly or through the head of the pancreas to

lie along the right posterior border of the hepatoduodenal ligament. A replaced or accessory left hepatic

artery may arise off of the left gastric artery and course transversely toward the base of the umbilical

fissure in the lesser omentum. In general, within the hepatic parenchyma, the hepatic arterial branches

course closely with bile duct branches and fairly closely with portal venous branches, but not always,

and anatomic variations should be suspected. The descriptions and frequency of hepatic arterial variants

have been well characterized by Michels.9

Intrahepatic Biliary Tree

The right and left livers are respectively drained by the right and left hepatic ducts, whereas the caudate

(segment I) is drained by several small ducts joining the confluence and the first several centimeters of

1457

both hepatic ducts. The intrahepatic ducts are tributaries of the corresponding hepatic ducts, which

penetrate the liver invaginating the Glisson capsule at the hilus. Bile ducts are usually located above the

corresponding portal branches, whereas hepatic arterial branches run inferiorly to the veins. The left

hepatic duct directly drains the bile ducts to segments II, III, and IV, which constitute the left liver. The

right hepatic duct drains the bile ducts from segments V, VI, VII, and VIII, which constitute the right

liver. Usually, the bile ducts from segments V and VIII join to first form the anterior sectoral duct and

the bile ducts from segments VI and VII join to first form the posterior sectoral duct prior to forming

the right hepatic duct (Fig. 57-9).

Figure 57-9. Intrahepatic divisions of the bile ducts and hepatic arteries.

Gallbladder

4 The gallbladder is a reservoir for bile located on the undersurface of the liver at the confluence of the

right and left halves of the liver. It is separated from the hepatic parenchyma by a cystic plate, which is

constituted of connective tissue applied to the Glisson capsule. The gallbladder may be deeply imbedded

into the liver or occasionally presents on a mesenteric attachment, but usually lays in a gallbladder

fossa. The gallbladder varies in size and consists of a fundus, a body, and an infundibulum. The tip of

the fundus usually reaches the free edge of the liver and is closely applied to the cystic plate. The

infundibulum of the gallbladder makes an angle with the body and may obscure the common hepatic

duct, constituting a danger point during cholecystectomy. The cystic duct arises from the infundibulum

of the gallbladder and extends to join the common hepatic duct. The lumen measures between 1 and 3

mm in diameter, and its length varies depending on the type of union with the common hepatic duct

(Fig. 57-10). Callot triangle is bounded by the common hepatic duct on the left, the cystic duct

inferiorly, and the cystic artery superiorly. Arterial blood reaches the gallbladder via the cystic artery,

which usually originates from the right hepatic artery. Several known variations in the origin and

course of the cystic artery are illustrated in Figure 57-11. The venous drainage of the gallbladder is

directly into the liver parenchyma or into the common bile duct plexus.

1458

Figure 57-10. Variations in the junction of the cystic duct and common hepatic duct.

Figure 57-11. Variations of the cystic artery.

Common Bile Duct

The cystic and common hepatic ducts join to form the common bile duct. The common bile duct is

approximately 8 to 10 cm in length and 0.4 to 0.8 cm in diameter. The common bile duct can be divided

into three anatomic segments: supraduodenal, retroduodenal, and intrapancreatic (Fig. 57-12). The

supraduodenal segment resides in the hepatoduodenal ligament lateral to the hepatic artery and anterior

1459

to the portal vein (Fig. 57-13). The course of the retroduodenal segment is posterior to the first portion

of the duodenum, anterior to the IVC, and lateral to the portal vein. The pancreatic portion of the duct

lies within a tunnel or groove on the posterior aspect of the pancreas. The common bile duct then enters

the medial wall of the duodenum, courses tangentially through the submucosal layer for 1 to 2 cm, and

terminates in the major papilla in the second portion of the duodenum (Fig. 57-12). The distal portion

of the duct is encircled by smooth muscle that forms the sphincter of Oddi. The common bile duct

usually joins the pancreatic duct to form a common channel before entering the duodenum at the

ampulla of Vater. Some patients will have an accessory pancreatic duct emptying into the duodenum.

5 The blood supply of the common bile duct is segmental in nature and consists of branches from the

cystic, hepatic, and gastroduodenal arteries. These meet to form collateral vessels that run in the 3 and

9 o’clock positions. The venous drainage forms a plexus on the anterior surface of the common bile duct

that enters the portal system. The lymphatic drainage follows the course of the hepatic artery to the

celiac nodes.

LIVER IMAGING

Computed Tomography

Computed tomography (CT) is widely available and quick and has become the main modality to initiate

the assessment of hepatic processes. It also has the advantage of being able to quickly assess other

organs within the abdominal cavity and chest. With the introduction of multidetector spiral CT, the

resolution of hepatic lesions is quite good. This scanning technique allows total hepatic imaging in

arterial, portal venous, and delayed phases after a rapid intravenous contrast bolus during a single

breath hold by the patient (Fig. 57-14). In addition, three-dimensional reconstructions can be created to

construct high-quality hepatic artery angiograms, portal venograms, and hepatic venograms. These

reconstructions play a vital role in the selection of appropriate donors for live donor liver

transplantation (Fig. 57-15). Drip infusion cholangiography with CT can provide distal intrahepatic duct

cholangiograms that with the three-dimensional arteriograms and venograms are vital in planning donor

hepatectomies and avoiding serious complications.

Figure 57-12. Anatomy of the extrahepatic biliary tree and pancreatic duct.

1460

Figure 57-13. Relationship of structures within the hepatoduodenal ligament.

Figure 57-14. Portal venous phase of computed tomography (CT) scan from a patient with a history of colorectal cancer and three

lesions in the liver. Lesion 1 in segment VIII is irregular and rim enhancing and was a colorectal cancer metastasis. Lesion 2

straddling segments IV and VIII has smooth borders, is not rim enhancing, and was found to be a cyst. Lesion 3 straddling segments

IV and III across the umbilical fissure is irregular and rim enhancing and was a colorectal cancer metastasis.

Magnetic Resonance Imaging

6 Magnetic resonance imaging (MRI) of the liver with gadolinium as a contrast agent is commonly used

1461