Hepatectomy

Introduction

Multiple factors have contributed to a significant increase in the current number of liver surgeries performed annually. Improvements in surgical and anesthetic techniques as well as in patient selection have reduced the mortality associated with liver resection to between 1% and 5% at experienced centers, with acceptable associated morbidity. The improved surgical outcomes associated with the increased incidence of newly diagnosed cancers of the liver and biliary tree, along with substantial improvement in the adjuvant treatment of metastatic colon cancer to the liver, has helped to establish liver resection as the primary treatment modality for many patients with hepatocellular carcinoma, cholangiocarcinoma, and metastatic colon cancer to the liver. Every resident and general surgeon should at least be familiar with the principles involved in liver resection, or hepatectomy.

Surgical Principles

A major advance in the ability to perform liver resections is the understanding of the segmental anatomy of the liver, as described by Couinaud in 1957. In addition to the portal vein, the arterial supply, biliary drainage, and hepatic outflow must also be considered in planning the resection. Because of the significant variations in liver mass, vascular and biliary anatomy, tumor location, and extent of resection margin, adequate preoperative imaging is critical.

For primary liver tumors, a margin of 1 to 2 cm is preferred. The resection margin for metastatic lesions is somewhat more controversial, but recent studies on resection of colorectal liver metastasis demonstrated a survival advantage with a resection margin of at least 1 cm. When a liver resection is planned, the remnant liver needs to have adequate mass for the patient as well as adequate arterial, portal, and hepatic vein flow. The remnant must also have adequate biliary drainage.

The liver is composed of eight segments based on the portal inflow into the organ (Fig. 14-1). Segments I to IV constitute the left lobe (colored purple, blue, and green on illustration) and segments V to VIII, the right lobe. Preoperative understanding of the patient’s underlying liver anatomy is critical when planning a liver resection. Because of the wide variability in all the hepatic vascular and biliary structures, as well as a considerable amount of variability in the relative sizes of the right and left lobes, imaging is performed to delineate the key structures that may be encountered during the resection (Fig. 14-2). The most useful studies are triple-phase computed tomography or a high-resolution magnetic resonance imaging with contrast (Fig. 14-3).

FIGURE 14–1 Liver segments and lobes: vessel and duct distribution.

FIGURE 14–2 Variations in origin and course of hepatic artery and branches.

FIGURE 14–3 Hepatic artery: magnetic resonance image and surgical view.
(CT image from Kamel IR, Liapi E, Fishman E. Liver and biliary system: evaluation by multidetector CT. Radiol Clin North Am 2005;43(6):977-97.)

Arterial supply to the liver is through the hepatic artery, which supplies branches to the right and left lobes. Variations in the arterial supply to the liver include an additional, accessory, or replaced right or left hepatic artery and an aberrant origin of the common hepatic artery (Fig. 14-4). The most common variants of the arterial blood supply to the liver include an additional or replaced right hepatic artery from the superior mesenteric artery. This vessel is usually one of the first branches off the superior mesenteric and courses behind the head of the pancreas, posterior to the portal vein and common bile duct, traveling directly into the right lobe of the liver.

FIGURE 14–4 Variations in cystic and hepatic ducts.

The biliary tree also has significant variations, which can add to the risk of biliary leaks from the cut edge of the liver. Bile leaks are one of the more common and problematic complications of liver resection. Maintaining continent drainage of the remaining segments is critical in preventing biliary complications. Comparison of preoperative imaging with intraoperative cholangiogram can often help clarify areas of confusion.

Considerable variations exist in the relative size of the right and left lobes of the liver (Fig. 14-5). In addition to the size of each lobe, the underlying health of the liver parenchyma must also be factored into the decision regarding the minimum amount of liver that must remain for the patient to avoid liver insufficiency. Patients with cirrhosis or hepatic steatosis may need larger residual volumes after resection to maintain adequate function (Fig. 14-6).