Christopher T. Siegel

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).

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.

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).

Right Hepatic Lobectomy

Various types of incisions can provide adequate exposure for a right lobe liver resection. One of the most common is the upper abdominal Mercedes incision, a bilateral subcostal incision with midline extension (Fig. 14-7, A). Other variations include midline, bilateral subcostal, or a right subcostal incision with upper midline extension. Adequate exposure with a self-retaining retractor is essential. To assist with fixation, Bookwalter upright posts can be placed in the right upper quadrant (RUQ) and in the left lower quadrant. This allows two-point fixation to the large ring and assists in optimization of surgical exposure (Fig. 14-7, B).

The liver dissection is begun in the hilum by mobilizing the gallbladder off the liver bed. The lateral border between segments IV and V approximates the dissection plane between the right and left lobes of the liver. The retroperitoneum and Gerota’s fascia, attached to the posterior right lobe of the liver, are incised to prevent liver lacerations of segments VI and VII, as the mobilization of the right lobe is begun (Fig. 14-7, C and D).

Once the inferior right lobe is free, the triangular ligament is divided along the liver to mobilize the right lobe out of the retroperitoneum. This dissection is continued superiorly to the entrance of the right hepatic vein into the vena cava. This maneuver separates the right lobe from the diaphragm. The dissection is continued posteriorly until the vena cava and short hepatic veins are fully exposed. Small short hepatic veins can be ligated and divided; larger ones can be closed with a 2.5-mm vascular stapler or suture-ligated (Fig. 14-7, E and F).

Once all the short hepatic veins are divided, the right hepatic vein can be encircled and controlled with a vessel loop (Fig. 14-8, G). At this time, attention returns to the hilum. The common bile duct can be followed to the bifurcation, and the right hepatic duct can be encircled with a vessel loop. Arterial branches lateral to the bile duct can be identified, ligated proximally and distally, and then divided. The bifurcation of the right and left portal vein branches can now be identified, and the right portal vein can be controlled proximally and distally, divided, and then oversewn, or it can be stapled with a vascular stapler (Fig. 14-8, H and I).

At this time, a demarcation plane should be evident on the surface of the liver. Although inflow vessels have been taken, better homeostasis can be obtained if inflow occlusion (i.e., Pringle maneuver) is performed.

After a 10-minute course of preischemic conditioning with an adequate recovery, the porta hepatis is clamped, the right hepatic vein is taken, and the liver parenchyma is divided (Fig. 14-8, J). Intraoperative ultrasound is useful at this point to mark a plane of dissection lateral to the middle hepatic vein and to mark branches from the right lobe that drain through the middle vein, if present. Liver parenchymal dissection can be done with a crush technique, an ultrasonic device, or high pressure water dissection (ERBE). Other techniques include using a stapler to divide the tissue or a bipolar cautery device.

After the parenchymal dissection is complete, the liver edge is cauterized with argon beam coagulation and then coated with an absorbable layer of fibrin glue. The surgeon then removes the portal clamp in a graded manner while watching for bleeding sites. A drain is left along the cut edge of the liver in case of biliary leak.

Left Hepatic Lobectomy

The left lobe of the liver comprises segments I to IV. The segments are defined by the portal branches. The left lobe lends itself better to segmental resection than the right lobe because of the easy access to the segmental branches of the left portal system. Segmental resection of the left lateral segment (segment II-III) or segment II-III-IV requires dissection further out into the porta hepatis to preserve the branches to the remaining segments. The hilar structures enter the lobe between segments III and IVb. Often, a bridge of liver tissue overlying the structures will need to be divided if segmental resections are planned. This allows access to the segmental portal and bile duct branches. Anomalous arterial and biliary anatomy is common for the left lobe.

Accessory or replaced left hepatic arteries will arise from the left gastric artery and travel in the gastrohepatic ligament to the liver. If planning a segmental resection of the left lateral segment, knowledge of the anatomy of the bile duct to segment IV is important to avoid inadvertent ligation or injury to the draining duct.

Exposure for surgery can be performed with a bilateral subcostal incision, a bilateral subcostal with a midline extension, or a midline incision.

The left lateral segment of the liver is mobilized by dividing the left triangular ligament (Fig. 14-9, A). The left segment is then retracted laterally and the gastrohepatic ligament opened. If present, an accessory or replaced left hepatic artery will travel in the gastrohepatic ligament to the liver. It can be ligated at this point in the dissection; otherwise, the peritoneum over the proximal hepatic artery lymph node is incised and the hepatic artery exposed. The hepatic artery is dissected proximally into the hilum to expose the left hepatic artery (Fig. 14-9, B).

If a formal left hepatectomy is being performed, the left hepatic artery can be ligated after it leaves the main hepatic artery. If segment I is to be left, the artery should be taken after it gives off the branch to segment I. Often, segment IV will have a separate branch off the main hepatic artery. If a formal left hepatic lobectomy is to be performed, the main hepatic artery can be followed to the common bile duct to see if segmental arteries to segment IV are present (Fig. 14-9, C).

Once the left hepatic artery is taken, the gallbladder can be dissected off the liver bed and the cystic artery and duct ligated and divided. The common bile duct is then followed to the bifurcation, and the main left duct is encircled with a vessel loop (Fig. 14-9, D). If segment I is to be left, the duct must be taken distal to the segment I bile duct takeoff. The duct can be taken early if performing a formal left lobectomy. If segmental resections are planned, it is often better to leave the duct until the parenchymal dissection, to facilitate identification of small ducts that travel into segments to be left.

At this time, the main left portal vein can be identified and encircled with a vessel loop (Fig. 14-10, E). The portal vein can be taken with a stapler or can be controlled with clamps, divided, and then oversewn. If the caudate lobe is to be left, the portal branch to the caudate must be saved.

The caudate lobe is mobilized off the vena cava. Short hepatic vein branches are ligated and divided to mobilize the left lobe off the vena cava. Large short hepatic veins can be easily taken with an endovascular GIA stapler. Once the mobilization is complete, the caudate lobe and left segment can be retracted lateral to help expose the left and middle hepatic veins (Fig. 14-10, F). These can be dissected off the vena cava and marked with a vessel loop.

The veins can be controlled and divided either with a vascular GIA stapler or between vascular clamps.

The demarcation plane of the right and left lobes should be evident. Using intraoperative ultrasound, the resection plane lateral to the middle hepatic vein can be marked on the surface of the liver. Using a parenchymal transection technique, the liver parenchyma is divided (Fig. 14-10, G). Larger vessels encountered in the parenchymal dissection can be taken with a stapler or suture-ligated (14-10, I). Once the parenchymal dissection is complete, the cut surface is cauterized with argon beam coagulation and covered with absorbable fibrin glue (14-10, J). A Pringle maneuver or portal inflow occlusion can be performed during the parenchymal dissection if significant bleeding is encountered during the separation of the liver.

A drain is left along the cut surface of the liver at the conclusion of the procedure to monitor for bile duct leak.

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