Although historically one of the later fields to develop, liver surgery is now widely performed for a variety of benign and malignant disorders. Safe liver resection has become possible due to a better understanding of hepatic anatomy, the development of more effective hemostatic techniques, and improved patient selection.

One of the most intriguing aspects of the liver is its remarkable capacity to regenerate lost tissue. Starting within hours after resection, the remaining liver cells begin to undergo division; within 1 month of surgery, the liver remnant will have regenerated back to its preoperative volume. During this period of regeneration, a patient undergoing liver resection must retain enough functional parenchyma to support vital functions. In an individual with a normal liver, up to 80 % of the liver parenchyma can be resected, without risk of postoperative liver failure. By contrast, the cirrhotic liver is markedly limited in its ability to regenerate. Depending on the degree of dysfunction, cirrhotic patients may not tolerate even a minor hepatectomy. Therefore, careful patient selection is critical to the practice of safe liver surgery.

Hepatic metastasectomy is one of the most common indications for liver surgery. While not indicated for all cancers, resection of liver metastases can prolong survival in certain tumor types. For example, while patients with metastatic pancreatic cancer do not benefit from resection of liver metastases, resection of colorectal liver metastases can significantly improve survival in appropriately selected patients (Fig. 8.1). These differences are partially due to differences in tumor aggressiveness, and also to the efficacy of available systemic chemotherapy for that tumor type.

In patients with metastatic colorectal cancer, several clinical features have been shown to identify the best candidates for hepatectomy. In general, patients who are most likely to benefit from resection of colorectal liver metastases are those who display less aggressive tumor biology, as evidenced by a long disease-free interval, no extrahepatic metastases, low carcinoembryonic antigen (CEA) levels, lack of lymph node metastases, and fewer and smaller liver lesions. Hepatic metastasectomy has also shown to be of survival benefit to select patients with metastases from other cancers such as a pancreatic endocrine tumor, carcinoid tumor, gastrointestinal stromal tumor, and sarcoma. Patients with liver metastases from other primaries may be advised to undergo hepatectomy on a case-by-case basis.

The liver can also develop primary tumors, including hepatocellular carcinoma (HCC), which arises from hepatocytes, and cholangiocarcinoma, which arises from the biliary cells of the liver. Of these, HCC is much more common, with the majority of cases developing in the setting of preexisting cirrhosis (Fig. 8.2). A wide variety of diseases can lead to cirrhosis of the liver including hepatitis B, hepatitis C, alcoholic liver disease, nonalcoholic fatty liver disease, alpha-1 antitrypsin deficiency, hemochromatosis, etc. It is important to recognize that all patients with cirrhosis are at risk for the subsequent development of hepatocellular carcinoma, regardless of the underlying etiology. In addition, hepatitis B is unique in its ability to cause HCC even in the absence of cirrhosis. In the USA, hepatitis C and alcoholic cirrhosis are the most common causes of HCC. By contrast, in much of East Asia and sub-Saharan Africa, infection with hepatitis B is by far the most frequent etiology. The recent development of a vaccine for hepatitis B has started to decrease the incidence of HCC in some countries; however limited distribution in developing countries remains a significant barrier.

HCC does not cause symptoms until advanced stages; therefore patients who are at high-risk must undergo routine imaging screening in order to detect HCC at a treatable stage. The only curative options for HCC are hepatectomy or liver transplantation. Thermal ablation of the tumor may be equally effective as surgery in patients with a single small lesion (e.g., <2 cm). If a patient is not a candidate for any of these therapies, less effective alternatives such as embolization may be considered (Fig. 8.3). HCC is predominantly fed by branches of the hepatic artery, therefore selective embolization of the hepatic artery creates tumor necrosis, while the surrounding normal liver parenchyma is preserved by blood from the portal vein. In patients with metastatic HCC, sorafenib is an oral agent that has been shown to prolong survival.