Key points

Introduction

Techniques and indications for resection of liver tumors have considerably evolved during the last 2 decades. Liver surgery can be performed more safely than ever and the number of liver resections has increased in the past years. Multimodal treatment for colorectal liver metastases has expanded the group of patients who are potentially eligible for liver resection. Surgical approaches to complex resection have been further augmented by a variety of electrosurgical devices and the increasing use of preoperative portal vein embolization to augment the size and function of the planned liver remnant.

The critical elements for safety in resectional hepatic surgery include meticulous preoperative evaluation, including assessment of liver function and delineation of hepatic anatomy. Intraoperative management involves the use of a low central venous pressure anesthetic technique and seamless communication between the anesthesiologist and the surgeon. Resection involves techniques to control the inflow into the liver, techniques to control the vascular outflow (hepatic veins), and techniques to divide the liver parenchyma and navigate within the liver. This article reviews these elements in detail.

Indications for liver resection

Although most resectional surgery is performed for primary or metastatic liver cancer, in selected cases liver resection is also performed for benign disease.

Preoperative functional evaluation

Preoperative prediction of size and function of the liver remnant is important mainly for resections in patients with underlying liver disease (eg, fibrosis/cirrhosis, chemotherapy-induced liver damage) and for extended resections with presumably small future liver remnants (FLRs). Of these, right trisectionectomy (or extended right hepatectomy, including resection of segments 4a and 4b) is the most common extended variation. FLR prediction can be performed using different approaches, including imaging-based volume calculations and/or functional assessment analyses such as the indocyanine green clearance rate. In healthy livers, FLR volumes of approximately 30% are sufficient for postoperative liver function. Although the imaging calculations provide an exact prediction of the FLR volume, extensive clinical experience is required to determine which patients may actually do well with an extended resection, particularly if the FLR volume is less than 30%. In surgery for metastatic colorectal cancer, extended preoperative treatment with chemotherapy may be associated with chemotherapy-associated steatohepatitis. This chemotherapy-associated process will compromise liver regeneration and must be considered when contemplating extensive resection. To increase the number of patients eligible for extended resection, portal vein embolization and staged hepatectomies have been introduced. Portal vein embolization increases the FLR volume in many cases, and this allows for resection of disease deemed unresectable initially.

Anatomy and terminology of liver resection

Couinaud outlined the anatomic framework for modern liver surgery by defining the segments of the liver according to the portal vein inflow. However, the recent increase in liver resection, its wide implementation in clinical practice, and the development of extended liver resections necessitated a more practical classification for daily clinical use. The scientific committee of the International Hepato-Pancreato-Biliary Association defined a joint classification in 2000 (the Brisbane classification). This classification defines 3 orders of liver resection: (1) right or left hepatectomy or hemihepatectomy; (2) right or left, anterior or posterior sectionectomy, and right or left hepatectomy plus left medial or right anterior section, respectively; and (3) segmentectomies. This comprehensive classification provides increased precision in describing resectional liver operations. It has been widely adopted in reporting outcomes of liver surgery; however, major confusion still stems from mistakenly using the term trisegmentectomy for trisectionectomy (extended right or left hepatectomy). This article uniformly uses the Brisbane terminology ( Table 1 ).

Technical considerations and outcomes after liver surgery

Compared with other major abdominal operations, surgery of the liver still carries a higher risk of perioperative or even intraoperative mortality. Hemorrhage and postoperative liver failure are the major factors associated with postoperative mortality. Technical advances have thus been mainly achieved through better resolution and use of intraoperative ultrasound, and the development of techniques allowing for meticulous inflow and outflow control. In addition, recent years have brought increasing focus on blood-sparing transection and more exact preoperative prediction of size and function of the liver remnant.

Intraoperative ultrasound of the liver should be used in all cases to determine the exact anatomy of the portal pedicles (inflow and indirect visualization of the biliary tree) and the hepatic veins (outflow), and the localization and extension of the tumors. To achieve this, high-resolution ultrasound is required, which incorporates duplex function and vascular Doppler capability. Ultrasound also helps determine whether additional lesions are present in the liver, particularly in the future liver remnant, and helps assess the relationship of the tumors to the intrahepatic vascular and biliary structures.

Once the exact anatomy has been determined, extensive mobilization of the right or left liver lobe (or both) is advisable. Although potentially time-consuming, this allows for inflow and outflow control, which limits blood loss in situations wherein intrahepatic control is difficult. Blood-sparing transection can be performed using a wide variety of techniques and devices, of which none has been shown to be clearly superior. Acceptable techniques include clamp fracture, staple transection, water jet dissection, and ultrasonic dissection. Although perhaps more time-consuming than other methods, many surgeons favor ultrasonic dissection for its ability to allow precise identification and control of intrahepatic pedicles and veins.

Positioning and setup

Patients should be positioned supine with both arms extended. This positioning provides access to both arms for intravenous therapy and provides the opportunity to extend a right subcostal incision laterally. The exception to this is if the surgeon anticipates using a right thoracoabdominal incision, which is sometimes used for very large tumors of the right liver. In this case, the ideal setup involves suspending the right arm over the patient’s head with an airplane splint and elevating the right chest slightly to facilitate chest exposure.

The operating lights should be positioned exactly before the patient is prepared. Because intraoperative ultrasound is required for precise definition of liver anatomy, placing the ultrasound device in the surgeon’s field of vision before starting the procedure is advisable. Once positioning and setup of the instrumentation is completed, a team time-out is performed. This procedure emphasizes the interaction of the surgeons with the anesthesiologists and nurses, and is the time to reiterate the potential risks of liver surgery, such as blood loss and hemodynamic instability. The need for a low central venous pressure, particularly during the transection phase, and for blood products in the operating room should also be discussed at this point.

Incisions and retraction

A multitude of potential incisions can be performed in open liver surgery, depending on the extent of resection and the preference of the surgeon. For (extended) right hepatectomy, the authors usually use a right subcostal incision with midline extension. The subcostal incision is performed at approximately a 3-fingers width below the costal margin, with a maximal extension to the iliac crest line on the right side. The midline incision is extended up to the xiphoid, sometimes along the sides of the xiphoid up to the sternum, to allow for better exposure of the suprahepatic vena cava and the hepatic veins. If mobilization of the liver is difficult, the incision may be extended to the left subcostally. In cases of large right-sided liver tumors, a thoracoabdominal incision is sometimes required. This procedure involves a midline incision with an extension across the right hemiabdomen, with additional extension to the right chest. The costal margin is divided and the chest is opened in the eighth or ninth intercostal space. The peripheral diaphragm is divided and later repaired. The left liver can also usually be accessed with the right subcostal incision with midline extension. If the left lateral segments are large and extensive mobilization of the left side is required, a bilateral subcostal incision (with or without midline extension) may be helpful.

Before the retractors are placed, the ligamentum of teres and the falciform ligament should be divided. This technique prevents unwanted tearing of the liver capsule and the parenchyma. A large number of self-retaining retractor systems are available, which allow for forced retraction of the upper and lower parts of the incision, using bilateral crossbars on top and 2 angled arms below. Several body wall retractors are used to expose as much of the liver as possible, whereas the porta hepatis is exposed with malleables.

Intraoperative ultrasonography

The authors use intraoperative ultrasonography and duplex ultrasound in all liver resections. After mobilization of the liver, the portal pedicle and hepatic vein anatomy are analyzed. Portal venous and hepatic arterial flow to the right and left side of the liver is determined; this is the baseline analysis, which is used for comparison after test-clamping the pedicles to the side of resection.

Hepatic venous anatomy is analyzed, with a particular emphasis on the route of the middle hepatic vein, which in many cases is precisely within the line of transection. Larger branches of the middle hepatic vein can be marked with electrocautery on the surface of the liver; this allows for early recognition of those during parenchymal transection.

The liver is then scanned for the tumor or metastasis. The findings are compared with the preoperative imaging, and additional lesions may be identified. The relation of the tumors to the portal pedicles and the hepatic veins is determined. The plane of resection is defined accordingly.