Liver Resection

Grade

ECOG

Fully active, able to carry all pre-disease performance without restriction

Restricted in physically strenuous activity but ambulatory and able to carry out work of a light or sedentary nature such as light house work, office work

Ambulatory and capable of all self-care but unable to carry out any work activities. Up and about more that 50 % of walking hours

Capable of only limited self-care, confined to bed or chair more than 50 % of waking hours

Completely disabled. Cannot carry on any self-care. Totally confined to bed or chair

Dead

Oken M, Creech R, Tormey D, et al. Toxicity and response criteria of the Eastern Cooperative Oncology Group. Am J Clin Oncol. 1982;5:649–655

After comprehensive assessment of patients’ overall health and functional status, in-depth evaluation of patients’ liver health is vital. Assessment starts by examining the risk factors for liver diseases such as congenital or familial syndromes, hepatitis, and alcohol intake. Please see Chap. 9 for liver diseases and syndromes. All patients should be specifically asked about alcohol intake history. These questions have a particularly important impact on treatments such as liver transplantation. Hepatitis testing can be selective, based on the presence of risk factors such as intravenous drug abuse, history of tattoos, high-risk sexual behavior, past episode of jaundice, or history of blood transfusions prior to 1990. All of the patients with hepatocellular carcinoma should be tested for hepatitis due to the known association.

The presence of cirrhosis and/or portal hypertension introduces unique challenges for liver surgery. In cirrhotic patients, a firm, nodular and enlarged liver poses technical difficulties in mobilization and parenchymal transection. Impairment of liver function after resection in cirrhotic patients is greater, may last longer and could result in liver failure. Additionally, potential liver regeneration is negatively impacted by cirrhosis. Therefore, the principles of parenchymal sparing should be strictly followed for cirrhotic patients. Portal hypertension imposes an increased risk for bleeding during surgery and in the postoperative period. A decreased platelet count is often used as a surrogate marker for portal hypertension rather than invasive measurement of hepatic vein pressure gradients.

Patients with biliary instrumentation have an increased risk of infections due to the colonized biliary tree associated with manipulation and/or stent placement. Postoperative alterations of immune system are thought to be a potential predisposing factor to infections. The risk of postoperative infection is particularly high in patients with cirrhosis and ascites or jaundice.

Assessment of Liver Function

There is no individual test to completely assess the liver’s functional status. Assessment requires analysis and interpretation of multiple factors. Accurate estimation of liver resection extent and the predicted remnant volume assists in prediction of the potential postoperative complications. It also guides the therapeutic decisions which may include a staged resection or hybrid procedures with incorporation of ablation techniques.

Recent improvements in anesthesia support, surgical techniques, and ICU care have led to a surgical mortality of less than 3 % following liver resections at many high volume institutions. However, overall morbidity related to liver failure following resection remains between 16 and 50 % [6, 7].

Currently, measures to assess preoperative liver function are broadly divided to three major categories: (1) Classification systems, (2) Dynamic Liver tests, (3) Predicting postoperative liver volume.

Classification Systems

While many systems have been proposed for risk stratification and selection of patients undergoing liver surgery, the Child-Turcotte-Pugh (CTP) scoring system is most commonly utilized [8, 9]. The parameters measured in this classification include presence or absence of clinical ascites and encephalopathy, serum albumin, total bilirubin, and the international normalized ratio (INR) . Based on clinical severity or measured laboratory value, each parameter will earn points. The final point total (which is a summation of all five categories) will classify the patient into three groups (A, B or C). These groups are used to stratify the patients’ liver synthetic and detoxification function (Table 35.2). Numerous studies have demonstrated the predictive validity of the CTP score as a surrogate for liver function and prognostic of outcomes. For example, in patients with cirrhosis, the 1-year mortality related to liver failure is less than 5 % for Child-Pugh class A patients, compared with 20 % and 55 % for class B and C patients, respectively. Child-Pugh class B cirrhosis limits candidates for liver resection, and prohibits a major hepatectomy. Class C cirrhosis is a contraindication for surgical intervention.

Table 35.2

Child-Turcotte-Pugh (CTP) scoring system

Points	1	2	3
Ascites	None	Mild to Moderate (diuretic controlled)	Severe
Encephalopathy	None	Mild	Severe
Bilirubin (mg/dL)	<2	2–3	>3
Albumin (g/L)	>3.5	2.8–3.5	<2.8
PT (sec > control) or	<4	4–6	>6
INR	<1.7	1.7–2.3	>2.3

INR international normalized ratio, PT prothrombin time

Class A: 5–6 points; Class B: 7–9 points; Class C: 10–15 points

Another classification system is the MELD (Model for End-Stage Liver Disease ) [10]. This system is used to assess patients for liver transplantation and estimates the 3-month predicted mortality. It is a logarithmic equation comprised of serum creatinine, total bilirubin and INR values to predict the anticipated mortality. MELD score has been increasingly used to provide a complementary predictive value to Child-Pugh score. Patients with a MELD score above 14 may be excluded from major surgical interventions.

Dynamic Liver Tests

Although not routinely used in North America, dynamic tests can provide additional information on the future liver remnant by evaluating hepatic uptake, metabolism and excretion capacity. Indocyanine green (ICG) clearance and Galactose Elimination Capacity (GEC) are two most commonly utilized quantitative tests.

ICG clearance test is validated as a valuable adjunct in quantifying liver function. ICG is a dye that is selectively taken up and cleared from the circulation by the liver and its clearance is an indicator of hepatocyte function. Studies, suggest that an ICG retention values after intravenous injection above 10–15 % at 15 min are considered abnormal and are used as a cutoff to identify patients at high risk for liver failure following liver resection [11].

Predicting Postoperative Liver Volume

Future liver remnant (FLR) refers to the residual liver volume after hepatic resection. It is one of the most important determinants of postoperative liver function. Underlying liver disease and its inherent impaired liver functional capacity requires a larger remnant liver to achieve the necessary hepatic function. Studies have suggested that for patients with normal liver parenchyma, FLR > 20–30 % is sufficient to avoid postoperative liver insufficiency. In cirrhotic patients with impaired baseline liver function, at least a 40 % FLR is recommended to compensate [12]. For patients who have received extensive systemic chemotherapy, FLR > 30 % reduces the rate of postoperative hepatic insufficiency (PHI) and may provide enough functional reserve for clinical rescue [13].

Three-dimensional Computed Tomography (CT) scan or Magnetic Resonance Imaging (MRI) has been utilized to perform preoperative volumetric analyses. Based on the predicted anatomical resection planes, software can calculate the corresponding remnant volumes. Image guided volumetry does not account for underlying parenchymal dysfunction and should not be used as the single decision variable. Inconsistencies can also occur when multiple, large or infiltrating tumors replace a large volume of the liver.

A number of techniques have been utilized to improve an insufficient FLR, in order to achieve a safe liver resection. These include portal vein embolization (PVE) and recently introduced ALPPS (Associated Liver Partition and Portal vein ligation for Staged hepatectomy). Portal vein embolization or ligation interrupts the flow and diverts the portal blood flow to the liver remnant, causing remnant growth. This effect is maximized in 4–6 weeks and is most effective for the patients with a normal liver [14]. ALPPS (Associated Liver Partition and Portal vein ligation for Staged hepatectomy) is a recent modification of staged liver resections that approaches resection in two steps. It relies on the regenerative capacity of the remnant liver after parenchymal transection and portal vein ligation in a short period of 1–2 weeks during a single hospitalization [15].

Imaging Modalities

The last critical component to the proper patient selection for liver surgery is to delineate the liver anatomy. It is crucial to outline the topography and characterize the liver pathology with its anatomical relationship to the critical structures. High quality preoperative cross-sectional imaging is imperative for this assessment.

Ultrasound (US) is an inexpensive, high resolution imaging technique that does not use ionizing radiation. Its versatility and real time imaging capability make it a useful screening tool. However, its sensitivity and specificity are lower than CT. Therefore it is not routinely used for preoperative planning. Intraoperative ultrasonography is an essential component of liver surgery. It is used for identifying the lesions, screen the remnant liver for occult disease, and ultimately determine resectability (Fig. 35.1a).

Fig. 35.1

Examples of different liver imaging modalities. (a) CT scan image of a liver lesion. (b) MRI imaging showing a solid liver tumor. (c) Ultrasonic image of a solid gallbladder lesion with posterior enhancement. (d) MRCP reconstruction of biliary tree. (e) ERCP imaging of biliary tree

To date, CT scan and MRI are the most reliable preoperative imaging modalities to evaluate the liver. In addition to the information gained about the liver, they are also used to evaluate for extrahepatic disease. CT volumetry is one of the most common means of predicting the volume of functional liver remnant following a proposed resection [16]. It typically involves the ratio of remaining volume to total liver volume (Fig. 35.1b). MRI is a cross-sectional scanning technique that uses magnetic fields and radiofrequency pulses to generate images with tissue contrast (Fig. 35.1c). MRI cholangiography (MRCP) is a technique that is utilized to specifically evaluate the biliary and pancreatic systems. Diagnostic quality images are obtained via this technique with high sensitivity and specificity for assessment of biliary duct dilations, strictures and other abnormalities (Fig. 35.1d) [17]. The images obtained by MRCP are very similar to ones acquired by Endoscopic Retrograde CholangioPancreatography (ERCP) (Fig. 35.1e) or Percutaneous Transhepatic Cholangiography (PTC) . In contrast to those invasive procedures, MRCP is noninvasive and avoids morbidities such as post procedural pancreatitis. MRCP also provides the ability of visualization of the extrabiliary anatomy, allowing for exclusion or inclusion of alternative diagnoses. However, this modality does not provide the potential of a tissue diagnosis and the opportunity for therapeutic interventions such as stent placement.

General Principles

The liver is the largest solid organ in the human body. It lies protected under lower ribs, closely molded to the undersurface of the diaphragm. Most of liver bulk is located in the right side of the body, secured by multiple ligaments.

Liver is divided into right and left lobes by Cantlie’s line which runs from gallbladder fossa anterior, to the IVC fossa posterior. These lobes are subdivided by the Couinaud classification into eight functionally independent segments. Each segment has its own vascular inflow, outflow, and biliary drainage. In the center of each segment, there is a branch of the portal vein, hepatic artery, and bile duct. In the periphery of each segment, there is vascular outflow through the hepatic veins.

Indications for liver resection vary widely from trauma to oncologic treatments (Table 35.3). Liver resections are divided into two major categories: Anatomic and non-anatomic. Anatomic resections follow the mentioned segmental divisions and could range from a single segment resection (Segmentectomy), to over six segment resections (Right Trisegmentectomy). Major hepatectomy is defined as resection of three or more Couinaud liver segments. Non-anatomic resection planes are not limited by these segmentations. For example, a wedge resection of liver parenchyma is considered non-anatomical resection. The International Hepato-Pancreato-Biliary Association (IHPBA) Brisbane 2000 terminology committee classifies the liver resections to five main categories [18]: (1) Right Hepatectomy: resection of segments V–VIII, (2) Left Hepatectomy: Resection of segments II–IV, (3) Extended Right Hepatectomy (Right Trisegmentectomy): Resection of segments IV–VIII, (4) Left Lateral Segmentectomy: Resection of segments II and III, (5) Extended Left Hepatectomy (Left Trisegmentectomy) : Resection of segments II, V, and VIII.

Table 35.3

Most common indications for liver resection