**2. Preoperative considerations**

Several factors are considered in determining the eligibility for PH, including the patient's health status (e.g. age, ECOG PS), tumor-specific factors (e.g. extent and tumor biology), and the reserve of the liver remnant. Determined by the degree of liver dysfunction and the size of the postoperative liver remnant. While there is no strict age limit, one must consider the liver's regenerative capabilities in elderly patients, and the patient's ability to tolerate the physiologic consequences of portal pedicle clamping and acute hemorrhage on their cardiopulmonary system. In addition, patients undergoing a minimally invasive approach must also be able to endure the effects of the pneumoperitoneum and reverse Trendelenburg positioning on their physiology.

Several different clinical staging systems exist to stratify patients according to prognostic variables [4]. One of the most commonly used is the Barcelona Clinic Liver Cancer (BCLC) system which incorporates tumor size, number of nodules and hepatic function as classified by the Child-Pugh score [5]. The system classifies patients into early, intermediate, advanced and terminal stages and proposes recommended treatment strategy. According to this staging system, only stage 0 or early stage patients with small tumors are recommended for surgical resection or liver transplant.

However, many view the BCLC criterion for resection to be restrictive. For patients with large tumors (beyond any down-staging or expanded OLT criteria) who are ineligible for OLT, PH is the only potentially curative treatment. With improvements in perioperative management, preoperative morphological assessment and manipulation of the future liver remnant, PH for large HCC has been safely performed with good oncologic outcome [6, 7]. Therefore, large tumor size alone is not a contraindication to PH, rather factors such as multiple or bilobar tumors, extrahepatic metastasis, involvement of the main bile duct, portal venous or other macroscopic vascular invasion, and portal hypertension are all relative contraindications to PH. When clinically not evident, portal hypertension can be evaluated by measuring the transjugular intrahepatic portosystemic gradient (PSG). PSG values greater than 10 mmHg are indicative of significant portal hypertension and these patients must be approached with caution.

85–90% of patients with HCC have concomitant liver dysfunction. It is critical to account for the degree of liver dysfunction in addition to the patient's overall functional and nutritional status. Patients with liver disease are often malnourished with diminished performance status and comorbid conditions. To help stratify clinical liver dysfunction, patients are classified by the Child-Turcotte-Pugh (CTP) score and the Model for End-Stage Liver Disease (MELD) system. These two systems classify patients based on physical exam and laboratory data, with increasing scores associated with higher overall surgical risk. In general, patients with CTP score up to B7, MELD score <9 without significant portal hypertension can be considered for PH. Patients with more severe liver dysfunction and HCC can be considered for OLT if they meet specific criteria [8, 9].

Assessment of the hepatic function and future liver remnant (FLR) is important for patient selection prior to surgical resection [10]. The volume of the FLR and the regenerative capacity are key predictors of postoperative morbidity. Several laboratory tests have been used to evaluate hepatic reserve in cirrhotic patients including assessment of clearance of indocyanine green, sorbitol and 99mTc-galactosyl serum albumin scintigraphy [11]. Preoperative volumetric analysis can be performed with 3D computerized tomography volumetry [12]. To minimize the chance of post-hepatectomy liver failure, data suggest a liver remnant to be at minimum >20% of preoperative liver volume in a normal functioning liver, >30% for patients who have undergone >3 months systemic chemotherapy and >40% in those with advanced liver disease [13, 14].

Several techniques for preoperative optimization of the FLR exist including portal vein embolization (PVE) and the associated liver partition with portal vein ligation for staged hepatectomy (ALPPS) [15]. Initially developed in 1986, PVE results in atrophy of the embolized segments and compensatory hypertrophy of the perfused segments [16], within approximately 4–6 weeks, with at least >10% growth of the FLR predicting adequate regeneration post-PH. PVE has been shown to reduce the rate of postoperative complications in select patients with chronic liver disease [17], and can also be used safely in patients undergoing concurrent chemotherapy for colorectal metastases. One study demonstrated improved prognosis after PH in patients with impaired hepatic function [18].

ALPPS was developed in 2007 to induce liver hypertrophy in patients planned for extended liver resections with marginal FLR. A two-step operation, the initial data demonstrated it to be quite effective with rapid hypertrophy [15], however, it has not gained wide acceptance secondary to significant morbidity and mortality and the need for larger scale studies [19–21]. However, there are more recent reports of "mini-ALPPS" where the procedure is performed minimally invasively and with limited peripheral division of the parenchyma.
