CHAPTER 36 Hepatic Tumors
Step1: Surgical Anatomy
♦ The typical benign tumors of the liver that require resection are mesenchymal hamartoma, adenoma, and focal nodular hyperplasia. Hepatoblastoma is the most common malignant liver tumor of childhood; it usually occurs within the first 3 years of life. Hepatocellular carcinoma, sarcoma, and epithelioid hemangioendothelioma, a low- to intermediate-grade malignant tumor, is less common and generally is seen in older children.
♦ The liver is separated into nine anatomic segments, each with an independent portal venous and arterial inflow and biliary and hepatic venous drainage. This segmental anatomy forms the basis for the design and implementation of a successful anatomic resection of the liver (Fig. 36-1).
♦ The hepatic veins divide the liver into four sections: right anterior and posterior, left medial, and lateral. The left and middle hepatic veins form a common trunk before entering the vena cava in 60% of patients.
♦ The right hepatic artery and portal vein enter the liver parenchyma shortly after branching. The left hepatic duct and left portal vein have a longer course after branching. Together they course to the base of the umbilical fissure, where they join the left hepatic artery before entering the liver parenchyma (Fig. 36-2).
Step 2: Preoperative Considerations
♦ In the case of malignant lesions, most commonly hepatoblastoma, there should be an expectation of paired inflow and outflow structures that remain intact with an adequate resection margin. In most of these cases, the resection will be anatomic (i.e., along one of the planes outlined by the hepatic veins). Ligation of the appropriate arterial and portal venous inflow produces a demarcation line that correlates with the safe line of division. Benign lesions, in many situations, can be resected along nonanatomic lines.
♦ Cross-sectional imaging for evaluation the tumor and its relationship to the vasculature of the liver is the key to preoperative planning. This imaging can be a computed tomography scan or a magnetic resonance imaging. The use of ultrasound with duplex scanning can be helpful for evaluation of both portal and hepatic venous anatomy, and it can be used intraoperatively as well. Good-quality imaging studies should identify replaced or accessory arterial anatomy and the presence of an accessory right hepatic vein.
♦ Routine laboratory evaluation including blood count and renal panel would be expected, especially for children who are between rounds of chemotherapy, to ensure bone marrow recovery. Blood should be available for the procedure. Prophylactic parenteral antibiotics are given within 30 minutes of incision time and as appropriate throughout the length of the procedure.
♦ There is definite user preference for selected equipment, but certain types of equipment can improve exposure and minimize blood loss.
Step 3: Operative Steps
♦ General endotracheal anesthesia is administered, and peripheral intravenous access is obtained. A nasogastric tube and a urinary catheter are placed for decompression and drainage.
♦ For children with planned anatomic resections or major nonanatomic resections, arterial and central lines are placed for monitoring and postoperative management. Consideration is given to intraoperative maintenance of a low central venous pressure to minimize bleeding during the division of the hepatic soft tissue.
♦ Patient positioning is supine with the arms at the sides; the draping allows access to the lower chest and the abdomen down to the pubis. The “baby table extension” is useful for infants and toddlers.
♦ The incision is generally bilateral subcostal with upper midline extension (Fig. 36-3). The upper midline extension provides excellent exposure of the suprahepatic vena cava, and the subcostal portion can be adjusted, depending on the specific anatomy of the tumor. For more limited resections, a subcostal or bilateral subcostal incision may suffice.
♦ The basic principles for all anatomic liver resections include control of the inflow and outflow vessels and parenchyma transection. The methods to achieve these principles are similar regardless of the particular lobe or segment of the liver being removed. For purposes of this section, the right hepatectomy will be used as the standard to illustrate the principles previously listed.
♦ The liver is carefully inspected and palpated to identify the tumor and any unexpected lesions and their relationship to the vascular structures. This must be completed before resection is begun.
♦ The ligamentum teres is divided along with the falciform ligament to expose the hepatic veins. The right lobe of the liver is mobilized by dividing the right triangular ligament. The right lobe should be mobile enough to be rotated out of the abdominal cavity (Fig. 36-4).
♦ The foramen of Winslow is palpated for identification of a replaced or accessory right hepatic artery and for the presence of any significant adenopathy (Fig. 36-5).
♦ The cystic duct and cystic artery are divided. The gallbladder is removed at this time for better visualization of the hilar structures. Cholecystectomy is not absolutely necessary at this particular time; however, right hilar exposure may be improved.
♦ The cystic duct stump is rotated anteriorly and medially to expose the portal vein behind the common bile duct, and the portal vein can be followed cephalad to its bifurcation. Ligation of small caudate branches will increase the mobility of the short right portal vein segment and allow for better control before ligation. The right hepatic artery should be encountered just anterior to the right portal vein branch. Both of these structures can be divided at this stage. Completion of this inflow division should produce a clear line of demarcation within the hepatic parenchyma to guide the soft tissue resection. The right hepatic duct can be left intact to be divided during the parenchyma dissection or identified and ligated at this stage of the operation (Fig. 36-6). In the presence of a single right hepatic duct that is extrahepatic, ligation during the hilar dissection will certainly improve exposure of the right portal vein.
♦ Mobilization of the right lobe is completed by separating the bare area completely from the diaphragm to expose the right hepatic vein and inferior vena cava further.
♦ With the right lobe rotated medially, the hepatic veins passing from the posterior aspect of the right lobe to the vena cava are divided from the inferior border of the liver, continuing cephalad until the right hepatic vein is clearly seen. This dissection will often include a portion of the caudate lobe, which courses circumferentially around the vena cava and will need to be ligated and divided. Be aware of the possibility of an accessory right hepatic vein, which will be encountered during this portion of the procedure. Once the right hepatic vein is completely exposed, it can be divided using a stapling device or vascular clamps and sutures (Fig. 36-7).
♦ The parenchyma transection is begun by scoring the capsule along the demarcation line using electrocautery. Many techniques are available for parenchyma transection, or as adjuncts, such as the ultrasonic dissector, the water-jet dissector, and the radiofrequency dissector. Older techniques such as the crush and clamp technique work well for most of the parenchyma with the assistance of the ultrasonic or water-jet dissector as the dissection approaches the hepatic veins. This is especially true in cases where the hepatic vein anatomy is unclear and the hepatic vein has not been controlled before beginning parenchyma transection. The safety of intermittent inflow occlusion using a Pringle maneuver has been documented. This technique may be used during the parenchyma division if needed.
Step 4: Postoperative Care
♦ At least for the immediate postoperative period, children are usually managed in the pediatric intensive care unit (PICU), where they can be carefully monitored for bleeding. Pain management is achieved with intravenous narcotics administered by the PICU team or by the anesthesia pain service.
Step 5: Pearls and Pitfalls
♦ Control of the appropriate hepatic vein might not be achievable until the parenchyma is divided. This can be done safely as long as care is taken during that portion of the dissection to identify the hepatic vein anatomy before transaction is done.
♦ On rare occasions the left portal vein branch arises from the right portal vein in the substance of the liver. This anatomic variation would be very important to identify if planning resection requiring division of the right portal vein.
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