Liver Transplantation: The Operation
Liver transplantation is an extreme surgical undertaking, both for the patient and the surgical team. There are two components to the operation.
Portal hypertension, vascular adhesions from previous surgery and coagulopathy make removing a cirrhotic liver a bloody affair. As the abdomen is opened care must be taken not to damage a recannalised para-umbilical vein if present, which shunts blood from the liver to the umbilicus, where it feeds the caput medusa.
The principles of hepatectomy are to divide the bile duct, hepatic artery and portal vein close to the hilum, leaving good lengths of vessels for subsequent anastomosis. The bile duct is divided first, then the hepatic artery. The portal vein may be left in continuity until the liver is fully mobilised, or it may be divided and joined end-to-side to the vena cava forming a temporary porto-caval shunt which decompresses the portal hypertension, reducing blood loss. The peritoneal attachments of the liver are divided, freeing the left lobe and mobilising the right lobe’s ‘bare area’ from the diaphragm.
The liver sits astride the inferior vena cava (IVC), and can be removed either with or without the ‘intrahepatic’ portion of IVC. The IVC must be removed if there is a tumour in close proximity to it; otherwise it may be left in situ and the liver removed from the IVC. This is done by dividing the small and multiple veins from the caudate lobe which drain directly into the anterior surface of the IVC, and then dividing the right, middle and left hepatic vein. Leaving the IVC has the advantage of maintaining venous return to the heart and not compromising renal vein outflow. Where the IVC is removed it may be necessary to place the patient on a veno-veno bypass circuit that shunts blood from the IVC below (via a femoral vein cannula) to the superior vena cava (SVC) above (via an axillary or internal jugular vein cannula). Typically flows of 2 to 3 litres/min are achieved in such a circuit.
Implantation of the new liver
The new liver usually requires minor surgery to make it transplantable. The phrenic veins that drain into the suprahepatic IVC are oversewn lest they bleed on reperfusion. The hepatic artery is isolated, as is the portal vein, to facilitate subsequent anastomosis; any branches are ligated.
Caval replacement: where the IVC has been removed with the old liver, the new liver is implanted by sewing the upper and lower ends of the IVC to the corresponding parts of the donor liver.
Caval conservation: where the IVC has been left in continuity, the new liver can be anastomosed either by sewing the suprahepatic IVC of the donor to the confluence of the recipient’s three hepatic veins which are opened out into one (‘classical piggyback’), or after oversewing the supra- and infrahepatic donor IVC, by sewing the anterior aspect of the recipient IVC to the posterior aspect of the donor IVC (cavo-cavostomy).
Portal vein anastomosis
The portal vein is usually joined directly to the new portal vein. If the recipient’s portal vein is thrombosed, a length of donor iliac vein may be used to join the donor portal vein to the recipient’s superior mesenteric vein.
Hepatic artery anastomosis
To avoid narrowing the artery at the anastomosis, it is usually performed at the site of branching where the diameter may be made larger; typical sites are the recipient hepatic artery or gastroduodenal artery bifurcation to the donor coeliac trunk or splenic artery bifurcation (see Figure 34). If the recipient artery is blocked then a length of donor iliac artery is used to provide a conduit to either the supracoeliac or infrarenal aorta.
Bile duct anastomosis
Simple end-to-end anastomosis is most commonly performed. Where there is a large size discrepancy, or prior duct disease (such as in primary sclerosing cholangitis or cystic fibrosis), the donor bile duct is joined to a length of jejunum (hepatico-jejunostomy) fashioned into a Roux-en-Y loop.
Since the liver produces most of the coagulation factors, the patient will usually need third-party clotting factors in the form of fresh frozen plasma during the hepatectomy and while anhepatic. Following reperfusion with recipient blood the new liver takes some time to produce its own clotting factors, so bleeding is common. Therefore it is important to pay careful attention to stopping all bleeding points before closing the abdomen, since they are unlikely to stop bleeding by themselves. Where there is significant ongoing bleeding it may be necessary to pack the liver with swabs and return 48 hours later to remove them, by which time the clotting should have returned to normal.
Split liver or live donor transplantation
The liver may be divided in a live donor, removing either the right lobe for another adult or the left lobe for a child. In the case of a deceased donor the splitting takes place on a back table, with the liver immersed in ice-cold preservation solution, producing part of a liver for each of two recipients. The surgeon then has half a liver to implant.
The left lateral segment for a child typically has just the left hepatic vein and left branches of the artery, portal vein and bile duct. The recipient’s vena cava is left in place and the liver placed on top of it.
A right lobe, which may or may not contain segment IV, has the donor vena cava and can be implanted with either caval conservation or caval replacement techniques. Whenever the liver is split there is an increased chance of ‘small for size’, where the liver substance is insufficient for the recipient, a situation that may be made worse by the longer cold ischaemia experienced when having to first split the liver. Transplantation of the right lobe from a split liver is associated with a 1.5 times greater risk of graft failure compared with using the whole liver; the extra risk is offset by being able to treat a child and adult with the same liver.