The first liver transplantation was performed by Thomas Starzl in Denver, Colorado, in 1963.1 Over the past 50 years, the field has experienced tremendous medical and surgical advancement, with 1- and 5-year survival approaching 90% and 75%, respectively, in most series. Successful transplantation involves a fascinating complex of donor and recipient factors, which represent the focus of this review.
Donor quality is one of the most important determinants of peritransplantation and posttransplantation organ function. Donors can be defined as standard criteria donors (i.e., good quality donors) or extended criteria donors, which may include steatotic livers, older donors, donors with positive serology, split livers, and donors after cardiac death (DCD). Other factors that affect organ quality are mechanism of death, hemodynamic instability that requires pressor support, and electrolyte derangement (sodium level at procurement >160 mmol/L). All of these factors along with predicted ischemia times are among the important variables that can help with the initial decision of whether or not to pursue the procurement of a liver. Ischemia time can be divided into cold ischemia time (CIT) and warm ischemia time (WIT). CIT begins when the liver is cooled with cold perfusion solution during organ procurement and ends when the organ is placed in the transplant field for implantation. The time from removal of the liver from ice until vascular reperfusion represents the WIT. During this period, the liver warms slowly to a temperature of 12.5°C while the caval and portal vein anastomoses are performed.2 CIT and WIT of 6 to 12 hours and 30 to 60 minutes, respectively, are acceptable, with shorter times being necessary when transplanting marginal donors to maximize early graft function. Matching donor and recipient characteristics is another important aspect of preoperative planning. For instance, older donors (>60 years) transplanted to hepatitis C virus recipients are associated with more aggressive posttransplantation hepatitis C virus recurrence,3 and a suboptimal organ (fatty livers, old grafts, or DCD organs) transplanted to a very sick patient often results in poor transplantation outcome.4
DCDs are donors who do not meet the criteria for brain death and must be pronounced dead after life support has been terminated and after a variable agonal phase (which should not exceed 30 minutes) and ultimately irreversible cessation of circulation. Livers procured from DCDs are more susceptible to primary nonfunction and chronic biliary complications, probably due to the hypoperfusion during the agonal phase. These are all important concepts when considering donor and recipient factors in the delicate phase of organ acceptance and transplantation.
Recipient Hepatectomy and Preparation for Implantation
Hepatectomy of the native liver is the first step of the operation. This can be a challenging procedure due to the intimate anatomical relationship of the liver with the retrohepatic inferior vena cava (IVC) in the setting of coagulopathy and portal hypertension. A history of previous upper abdominal surgery can make the operation even more hazardous.
Hepatectomy can be performed using one of two techniques: the conventional technique or the piggyback technique. In the conventional technique, the native retrohepatic IVC is removed en bloc with the liver. The donor vena cava (always procured along with the liver) is anastomosed in an end-to-end fashion to both the suprahepatic and infrahepatic IVC to recreate the original anatomical situation (Fig. 1A,B). In the piggyback technique, the liver is completely dissected from the IVC, which is therefore preserved and only partially clamped at completion of the hepatectomy. A common cuff is created by joining the three hepatic vein orifices together, and the donor suprahepatic cava is anastomosed in an end-to-side fashion to the common cuff of recipient hepatic veins (Fig. 2). The retrohepatic donor vena cava (i.e., the cul-de-sac) is ligated. One of the major advantages of this technique is that the venous return is preserved during the anhepatic phase. Furthermore, only one IVC anastomosis is performed, shortening the anhepatic phase time. This is the only technique possible when the IVC is not present in the graft (i.e., in living donors and split livers).
The conventional technique requires complete occlusion of the vena cava. Consequently, some surgeons prefer to use a veno-venous bypass during the anhepatic phase to avoid hemodynamic instability caused by total caval occlusion. Many other surgeons rarely if ever use the bypass technique, however, and rely on advanced anesthesia techniques and a more rapid implantation to achieve the same results. The conventional technique does not require the sometimes tedious dissection of the caudate lobe from the vena cava, making the hepatectomy easier and faster. The decision between the conventional technique or the piggyback technique is most often made according to a surgeon's experience and personal preference.5, 6 In our program, we use the conventional technique in 40% to 50% of cases, mostly without the use of veno-venous bypass. No study in the literature has proven superiority of one technique over the other.
Portal Vein Anastomosis
After completing the IVC anastomosis, portal vein anastomosis is performed in an end-to-end fashion and the liver is reperfused. Reperfusion is one of the most critical parts of transplantation. This can be characterized by profound hemodynamical instability (bradycardia and hypotension) and is the result of the sudden introduction in the systemic circulation of cold and cytokine-rich graft effluent. To avoid profound reperfusion syndrome, the liver is flushed with room temperature saline and then with systemic blood from either the portal vein or the IVC to wash and warm the graft just prior to formal reperfusion.
Some degree of portal vein thrombosis may be present in up to 13% of transplants.7 This must be dealt with via simple portal thrombectomy or secondarily with portal vein replacement with venous grafts (typically the donor iliac vein is used as a conduit) interposed between the donor portal vein and a recipient splanchnic vein (portal vein, superior mesenteric vein, coronary vein, or a large porto-systemic collateral). In selected cases, especially when there is a well-developed spleno-renal shunt, the left renal vein can be used as an excellent source of portal inflow.
Hepatic Artery Anastomosis
The most common and durable approach to hepatic artery reconstruction is an end-to-end anastomosis between the donor's celiac axis and the recipient's common hepatic artery just at the confluence with the gastroduodenal artery (Fig. 3A). Depending on surgeon preference and anatomical factors (e.g., arterial variants, vessel diameter, living donor grafts), the level of the reconstruction may vary.
The most common deceased donor arterial anatomical variant is the presence of a right arterial branch originating from the superior mesenteric artery (∼15% of cases) (Fig. 3B).8 Different back table techniques are used to reconstruct this variant; the focus of the reconstruction is to allow for only one simple anastomosis in the recipient. The easiest and most common reconstruction technique is the anastomosis of the separate right hepatic branch to the stump of the donor gastroduodenal artery.
In the case of a left accessory hepatic artery (∼10% of cases),8 this branch takes off from the donor's left gastric artery (Fig. 3C). This is preserved during donor surgery, and the arterial anastomosis is performed as described above between the donor's celiac axis (therefore proximal to the accessory artery) and the recipient's common hepatic artery. The use of running versus interrupted suture in the arterial anastomosis is usually subject to the diameter of the vessel (interrupted used for smaller vessels).
During procurement, these accessory arteries may go unrecognized and become injured. Most injuries can be identified and reconstructed at the back table. For severe injuries that defy attempts at reconstruction, it is good to remember that the replaced left hepatic artery is usually an accessory artery, and ligation or thrombosis should not create drastic consequences, as there are rich collaterals within the umbilical fissure. The replaced right hepatic artery is usually the only arterial supply to the right lobe and proximal bile duct, and lack of patency can have far more severe manifestations of biliary leak, biliary stricture, and right lobe ischemia with abscess.
In case of poor recipient arterial inflow that may be caused by celiac stenosis or inadvertent damage to the common hepatic artery during hepatectomy, an interpositional arterial graft (usually the iliac artery of the donor) is placed between the infrarenal or supraceliac aorta and the donor celiac axis.
Every effort should be made during the operation to assure early and late hepatic artery patency. Early hepatic artery thrombosis necessitates thrombectomy and reconstruction if it is identified before hepatic necrosis ensues; if not, and the liver is severely damaged, it may require early retransplantation. When hepatic artery thrombosis occurs later, it may be first recognized when the patient presents with fever and hepatic abscess. Although this may also ultimately require retransplantation, many grafts can be salvaged with conservative supportive therapy aimed at taking advantage of the development of collaterals that can supply adequate perfusion and oxygenation to allow for hepatic parenchymal healing. Careful study of triphasic computed tomography scans and duplex ultrasound images often reveal patent intrahepatic arterial branches despite the presence of a main hepatic artery thrombosis.
Following the vascular anastomosis and the establishment of good hemostasis is the donor cholecystectomy and biliary reconstruction. The preferred anastomosis is duct-to-duct between the donor and recipient common bile ducts. When there is unacceptable duct size mismatch or the recipient bile duct is unusable (primary sclerosing cholangitis), a hepatico-jejunostomy with a defunctionalizated Roux-en-Y intestinal loop is performed (Fig. 4).
The duct-to-duct anastomosis is usually performed without the use of a T-tube. Although once very popular, removal of T-tubes was found to be associated with a high rate of morbidity due to insertion site leak that often required emergent hospitalization and endoscopic retrograde cholangiopancreatography and stenting. As anastomotic techniques became more refined, internal stents and T-tubes fell into disfavor.9
Living Donor Factors
The imbalance between organ supply and demand has pushed the transplant community to look at ways to expand the donor pool. Living donor liver transplantation is one option, despite its indisputable ethical and surgical challenges (Fig. 5A,B). This type of transplantation can be performed between an adult donor and either a pediatric or adult recipient. Because donor safety is of paramount importance, only healthy donors in which the future liver remnant will be more than 35% are candidates for this procedure. The technical challenges of the donor and recipient operation are beyond the scope of this review; suffice it to say, however, that the basis of the techniques have evolved and have been refined from those used in deceased donor transplantation described above.10