Liver transplantation techniques

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mohammed Abdelwahed M.D[2]

Liver trasnsplantation Microchapters
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Patient Information
Overview
Historical Perspective
Indications
Pre-surgical management
Choice of donor
Epidemiology and Demographics
Techniques
Complications
Acute rejection
Immune therapy
Post-surgical infection
Prognosis

Liver transplantation techniques

Left lobe transplantation 

• The left and middle hepatic veins, left hepatic artery, and left portal vein are dissected.
• Small portal vein branches are ligated. The left bile duct is divided
• Vascular and biliary structures entering segment 4 are divided or left intact.
• The parenchyma is transected and then the left hepatic artery and left portal vein are divided, releasing the graft.
• The middle hepatic vein is removed with the graft when a full lobectomy is performed. [26-28].

Right lobe transplantation

•  The right lobe accounts for approximately two-thirds of the liver mass and provides adequate tissue to support the metabolic needs of an adult recipient. The right lobe also fits correctly into the right subphrenic space, making the vascular anastomoses easier to perform. However, the extent of the resection may put the donor at increased risk for complications compared with donation of smaller segments. Furthermore, right lobe grafts are prone to a variety of technical complications.
• Techniques for right lobe transplantation vary, but the following represents a standard approach. After cholecystectomy, intraoperative ultrasound may be used to delineate the position of the hepatic veins and portal branches [31-33]. The right hepatic artery and right portal vein are dissected, followed by the retrohepatic vena cava, isolating the origin of the right hepatic vein. The middle hepatic vein is not dissected at most centers, although accessory hepatic veins greater than 5 mm may be preserved to improve outflow from the graft [32]. The right bile duct is isolated, completing mobilization of the right lobe. The liver parenchyma is transected using an ultrasonic scalpel (Cavitron). Doppler ultrasound may be used to assess inflow to the remaining left lobe. The main vessels are then divided and the isolated right lobe is flushed with preservative solution in preparation for implantation. Any bleeding of the donor's left lobe is controlled with sutures and fibrin glue is applied to the cut surface prior to closure.
• Implantation of the graft starts with end-to-end anastomosis of the donor and recipient right hepatic veins. A portoportal anastomosis is then made between the donor right portal vein and the portal vein of the recipient. The hepatic artery anastomosis is completed using microvascular techniques. Next, an end-to-side hepaticojejunostomy (and increasingly commonly, duct-to-duct anastomosis) is performed with or without internal stent placement, followed by abdominal closure (figure 1). Serial Doppler ultrasound is performed in the postoperative period.

Donor risk index  [51]

The parameters most strongly associated with graft loss include increasing donor age, donation after cardiac death, and use of split/partial grafts. Other risk factors include African American donors, shorter donors, death due to cerebrovascular accident, and causes of brain death other than trauma or anoxia.

Modified donor harvesting technique 

A small randomized trial compared the impact of a modified double perfusion (MDP) liver harvesting technique to single aortic perfusion on graft survival in suboptimal livers. The MDP technique consisted of aortic and portal cooling with clamping of the splenomesenteric vein inflow. Use of the MDP technique was associated with a lower rate of PNF and higher six-month patient and graft survival [61].

Hepatitis C-positive donors 

Transplantation of livers from hepatitis C virus-positive (HCV+) donors into HCV+ recipients initially raised concerns that aggressive recurrent liver disease would result from introduction of new viral strains into the recipient. However, studies with up to five years of follow-up, along with the advent of interferon-free direct-acting antiviral treatments for HCV have reduced those concerns [62-64], and the use of HCV-positive livers has increased from 7 percent in 2010 to 17 percent in 2015 [65].

Outcomes in recipients of HCV+ grafts are discussed separately.

Hepatitis B-positive donors 

Transplantation of organs from donors with serologic markers for past HBV infection has the potential to increase the donor pool, particularly in regions where HBV carriers are frequent (such as the Mediterranean region and Asia). It is generally recommended that grafts from hepatitis B core antibody (HBcAb)-positive donors should be offered to hepatitis B surface antigen (HBsAg)-positive recipients, although recipients who lack HBV markers may also be eligible provided that they receive effective HBV prophylaxis post-transplantation. The use of either hepatitis B immunoglobulin (HBIG) or an oral antiviral agent reduces the risk of HBV infection in HBsAg-negative patients who receive an HBcAb-positive liver [66-69].

Machine liver perfusion

hypothermic machine perfusion and normothermic ex-vivo liver perfusion (NEVLP)

limiting the deleterious effects of cold ischemia on extended criteria grafts such as DCD and steatotic livers [74-76]

A phase 1 study provided proof of concept for the use of an ex-vivo circuit to maintain liver allografts in a physiologic state by perfusion with blood containing oxygen and nutrients at a temperature of 37°C during transportation and storage [74]. NVELP allows for assessment of graft function including metabolic and perfusion parameters and bile flow, which have the potential to predict graft viability in an effort to minimize primary graft non-function with use of extended criteria donor livers [75].

SPLIT-LIVER TRANSPLANTATION 

Splitting livers into right and left lobes for transplantation has been investigated as a way to increase the supply of donor organs.

A working group appointed by the American Society of Transplant Surgeons and the American Society of Transplantation has advocated the institution of a national policy for splitting appropriate donor livers into left lateral and extended right grafts for transplantation into a pediatric and an adult recipient, respectively [77].

Many suitable livers are reduced in size for pediatric transplantation, and are not split with an adult recipient. According to the analysis of the working group, approximately 20 percent of donors could be split, increasing the total number of liver transplant recipients in the United States by up to 1000 annually. Outcomes of in situ liver splitting for adult/child pairs have been comparable to whole graft transplantation.

In a study of 106 split liver transplantations, adult 1-, 5-, and 10-year survival rates were 93, 77, and 73 percent, respectively, with graft survival rates of 89, 76, and 65 percent, respectively [78].

For children, 1-, 5-, and 10-year survival rates were 84, 75, and 69 percent, respectively, with graft survival rates of 77, 63, and 57 percent, respectively.

MARGINAL LIVER GRAFT OUTCOMES 

The use of marginal or extended criteria liver grafts may lower the risk of mortality on the liver transplant waiting list without impacting patient or graft survival.  [80]

Marginal liver grafts included those with any of the following characteristics:

●Liver donor age >70 years

●Livers discarded regionally and shared nationally

●Livers from hepatitis C positive donors

●Livers with cold ischemia time >12 hours

●Livers from donation after cardiac death donors

●Livers with >30 percent steatosis

●Livers split between two recipients