Patient selection criteria for liver transplantation.
The demand for liver transplantation has progressively increased in the setting of a relatively fixed cadaveric organ supply over the past 5 years. An increasing percentage of listed patients are dying waiting for an organ, with additional listed candidates being disqualified as they became too sick for transplantation. This disparity between organ demand and supply has led to continued reassessment of selection and listing criteria for transplantation as well as periodic revisions of allocation and distribution policies for cadaveric livers. The minimal listing criteria adopted in the United States in the late 1990s initially served to prevent inappropriate organ allocation to patients who had risen to high priority for a donor organ simply because they had been listed early and had a longer total waiting time. Many of these patients had lesser disease severity and immediate need for transplantation than other patients competing for the same donor organ but listed later in the natural history of their end-stage liver disease. The United Network for Organ Sharing has continuously revised organ allocation and distribution policies in an attempt to balance the ethical principles of medical justice and utility, which potentially conflict with one another. The principle of justice advocates for the sickest patient who has been waiting for the longest time, whereas that of utility favors the patient with the highest likelihood of achieving successful outcome. Throughout all of the changes in organ allocation rules, patients with fulminant hepatic failure have continued to receive the highest priority for organs. The Model for End-Stage Liver Disease (MELD) has replaced the Child-Turcotte- Pugh system for assessing disease severity and predicted mortality in patients with chronic liver failure. However, the use of MELD has favored listed candidates who have the worst post-transplant survivals. Other options that are being explored to expand the donor pool include the use of marginal donors, split liver transplants, living donors, and domino transplants, with xenotransplantation still remaining experimental.