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Before Transplantation | Liver

LIVER TRANSPLANTATION

In the past 20 years, liver transplantation has become a standard treatment for patients with acute liver failure, end-stage chronic liver disease, certain metabolic diseases and in some types of liver cancers.

MATCHING LIVER FROM A DECEASED DONOR

To match organs between deceased donors and potential recipients, there is a centralized computer network — called UNetSM — available 24 hours a day, seven days a week. The network – run by the United Network for Organ Sharing (UNOS) — links all transplant hospitals and organ procurement organizations using secure passwords.

Medical information about the deceased donor is matched against transplant candidates. In general, this "match run" automatically creates a ranked list of suitable candidates for each organ based on several factors including:

• Blood type
• MELD score of the recipient
• Time on the waiting list
• Geographic factors (distance between the potential recipient and the donor)
• Degree of medical urgency

Liver Allocation from Deceased Donors

Patients on a waiting list for a liver transplant are assigned a status code indicating their risk of death or degree of medical urgency. This status code is called the MELD (Model for End-Stage Liver Disease) or PELD (Pediatric End-Stage Liver Disease) score. The system offers livers to candidates with the highest MELD/PELD scores first. Patients with acute liver failure who require liver transplantation are a special category on the waiting list, ranking highest in a classification called "Status 1".

In adults, the MELD score ranges from 6 (less ill) to 40 (gravely ill). The number is calculated using the most recent laboratory tests. The lab tests that are used to calculate are:

• Bilirubin (measures bile excretion by the liver)
• Creatinine (a measure of kidney function)
• International Normalized Ratio (measures the liver’s ability to make blood clotting factors)

Geographic factors are also considered.

There are four levels within the MELD severity scale that determine how frequently the score is required to be updated:

• Greater than or equal to 25: Weekly lab test are required to update score
• 24-19: Monthly lab tests are required to update score
• 18-11:Lab tests are required every 3 months to update the score
• Less than or equal to 10: Lab tests are required every 12 months

To calculate your MELD score, you can use the UNOS MELD calculator

Expanding the Pool of Donated Livers

There several ways to increase the pool of livers from deceased donors including splitting the liver from a single donor and accepting organs from "extended criteria donors" (ECD). Although there is no universally accepted definition of ECD, some of the criteria are advanced donor age; longer time that the donated liver is without blood supply; need for medications to increase blood pressure in the donor; and donation after the donor’s heart stops beating.

Transplant doctors continue to evaluate the risks to the recipient associated with ECD organ transplantation.

LIVER SUPPORT SYSTEMS

Artificial liver support systems have been developed to help the liver remove toxins from the body. Although experimental, these systems provide temporary support to allow the liver to regenerate on its own or until a suitable organ becomes available for transplantation.

FINDING A LIVING DONOR

Living donor liver transplantation involves taking part or all of one of the two lobes of the donor's liver and transplanting it into the recipient.

Some living donors are related to the organ recipient — genetically and/or emotionally — whereas others are not. Some individuals donate an organ explicitly for a single recipient.

The types of living organ donations are described below:

Related

Blood relatives of transplant candidates are considered related living donors. These include:

• Siblings
• Parents
• Other blood relatives

Non-Related

Individuals not related by blood but with an emotional bond to the transplant candidates are considered unrelated living donors are. These include:

• Wife or husband
• In-law relatives
• Friends, neighbors, co-workers

Non-Directed

Non-directed donation refers to donation by altruistic or "good Samaritan" donors who are anonymous to the recipient.

References
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Childress. Organ Donation: Opportunities for Action. National Academies Press: Washington, DC; Report of the Institute of Medicine Committee on Increasing Rates of Organ Donation
Gordon. Surg Today. 2009;39:746-51.
Guiding principles on human organ transplantation. World Health Organization. Lancet 1991;337:1470–1471
Lopez. Mt Sinai J Med. 2006:1056-66
OPTN: Organ Distribution. Allocation of Livers. Policy 3.6
Truog. Med Ethics. 2005;12:5-8.