More than 100,000 Americans are currently on transplant waiting lists, according to the Organ Procurement and Transplantation Network, U.S Department of Health and Human Services.
Of them, around 11,403 need a liver. Approximately twelve people on the waiting lists die each day.
Though most liver transplants (95 percent) are whole livers from deceased donors, partial transplants from liver donors are on the rise as the liver can regenerate itself.
The number of living donor liver transplants performed in 2019 was 30 percent higher than in 2018, but the gap between the demand for liver transplants and the number available is increasing by the day. And as per clinical practice, donor livers cannot be stored for more than 12 hours on ice before transplantation, so the number of organs that can be matched to transplant recipients is limited.
But, there is hope.
A promising technique
A patient who received a human liver that was preserved for three days outside of the body using machine perfusion remains healthy after one year, according to a paper published in Nature Biotechnology.
This technology is likely to increase the number of livers available for transplantation whilst allowing surgery to be scheduled days in advance, saving lives.
Pierre-Alain Clavien and colleagues demonstrate the preservation of a human liver for three days outside of the body using a machine that performs a technique known as ‘ex situ normothermic perfusion’.
The technique involves the organ, while outside the body, being supplied with a blood substitute at normal body temperature. The liver was transplanted into a patient suffering from several serious liver conditions, including advanced cirrhosis and severe portal hypertension.
The transplanted liver functioned normally. It sustained only minimal injury as the blood flow from internal blood vessels returned. A basic immunosuppressant regime was needed during the first six weeks after transplantation.
Without any signs of liver damage, such as rejection or injury to the bile ducts, the patient rapidly recovered their quality of life.
They continue to remain healthy one year after surgery.
A platform to investigate novel therapeutic interventions
According to the paper Maximizing organs for donation: the potential for ex situ normothermic machine perfusion, the technique provides a distinct opportunity to objectively assess donor organ function outside the donor body. It could then recondition those who were deemed unsuitable on initial evaluation to implantation in the recipient.
The study also states that normothermic perfusion provides a platform to aid the 'use of established and novel therapeutics', without worrying about the side effects that are usually taken into concern when treating the patient.
Contrary to the conventional static cold preservation, ex situ machine perfusion is also likely to better preserve donor's livers.
More research necessary
The waiting list is by no means like a queue. People who are in critical condition with acute liver failure go straight to the top of the list. The majority of people on the list would have chronic liver failure and/or liver cancer. Healthcare providers use a scoring system to rank their conditions.
The scoring system for chronic liver disease is called MELD (Model for End-Stage Liver Disease) or PELD (Pediatric End-Stage Liver Disease). It is calculated by blood test results.
Though ex situ normothermic perfusions could be a gamechanger in the field and reduce the number of people on waiting lists, the authors caution that further research with more patients and longer observation periods is imperative.