PhD Student Alex Chan Develops Algorithm Leading to Rare Three-Way Liver Exchange, Easing Shortage of Organs
A rare three-way exchange of liver transplants in Pakistan was made possible with a new algorithm developed by Stanford Health Policy PhD student Alex Chan. The transaction was one of the world’s first documented three-way liver exchanges and the first to use a new liver exchange algorithm that finds optimal matches from a pool of candidates.
On March 17 of this year, six operating rooms at the Pakistan Kidney and Liver Institute were prepped for six simultaneous surgeries. On three operating tables were patients with end-stage liver disease. On the other three were their relatives — a daughter, a son and a wife — who had agreed to donate a portion of their livers.
The donations, however, weren’t staying in the family. Due to blood type or size, each of the donors’ livers was incompatible with the relative in need of a transplant. A sophisticated algorithm had matched the three pairs of relatives, orchestrating a three-way liver exchange that allowed each patient to receive a compatible, life-saving liver from a stranger.
The transaction was one of the world’s first documented three-way liver exchanges and the first to use a new liver exchange algorithm that finds optimal matches from a pool of candidates. The algorithm, developed by Alex Chan, a graduate student economist working on health policy at Stanford Medicine, has the potential to increase the number of liver transplants, especially in countries like Pakistan, where living donors are the norm.
“Liver exchanges really benefit transplant systems that depend on living donor transplants,” Chan said. “In places like Pakistan, India or South Korea, more than 90% of organs come from living donors because of cultural preferences to keep the body intact after death.”
In the United States, where deceased donors are more common, only 6% of liver transplants in 2021 came from living donors.
To discourage the sale of organs, Pakistan further restricts transplants by requiring that transplant candidates co-register with a donor who is a close relative. As a result, some 30% to 50% of liver transplant candidates in Pakistan are unable to find a compatible donor, and about 10,000 people there die each year waiting for an organ.