Left: Doctor examining kidneys of patient in clinic. Center: Kidney dialysis patients. Right: Digital illustration of a kidney.

From Matching Theory to Matching Kidneys

Decades of NSF funding for economic and algorithm research has facilitated thousands of lifesaving kidney transplants every year.

In a race against time, thousands of Americans await a lifesaving kidney transplant. But the chances of finding a compatible donor from their circle of friends and family is slim.

Thanks to the U.S. National Science Foundation, people awaiting transplants now benefit from a computerized kidney matching system that expands the pool of potential live kidney donors (who can donate a kidney without it harming their health) to the entire nation.

Surgeons performing surgery


During the 1980s and 1990s, NSF supported groundbreaking research in economic game theory, including matching theory, which focuses on creating mutually beneficial partnerships, like matching doctors with hospital positions.

In the early 2000s, Alvin Roth and a team of NSF-funded researchers applied matching theory to a new problem: kidney exchange — creating a computerized system that quickly and efficiently matched kidney recipients to compatible live donors.

Their work led to the establishment of the New England Program for Kidney Exchange in 2005, which allowed doctors to arrange lifesaving kidney exchanges for patients in the New England area. And in 2010, the NSF-powered matching system went nationwide.

Future of organ exchange

NSF continues to support advanced matching algorithms, improving the match quality of transplanted organs and increasing the number of successful live donation transplants.

During the 2010s, NSF-powered matching algorithms expanded beyond kidneys to include liver lobe exchanges and multi-organ ("cross-organ") exchanges. This NSF-funded research even led to the world's first liver-kidney swap in 2019, a multi-organ exchange of both a liver and a kidney between two pairs of living donors and recipients.

Four years later in 2023, United Network for Organ Sharing — a nonprofit that manages the U.S. organ donor transplant system — launched the first multi-center liver lobe exchange program.

A diagram where two donors who aren't compatible with their family members who they intended to donate organs to instead donate to each other's intended recipients, who they are compatible with.
A diagram of a kidney-liver donation chain.

Credit: U.S. National Science Foundation

Paying it forward

Today, the majority of live-kidney transplants occur as part of a Never-Ending Altruistic Donor (NEAD) chain.

Pioneered at Johns Hopkins Medicine and funded in part by NSF, a NEAD chain or "daisy chain" begins when one altruistic donor (a donor without a designated recipient) donates a kidney to a person waiting for a transplant. That recipient's willing — but incompatible — donor gives to another person waiting, and so on. Each living donor in this system gives to a stranger, and the chain of donors is kept going as long as possible.

The University of Alabama at Birmingham's ongoing kidney chain is the nation's longest kidney transplant chain, providing more than 100 people with a new lease on life.

A diagram where a non-directed donor donates a kidney to a recipient whose initial donor was incompatible. The incompatible donor donates to a second recipient, and so on.
A diagram of a kidney donation chain.

Credit: U.S. National Science Foundation