Editor’s note: this story has been updated with a correction on the percent of offers of living donors accepted by transplant centers. That percentage has improved from 15% in  2007 to 50% today.

ORLANDO, Fla. — Good things don’t always have to come to an end. But they may need some re-tooling at times.

Economist Alvin Roth, PhD, believes that about the kidney exchange program he developed with transplant surgeons back in the late 1990s. He is one of the founders of the New England Program for Kidney Exchange, a registry and matching program that pairs compatible kidney donors and recipients. He, along with fellow economist Lloyd S. Shapley, were awarded the Nobel Memorial Prize in Economic Science in 2012 for their work on market design and matching theory. For Roth, that included paired exchange programs for organ donations.

The idea of the exchange is simple, yet the moving parts can be complex. Individuals wanting to donate an organ to a loved one may not have the correct blood type. The exchange creates a pathway for that person to donate their kidney to someone else, in exchange for a kidney from a donor compatible with their loved one. Thus, two donated organs are paired and exchanged and transplanted into recipients with the correct blood type. The surgeries are performed at the same time so one individual can’t back out of donation.

But Roth, the keynote speaker at the National Kidney Foundation’s Spring Clinical Meetings last week, knew after that first paired exchange at a Rhode Island hospital in 2000 that there were ways to expand the benefit. That first paired exchange grew in size; a chain at the University of Wisconsin last year involved 68 people (34 donors and 34 recipients) at 26 hospitals nationwide. The University of Alabama has the record for transplants within a single hospital system.

Organ donations slowing down

But while the exchange programs have lead to dozens of successful transplants being performed, they are dependent on one important ingredient: living donors.

Deceased donor transplants vs living donor transplant 2012 to 2016

Source: United Network for Organ Sharing, 2016. Reprinted with permission.

While there were 6,000 kidney transplants from live donors performed in 2016, the annual number of donors has remained stagnant from 2012 (5,619) to 2016 (5,629).

The good news is that there were 200 non-directed donor kidneys in kidney exchanges that took place last year. A non-directed donor is someone willing to donate an organ to a recipient without requiring a donor in exchange. Such donations may help expand the number of donors within an exchange, said Roth.

Aside from the slowdown in donations, there are other reasons why the large kidney exchanges have lost some steam.

  • Hospitals, particularly smaller transplant programs, are opting for the simple four-person exchange (two donors/two recipients) and avoiding the more complicated exchanges.
  • While the acceptance rate of “offers” to donate kidneys for an exchange has improved—in 2007 about 15% of offers resulted in transplants; today, that is up to 50%—they can be rejected for various medical reasons.  That can derail a complex transplant chain. An organization called the Alliance for Paired Donation has helped transplant centers to create thresholds for donated organs, so that the exchange programs can better predict when organs will be rejected.
  • Organ acquisition charges vary considerably between hospitals, so it’s difficult for the costs in an exchange to be evenly distributed.

Including deceased donors in kidney exchanges

To help with the slowdown in living donation rates, some transplant exchange advocates are looking at the value of including deceased-donor kidneys. Walter Reed Military Hospital in Bethesda, Md. is starting such a chain, said Roth.