Advances in kidney exchange, in the New England Journal of Medicine

One of the satisfying things about the ongoing collaboration between economists and kidney surgeons is that sometimes the results are very concrete. Today's New England Journal of Medicine reports on such a case in the article: Rees, Michael A., Jonathan E. Kopke, Ronald P. Pelletier, Dorry L. Segev, Matthew E. Rutter, Alfredo J. Fabrega, Jeffrey Rogers, Oleh G. Pankewycz, Janet Hiller, Alvin E. Roth, Tuomas Sandholm, Utku Ünver, and Robert A. Montgomery, “A Non-Simultaneous Extended Altruistic Donor Chain,” New England Journal of Medicine, 360;11, March 12, 2009. The paper reports a chain of kidney surgeries that resulted in ten transplants. It began with an altruistic donor, and was able to accomplish so many transplants because they didn't all have to be done simultaneously. There's a simple economic idea at work here. Mostly in kidney exchange, all the surgeries are done simultaneously. The reason is that if two patient-donor pairs are exchanging kidneys, and if one pair were to donate a kidney to the other first, and the other were subsequently unable or unwilling to reciprocate, the pair that donated the kidney would be severely harmed; not only wouldn't they get the kidney they had been counting on, but they would have donated their donor's kidney and thus be unable to participate in a future exchange. But if there is an altruistic donor who doesn't have a specific patient in mind, and if he or she gives to a patient-donor pair, and they can't subsequently continue the chain, that is a loss, but no one is irreparably harmed. So, when chains begin with an undirected donor, they don't have to be simultaneous, since the costs of a breach are less. Mike Rees and the Alliance for Paired Donation are the heroes of this story: here is the APD's press release. Here's a story from the Boston Globe, that emphasizes the Boston/economist connection of Roth, Sonmez and Unver: Kidney-transplant chain broadens donations. Here's an article from the Pittsburgh Post Gazette that takes note of the collaboration with Carnegie Mellon computer scientists, represented in the NEJM paper by Tuomas Sandholm: Altruistic kidney donations.