The AP reported on Dec 14 that three kidney transplant chains involving a total of 26 patients has just been completed at Georgetown University Hospital and Washington Hospital Center, both in Washington DC. Each chain started with an altruistic donor, one of whom is a volunteer for the National Kidney Foundation who wanted to “walk the talk.” The article indicates that the number of surgeries could have been greater, but one donor-recipient pairs was dropped because of health issues and one of the chains was broken when a recipient was unable to tolerate the anesthesia and his surgery was halted. The donor kidney was given to another patient who was not paired with an unmatched donor, stopping the chain. The AP provided a slideshow of images on Dec 15 and a chart outlining the chain of donors and recipients.
Flowchart showing three intertwined exchanges. Image from Georgetown University Hospital
Unfortunately, the article doesn’t make clear why all the surgeries were done in a short time span. Each chain could have been done separately. Further, one of the advantages of chains started by altruistic donors is they eliminate the need for simultaneous surgeries, as explained below. For an example of a long slowly growing chain see a Nov 2009 blog post that highlights a single chain involving 21 patients that has been going on for over two years now.
In a 2-pair exchange (see figure below), two unmatched pairs, labeled 0 and 1, agree to swap donors. The exchanges are almost always done simultaneously. If they do not, there is a risk of the following scenario. Let’s say the donor in pair 0 and recipient in pair 1 complete the transplant. Then later, before the transplant between the donor in pair 1 and recipient in pair 0 can take place, the donor is no longer available (either because of health reasons or the donor declines the surgery). Now the recipient in pair 0 is in a much worse position. He/she does not get a kidney and will no longer have an unmatched donor available to re-enter the exchange.
Two-pair kidney swap. Image by George Taniwaki
The need for simultaneous surgeries is eliminated with chains started by altruistic donors. As can be seen below, if any donor becomes unavailable, the next unmatched pair in the chain is only slightly worse off than before. The recipient no longer has a matched kidney available, but can re-enter the exchange to find a new one.
Kidney chain. Image by George Taniwaki
A very surprising fact about the chain started by the altruistic donor at the NKF is that he was not the first person in his chain to donate chronologically. I have never seen this before in any other donor chains I have read about. At least two of the recipients in his chain received transplants after their donors gave their kidneys to someone else. This can be seen clearly in a diagram provided by the hospital.
[Update1: I added a link to the chart and added comment that the chains could have been longer.]
[Update2: Added comment that new diagram provided by Georgetown Hospital reveals an unusual aspect of this chain is that the donations were not sequential.]