"Daisy chain" transplants expand patients' options

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"Daisy chain" transplants expand patients' options
Breakthrough method pioneered at Hopkins Hospital may allow endless swaps of precious kidneys for life-saving surgery
By: Lindsey Hutzler
Posted: 4/2/09
Patients with end-stage kidney disease now have an exciting new surgical option. Researchers at the School of Medicine have proposed an alternative method for the matching of patients with kidneys for transplant, thus opening the opportunity for far more life-saving operations.

A major problem with transplants has always been the lack of available organs. Even though many Americans have signed donor cards, the process of matching the appropriate organ to the appropriate recipient takes time.

Currently, most people awaiting a kidney transplant are put on a national list that ranks individuals based on medical urgency and other factors.

Because it takes so long to get to the top of the list, and even the most urgent cases must still wait for an organ that is a biochemical match, transplant patients may have to wait months on dialysis.

The solution, pioneered by Hopkins transplant surgeons, is the "daisy chain" operation. Say a patient, Andrea, needs a kidney of a certain blood type. Her husband, Bryan, is not a match for Andrea, but he is a match for a stranger named Chris. Chris's wife, Diana, is a match for a patient named Emily, and so on.

Theoretically this chain can go on indefinitely, limited only by the number of matches that can be made. Matches are often made among spouses, but sometimes another relative or a close friend steps in.

In a daisy chain transplant, a so-called altruistic donor is needed to give a kidney to one person who doesn't have any match in the chain. The donor is considered altruistic because she is giving up a kidney without receiving one for a loved one in exchange.

If Diana donates her kidney to Emily but no one in the chain has a suitable kidney for Chris, an altruistic donor - Fred - may step in and offer his kidney.

Surgeons set up the chain so everyone gets a kidney and no one backs out. The greatest benefit is that this method bypasses the long wait of the national organ transplant list, while still helping some of the sickest individuals on the list.

The daisy chain, also known as a "non-simultaneous, extended, altruistic donor" (NEAD) chain, was developed and tested at Hopkins Hospital, and was derived from the basic idea of a domino kidney donation. The main difference is that the altruistic donor steps in at the very beginning of the chain in a daisy chain transplant. As a result, the operations do not need to be performed simultaneously. Domino kidney transplants were pioneered at Hopkins as well.

Medical professionals are able to match donors and recipients within a pool of candidates based on the crucial characteristics of blood and tissue antigens, which are unique proteins that the immune system uses to recognize cells or tissues as "native" or "foreign."

Organ rejection happens when the donor's and recipient's antigens are antigenically mismatched, causing the recipient's body to attack the donated organ.

This technique will give many more patients a second chance at life, as it increases the number of organs available to those who are difficult matches.

Surgeons at Hopkins Hospital were among the first in the nation to perform such a transplant in 2001 and have most recently completed a three-way swap through multiple hospitals both domestically and abroad in 2007.

A paper on the subject appears in the March 12 issue of the New England Journal of Medicine.

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