Hopkins Study Shows Living Kidney 'Paired Donation' An Effective Strategy In Overcoming Donor-recipient Incompatiblities

In the study, published in the Oct. 5 issue of The Journal of theAmerican Medical Association, Hopkins surgeons report successfullyperforming KPD transplants on 21 out of 22 kidney patients whosewilling donors were incompatible by matching them up with otherincompatible pairs. Robert Montgomery, M.D., Ph.D., the director of theComprehensive Transplant Center at Hopkins and lead researcher in thestudy, said the results could pave the way to a national matchingregistry that would enable hundreds and perhaps thousands of patientswho cannot receive a kidney from a loved one to be transplanted byexchanging donors with a stranger.

"This is especially important," Montgomery said, "because it offershope to patients who have compatibility issues that make it difficultfor them to find suitable donors."

KPD is a process in which living incompatible donor-recipientpairs are matched with other living incompatible donor-recipient pairsin order to find successful matches. For example, an incompatibledonor-recipient pair with blood types A and B, respectively, might besuccessfully matched with a donor-recipient pair who has the oppositeincompatibility --- blood types B and A. The kidneys would be exchangedbetween the two pairs so that the A recipient then would receive an Akidney and the B recipient a B kidney.

Montgomery, an associate professor at Hopkins, said KPD is alsoeffective with patients who have tissue incompatibilities. Tissueincompatibility can occur when a patient --- who has either beenpregnant or had a blood transfusion or a previous transplant --- mountsan immune response against the foreign tissue. The condition, calledHLA antigen sensitization, can cause a kidney to be rejected and makepatients incompatible with donors who share their tissue type. As aresult, donor matches are more difficult to find.

"This study shows that KPD can be done with high degree ofsuccess and should be adopted widely with the help of a national KPDlist," Montgomery said. "If you increase the pool of donor-recipientpairs, you increase the number of possible matches."

The study, conducted at Hopkins from June 2001 to November2004, involved kidney transplants performed on 22 recipients referredto Hopkins from all over the United States. Twenty-one of thetransplants were successful. One transplant was unsuccessful becausethe kidney failed.

There are 63,275 patients in United States waiting for kidneytransplants. In many parts of the country, patients wait three to fiveyears for a deceased donor organ. Over the past decade, the number oflive donors has tripled, making it now the most common source ofkidneys for transplantation. Tissue and blood type incompatibilitiesremain the most significant barrier to further expansion of livedonation.

There is a national network already in place that matches deceased-donor kidneys with compatible recipients.

"A similar system now needs to be in place for living donors," Montgomery said.

A matching system for living donors is essential since about 36percent of living donor-recipient pairs will likely be blood-typeincompatible, and about 30 percent of the patients currently on thekidney recipient list have HLA antigen sensitization, Montgomery said.

Montgomery said there are roughly 2,000 to 3,500 patients inthe United States who have living incompatible donors. With KPD, abouthalf of those patients could find a compatible match.

"The only significant gains in finding available kidneys for these patients are likely to come from KPD," Montgomery said.

Live-donor transplants have distinct advantages overdeceased-donor transplants, according to Montgomery. Aside fromcircumventing the long waiting period for deceased-donor kidneys,live-donor kidneys generally last twice as long and work immediately.Kidneys procured from deceased donors can take days or weeks to startfunctioning normally, which means longer hospital stays. Finally, it isless expensive to use a live donor. With deceased-donor kidneytransplants, there are costly acquisition fees related toidentification, management and shipping of the kidney, as well as thecost of the additional hospitalization, Montgomery said.

The Johns Hopkins' Comprehensive Transplant Center has had aKPD program since 2001. In August 2003, Johns Hopkins surgeonsperformed the world's first "triple swap" kidney transplant operation,transplanting the kidneys from three donor and recipient pairssimultaneously.

Other investigators involved in the study, conducted solely atHopkins, were Daniel S. Warren, Andrea A. Zachary, Lloyd E. Ratner,Dorry L. Segev, Janet M. Hiller, Julie Houp, Mathew Cooper, LouisKavoussi, Thomas Jarrett, James Burdick, Warren R. Maley, J. KeithMelancon, Tomasz Kozlowski, Christopher E. Simpkins, Melissa Phillips,Amol Desai, Vanessa Collins, Brigitte Reeb, Edward Kraus, Hamid Rabband Mary S. Leffell.