A Johns Hopkins study has affirmed the success of
living kidney "paired donation" as a means of efficiently
finding more kidney donors who are a match for patients in
In the study, published in the Oct. 5 issue of The
Journal of the American Medical Association, Johns
Hopkins surgeons report successfully performing KPD
transplants on 21 out of 22 kidney patients whose willing
donors were incompatible by matching them up with other
incompatible pairs. Robert Montgomery, the director of the
Comprehensive Transplant Center at Johns Hopkins and
lead researcher in the study, said the results could pave
the way to a national matching registry that would enable
hundreds and perhaps thousands of patients who cannot
receive a kidney from a loved one to be transplanted by
exchanging donors with a stranger.
"This is especially important," Montgomery said,
"because it offers hope to patients who have compatibility
issues that make it difficult for them to find suitable
KPD is a process in which living incompatible
donor-recipient pairs are matched with other living
incompatible donor-recipient pairs in order to find
successful matches. For example, an incompatible
donor-recipient pair with blood types A and B,
respectively, might be successfully matched with a
donor-recipient pair who has the opposite incompatibility
— blood types B and A. The kidneys would be exchanged
between the two pairs so that the A recipient would receive
an A kidney and the B recipient a B kidney.
Montgomery, an associate professor, said KPD is also
effective with patients who have tissue incompatibilities.
Tissue incompatibility can occur when a patient who has
either been pregnant or had a blood transfusion or a
previous transplant mounts an immune response against the
foreign tissue. The condition, called HLA antigen
sensitization, can cause a kidney to be rejected and make
patients incompatible with donors who share their tissue
type. As a result, donor matches are more difficult to
"This study shows that KPD can be done with high
degree of success and should be adopted widely with the
help of a national KPD list," Montgomery said. "If you
increase the pool of donor-recipient pairs, you increase
the number of possible matches."
The study, conducted at Johns Hopkins from June 2001
to November 2004, involved kidney transplants performed on
22 recipients referred to Johns Hopkins from all over the
United States. Twenty-one of the transplants were
successful. One transplant was unsuccessful because the
There are 63,275 patients in the United States waiting
for kidney transplants. In many parts of the country,
patients wait three to five years for a deceased donor
organ. Over the past decade, the number of live donors has
tripled, making it now the most common source of kidneys
for transplantation. Tissue and blood type
incompatibilities remain the most significant barrier to
further expansion of live donation.
There is a national network already in place that
matches deceased-donor kidneys with compatible
"A similar system now needs to be in place for living
donors," Montgomery said.
A matching system for living donors is essential since
about 36 percent of living donor-recipient pairs will
likely be blood-type incompatible, and about 30 percent of
the patients currently on the kidney recipient list have
HLA antigen sensitization, Montgomery said.
Montgomery said there are roughly 2,000 to 3,500
patients in the United States who have living incompatible
donors. With KPD, about half those patients could find a
"The only significant gains in finding available
kidneys for these patients are likely to come from KPD,"
Live-donor transplants have distinct advantages over
deceased-donor transplants, according to Montgomery. Aside
from circumventing 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 start functioning
normally, which means longer hospital stays. Finally, it is
less expensive to use a live donor. With deceased-donor
kidney transplants, there are costly acquisition fees
related to identification, management and shipping of the
kidney, as well as the cost of the additional
hospitalization, Montgomery said.
The Johns Hopkins Comprehensive Transplant Center has
had a KPD program since 2001. In August 2003, Johns Hopkins
surgeons performed the world's first "triple swap" kidney
transplant operation, transplanting the kidneys from three
donor and recipient pairs simultaneously.
Other investigators involved in the study, conducted
solely at Johns Hopkins, were Daniel S. Warren, Andrea A.
Zachary, Lloyd E. Ratner, Dorry L. Segev, Janet M. Hiller,
Julie Houp, Mathew Cooper, Louis Kavoussi, Thomas Jarrett,
James Burdick, Warren R. Maley, J. Keith Melancon, Tomasz
Kozlowski, Christopher E. Simpkins, Melissa Phillips, Amol
Desai, Vanessa Collins, Brigitte Reeb, Edward Kraus, Hamid
Rabb and Mary S. Leffell.