Oct. 11, 2000 -- Time is life when it comes to transplanting a kidney. The sooner someone who needs a kidney gets one, the longer he or she is likely to live afterward. And the sooner a donated kidney is transplanted, the better its chances for lasting and functioning well in its new owner. That's why many doctors think it's best to give kidneys to patients who are in the same geographical area as the donor, instead of shipping them around the country.
But a new study published in TheNew England Journal of Medicine shows that matching the donated kidney to the recipient's body is equally important. Most kidney transplants fail because of rejection, when the recipient's immune system attacks the new kidney because it recognizes it as being foreign. When proteins found on the surface of the donor kidney, called HLA markers, closely match those of the recipient's own tissues, the kidney is less likely to be rejected.
In October 1987, the United Network for Organ Sharing (UNOS) established a national kidney-sharing program, hoping to increase the number of HLA-matched transplants by seeking good matches through a nationwide pool.
"When a donor kidney becomes available, we report the HLA [markers] to the central computer in Richmond, Va. Everyone in the U.S. waiting for a kidney is on that list, so the computer can quickly find the best possible match for the kidney," researcher J. Michael Cecka, PhD, a professor of pathology at University of California, Los Angeles, tells WebMD.
Cecka's study analyzed more than 7,000 HLA-matched and 80,000 HLA-mismatched kidney transplants, in which the kidneys came from people who had agreed to donate their organs when they died. More than half of the matched transplants done through the UNOS program lasted for 10 years, compared with about a third of the mismatched transplants. The matched transplants not only lasted longer but were less likely to be rejected.
Even though matched kidneys had to be shipped to the donor, the transplants took place in 23 hours, on average -- only one hour longer than for those in which kidneys were given to HLA-mismatched local recipients.
"Kidney sharing for the purpose of achieving good HLA matches is much more accepted in central Europe than in the U.S., where it still is considered controversial," Gerhard Opelz, MD, a professor of immunology at the University of Heidelberg, Germany, tells WebMD. Opelz was not involved with the U.S. study but is coordinator of the Collaborative Transplant Study, which involves more than 300 transplant centers in 45 countries.
"Our international study shows that the results are very similar in all geographical regions of the world; it is just the perception of clinicians that differs," Opelz says. "Hopefully, this new paper will influence the policy-making body in the U.S."
Another finding of the new study was that HLA-matched kidneys given to black recipients who had high blood pressure lasted only half as long as they did in black recipients with other causes of kidney failure.
"This study shows that not even matched grafts work very well in blacks, especially those with [high blood pressure]. We need to work on improving outcome in this group," says Charles F. Shield, MD, who reviewed the study for WebMD. Shield is director of organ transplantation at Via Christi-St. Francis Hospital in Wichita, Kan.
People with unusual tissue types have more difficulty in getting a matched kidney. Only 3% of black patients in TheNew England Journal of Medicine study received a matched kidney, as most donors were white, and black patients tend to be more difficult to match for HLA markers.
"To add some justice to the system, we factor other things into the decision of who gets the kidney, such as waiting time. Children get higher priority," Cecka says. "Unfortunately, those that are on top of the list because they've been waiting the longest are often the worst candidates."
The National Allocation Program assigns a set number of points for each of the factors, then determines the best possible match, Cecka explains. Only 20% of donated kidneys find an acceptable HLA match, and the rest get transplanted locally.
The researchers note that age should be among the factors taken into consideration. Many kidneys are from older donors, which could fail prematurely in younger recipients, they say.
"We're studying alternate methods to speed up the waiting time before transplantation," Cecka says. "But the biggest problem is simply that there are more people waiting than there are available kidneys." As of Sept. 30, more than 46,000 people in the U.S. were waiting for kidney transplants, the UNOS says. And in 1999, more than 6,000 patients died while waiting for an organ transplant.
Living donors now make up almost half of kidney donations. Kidneys are donated mostly to blood relatives but also to spouses, friends, and even strangers. Lack of understanding and communication sometimes stops organ donation -- the family is always asked to approve cadaver organ donation -- and may decline unless their relative's wishes were clear.
For more information about organ donation, visit the United Network for Organ Sharing web site at www.unos.org.