UF researchers link longer kidney transplant waiting times to poorer outcomes

November 25, 2002

GAINESVILLE, Fla.--The longer patients on dialysis wait for a kidney transplant once they develop end-stage renal disease, the worse they fare, University of Florida researchers report in the Nov. 27 issue of the journal Transplantation.

The findings reinforce the benefit of transplantation over dialysis for these patients and highlight the importance of placing them on the transplant list as early in the course of their disease as possible, said Dr. Bruce Kaplan, a professor of medicine and of pharmacology and therapeutics at UF's College of Medicine. Dialysis is a mechanical means of filtering toxins from the bloodstream a few times a week, a function the kidneys normally perform around the clock.

"Dialysis keeps you alive, but you do not get the same benefit as with transplantation," said Kaplan, also medical director of the kidney and pancreas transplant program at Shands at UF medical center in Gainesville. "Yet as recently as a year or two ago, people weren't really aware of how bad it was to wait for a kidney. But the time you spend waiting has a huge impact. It becomes critically important, therefore, to get a transplant as soon as possible."

Patients who await transplant for two years, for example, have a three times greater chance of losing their kidneys than those who wait less than six months, he said. UF researchers speculate patients who were on dialysis the longest were sicker at the time of transplantation, which might explain why they didn't do as well as those on dialysis for a short time.

The other key finding: Although patients who receive a kidney from a living related donor typically do better than those who get one from a cadaver, UF physicians found that those benefits fade if patients wait for the living donor organ for two years or longer.

"Our study showed that if you got a cadaveric donor kidney in less than six months or you waited two years to get a live donor kidney, the results were pretty much the same," Kaplan said.

"Everyone in the transplant community is used to saying that living related donors are just better than cadaveric donors," he added. "We assumed a living related donor organ was better because it was coming from a known source, and it could be transplanted right away, without being put on ice and transported. Much of the benefit of a live donor kidney is actually the shortened waiting time. That's why waiting time is modifiable as a risk factor. You can be referred for transplantation earlier and get into the transplant system quicker. And you could try to find a live donor kidney."

Up to now no one had ever assessed whether living donor transplantation was as good as cadaveric transplantation if the patients had to wait, said study co-author Dr. Herwig-Ulf Meier-Kriesche, an associate professor of medicine at UF and the clinical director of renal transplantion.

"Not only is the quality of the donor organ you get important--and living donor transplants are often ideal--if you wait long enough, recipients will not be able to take advantage of the great quality organ they're getting because their health will have deteriorated," Meier-Kriesche said.

Despite these findings, patients should understand that even if they must wait years for the procedure, transplantation still confers tremendous benefit over dialysis, Kaplan said. Other scientists have shown that even after waiting three years, patients live an average of 10 years longer if they undergo transplantation.

"It's better to get the transplant earlier, but even if you get it late, you're still getting an enormous benefit," he said. "Kidney transplantation is pretty much a lifesaving therapy."

Nearly half a million Americans have been diagnosed with end-stage renal disease--their kidneys have failed to a point that without dialysis or transplantation they would die within a relatively short time. Diabetes and high blood pressure are the leading causes of end-stage renal disease. As the incidence and prevalence of those conditions nears epidemic rates--and as the population ages--the number of patients with kidney failure is projected to skyrocket by 2010, according to officials with the U.S. Renal Data System.

Meanwhile, about 50,000 patients are currently awaiting kidney transplantation, a number expected to double by 2010, according to the United Network for Organ Sharing. Yet the availability of donor kidneys is strikingly low. Each year, only 10,000 kidney transplants are performed in the United States. Most patients who undergo transplantation have waited up to three years for an organ.

UF physicians analyzed data from the U.S. Renal Data System and the U.S. Scientific Renal Transplant Registry for transplants performed between 1988 and 1998 to quantify the effect of waiting time on donor organ outcome and patient survival. Specifically, they studied medical records to determine the outcome of 2,500 pairs of cadaveric kidneys; each pair was taken from the same donor. In each case, one kidney went to a patient who had been on dialysis for less than six months, while the other went to a patient who had been on dialysis for more than two years.

After a decade, organ survival rates were significantly worse in patients receiving cadaveric organs who had undergone more than two years of dialysis: 39 percent versus 69 percent for transplant patients on short-term dialysis. For those receiving living donor related organs, nearly half the organs survived in patients who had been on dialysis for a prolonged period, compared with a full three-quarters in patients who had been on short-term dialysis.

"Obviously, it's very important for the patients to know what their options are, and these options need to be discussed and thoroughly reviewed with a nephrologist [kidney specialist]," Meier-Kriesche said. "Nephrologists can slow the time to end-stage renal disease. This is a very important point because a lot of patients who approach end-stage renal disease are not followed by nephrologists. These patients end up on dialysis and then start looking for options. It takes time to find a potential living donor, so they may already have been on dialysis for one or two years before getting their living transplant."

The take-home message: Patients should discuss transplantation with their physician and be tested as soon as possible to see whether they are candidates for the procedure, Kaplan said.

"This is an important issue because it may help to improve outcomes in the future," he said. "An early transplant seems to be the optimal thing to do, but whenever you do get your transplant it's still beneficial."
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For more information contact: Melanie Fridl Ross, 352/690-7051, e-mail: UFCardiac@aol.com

University of Florida

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