Potential kidney donors can stop worrying about the long-term effects such a donation might have on their health and longevity.
The first long-term study of kidney donors has found that people who give kidneys to others not only have a normal life span, they also have fewer kidney problems than the general population -- perhaps because they are healthier to begin with. "We've suspected all along that kidney donation is a safe practice, but there has never been a long-term study with large numbers of patients in the United States," said Dr. Hassan N. Ibrahim of the University of Minnesota Medical School, who led the study.
The report published today in the New England Journal of Medicine analyzed the outcome for nearly 3,700 donors who were studied for as long as 40 years.
"We're hoping that these results will make the decision to donate easier for people and alleviate anxiety about living with one kidney," he added.
Kidneys are the most commonly transplanted organ in the United States, with 8,816 transplants performed last year with organs from deceased donors and 4,927 from living donors, according to the United Network for Organ Sharing, or UNOS.
But the need is growing dramatically because of sharp increases in diabetes and high blood pressure, the most common causes of kidney failure.
The National Kidney Foundation estimates that there are 350,000 Americans suffering from end-stage kidney disease, with about 67,000 dying each year without even making it onto the waiting list for transplants. That list currently sits at 78,210, according to UNOS, and the wait for a donor is about five to seven years -- longer than most of the victims survive.
The alternative to transplants is kidney dialysis, but it is a poor substitute because it does not fulfill many of the secondary functions of the kidney, such as the production of hormones. As a consequence, about 20% of dialysis patients die each year.
Earlier studies had suggested that living donors might be the answer. Small studies of World War II war injuries showed that soldiers who lost a kidney in battle were able to function effectively with their remaining kidney, and in the 1960s surgeons began experimenting with living-donor transplants. Such transplants grew increasingly popular, with the number peaking at 6,647 in 2004.
Joel Newman, a UNOS spokesman, noted that there were a couple of highly publicized deaths of living donors early this decade during surgery, leading hospitals to be more selective in whom they would allow to donate.
And Dr. Bryan Becker of the University of Wisconsin School of Medicine and Public Health, president of the National Kidney Foundation, noted that the growing incidence of diabetes and hypertension that has precipitated the need for more donations has also restricted the number of potential donors. People with such conditions, which increase the risk of kidney problems, are not eligible to donate.
Ibrahim and his colleagues collected data on the 3,698 people who donated kidneys at the University of Minnesota between 1963 and 2007 and compared them to a similar number of healthy patients matched for age, gender, body weight and other factors.
The donors "have a very comparable life span" to that of the controls, Ibrahim said, and "it might be better."
Only 11 of the donors themselves developed end-stage kidney disease. That is a rate of 180 cases per million persons per year, compared with the rate of 268 cases per million persons per year in the general population.
The team also studied a representative sampling of 255 donors more intensively. For many years, Ibrahim said, medical schools have taught doctors-to-be that the donors are more likely to develop high blood pressure or protein in the urine, a sign of early kidney disease.
But the new results found that they are not. These "surprising findings," he said, emphasize that these risks have nothing to do with kidney donation but are related to age, weight and other factors."
The donors' mental and physical quality of life were also at least as high as those of the general population, they found.
As a result of these findings, "we are now able to quantify risks to donors in ways we have not been able to do with quite as much accuracy as before," Becker said.
Ibrahim attributes the results in large part to the fact that physicians screen donors carefully for good health. But he also believes that the donors simply feel better about themselves "for having made a difference in the person to whom they donated a kidney."