WASHINGTON, Feb. 11-- Those who donate a kidney have an "extremely low" risk of developing kidney failure in their remaining organ, U.S. researchers said Tuesday.

Researchers from the John Hopkins University reported in the Journal of the American Medical Association (JAMA) that the risk for kidney donors is much lower than in the population at large, even when compared with people who have two kidneys.

That may be due to the fact that before allowing people to donate an organ, they undergo an extensive screening process to make sure they are healthy enough to survive with just one kidney, the researchers said.

In a previous study, the same researchers found that the risk of death from any cause for kidney donors is extremely low.

They believed that both findings should give reassurance to people wishing to donate a kidney.

To conduct the study, Dorry Segev, a transplant surgeon at the John Hopkins Hospital and his colleagues analyzed medical records of 96,217 adults in the United States who donated kidneys between April 1994 and November 2011 and were followed for up to 15 years after transplant.

The researchers paired these data with information from 20,024 participants in a national health and nutrition examination survey to form two comparison groups, one representative of the general population and one of individuals healthy enough to donate a kidney but who did not do so.

They found that the lifetime rate of kidney failure in donors is 90 per 10,000, as compared with 326 per 10,000 in the general population of non-donors.

In individuals who were as healthy as donors but did not donate, the risk was lower, at 14 per 10,000, they added.

Race also appears to play a role. After 15 years, the risk of kidney failure that the researchers were able to associate with giving a kidney was 51 per 10,000 in African-American donors and 23 per 10,000 in white donors.

In other words, out of every 10,000 donors, 51 African-American donors and 23 white donors are expected to develop kidney failure who would likely not have had they not donated a kidney.

It represents an increased risk, but of a rare event, the researchers noted.

Donating a kidney "is a very personal decision and not one without risk, but this study reminds us that the risk is low enough that most providers in the transplant community feel comfortable letting healthy donors take it, and most potential donors are comfortable enough agreeing to take the risk," Segev said.

"It's certainly safer than many other things we choose to do in our lives," he said.

The researchers added that those few who do experience complications that lead to kidney failure are also given very high priority on transplant waiting lists.