LONDON (Reuters) - Kidney transplants from living donors have surged worldwide over the past decade, researchers said Wednesday, adding more organs are still needed from people who have just died.

They estimated 27,000 transplants take place every year from living donors -- representing 39 percent of all kidney transplants -- with majority in the United States, Brazil, Iran, Mexico and Japan.

"Our study shows that living donor kidney transplant rates have steadily risen in most regions of the world increasing its global significance as a treatment option for kidney failure," the researchers wrote in Nature's journal, Kidney International.

Better understanding of these global rates is important as severe kidney disease requiring transplants rises worldwide due to aging populations and unhealthy diets leading to diabetes and other conditions, they said.

Researcher Lucy Horvat and her colleagues at the University of Western Ontario in Canada said understanding who donates and why in different countries can help officials find ways to increase kidney and other organ donations.

"This is the first comprehensive report of its kind and it emphasizes the growing significance of living kidney donation worldwide," Horvat said in a telephone interview.

A kidney transplant can get a person off dialysis and back to a normal life but the shortage of deceased donors pushes more people to seek an organ donation from a friend or relative, Horvat said.

Her team analyzed data from health registries, transplant networks, published studies and national health ministries in 69 countries.

They estimated the number of living kidney donor transplants grew over the last decade, with more than half of the countries reporting at least a 50 percent increase.

The researchers said Saudi Arabia ranked highest in the world for its living kidney donation rates, with most donors unrelated to the recipients.

Iran came in third and has no waiting list, likely due to a controversial system under which patients can pay for donated kidneys.

The researchers only reported legal living donations and said the overall number is likely higher.

The World Health Organization estimates about 10 percent of all organ transplants worldwide involve unacceptable or illegal transplants.

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