EUGENE (Oregon) • At the 2012 London Olympics, Aries Merritt of the United States won a gold medal in the 110m hurdles. Several weeks later, he shattered the world record in 12.80 seconds, which still stands.

A year later, he faded to sixth at the 2013 world track and field championships in Moscow. He had none of his usual acceleration over the final five of 10 hurdles. Something was wrong.

By October 2013, Merritt felt tired, drowsy. Food passed quickly through him. His ankles began to swell. He pressed his fingers against his legs and the indentation remained, he said, "like a marshmallow".

Alarmed, he went to the emergency room at the Mayo Clinic in Phoenix, where he had recently moved. Doctors discovered that he had a rare, acute and rapidly progressing kidney disease known as collapsing focal segmental glomerulosclerosis, or collapsing FSGS.

His kidneys had minimal function and were scarred and as wrinkled as prunes.

Dr Leslie F. Thomas, the kidney specialist who treated Merritt, said the cause of collapsing FSGS in the hurdler was not known. Had the disease progressed unabated for a "few months," he said, Merritt would probably have experienced complete kidney shutdown.

He also became anaemic. Last Sept 1, he underwent a transplant with a kidney donated by his older sister.

Remarkably, four days earlier, he won a bronze medal at the world track and field championships in Beijing. Merritt's kidney function was less than 20 per cent at the time, Dr Thomas said.

Beginning yesterday, Merritt will attempt to qualify for another Olympic team at the national track and field trials, with the aim of winning a second gold medal next month at the Summer Games in Rio de Janeiro.

He has seldom raced this season. His speed has not fully recovered, and each time his trail leg clears a hurdle, his right thigh slaps against his abdomen, leaving him with a numbing, tugging feeling and the occasional spasm.

Still, Merritt, who will turn 31 on July 24, said: "I need to go to Rio. If I can run, I need to be able to defend my title. I need to make a way out of no way."

His doctors are concerned about the Zika virus in Rio, he said, because he is taking drugs that suppress his immune system. But skipping the Olympics, his sport's most visible competition, is not an option for him.

"He has a part of me," said Merritt's sister, Latoya Hubbard, who donated her kidney to him.

"He has something that is helping him, like he has the best kidney in the world right now."

NEW YORK TIMES