Pedro Rivera, a phlebotomist at Roper Hospital Berkeley, has suffered the trials of being on a transplant waiting list and enduring near-daily dialysis since his kidneys began to fail him seven years ago.

Kristy Hill, an oncology nurse at the same hospital, noticed the way Rivera spoke gently and compassionately to her patients during the two years the pair worked together.

"I really don't need two kidneys," she recalled saying.

Hill, 34, approached her co-worker in May.

"What's your blood type?" she asked him. "Could you take a kidney from a living donor?"

"Yeah, do you know someone?" Rivera, 43, replied with a chuckle.

The kidneys' main function is to clear waste from the blood. The two organs also regulate salt and potassium and produce hormones that affect blood pressure and red-blood cell production. A healthy person can live with one kidney, which will compensate for the lost organ.

After three months of testing, Rivera successfully received one of Hill's kidneys Wednesday in a transplant performed at Medical University Hospital. By Wednesday night, both were resting in their hospital rooms, expected to leave the hospital in the coming days.

The two discussed their procedure -- and their budding friendship -- earlier this week.

Rivera, who also works as a volunteer firefighter in Berkeley County, had been tethered to a dialysis machine three hours a day, six days a week for the past seven years.

This spring, he spoke about the procedure for becoming an organ donor during a health care forum at Roper. Hill, who knew her co-worker needed a kidney, was in the audience. She was surprised by what Rivera hadn't said.

"I can't believe he didn't say anything about himself," she told herself.

Hill approached him about her willingness to be his donor within days of the forum.

"I thought she was crazy," Rivera recalled. "But I could tell by her face she was very serious."

Hill, who'd already discussed the possibility with her husband, was sure of her commitment.

"Pedro held my hand," she recalled. "He said, 'have you really thought about this?' "

Blood tests soon confirmed that Rivera's body could accept Hill's kidney. Hill called Rivera to tell him the news.

"He said, 'I've gotta go! I've gotta go call my wife,'" Hill remembered.

Rivera, a native New Yorker, reflected on Hill's kindness.

"Who would know this girl from South Carolina would donate to me?" he said.

Hill, who treats cancer patients, explained her decision.

"When my patients come in, they're not doing so great," she said. "Pedro would sit and talk with them. Instead of just waiting in the treatment room, my patients had someone who'd listen and hang out with them."

She dismisses questions about the burden of the surgery.

"I saw Pedro as someone who was a blessing to the people around him," she said. "I want to help him live a longer, happier life."

Rivera, who checks in on his friend at work when he can, thought about how his life will change.

"I'm going to have lots more free time," he said.