A genetically modified pig kidney worked inside a 66-year-old US man for 271 days, the longest recorded time for a pig kidney to function in a human body. The procedure gave Tim Andrews a record-breaking break from dialysis while he waited for a human donor organ, and it has renewed interest in a technology that could one day change how kidney failure is treated.
Andrews received the experimental transplant at Massachusetts General Hospital in January 2025. He had developed end-stage kidney disease linked to type 2 diabetes, and his condition was becoming difficult to manage. Before the procedure, he was running out of options.
"I had a little bit of a shortage of time, it becomes very depressing," Andrews said, describing life before the transplant.
The pig kidney started working immediately. For nine months, it kept him off dialysis. Doctors saw early signs of rejection and controlled the reaction with medication. But after about six months, the organ's blood vessels began developing problems. The kidney became inflamed and later stopped working. Doctors did not find antibodies attacking the kidney, so the exact reason for the failure is still unclear.
The kidney was removed in October 2025. Andrews spent another 82 days on dialysis before receiving a human donor kidney in January 2026, which doctors say is currently working well.
"I had a little bit of a shortage of time, it becomes very depressing," Andrews said, explaining what life was like before receiving the pig kidney. The experimental procedure gave him something he had been missing. "Hope is the biggest thing, the chance to be free from the [dialysis] machine and live your life."
The procedure is called kidney xenotransplantation. Scientists genetically modify pig organs to reduce the risk of rejection and make them more compatible with the human immune system. They remove pig genes that trigger strong human immune reactions, add human genes that help the organ avoid rejection, and reduce the risk of viruses naturally found in pigs affecting humans. The goal is to make the pig kidney look less like an outsider to the human body.
The need is urgent. More than 90,000 people in the United States are waiting for kidney transplants, according to transplant data. Kidneys from pigs are similar in size to human kidneys and perform many of the same functions, which is why researchers believe they could become another source of organs.
Dr Leonardo Riella from the Mass General Brigham Centre for Transplantation Sciences said the shortage of human organs remains a major challenge. "We are working really hard to bring hope and we truly feel that xenotransplantation can be an alternative for patients who don't have a living donor," he said.
Researchers believe a successful pig kidney could potentially last for decades, similar to a human donor kidney, although this is still being studied.
Kidney xenotransplantation remains experimental and has only been used in very limited cases. In 2025, the US Food and Drug Administration approved the first human clinical trials for the procedure, allowing researchers to properly test whether it is safe and effective.
Scientists say the goal is not to replace human kidney donations completely. It is to create another option for people who have no living donor or who may wait years for a transplant. Andrews' case shows both sides of the technology. It lasted 271 days and gave him nine months without dialysis. It also failed for reasons that are not yet fully understood.
For patients spending years attached to dialysis machines, even a temporary solution could mean more time. Andrews now has a human kidney that is working well. The pig kidney that gave him those 271 days is gone, but the data from his case will inform the clinical trials now getting underway.
According to Pulse.ng.
