World first: Pig kidney saves man facing 7-year dialysis death sentence

Medical Miracle: A genetically modified kidney worked in a man for 271 days. It is the longest a kidney from an animal has worked in a human so far, offering hope to patients waiting for a human donor.

The transplant was carried out on Tim Andrews, a 66-year-old man who was suffering from renal failure after he developed severe kidney disease caused by type 2 diabetes. The procedure took place on January 25, 2025.

Doctors at Mass General Brigham said the case shows how pig organs could potentially be used as a temporary “bridge” for patients who need a kidney while they wait for a human donor.

The transplanted kidney started working immediately after the operation and continued to function for 271 days, according to details published recently in the medical journal The Lancet.

The organ eventually stopped working and had to be removed in October 2025. Andrews then underwent dialysis for 82 days before receiving a kidney from a human donor in January this year. His new kidney is now working well.

Andrews had been told that he could have to wait seven years for a human kidney. Patients who depend on dialysis live for an average of about five years, leaving him with little time while waiting for a transplant.

“I had a little less time. It gets very frustrating,” he said.

He described the idea of receiving a pig kidney as a source of “hope” and “a light at the end of a dark tunnel”.

“Hope was the biggest thing that gave me the opportunity to get off the machine and live my life,” he said.

The shortage of human organs has led doctors and scientists to study xenotransplantation, a process in which organs from animals are transplanted into humans.

About 100,000 people in the United States are waiting for a transplant, while only around 25,000 procedures are carried out each year. In the United Kingdom, more than 7,000 people are on the waiting list for a kidney transplant.

Pigs are considered one of the most suitable animals for xenotransplantation because their organs are close to human organs in size. Humans also have decades of experience raising pigs.

A normal pig kidney cannot simply be removed and transplanted into a human body. The human immune system recognises the organ as foreign and can launch a powerful response that destroys it.

Within minutes, holes can start forming in the kideny, cells can suffer widespread damage and blood can begin clotting in the organ, causing it to turn dark.

Researchers have therefore developed genetically modified Yucatan miniature pigs. Their genes have been modified in 69 ways to make their organs more compatible with the human body.

Some of the changes remove features from pig cells that can be recognised and attacked by the human immune system. Researchers have also added some human DNA to create a form of camouflage that helps hide pig tissue from immune cells.

Other genetic changes are engineered to disable viruses hidden in pig DNA, reducing the risk of infection after transplantation.

Andrews’ case provides the longest recorded period of function for a transplanted pig kidney in a human patient.

Early signs suggested that his immune system was rejecting the organ, but doctors successfully treated the problem by changing his medication.

However, around six months after the transplant, the blood vessels in the kidney began to suffer damage. The organ developed swelling and eventually stopped working.

Doctors said they could not determine the exact cause because they found no signs of an antibody attack against it.

They said shortage of organs available for transplant meant “we are in a crisis”.

“We are working very hard to provide hope. We truly believe xenotransplantation could be an option for patients who don’t have a donor. It could potentially allow us to bypass dialysis and get them to transplantation,” said Dr Leonardo Riella from Mass General Brigham’s Center for Transplantation Sciences.

The doctors wrote in The Lancet, “This case demonstrates both the potential and challenges of clinical kidney xenotransplantation.”