Pig kidney remained functional for 271 days in an American patient

A pig kidney transplant has set a new record after the organ functioned for 271 days in the body of a man from the United States.

Tim Andrews, 66, was living with end-stage kidney disease and underwent the procedure on January 25, 2025. The kidney began working immediately and was removed in October of the same year.

After the pig organ was removed, Andrews spent 82 days on dialysis until a human donor was found in January this year. The kidney transplanted from the donor is functioning well.

For Andrews, the procedure meant several months free from dialysis, a process that uses a machine to filter the blood. He described the transplant as a source of “hope” and as “a light at the end of the tunnel.”

“I was running out of time… it becomes very depressing,” he said, referring to the wait for a human organ.

“Hope is the biggest thing, the chance to be free from the dialysis machine and to live your life,” Andrews said.

Doctors at Mass General Brigham consider the case an important indication of the possibilities offered by xenotransplantation, the use of animal organs for transplantation into humans.

Researchers hope that pig kidneys can serve as a “bridge” for patients waiting for a human transplant. According to doctors, the shortage of organs has created a crisis, while this approach could offer an alternative for people without living donors and spare them long periods of dialysis.

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

Andrews had learned that it could take around seven years for him to reach the top of the transplant list. Meanwhile, patients who remain on dialysis have an average life expectancy of around five years.

Pigs are considered one of the most suitable animals for xenotransplantation because their organs are similar in size to human organs and there is extensive experience in breeding the species.

A regular pig organ cannot be transplanted into a human because the immune system would immediately recognize it as a foreign body and trigger a powerful rejection response.

To overcome this obstacle, researchers have developed miniature Yucatan pigs whose organs are genetically modified. The pig used in Andrews’s procedure had undergone 69 genomic modifications.

These changes are intended to remove certain characteristics of pig cells that are attacked by the human immune system, add human DNA to help camouflage the tissue, and deactivate viruses that may be present in the pig’s DNA.

However, the kidney did not manage to function indefinitely. Signs of rejection by the immune system were observed during the first few months, but doctors were able to treat them by changing the medications.

After about six months, the organ’s blood vessels began to deteriorate. The kidney became inflamed and then began to fail. The exact reason has not yet been determined, as doctors found no signs of antibodies attacking the pig organ.