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Transplanted pig kidney works in US man's body for record 271 days

James GallagherHealth and science correspondent
Kate Flock/Massachusetts General Hospital The image shows three adults standing closely together in a hospital hallway. The person in the centre is wearing a bright blue polo shirt, while the individuals on the left and right are wearing white medical coats, with a stethoscope visible around the neck of the person on the right. Fluorescent ceiling lights illuminate the corridor, and doors and windows line the walls behind the group. Small embroidered text is visible on the medical coats.Kate Flock/Massachusetts General Hospital
Patient Tim Andrews (centre) with Dr Tatsuo Kawai (left) and Dr Leonardo Riella (right)

A kidney transplanted from a pig has worked inside a patient for 271 days – the longest on record, say US doctors.

Tim Andrews said the transplant gave him "hope" and spared him months of needing to go to hospital to have his blood filtered by a dialysis machine.

The team at Mass General Brigham hospital say their work shows pig organs can be used as a "bridge" until a human transplant becomes available.

But the pig organ eventually failed and was removed so Andrews needed a short bout of dialysis before a donor was found.

Doctors and scientists are exploring xenotransplantation – using organs from other species – due to shortages of organs for transplants.

In the US, around 100,000 people are waiting for a kidney while only 25,000 transplants occur each year. More than 7,000 people in the UK are on the kidney transplant list.

Andrews was told it could take seven years to get to the top of the list, but that people live only five years, on average, on dialysis.

"I had a little bit of a shortage of time… it becomes very depressing," he said.

But he described the idea of a pig transplant as "hope" and the "light at the end of the tunnel".

"Hope is the biggest thing, the chance to be free from the [dialysis] machine and live your life."

Kate Flock/Massachusetts General Hospital The image shows a hospital room with a patient seated in an adjustable bed, wearing a bright blue polo shirt and patterned dark trousers. A healthcare worker dressed in blue scrubs, gloves, a face mask, and a stethoscope is standing beside the bed and handling tubing connected to a medical access point on the patient's upper chest. Various items including syringes, medical packaging, paperwork, and a disposable cup are arranged on a bedside table in the foreground. The room contains hospital equipment such as wall-mounted oxygen and suction outlets, monitoring devices, intravenous poles, and cables connected to equipment near the bed.Kate Flock/Massachusetts General Hospital
Tim Andrews preparing for surgery in January 2025
Kate Flock/Massachusetts General Hospital A close-up view shows gloved hands handling a translucent pink plastic bag on a covered medical table. Inside the bag is a cylindrical container holding red fluid, with a white lid visible near the top. Another gloved hand reaches toward a metal surgical instrument resting on the edge of the table. The background is softly out of focus, revealing a clinical environment with people in blue medical scrubs and equipment. Kate Flock/Massachusetts General Hospital
The donor kidney had been harvested from a genetically modified pig to make it suitable for human donation
Kate Flock/Massachusetts General Hospital A tightly framed photograph shows several members of a surgical team gathered closely during a procedure. Each person is wearing blue surgical clothing, face masks, and magnifying lenses mounted on protective eyewear. The image focuses on their faces and equipment as they lean inward and look down toward an area outside the frame. Bright operating-room lighting illuminates the scene, while the background remains softly blurred in shades of blue. The composition emphasises concentration, precision, and the collaborative nature of a medical procedure.Kate Flock/Massachusetts General Hospital
Surgeons attached the pig kidney to the blood vessels inside Tim Andrews' body so the organ could filter the blood.
Kate Flock/Massachusetts General Hospital The image shows two adults standing together in a narrow area with grey stone or ceramic tiled walls. One person is wearing a bright blue polo shirt and holding a folded grey garment, while the other is dressed in a light-coloured padded winter coat with a thick red knitted scarf and glasses. The two individuals are positioned very close to one another, with an arm wrapped around the other's shoulder. The composition is tightly framed around the pair, drawing attention to their physical closeness.Kate Flock/Massachusetts General Hospital
An emotional Tim Andrews and his wife Karen share an embrace while leaving Massachusetts General Hospital on Feb 1, 2025

Pigs are seen as the ideal animal for xenotransplantation. Their organs are roughly the right size and there have been years of experience farming them.

But you cannot just pop down to the farm and take a kidney from a pig and put it into a person. The human body would immediately identify the organ as foreign and launch a devastating immune assault that would destroy the kidney. It would turn black in minutes as holes are ripped in every cell and the organ clots from the inside.

So researchers have developed Yucatan miniature pigs that have gone through 69 genomic modifications to "humanise" their organs.

These modifications strip out some features of pig cells that our immune system spots and attacks; add some human DNA that acts like camouflage netting to help hide the pig tissue from the immune system and further tweaks disable viruses that hide inside pig DNA to prevent infection.

Andrews had end stage kidney disease as a result of type 2 diabetes and his kidney's were failing.

He was 66 years old when he had the xenotransplant on January 25, 2025.

The transplanted pig kidney worked immediately, according to details just published in the Lancet medical journal.

The kidney continued to function for 271 days until it was removed in October that year. Tim then needed dialysis for 82 days until he had an organ from a donor in January of this year. That organ has been working well.

Dr Leonardo Riella, from the centre for transplantation sciences at Mass General Brigham said the shortage of organs available for transplant meant " we are in a crisis".

"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 where we could potentially bypass dialysis and get them to a transplant," he said.

There were early signs Andrews' organ was being rejected by the immune system, but that was successfully treated by adjusting his medication.

However, after around six months the blood vessels in the kidney started to become damaged and the organ inflamed and then it started to fail.

It is not clear exactly why as there were no signs of antibodies attacking the pig kidney.

In their Lancet write-up the doctors state: "This case illustrates both the promise and the remaining challenges of clinical kidney xenotransplantation."