A man with end-stage kidney failure was kept off dialysis for nine months after being given a genetically modified organ from a pig.

The world-first procedure was carried out by the US-based Mass General Brigham academic centres and hospitals, which said the transplant was intended to be temporary before a permanent human donor could be found.

It marks the longest dialysis-free survival after a pig kidney transplant in a living human, as well as the first transition from pig-to-human kidney transplantation.

Tim Andrews had end-stage kidney failure from Type 2 diabetes. He was 66 when he received the pig kidney in the US in January last year, the team said in the Lancet medical journal.

He lived successfully with the genetically edited organ for 271 days before moving to short-term dialysis and receiving a donor human kidney.

The animal-to-human transplant – known as a xenotransplant – started working immediately. Only after six months did damage develop in the kidney's blood vessels, which then progressed to organ failure, at which point it was removed.

Mr Andrews told a CNN documentary that his genetically modified transplant was a "miracle": "I was alive, and I hadn't been in a long time."

Researchers said no pig viruses or other pig pathogens were detected at any point.

Dr Leonardo Riella, the study's lead author, from the centre for transplantation sciences at Mass General Brigham, said that a shortage of donor organs "is the greatest crisis we have right now in transplantation".

"We know that the best treatment option for patients with end-stage kidney disease who have developed renal failure is transplantation," he added, "but we simply don't have enough human organs to transplant in a timely manner.

"Our vision is that xenotransplantation could help address this gap – initially as a bridge to get patients off dialysis while they wait for a human donor kidney, and potentially, as we establish long-term safety and durability, as a destination therapy in its own right."

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Dr Riella also praised patients willing to take on the experimental transplants as "the true pioneers", adding: "Without their trust and courage, we would not be able to do what we do."

Researchers added that the findings support pig kidney transplantation as potentially a bridge for people facing long waits for a human kidney, while highlighting the need for further research.

Another pig kidney transplant to a living human was undertaken in 2024 at Massachusetts General Hospital, where the patient survived 52 days before dying from heart issues unrelated to the transplant.

Dr Rommel Ravanan, chief medical officer for NHS Blood and Transplant in the UK and a consultant nephrologist, said the US and China have reported several similar transplants since 2022.

There are currently no clinical trials in the UK for a similar procedure, although regulators have looked into how they would work.