Man lives with pig kidney for nine months before receiving human transplant in world first

A man with end-stage kidney failure lived without dialysis for nine months after receiving a genetically engineered pig kidney before successfully going on to receive a human donor organ, in a world first that could open up a new approach to tackling the shortage of kidneys available for transplantation.

Tim Andrews was 66 when surgeons at Massachusetts General Hospital in the US transplanted the pig kidney in January 2025 as an experimental treatment for kidney failure. The organ functioned for 271 days without Andrews requiring dialysis, representing the longest period of dialysis-free survival recorded in a living person following a pig kidney transplant.

Doctors were subsequently able to remove the pig kidney and successfully transplant a kidney from a deceased human donor, making Andrews the first patient to transition from a pig kidney to a human kidney transplant. The case has now been reported by researchers from Mass General Brigham in The Lancet and provides important evidence that receiving an animal organ does not necessarily prevent a patient from later receiving a human one.

The pig kidney began functioning immediately after transplantation, although Andrews experienced an early episode of immune rejection which doctors were able to treat. After around six months, his immunosuppressive medication had to be reduced because he developed an infection, and the kidney subsequently experienced inflammation and damage to its small blood vessels. Its function eventually deteriorated to the point that the organ was removed after 271 days.

Andrews briefly returned to dialysis before receiving a human donor kidney in January 2026. One of the major questions for doctors was whether exposure to the pig organ could have changed his immune system in a way that made a later human transplant more difficult, but researchers found no evidence that this had happened. His new human kidney began functioning immediately after transplantation.

Doctors also closely monitored Andrews for the possibility of infections being transmitted from the pig organ, with no pig pathogens detected during the study. The risk of animal-to-human infection remains one of the areas being closely investigated as scientists explore whether xenotransplantation could eventually become a viable treatment.

Xenotransplantation involves transplanting cells, tissues or organs from one species into another. Pigs are considered particularly promising potential organ donors because their organs are similar in size to those of humans, while advances in gene editing allow scientists to make changes designed to make the organs more compatible with the human immune system.

The research is being driven in large part by the continuing shortage of human donor kidneys. Patients with kidney failure can spend years receiving dialysis while waiting for a suitable organ, and some die before one becomes available. Scientists hope genetically engineered pig kidneys could eventually provide another option for some of those patients.

The world’s first transplant of a genetically engineered pig kidney into a living person was performed at Massachusetts General Hospital in March 2024. The recipient, Richard Slayman, died around seven weeks later, with the hospital saying at the time there was no indication his death had been caused by the transplant.

Since then, a small number of patients have received genetically engineered pig kidneys as researchers gather evidence about how long the organs can function and how the human immune system responds to them. The treatment remains highly experimental and is not yet an alternative routinely available to people with kidney failure.

Andrews’ case raises the possibility that pig organs could have another role even if they do not initially last for the remainder of a patient’s life. A genetically engineered kidney could potentially act as a bridge, allowing someone to live without dialysis while they continue waiting for a suitable human organ.

That could be significant because it would mean patients would not necessarily have to choose between an experimental animal transplant and remaining eligible for a human kidney. In Andrews’ case, the pig kidney provided functioning renal support for almost nine months without preventing him from later undergoing a successful human transplant.

Researchers caution that much more evidence is needed before the approach could become widely available. Questions remain about how long genetically engineered organs can survive, how rejection can best be controlled, the risk of infection and the long-term effects of the powerful immunosuppressive medicines recipients require.

For Andrews, however, the experimental transplant achieved something important even though the pig kidney ultimately failed. It kept him free from dialysis for 271 days and helped bridge much of the period until a human donor kidney became available.

His successful human transplant now suggests that animal organs may eventually have a role not only as potential replacements for human organs, but as a way of buying patients valuable time while they wait for one.

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