Tim Andrews, 66, spent 271 days without a single dialysis session after surgeons at Massachusetts General Hospital gave him a genetically edited pig kidney in January 2025.
When the organ began to fail last October, he went back on dialysis, and this January he received a human donor kidney that started working immediately.
His case, published in The Lancet on September 3, is the first published account of a pig organ serving as a working bridge to a human transplant.
The Mass General Brigham team argues that xenotransplantation, the use of animal organs in people, can buy time for patients stuck on a long waiting list.
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What actually happened inside the patient
Andrews had lived with end-stage kidney disease caused by type 2 diabetes and had been on dialysis for more than two years.
His O blood type made a human match especially difficult, and Mass General Brigham notes his likely wait was five to ten years.
The pig kidney, supplied by eGenesis in Cambridge, Massachusetts, carried 69 changes to its genome.
Ten alterations were designed to prevent immune rejection and blood clotting problems in a human, and 59 more inactivated ancient retroviruses buried in the pig genome that could in theory infect a person.
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The organ started working right away.
An early episode of T-cell-mediated rejection, in which the body's immune cells attack the transplant, was treated successfully.
No pig viruses were detected in Andrews during the months that followed.
Why the pig kidney eventually failed
At around six months, doctors reduced Andrews' immunosuppression so his body could fight off an infection.
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Soon after, the transplant developed injury and inflammation in its small blood vessels, and function declined until surgeons removed the kidney on October 23, 2025.
Andrews went back on dialysis, then received a human kidney in January 2026.
That organ, the researchers report, functioned immediately and showed no sign that his immune system had been sensitized by the pig kidney, an important reassurance for future patients hoping xenotransplantation will not spoil their chances of a later human transplant.
"The organ shortage is the greatest crisis we have right now in transplantation," said Dr. Leonardo Riella, medical director for kidney transplantation at Mass General Brigham and lead author of the paper.
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What it means for the waiting list
More than 95,000 Americans are on the kidney transplant list, part of a broader U.S. transplant waiting list of over 103,000 people.
Kidney candidates typically wait one to five years, and thousands die each year before an organ becomes available.
Andrews is the second person in the United States to receive a genetically edited pig kidney and live long enough to be discharged home.
Earlier attempts, including in an Alabama woman whose pig kidney was removed after about 130 days in the spring of 2025, ended sooner.
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An earlier surgery in New York showed that pig organs could function inside a person at all.
Andrews' 271 dialysis-free days push the question forward: can a pig organ hold up long enough to keep someone healthier while they wait?
The Mass General team stops well short of claiming pig kidneys are ready for routine use.
Both eGenesis and United Therapeutics are preparing formal clinical trials to answer that question in more patients.
For anyone facing end-stage kidney disease, decisions about dialysis, transplant listing and treatment options still need to be worked through with a nephrologist.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.