A woman has lived with a pig kidney for more than nine months without requiring dialysis, marking a record-setting achievement. The operation took place at Massachusetts General Hospital on November 22, 2025. As of September 1, 2026, the kidney has been functioning for 285 days, according to eGenesis, a Cambridge, Massachusetts-based biotech company that utilized Crispr gene editing to make the organ suitable for human transplantation. The previous record for a person living with a transplanted pig kidney was 271 days, held by Tim Andrews.
Individuals in need of a kidney transplant typically wait three to five years on average, although this can vary based on blood type and other factors. During this waiting period, many patients require dialysis, a procedure that connects a person's blood vessels to a machine that removes excess fluid and waste from the bloodstream. Dialysis usually involves four-hour sessions three times a week and can lead to damage of blood vessels over time, making it challenging for patients.
Pig kidneys are being explored as a potential alternative to human organs, as they are similar in size and function. Scientists are genetically modifying these organs to prevent immediate rejection and minimize the risk of transmitting pig viruses to transplant recipients. Mike Curtis, CEO of eGenesis, stated that patients' health deteriorates the longer they are on dialysis, and the chances of receiving a human transplant do not increase quickly enough to match their declining health.
The woman who has surpassed the nine-month milestone is the fifth individual to receive an eGenesis kidney through an expanded access regulatory pathway. This pathway, sanctioned by the Food and Drug Administration (FDA), allows patients with serious or life-threatening conditions to access experimental treatments when no viable alternatives exist.
Andrews, who received a pig kidney in January 2025, had it removed in October 2025 due to decreasing kidney function. He returned to dialysis but subsequently received a human kidney transplant in January 2026. Another individual also successfully received a human transplant after having a pig kidney for eight months, according to eGenesis.
The surgical team that performed the transplants published a paper in The Lancet medical journal detailing Andrews’ experience, noting that his pig kidney failed due to thrombotic microangiopathy, which involves the formation of tiny blood clots in the transplanted organ. The team is using this information to modify the immunosuppressant medications for pig kidney recipients and the frequency of their administration. Recipients of human organ transplants also require immunosuppressive drugs to prevent organ rejection, which can occur at any time after the transplant.
Currently, kidneys are the most in-demand organ, with over 95,000 individuals waiting for a transplant in the United States. However, due to a shortage of donor organs, fewer than 28,000 kidney transplants were performed in the U.S. in 2025. The FDA has approved eGenesis to conduct a formal trial involving up to 33 patients aged 50 to 70 with kidney failure who are on the waitlist for a human kidney. This trial is scheduled to begin in 2027, but eGenesis plans to perform additional transplants under the expanded access pathway in the interim. The company's next objective is to achieve a functioning transplanted pig kidney for one year.