Surgeons in New York have successfully attached a kidney grown in a genetically altered pig to a human patient and found that the organ worked normally, a scientific breakthrough that one day may yield a vast new supply of organs for severely ill patients.

Although many questions remain to be answered about the long-term consequences of the transplant, which involved a brain-dead patient followed only for 54 hours, experts in the field said the procedure represented a milestone.

“We need to know more about the longevity of the organ,” said Dr. Dorry Segev, professor of transplant surgery at Johns Hopkins School of Medicine who was not involved in the research. Nevertheless, he said: “This is a huge breakthrough. It’s a big, big deal.”

Researchers have long sought to grow organs in pigs suitable for transplantation into humans. A steady stream of organs — which could eventually include hearts, lungs, and livers — would offer a lifeline to the more than 100,000 Americans currently on transplant waiting lists, including the 90,240 who need a kidney.

Twelve people on the waiting lists die each day. An even larger number of Americans with kidney failure — more than a half-million — depend on grueling dialysis treatments to survive. In large part because of the scarcity of human organs, the vast majority of dialysis patients do not qualify for transplants, which are reserved for those most likely to thrive after the procedure. READ MORE