But only a tiny fraction of transplant patients are candidates for the operation: certain children with acute liver failure  probably fewer than 100 a year in the United States, where 525 under 18 had liver transplants last year. The operation is a difficult one. It is longer and more risky than a standard transplant, and surgeons caution that patients have to be selected carefully because not all can withstand the surgery.

Image CHILD’S PLAY Jonathan and his sister, Kailey, 6, said they were looking for fossils on Friday in the backyard of their home in Miami. Credit... Oscar Hidalgo for The New York Times

The surgery was first tried in Europe in the early 1990s, and later in the United States. But the results were mixed  the liver did not always regenerate  and it never really caught on. (In medical journals, it is called auxiliary partial orthotopic liver transplantation.) Dr. Kato said the results may have been poor because the early attempts included adults.

“I think the key is children,” he said.

The best candidates are children with acute hepatic failure, a deadly condition in which the liver suddenly stops working, often for unknown reasons. Although the liver might be able to recover, it cannot do so fast enough to prevent brain damage and death from the toxins that build up. The only way to save the life of someone with this condition is to perform a transplant  or a partial one. Such partial transplants do not work for chronic liver diseases that cause scarring because it prevents the liver from regenerating.

All told, Dr. Kato has performed the surgery on seven children, ranging in age from 8 months (Jonathan) to 8 years, at Jackson Memorial. So far, the patient’s own liver has recovered in six of the seven children, and they no longer require antirejection drugs, Dr. Kato said, adding that he expected the need for the drugs to taper off soon for the seventh. In four, he described the transplant as “melting” away completely on its own, but two others, including Jonathan, needed surgery to remove a remnant or clear up an infection.

Dr. Kato’s first case was in 1997. That child spent three months in intensive care. “We didn’t think it was successful,” he said. But after two years, the liver had fully recovered.

“That gave us the idea this was something worth doing,” Dr. Kato said.

Other surgeons have tried the procedure. Dr. Alan Langnas, director of liver transplantation at the Nebraska Medical Center, said he had performed it on about 10 patients, mostly children, in the last 15 years. In some cases, he said, the patient’s liver did not regenerate. At least one required a second transplant.

“I think the success has always been a little mixed,” Dr. Langnas said. “It depends on the patient selection and how well their native liver recovers. But I think it is an important option for some patients.”