In a pass-it-on process that saved two lives, a liver from a deceased donor was transplanted into a patient with a life-threatening metabolic condition, whose otherwise-healthy liver was then transplanted into another patient with a different deadly disease.

It's called a domino transplant, and surgeons from Children's Hospital and the University of Pittsburgh Medical Center performed the sequential operations May 30.

"Everyone is doing well," said Dr. George Mazariegos, director of Children's Hospital's Hillman Center for Pediatric Transplantation.

His patient, Nikolai Rudd, 32, of North Adams, Mass., has maple syrup urine disease, or MSUD, an inherited disorder in which the body cannot properly metabolize certain amino acids. In severe forms, the amino acid buildup can lead to neurological problems, such as seizures and coma.

Like other MSUD patients, Mr. Rudd avoided foods that contain the culprit amino acids. Still, even a minor illness like the flu could have serious, even fatal consequences for him, Dr. Mazariegos said.

But "if you transplant a normal liver into those patients, you cure the disease," the doctor said. The donor organ supplies about 10 percent to 15 percent of the necessary enzyme. Brain and muscle could also produce sufficient amounts, but they cannot be transplanted.

The MSUD patient's liver is otherwise healthy, so it can be transplanted into a patient with liver disease whose other tissues will produce the needed enzyme, Dr. Mazariegos explained.

Larger pediatric or adult MSUD patients are better candidates for the domino process, he added. Greater surgical sophistication is required to remove a liver from a living person for transplant into someone else, and blood vessels in bigger livers are easier to connect in the recipient of the MSUD liver.

After Mr. Rudd got his transplant, his own liver was transferred by UPMC transplant surgeon Dr. Amadeo Marcos into James Paulshock, 64, of Sugarloaf, Luzerne County, who had a bile duct disease called primary sclerosing cholangitis.

Mr. Paulshock "needed a liver soon and was unlikely to get a quality organ," Dr. Mazariegos said. "[His] liver was one of the sickest I've ever seen."

Both patients are now doing well. Mr. Rudd is now able to eat any food, and his amino acid levels, like Mr. Paulshock's, have been in the normal range.

Children's began its liver transplant program for MSUD patients two years ago. About 20 have received organs so far, and currently two patients are candidates for the domino procedure.

"There's a big scarcity of organs, especially livers," Dr. Marcos said. "We're doing everything we can to maximize the use of these organs."

About 100 domino transplants have been done since 1987, mostly with patients who have amyloidosis, a rare and potentially fatal disease that occurs when substances called amyloid proteins build up in the body's organs. Recipients of those livers sometimes develop complications related to the disease.

This is the second time in the United States that a domino transplant has been done with an MSUD patient.