Computer Science Idea Triggers First Kidney-Liver Transplant Swap
Sandholm says multi-organ exchanges could boost number of transplants
Aliana Deveza was desperate. Her mother's health was failing after years of fighting a hereditary kidney disease. Aliana wasn't a good donor candidate for her mother because she eventually might face the same disease herself.
But what if she donated part of her liver instead? Specifically, what if she donated part of her liver to a patient who needed it and then a loved one of that patient donated a kidney to her mother?
It wasn't Aliana's idea, but one she gleaned from a research paper by Tuomas Sandholm, the Angel Jordan Professor of Computer Science at Carnegie Mellon University, and one of his former students, John Dickerson. She embraced the idea, however, and set in motion events that culminated in what is believed to be the world's first kidney-liver swap.
In July 2017 at UCSF Medical Center in San Francisco, Aliana, of Gilroy, California, donated a little more than half of her liver to Connie Saragoza de Salinas of Sacramento, California. Saragoza's sister, Annie Simmons, of Boise, Idaho, donated one of her kidneys to Aliana's mother, Erosalyn Deveza.
"Everyone's doing well now," said Aliana, now 23 and a psychology major at the University of California, Santa Cruz, though her mother subsequently was treated for breast cancer. "Things were a little rough for her for a while," Aliana acknowledged. In her own case, her liver rapidly regenerated and she considers herself in good health.
Neither Sandholm nor Dickerson, now an assistant professor of computer science at the University of Maryland, had any idea the kidney-liver swap they inspired had taken place until April. That's when a case report by the UCSF surgeons describing the historic transplant was published in the American Journal of Transplantation.
"Multi-organ exchange is something I thought would be really cool," Sandholm said of the research paper he and Dickerson wrote, which explored the potential for kidney-liver swaps to increase U.S. organ transplants overall. "I didn't anticipate it would be performed anytime soon because there are so few live donors for livers."
Sandholm already has played a key role in the expansion of kidney paired-donation (KPD) transplants. In these cases, mismatched donor-recipients - a donor who is willing to donate a kidney, but is biologically incompatible with the recipient - are matched with other donor-recipients in the same situation. The first donor donates to the second recipient, while the second donor donates to the first recipient, thereby enabling two transplants.
Sandholm, his students and collaborators devised computer algorithms that made it possible to make KPD matches using a national pool of candidates, making matches more likely, and enabled chains of kidney swaps that involve multiple donor-recipient pairs.
The first kidney swaps resulting from his algorithms took place in 2006. The United Network for Organ Sharing (UNOS), the nonprofit that manages the U.S. organ transplant system, adopted his algorithms for a national kidney exchange that began in 2010. Thousands of donor-recipient pairs have been matched, resulting in hundreds of kidney transplants, Sandholm noted. About 70 percent of U.S. transplant centers now participate in the UNOS national kidney exchange.
In their paper, published in the Journal of Artificial Intelligence Research, Dickerson and Sandholm calculated that combining the kidney exchange with a liver lobe exchange could match 20 to 30 more candidates a month than would be possible with separate liver and kidney exchanges. That would be an increase of about 10 percent.
Importantly, an increase in liver transplants would translate into lives saved. Though kidney dialysis can keep people with failing kidneys alive, no such life-saving treatment is available for someone with a failing liver.
When Aliana read the paper in 2015, she thought the computer scientists were describing an existing scheme for kidney-liver swaps.
"I didn't realize that it was just theoretical," she said. But it met her needs, so she began calling hospitals in California, trying to learn how she and her mother could join such an exchange. Most of the people she called had no idea what she was talking about, much less where to transfer her call. At UCSF Medical Center, however, Dr. John Roberts, a liver transplant surgeon, returned her call. "He said it was an interesting thought."
He referred her to a transplant coordinator and she and her mother were approved by the transplant program in January 2016. But finding a suitable exchange took 18 months, in part because Aliana's small physique meant they would need to find a recipient of similar size.
Saragoza, who had primary biliary cirrhosis, and Simmons ultimately were matched. Simmons had originally planned to donate part of her liver to her sister, but her liver wasn't of sufficient size.
According to the case study recently published by Roberts and kidney transplant surgeon Dr. Nancy Ascher, every indication was that the transplant recipients would have normal outcomes. The major concern prior to surgery was ethical: the risk Aliana was assuming as a liver donor was far greater than Simmons' risk as a kidney donor, and the life-enhancing benefits to her mother were less than the life-saving benefits to Simmons' sister.
"My parents and family were a little hesitant," Aliana said. "But I really wanted to push for the transplant because it was my mom. It was getting to the point where her condition was really painful. I wasn't too worried about myself; I was in good hands with the doctors at UCSF."
Sandholm said he's not sure whether multi-organ exchanges will catch on the same as KPD transplants. At this point, for instance, no system exists for pooling donor-recipient pairs and making matches. But he said it is heartening to see that an idea born in a computer science lab resulted in a first-of-its-kind operation that saved lives.
"Computer scientists have a lot of wild ideas, and this one just seemed so out there," Sandholm said. "It's just very cool that this turned out so well. We're happy for all of the patients."