The fat in a donor liver and the fat in the recipient increase risk for death after transplant, according to results from a new study. This does not mean that obese patients should be denied liver transplants, or that high-macrosteatosis livers should be thrown away, said Patrick Northup, MD, from the University of Virginia School of Medicine in Charlottesville.

Rather, he said, these results support the practice of selecting leaner livers for fatter recipients and vice versa. "Some people would look at this and say, 'this is what we already do.' I think our paper helps quantify the risk," he told. The finding also has implications for the way patients are ranked on the national liver transplantation waiting list.

That ranking was devised when hepatitis C was the predominant liver disease, Northup explained. But the incidence of hepatitis C peaked in 1989, dropped steadily until 2006, and only recently began to increase again. At the same time, obesity rates have soared, increasing the prevalence of nonalcoholic steatohepatitis.

"Transplant has changed a lot over the past 15 or so years. It's been our impression that patients are sicker going into transplant," he said. "And just about every organ we use these days has some risks associated with it. The data we go by to determine which organs go into which patients are pretty outdated, frankly."

In the past, Northup remembers imposing a cutoff body mass index (BMI) of 35 kg/m2 for liver transplant eligibility. "We made patients lose weight before they could get a transplant," he said. But the threshold for liver transplantation has steadily crept up, sometimes reaching a 40 kg/m2.

In their own clinic, Northup and his colleagues noticed that obese liver recipients and recipients of highly macrosteatotic livers fared worse than normal-weight recipients and recipients of livers with macrosteatosis in the normal range.

High-Macrosteatosis Grafts in High-BMI Recipients

So the team analyzed 23,504 liver donors and recipients who underwent graft biopsy before successful transplantation. Grafts were defined as highly macrosteatotic livers if the steatosis was at least 30% on biopsy. Obesity was defined as a BMI above 35 kg/m² after adjustment for ascites volume.

The cases were divided into four cohorts: high-macrosteatosis grafts in high-BMI recipients; normal grafts in high-BMI recipients; high-macrosteatosis grafts in normal-BMI recipients; and normal grafts in normal-BMI recipients.

Overall, 2675 of the liver recipients had a high BMI and 2002 of the livers were highly macrosteatotic. There were no clinical differences in the cohorts for age, the model for end-stage liver disease (MELD) score, serum sodium at transplant, or time spent on the waiting list.