The research team said the hospitals should be reviewed since they authorized both procedures despite medical findings that found most liver recipients with kidney damage recover kidney function after their initial transplant, the Pittsburgh Tribune-Review reported Sunday.

"People are concerned organs may be placed when they're not necessarily required," university liver specialist Dr. Connie L. Davis said. "You want to give (an organ) to people who need it and not to people who don't. You don't want the extra surgery, the extra risk and the extra expense."

The researchers said after receiving a new liver, 95 percent of patients with short-term kidney failure experience improved kidney function.

In 2007 alone, a total of 424 kidney-liver transplants were conducted in the United States and the researchers say most were likely unnecessary.

The Tribune-Review said the researchers' findings will be part of a review next month by the United Network for Organ Sharing.