Some donated kidneys that could be utilized are instead being tossed out. This has prompted researchers to call for changes in the organ transplant system.

About 116,000 people are on the national transplant waiting list.

Almost 83 percent of them are in line for a kidney.

More than 5,000 people in the United States die each year waiting for a kidney transplant.

Despite these facts, nearly 1 in 5 donor kidneys wind up being discarded.

Some researchers wanted to understand why this is the case and if these organs could be better utilized.

In a new study, the researchers say the discard rate of kidneys is growing as an organ donation shortage continues.

Dr. Sumit Mohan and Dr. S. Ali Husain, both from Columbia University Medical Center, reviewed data from deceased donors who had one kidney used and the other discarded between 2000 and 2015.

Based on information from 88,209 donors, they noticed that the discarded kidneys from the donated pairs typically had unappealing traits, but the transplanted kidneys that shared many of the same traits performed well after transplantation.

“We therefore concluded that many of these discarded kidneys were in fact quite usable, and that systems-level changes are needed to encourage better utilization of this valuable but scarce resource,” Husain said in a statement.

In the United States, organs are allocated by a centralized system that’s managed by the United Network for Organ Sharing (UNOS), which holds the Organ Procurement and Transplantation Network contract from the U.S. Health Resources and Services Administration (HRSA).

There’s a clear allocation system and a well-defined priority system used to allocate these organs. But the system can’t force anyone to accept an organ offer.

“That decision lies with the transplant center and ultimately with the patient it is offered to,” Husain said.

Husain explained that it’s not easy to assess kidneys for transplantation.

Many centers rely on biopsy data, but he said that’s probably not the best way to evaluate organs.

The allocation system uses a Kidney Donor Risk Index.

This is a complex composite score to help clinicians, but it’s not perfect, Husain said.

Age is another factor in evaluating kidneys for transplantation.

Doctors must assess whether a kidney from a 65-year-old donor, for example, is appropriate for a 25-year-old recipient.

“This makes a difficult decision even more complex, and given the time-sensitive nature of the process, a final decision has to be done in a very short span of time,” Husain said.

Darren Stewart, MS, a senior research scientist and data science lead with UNOS, explained that kidneys from young donors without chronic diseases tend to last longer and are typically used.

On the flip side, kidneys from some donors with diseases may put a recipient at risk and shouldn’t be transplanted.

Although there’s a lot of published research identifying donor factors that lead to better outcomes for transplant recipients, there’s no universally agreed upon answer on the performance of what Stewart dubs a “gray area” kidney.

“There is much debate in the transplant community about whether data gathered from taking a biopsy of the kidney is associated with post-transplant prognosis, and often biopsy findings are cited as a reason for discard,” he said.

Stewart said that logistical issues also come into play in determining if an organ is discarded.

“If offers of a donated kidney are declined by transplant centers, the organ’s time outside the body increases, rendering less than optimal kidneys even less desirable,” Stewart explained.

Reasons for discarded kidneys go beyond clinical, Husain added.

“There are also systemic reasons contributing to the discard of kidneys as evidenced by increasing rates of discard on the weekend and variations in organ acceptance across the country,” he noted.

Part of the reason why kidneys are being turned away is because regulatory agencies emphasize post-transplant performance, but don’t focus on the downsides of being too selective about which organs are accepted.

“Lowering discard rates would require policy revisions from HRSA and UNOS to help improve organ utilization to maximize the number of patients transplanted, rather than merely the immediate short-term outcomes, which are already excellent,” Husain explained.

He said that exceptions to the allocation system and being able to fast-track allocation of certain organs, as is done in parts of Europe, should be considered in the United States.

Stewart suggested a few ways to improve the system.

Integrating the likelihood a patient and a center will accept a kidney into the system algorithm would help.

That could ensure that hard-to-place organs are offered first to those who will most likely accept them.

The current system is largely based on waiting time (years on dialysis).

Many patients at the top of the list may not accept a less than optimal kidney and prefer to wait for a more ideal kidney, he said.

It could also help if transplant centers made more effective use of patient-specific acceptance criteria, as it would get the organ to an appropriate candidate at a willing center more quickly.

Another way to advance the system is to look at transplant centers’ tolerance for clinical risk.

Performance is gauged mostly on how well recipients fare, but measurements such as offer acceptance rates or transplantation rates aren’t factored in as heavily.

“This is thought to cause risk aversion and centers being hesitant to accept less than ideal kidneys because of concerns about their center’s post-transplant clinical outcomes,” he said.

Finally, Stewart said finances must come into play.

Neither the age of the donor or donor medical factors are considered when transplant hospitals are reimbursed for the cost of kidney transplantation by insurers and the Centers for Medicare and Medicaid.

Less than ideal kidneys that may be appropriate for some patients can lead to higher rates of complications, which is linked to higher post-transplant care costs.

“This reality can cause transplant centers to become hesitant to accept too many such kidneys out of concerns for financial viability,” he said.

Experts say the figures on discard rates aren’t necessarily an indication that the organ allocation process isn’t working.

“A higher discard rate is not necessarily bad for patients,” Stewart said.

The discard rate rose steadily in the early 2000s, from about 13 percent to 19 percent. But the reason was organ procurement organizations became more intentional about recovering organs from all potential donors, including those with nonideal organ function.

In 2003, the U.S. Organ Donation Breakthrough Collaborative instituted the mantra, “Every organ, every time,” to try and expand the pool of donors.

While donors and transplants did increase, there were more organs that weren’t able to be used for transplantation as well.