Sick patients in desperate need of a kidney transplant could be waiting far longer than they need to, according to new information from Columbia University Medical Centre.

One in every five kidneys donated from an organ donor is not used, and a team from Columbia led by Dr Sumit Mohan and Dr S. Ali Husain are questioning why. In the US alone, about 96,000 people are waiting for a kidney transplant.

The research studied 88,000 patients and found that kidneys were disposed because they had "unappealing" characteristics. Confusingly, in some cases transplants took one kidney from a donor but disposed of the other.

"It is obviously impossible to tell with certainty what would have happened to any discarded kidney if it had been used instead," Mohan said according to Futurism. "As a result, it has been difficult to categroize these discards as 'appropriate' or 'inappropriate'."

"We therefore aimed to identify kidney donors from whom one kidney was used but the partner kidney in the pair was discarded. By doing so, we could control donor characteristics to better understand the reasons for discard, and whether concerns about using certain kidneys were justified."

organ donation
A kidney transplant at The Queen Elizabeth Hospital Birmingham on June 9 2006, England. Getty Images

Almost 5,000 people died in 2014 in the US while waiting for a kidney, and about 3,700 became too sick to receive a transplant.

"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.

Kidney donations are always more effective when given by a close family relative, the NHS says.

The UK's waiting list is much better than the US, however people are still relying on a transplant. Between April 2014 and April 2015, 3,000 kidney transplants took place and 5,000 more people were left on the waiting list.