In the United States last year, more than 4,700 people died waiting for a lifesaving kidney transplant. Yet in each of the past five years, more than 2,600 kidneys recovered from deceased donors wound up going to waste, highlighting an inefficient donor-matching system in drastic need of an overhaul. What can health regulators change to ensure the much-needed organs go to people in dire need? Here, a brief guide to the problem:

Why are the kidneys thrown away?
"Some kidneys are in pristine condition when they are donated," says Art Caplan at NBC News, "some are not." Many donor kidneys have health problems that are only discovered after donors have died. And yet, many experts agree that a "significant number of discarded kidneys — perhaps even half, some believe — could be transplanted" if the system for allocating them did a better job of matching faster, says Kevin Sack at The New York Times

How does the current system work?
For the past 25 years, it's largely been a case of "first come, first served," says Sack. The government's Organ Procurement and Transplantation Network, which tracks the more than 93,000 people in need of a transplant, divides the country into 58 donation districts. When a kidney becomes available, the rules stipulate that it be offered first to the candidate in the area who has waited the longest. Extra consideration is given to children, to candidates whose blood chemistry is hard to match, and to recipients who match up well with the donor. If no recipient is found, the electronic search expands to the region before going national. 

What's wrong with that?
The outdated system fails to take into account the projected life expectancy of the recipient or the urgency of the transplant, unlike current systems for heart and lung donors. (For example, sometimes younger, healthier kidneys go to recipients who only have a few years left to live.) Some argue that record-keeping is imprecise, and the relatively short window of organ procurement — surgeons can only keep a kidney "on ice" for 24 to 36 hours — gives busy hospitals an hour or so to respond. In 2011, for example, 2,644 of the 14,784 kidneys recovered from donors were thrown away (18 percent), according to the United Network for Organ Sharing. Nearly 500 of those were not transplanted because a recipient could not be found in time. 

How can we fix the system?
A recent simulation by the Scientific Registry of Transplant Recipients demonstrated that a more efficient computerized matching system could add 10,000 years of life from one year's worth of transplants. But so far, the politics of rationing kidneys has "thwarted all efforts at revision," says Sack. Now, the committee is considering a plan to allocate the top 20 percent of kidneys to candidates expected to survive the longest (placing older patients at a disadvantage), while divvying up the remaining 80 percent the old way. "There is no doubt that organs that can help somebody and have a survival benefit are being discarded every day," says Dr. Dorry Segev, a transplant surgeon at John Hopkins University School of Medicine in Baltimore. Unfortunately, a decision isn't expected to be made about revamping the system until next June.

Sources: Fox News, NBC News, The New York Times