(CNN Newsource) – A new study has found that the U.S. is throwing away at least 3,500 donated kidneys every year. 

The study was published in JAMA Internal Medicine.

It found that between 2004 and 2014, more than 17% of donated kidneys were discarded, and since the study ended, that number has only grown. 

In 2016, about 20% of donated kidneys were discarded.

More than 37,000,000 Americans have chronic kidney disease, and 5,000 die each year waiting for a new organ. 

The study’s authors believe this problem stems partly from transplant centers that are reluctant to take a chance on an organ that isn’t in the best shape.

Also, the U.S. doesn’t have a universal method to determine which kidneys get transplanted and which get discarded.