June 21, 2012 — Kidney injuries among high school varsity athletes are so rare that even youth with only one kidney should be allowed to play, researchers at the University of Virginia School of Medicine have concluded after conducting a groundbreaking survey of the frequency of such injuries.

The researchers' findings, published online in the journal Pediatrics, shed light on the frequency and severity of kidney injuries among young athletes. Because of the lack of hard data on the matter, doctors often recommend that youth with only one kidney not be allowed to participate in contact sports.

"Many people have restricted that activity in the past because of concern about the loss of the kidney, but we've been able to show that the risk is really extraordinarily small," said U.Va. researcher Dr. Victoria Norwood. "Children with single kidneys – and it's important to note normal single kidneys – are really at exceedingly minimal risk from routine contact sports and therefore should be allowed to participate as they and their families desire."

After reviewing more than 23,600 injuries among varsity athletes reported between 1995 and 1997, the researchers determined there were only 18 kidney injuries. None was catastrophic or required surgery. In comparison, there were 3,450 knee injuries and 2,069 head/neck/spine injuries, in addition to 1,219 cases of mild traumatic brain injury.

Norwood, division chief of pediatric nephrology at the U.Va. Health System, said she realized the need for hard numbers after speaking to fellow physicians over the years. Many told her that they sidelined youth with only one kidney because they lacked data suggesting it was safe to let them play.

"People were forced to make decisions over the years without any real evidence," Norwood said. "I thought it was rather silly to send kids out to play football with only one spinal cord, one brain and one spleen, but restrict them from the same activity if they had only one kidney."

She noted that children and teens with only one kidney would be kept off the gridiron even as they were allowed to engage in other activities that actually pose much greater kidney risk.

"Football seems to cause the most concern for physicians, not realizing that they were not restricting downhill skiing, horseback riding or bicycling," Norwood said. "Those are activities that are not intended as contact sports, but the truth of the matter is you do hit things in those activities, and when you do, the outcome can be quite catastrophic."

The most common reason children have only one kidney, she said, is because of a birth defect. She noted that there is very little chance that youth sports could generate the force necessary to damage a kidney severely.

The researchers hope the study results will allow the American Academy of Pediatrics to offer more specific recommendations on the subject. The academy's current stance is a "qualified yes" on the question of whether athletes with one kidney should be allowed to play, but that position leaves physicians with little specific guidance, so most just say no.

Norwood said she hopes the new data will enable the academy to elaborate so that physicians will feel more comfortable allowing young athletes to take the field.

"In today's world, where kids get too little exercise anyway, we have an obesity epidemic," she said. "The last thing we need to do is discourage exercise of any type, unless there is real evidence behind that restriction."