Reducing radiation exposure in kids with kidney stones

A kidney stone seen on CT (James Heilman/Wikimedia Commons)
A kidney stone seen on CT (James Heilman/Wikimedia Commons)
Two national trends have preoccupied Caleb Nelson, MD, MPH, and his colleagues in the Boston Children’s Hospital’s Urology Department over the past few years. One is the rise in overall exposure to medical radiation. The second is specifically the increased use of computed tomography (CT) scans—rather than clinician-preferred ultrasound—in children with kidney stones.

“We see a lot of kids with stones, and there is a clinical need to better manage their condition,” Nelson explains. “Medical radiation is a risk factor for problems down the road, and we know that the amount of radiation people are receiving has gone through the roof in recent years.”

How big is the problem? Nelson cites data collected on radiation exposure on the U.S. population from 1987 to 2006 by the National Council on Radiation Protection and Measurements (NCRP). At the beginning of the study, about 18 percent of all radiation exposure was medical. By 2006, that number had grown to 48 percent (see chart below). While a number of tests and procedures contributed to that rise, “CT is such a big hit of radiation every time, it largely drove the increase,” Nelson says.

Radiation exposure sources--then and now.
Radiation exposure sources--then and now.
Looking specifically at CT use in the diagnosis of pediatric kidney stones, Nelson and his colleagues found more disturbing data. Ultrasound, which does not produce radiation, has been accepted in the pediatric community as the preferred approach for the initial study for kidney stones. However, Nelson cites an upcoming study based on emergency room data indicating that, among children, ultrasound is only used in 13 percent of kidney stone cases while CT scans are used 87 percent of the time. “That’s the exact opposite of what it should be,” he claims.

A number of factors might explain why CT is used more often than ultrasound. Ultrasound imaging requires a technician, but CT scans do not, making CT easier to perform. Moreover, Nelson says, some smaller hospitals simply cannot staff their ultrasound equipment 24 hours a day, but most do so with their CT machines.

Although images produced by an ultrasound are not as good as CT, “they are 90 percent as good—and much safer for the patient,” Nelson adds. Both methods, he asserts, are good for diagnosing a stone, “but you’d rather have less radiation. We need to be smarter about how we conduct tests.”

For Nelson and his team, this is a safety and quality of care issue. “If you’re talking about tens of thousands of kids, you may miss a few things with ultrasound,” he says, “but the greater good is to limit the exposure of radiation to the population.”

To get to this greater good, Nelson and his colleagues have instituted some changes at their own hospital. For example, they have developed a checklist for reviewing settings and protocols for using a fluoroscopy machine, which produces real-time X-ray images. Used before patients go in for surgery, the list calls on doctors and technicians to record preoperative patient characteristics, operative factors, fluoroscopy settings and radiation exposure before the machine is turned on. Shortly after the checklist system was implemented, radiation exposure levels went down between 80 and 90 percent, Nelson says. Now, these laminated checklists are attached to every fluoroscopy machine in their department.

The checklist is simple, it’s effective, and, Nelson asks, “if it was your kid, would you want us running through a quick checklist, or would you want us to just start zapping away?”

For Nelson and his colleagues, the work continues on a number of fronts in urology, including studies on epidemiologic trends in pediatric urolithiasis (kidney stones) at U.S. children’s hospitals, costs associated with initial imaging of febrile urinary tract infection and the impact of pediatric genitourinary diagnostic imaging tests on patients and families.