Rise in kidney stones in kids and higher radiation imaging

Two papers document trends in cases, diagnostic imaging and treatment

September 29, 2010
Boston, Mass. - The proportion of children with kidney stones at pediatric hospitals across the country has tripled in the last 10 years, researchers at Children's Hospital Boston report in the September Journal of Urology.

"This is the first national broad-based study looking at outpatient data that confirms the incidence of stones in kids seems to be increasing," said Caleb Nelson, MD, MPH, co-director of the Children's kidney stone center and the study's senior author. The proportion of kidney stones among all patients at children's hospitals increased about 10 percent a year, from about 18.4 per 100,000 patients in 1999 to 57.0 per 100,000 in 2008, the study showed.

"If you look at the raw numbers, the upward trend goes through the roof," Nelson said. "The increase is not so dramatic when you adjust for hospital volume, but it is still there."

In a companion paper in the October Journal of Urology, the researcher team also identified a worrisome rise in higher-radiation imaging to diagnose the stones. They report a shift in diagnostic imaging of stones toward higher-radiation computerized tomography (CT) and away from plain x-ray and ultrasound. They also found a four-fold difference in surgery rates among pediatric hospitals. "The biggest factor in CT use or surgery rates was the hospital," said first author Jonathan Routh MD MPH, a fellow in pediatric urology at Children's. "With that high level of variability, odds are that there are a lot of kids getting inappropriately overtreated or undertreated."

"In an era of rapidly increasing radiation doses from medical testing, this trend is worrisome," write the researchers, who cite a small but measurable extra cancer risk in children. Of nearly 8,000 children in the study, more than 2,600 underwent multiple CT scans, as many as eight each.

Both papers analyze the data from the Pediatric Health Information System, a national database of administrative and billing data from more than 40 freestanding pediatric hospitals. The database tracks individual patients over time and includes emergency room and outpatient surgery visits but not outpatient clinic visits at the hospital. A total of 7,921 children were diagnosed with kidney stones from 1999 to 2008 at member pediatric hospitals.

Although on the upswing, kidney stones in children remain relatively uncommon, about half the rate of appendicitis in the same pediatric hospital population, the researchers calculated. Speculation about the causes for the increase in stones in kids ranges from nutrition to global warming. Studies in adults have implicated obesity and dietary salt, both of which are on the rise in pediatric populations, Routh said.

"We don't have a good handle on why it may be going up," said Nelson, who notices his patients tend to be healthy-weight teens who may not drink sufficient water or who may have a family history of kidney stones.

CT is the gold standard for stone diagnosis in adults, Nelson and his co-authors write, but the relatively increased CT radiation dose in children has led many experts to advocate ultrasound as the preferred imaging in children suspected of having kidney stones. In children, ultrasound diagnosis and followup seems to be clinically equivalent to CT, another team of Children's researchers reported last year.

"Here at Children's, our radiologists are aggressive about radiation reduction, and CT scans are used sparingly," said Nelson, assistant professor of surgery at Harvard Medical School. The researchers recommend more specific evidence-based clinical guidelines to decrease variation and improve outcomes.

The studies were funded by the U.S. Agency for Healthcare Research and Quality.

Trends in Imaging and Surgical Management of Pediatric Urolithiasis at American Pediatric Hospitals

Epidemiological Trends in Pediatric Urolithiasis at United States Freestanding Pediatric Hospitals

Erin McColgan

Children's Hospital Boston is home to the world's largest research enterprise based at a pediatric medical center, where its discoveries have benefited both children and adults since 1869. More than 1,100 scientists, including nine members of the National Academy of Sciences, 12 members of the Institute of Medicine and 13 members of the Howard Hughes Medical Institute comprise Children's research community. Founded as a 20-bed hospital for children, Children's Hospital Boston today is a 392-bed comprehensive center for pediatric and adolescent health care grounded in the values of excellence in patient care and sensitivity to the complex needs and diversity of children and families. Children's also is the primary pediatric teaching affiliate of Harvard Medical School. For more information about the hospital and its research visit: www.childrenshospital.org/newsroom.