Kidney Stone Imaging Guidelines Not Being Followed in Kids

Diana Phillips

October 28, 2014

The "go-to" imaging modality for suspected kidney stones in children is computed tomography (CT), despite national guidelines recommending ultrasound as the preferred initial imaging, according to results from a recent study.

More than half of children with nephrolithiasis in a cross-sectional analysis of national insurance data underwent initial CT imaging compared with fewer than one quarter who had ultrasound performed first, Gregory E. Tasian, MD, from the Children's Hospital of Philadelphia in Pennsylvania, and colleagues report in an article published online October 27 in Pediatrics.

The analysis further indicated substantial geographic variability in initial CT use across the country, with the highest prevalence observed in Midwestern and southern states and the lowest in northeastern states, the authors write. Even in states with relative low initial CT use, more than 40% of children underwent CT alone or before ultrasound, they state.

Imaging protocols for children with suspected nephrolithiasis developed by the American Urological Association in 2013 and the European Society for Pediatric Radiology in 2009 recommend CT only if initial ultrasound is nondiagnostic, in an effort to limit unnecessary exposure to medical radiation in these children.

For the analysis, the investigators performed a cross-sectional study of a national sample of privately insured children younger than 18 years from 2003 to 2011 and identified 9642 children with a medical code for a kidney stone event, including a primary diagnosis of nephrolithiasis in the outpatient setting or the emergency department, surgical procedures for the condition, and/or stone diagnosis in the inpatient setting. Of the children who met those criteria, 9228 underwent imaging studies during a stone episode. The researchers excluded states with fewer than 10 children with stone events during the study period from the final analysis.

During the period of study, an average of 63% of children in the United States underwent CT as the first imaging study during a stone event, the authors report. The proportion of children who had initial CT during a nephrolithiasis episode varied by state from 41% to 79%. During the study period, an average of 24% underwent ultrasound as the initial imaging study. Kidney, ureter, and bladder X-ray and intravenous pyelogram made up the remaining 13%.

The highest odds for initial CT use were observed for children living in the East South Central states of Alabama, Kentucky, Mississippi, and Tennessee, whereas the lowest odds were observed for children in the New England states of Connecticut, Maine, Massachusetts, and New Hampshire.

"Older children were more likely to undergo initial CT," the researchers observe, noting that adolescents in particular "were nearly 9 times more likely to undergo initial CT than were 2- to 5-year olds.... Girls, in whom abdominal and pelvic radiation has a higher lifetime attributable risk of cancer than boys, were more likely to have CT,” they add.

With respect to diagnostic imaging utilization over time, "CT use anytime during the kidney stone episode increased from 60% in 2003 to 77% in 2007, and then gradually declined," the authors write, whereas overall ultrasound use remained stable, at 24% to 31%, throughout the study period.

The public health implications of unnecessary radiation exposure are heightened by the rising incidence of kidney stones in children during the past 25 years and by the fact that multiple imaging studies are often performed for the same kidney stone episode, the authors explain.

The observed geographic variability in initial CT use parallels regional differences in per capita Medicare spending, "which has been attributed to geographic differences in physician evaluation and management practices," the authors write. As such, they note, "we hypothesize that CT use to evaluate children with nephrolithiasis differs across the country due to engrained practice patterns or resources specific to local medical communities."

Given that clinical guidelines have been shown to reduce variability and improve processes of care, as well as outcomes, future studies "should assess awareness of these guidelines and determine the physician, institutional, and community characteristics that serve as barriers to implementation of recommended imaging practices," the authors stress. "Additionally, interventions to decrease initial CT use should be developed."

This research was supported by the National Institutes of Health and the National Institute of Diabetes and Digestive and Kidney Diseases. The authors have disclosed no relevant financial relationships.

Pediatrics. Published online October 27, 2014. Abstract


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