Current Imaging Practices for Kidney Stones Deviate From Guidelines

Oct 27 2014

Current Imaging Practices for Kidney Stones Deviate From Guidelines

kidney_stonesKidney specialists across the country agree that the incidence of kidney stones is rising among children, but clinicians are unsettled on which imaging technology to choose first when diagnosing the condition, despite current guidelines that recommend ultrasound as the initial imaging study.

The Division of Urology at The Children’s Hospital of Philadelphia used to treat just a handful of children with kidney stones a year; now the multidisciplinary team at the Pediatric Kidney Stone Center evaluates and manages children with kidney stones on a daily basis.

A kidney stone develops when some substances that are normally found in the urine become highly concentrated and form solid crystals. Stones usually begin causing symptoms when they block the outflow of the urine to the bladder.

“Kidney stones truly have become a disease of childhood,” said Gregory E. Tasian, MD, MSc, MSCE, a pediatric urologist and epidemiologist at The Children’s Hospital of Philadelphia, who was the lead author of a study appearing in the November 2014 issue of Pediatrics that looked at the prevalence of the first imaging study that children obtain when they are evaluated for kidney stones.

The American Urological Association and The European Society of Paediatric Radiology recommend that a ultrasound be used as the initial imaging study to help clinicians to find a stone and look for any signs of blockage. The guidelines reserve computed tomography (CT), which delivers ionizing radiation and is associated with an increased risk of cancer in children, for cases when the ultrasound is nondiagnostic and the clinicians’ suspicion of kidney stones remains high.

“Stones can recur, so over a lifetime, a patient can be exposed to a lot of radiation both in the evaluation and then the treatment of stones,” Dr. Tasian said. “We want to limit the use of radiation when we can. By using ultrasound as the initial screening tool, we are able to identify the majority of clinically important stones and spare the child radiation.”

The Urologic Diseases in America Project, sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases, supported the study led by Dr. Tasian to see how closely U.S. hospitals and clinics follow the current guidelines. The cross-sectional study focused on 9,229 children with urinary stones located in the kidney, also known as nephrolithiasis, who underwent imaging from 2003 to 2011. The study team obtained data from MarketScan, a robust database of commercial insurance claims.

The study’s results showed that clinicians deviated frequently from the recommended guidelines. Overall utilization of CT was high: An average of 63 percent of children underwent CT as the first imaging study during a kidney stone episode. Only 24 percent of children with suspected nephrolithiasis underwent ultrasound as the initial study.

“The findings also suggest that there is substantial regional variability in the use of CT,” Dr. Tasian said. “Yet even in states with the lowest initial use of CT, the prevalence was about 40 percent, and it reached almost 80 percent in some of the higher utilizing states.”

The study’s authors suggest that because the availability of CT has increased over the last 20 years and it is recognized as a reliable diagnostic tool to evaluate adults with kidney stones, clinicians are engrained in the practice patterns or resources specific to their local medical communities. They may not be aware that current best practices recently reported in the New England Journal of Medicine demonstrate that ultrasound can be used as effectively as CT to diagnose kidney stones in adults — at a lower cost and without radiation exposure.

Dr. Tasian and colleagues encouraged future studies to determine the barriers to awareness and implementation of recommended imaging practices that aim to decrease the use of ionizing radiation. Researchers also could test the effectiveness of interventions that attempt to change clinical practice and reinforce the use of ultrasound as the initial screening tool, such as clinical pathways and clinical decision support systems.

Addressing these factors promptly is imperative, if the trend that shows the incidence of kidney stones increasing among children by 10 percent annually continues. While the reasons behind this shift in epidemiology are not well known, some clinicians suspect that the rise in obesity rates, less active lifestyles, diets high in salt, and not drinking enough water may be causing more children to have kidney stones.

A recent study by Dr. Tasian also proposes that climate change may play a role, as warmer days may contribute to dehydration, which leads to a higher concentration of calcium and other minerals in the urine that promote the growth of kidney stones.

Jose E. Pulido, MD, of the Division of Urological Surgery at the University of Pennsylvania’s Perelman School of Medicine; Ron Keren, MD, MPH, of CHOP’s Center for Pediatric Clinical Effectiveness; and Urologic Diseases in America Project collaborators from the RAND Corporation and the University of California, Los Angeles also contributed to the CT imaging for kidney stones study.