Study: Ultrasound over CT for initial stone Dx

Ultrasound should be the initial diagnostic imaging test utilized for diagnosing kidney stones in order to reduce the higher radiation exposure associated with computed tomography, say the authors of a recent study.

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In the randomized controlled trial, which was published in the New England Journal of Medicine (2014; 371:1100-10), the authors assigned 2,759 patients who came to hospital emergency departments with suspected cases of kidney stones into one of three groups: initial diagnostic testing by point-of-care ultrasound (in the ED), radiology ultrasound, or abdominal CT scan.

After 30 days, the authors found no significant differences among the three groups in the rate of high-risk diagnoses of kidney stones with complications that could have been related to missed or delayed diagnoses, according to a press release from the Agency for Healthcare Research & Quality, which funded the study. After 6 months, they found that the proportion of patients with confirmed diagnoses of kidney stones was similar for all three study groups, but patients who initially received a CT scan had significantly higher radiation exposure than patients in the two ultrasound groups.

Some patients in the ultrasound groups went on to have additional testing, some of which included CT scans. This resulted in an average radiation exposure of about half that of the CT group.

The authors found no significant differences among the three groups in the rates of serious adverse events, pain, return trips to the ED, or hospitalizations.

Although CT scans are currently favored by ED physicians for diagnosing stones, ultrasound should be used initially instead, said senior author Rebecca Smith-Bindman, MD, of the University of California, San Francisco, in a press release from that institution.

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“Ultrasound is the right place to start,” Dr. Smith-Bindman said. “Radiation exposure is avoided, without any increase in any category of adverse events, and with no increase in cost.”

“Our results do not suggest that patients should undergo only ultrasound imaging,” the authors said, “but rather that ultrasonography should be used as the initial diagnostic imaging test, with further imaging studies performed at the discretion of the physician on the basis of clinical judgment.”

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