Ultrasonography as the initial diagnostic imaging test is sufficient for diagnosing most cases of suspected nephrolithiasis, thus sparing many patients from having to undergo computed tomography (CT), according to a new study.

Rebecca Smith-Bindman, MD, of the University of California San Francisco, and colleagues randomly assigned 2,759 patients presenting to emergency departments with suspected nephrolithiasis to undergo initial diagnostic ultrasonography performed by an emergency physicians (point-of-care ultrasonography), ultrasonography by a radiologist (radiology ultrasonography), or abdominal CT. Of the 2,759 patients, 908 underwent point-of-care ultrasonography, 893 underwent radiology ultrasonography, and 958 underwent abdominal CT.

The incidence of high-risk diagnoses with complications in the first 30 days was 0.4% and did not differ significantly by imaging method: 0.7%, 0.3%, and 0.2% in the point-of-care ultrasonography, radiology ultrasonography, and CT groups, respectively, the researchers reported in The New England Journal of Medicine (2014371:1100-1110).

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The mean 6-month cumulative radiation exposure was significantly lower in the ultrasonography groups than the CT group, the researchers noted. The proportion of patients experiencing serious adverse events did not differ significantly among the groups: 12.4%, 10.8%, and 11.2% of the point-of-care ultrasonography, radiology ultrasonography, and CT groups, respectively.

Return emergency department visits, hospitalizations, and diagnostic accuracy also did not differ significantly among the groups.

“Our results do not suggest that patients should undergo only ultrasound imaging, but rather than ultrasonography should be used as the initial diagnostic imaging test, with further imaging studies performed at the discretion of the physicians on the basis of clinical judgment,” Dr. Smith-Bindman’s group wrote.

Each study group had some patients who underwent additionally imaging, although this was more common in the ultrasonography groups, the investigators pointed out. Most patients in the ultrasonography groups, however, did not undergo CT, and still there was no increase in any category of serious adverse events among those assigned to ultrasonography, they stated.