AHRQ Study Finds Ultrasound as Effective as CT in Diagnosing Kidney Stones Without Added Radiation Risk

Broader use of ultrasound in diagnosing kidney stones may be effective and result in less exposure to potentially harmful radiation, according to a new study funded by AHRQ. Abdominal computed tomography (CT) scan has become the most common initial imaging test for suspected cases of kidney stones. However, CT scans expose patients to potentially harmful radiation doses, can reveal findings that lead to unnecessary care and are more costly to perform than ultrasonography. Ultrasound does not expose patients to radiation, can be performed in the emergency or radiology department and is less expensive than CT. The results do not suggest that patients should undergo only ultrasound imaging, 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. An article, “Ultrasonography Versus Computed Tomography for Suspected Nephrolithiasis,” was published along with anabstract September 17 in the New England Journal of Medicine.

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2014 Sep 18;371(12):1100-10. doi: 10.1056/NEJMoa1404446.

Ultrasonography versus computed tomography for suspected nephrolithiasis.

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Abstract

BACKGROUND:

There is a lack of consensus about whether the initial imaging method for patients with suspected nephrolithiasis should becomputed tomography (CT) or ultrasonography.

METHODS:

In this multicenter, pragmatic, comparative effectiveness trial, we randomly assigned patients 18 to 76 years of age who presented to the emergency department with suspected nephrolithiasis to undergo initial diagnostic ultrasonography performed by an emergency physician (point-of-care ultrasonography), ultrasonography performed by a radiologist (radiology ultrasonography), or abdominal CT. Subsequent management, including additional imaging, was at the discretion of the physician. We compared the three groups with respect to the 30-day incidence of high-risk diagnoses with complications that could be related to missed or delayed diagnosis and the 6-month cumulative radiation exposure. Secondary outcomes were serious adverse events, related serious adverse events (deemed attributable to study participation), pain (assessed on an 11-point visual-analogue scale, with higher scores indicating more severe pain), return emergency department visits, hospitalizations, and diagnostic accuracy.

RESULTS:

A total of 2759 patients underwent randomization: 908 to point-of-care ultrasonography, 893 to radiology ultrasonography, and 958 to CT. The incidence of high-risk diagnoses with complications in the first 30 days was low (0.4%) and did not vary according to imaging method. The mean 6-month cumulative radiation exposure was significantly lower in the ultrasonography groups than in the CT group (P<0.001). Serious adverse events occurred in 12.4% of the patients assigned to point-of-care ultrasonography, 10.8% of those assigned to radiology ultrasonography, and 11.2% of those assigned to CT (P=0.50). Related adverse events were infrequent (incidence, 0.4%) and similar across groups. By 7 days, the average pain score was 2.0 in each group (P=0.84). Return emergency department visits, hospitalizations, and diagnostic accuracy did not differ significantly among the groups.

CONCLUSIONS:

Initial ultrasonography was associated with lower cumulative radiation exposure than initial CT, without significant differences in high-risk diagnoses with complications, serious adverse events, pain scores, return emergency department visits, or hospitalizations. (Funded by the Agency for Healthcare Research and Quality.).