Smith-Bindman, C. Aubin, J. Bailitz, et al. Ultrasonography versus computed tomography for suspected nephrolithiasis. N Engl J Med, 371 (2014), pp. 1100–1110.
Why this study is important
The use of non-contrast CT has been the gold standard for diagnosing renal colic despite suggestion that ultrasound could also be used as an effective tool in the emergency department. CT has several downsides which include increased cost, exposure to radiation, and time spent in the ED, so an investigation of other options could potentially benefit patients as well as emergency departments.
What we already know about the topic
CT has been shown to be very sensitive and specific for the diagnosis of renal stones, though a random controlled head-to-head trial between ultrasound and CT including their rates of adverse outcomes had not yet been done prior to this study.
Brief overview of the study
2759 adult (18-76 years of age) patients across 15 different sites with a primary suspected diagnosis of kidney stone were enrolled in the study. Patients were randomly selected to be part of either an ED point-of-care ultrasound group, a radiology ultrasound group, or CT, with an intention-to-treat model so that providers could decide after primary randomization if they wanted further imaging. Primary outcomes were defined as a high risk diagnosis (life-threatening complication from missed or delayed diagnosis), cumulative radiation exposure and total costs. There was no significant difference in adverse outcomes or secondary outcomes such as sensitivity/specificity, length of stay, pain, ED returns, admissions between the three groups, but the radiation exposure and cost of ED visit was significantly lower in the POCUS group.
This was not a blinded study as physicians were aware of which group the patients had been sorted into, no other significant limitations.
Take home points
Consider using POCUS instead of CT scan for select patients with a high-suspicion of uncomplicated kidney stone to reduce costs and total radiation without an increase in missed serious diagnosis.