Small Urinary Stones May Not Require CT Scans

New study suggests that emergency bedside ultrasound suffices for stones smaller than 6 mm.
New study suggests that emergency bedside ultrasound suffices for stones smaller than 6 mm.

Bedside ultrasound (US) may help emergency department physicians decide which patients with renal colic require treatment, according to study findings published in the Western Journal of Emergency of Medicine (2014;15:96-100).

The study, led by Jeff Riddell, MD, of the University of California San Francisco-Fresno, included 125 patients with computed tomography (CT)-proven renal calculi and documented bedside US results. The overall sensitivity of US for detecting hydronephrosis was 78.4%. The overall sensitivity of a positive US finding of either hydronephrosis or visualized stones was 82%. The sensitivity of bedside US for detecting hydronephrosis was significantly higher among patients with stones 6 mm or larger than among those who had smaller stones (90% vs. 75%).

Abnormal US findings or the presence of hematuria enabled identification of all patients with stones 6 mm or larger who would benefit from medical expulsive therapy.

Dr. Riddell and his colleagues stated that in their study, patients without evidence of stones on emergency department bedside US and without hematuria could be safely assumed to have stones less than 6 mm if detected on CT. “Given that these smaller stones typically do not require surgical intervention and do not appear to benefit from medical expulsive therapy, we hypothesize that clinical assessment followed by urinalysis and bedside US could obviate the need for CT in this subset of patients,” they noted.

Dr. Riddell's group noted that non-contrast CT is widely considered the gold standard for diagnosing urinary stones in emergency department patients, but it is costly and time-consuming and it exposes patients to significant doses of ionizing radiation.

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