Emergency bedside ultrasound exhibits improved sensitivity in urinary stone detection

Emergency department bedside ultrasonography demonstrated high sensitivity as stone size and number increased in a population of patients with CT-proven urinary stones, according to a study published in the Western Journal of Emergency Medicine.

Though non-contrast CT is largely used for the diagnosis of urolithiasis, or urinary stones, in emergency department patients, the technology does not come without its issues. According to lead author Jeff Riddell, MD, of the University of California, San Francisco-Fresno, and colleagues, non-contrast CT is costly, time-consuming and emits significant amounts of ionizing radiation. However, ureteral stones are also detected through the presentation of hydronephrosis on bedside ultrasound. Riddell and colleagues evaluated trends in sensitivity related to stone size and tumor on both CT and ultrasound.

The study, which was a structured, retrospective chart review, included 125 patients who had both CT-proven renal calculi and documented bedside ultrasound results. The researchers found that the overall sensitivity of ultrasound for detection of hydronephrosis was 78.4 percent. The overall sensitivity of a positive ultrasound finding of either hydronephrosis or visualized stones was 82.4 percent.

A statistically significant difference was observed in the detection of hydronephrosis in patients with a stone greater than or equal to six millimeters and those with a stone smaller than that length. Sensitivity was 100 percent for patients with three or more stones.

“In our population with CT-proven urolithiasis, ED bedside ultrasonography had similar overall sensitivity to previous reports but showed better sensitivity with increasing stone size and number,” wrote Riddell and colleagues. “We identified 100% of patients with stones ≥6 mm that would benefit from medical expulsive therapy by either the presence of hematuria or abnormal ultrasound findings.”