Bedside renal ultrasound in the evaluation of suspected ureterolithiasis

To determine whether ultrasound changes emergency physicians' estimated likelihood of acute ureterolithiasis in patients with flank pain.

This prospective, observational study enrolled patients awaiting computed tomographic (CT) scan for presumed renal colic. Using a visual analogue scale, treating physicians estimated the likelihood of acute ureterolithiasis based first on clinical findings and urinalysis, then after ultrasound, and finally after CT. A 20% change in estimated likelihood was considered clinically significant. Test characteristics of ultrasound for any ureteral stone and for those greater than or equal to 5 mm in size were determined.

One hundred seven patients were enrolled. Sensitivity, specificity, and negative predictive value of ultrasound for stones observed on CT were 76.3% (95% confidence interval [CI], 59.4%-88.0%), 78.3% (95% CI, 66.4%-86.9%), and 85.7% (95% CI, 74.1%-92.9%) respectively, and for stones >5 mm 90.0% (95% CI, 54.1%-99.5%), 63.9% (95% CI, 53.4%-73.2%), and 98.4% (95% CI, 90.3%-99.9%), respectively. Ultrasound significantly impacted the estimated likelihood of disease in 33 of 107 cases (30.8%, 95% CI, 22.5%-40.6%). Computed tomography further significantly changed physicians' impression of disease in 55 of 107 cases (51.4%, 95% CI, 41.6%-61.1%).

Bedside renal ultrasound had only a limited impact on the physicians' clinical impression of patients with possible ureterolithiasis. The sensitivity of sonographic hydronephrosis was modest for detecting any ureteral stone, but much better for detecting a large stone. Further study is needed to define the precise role ultrasound should play in evaluating patients with suspected ureterolithiasis.