Ultrasound versus computerized tomography for evaluating urolithiasis.

Purpose: We prospectively evaluated the precision of ultrasound and computerized tomography to diagnose urinary stones in children and determined whether these differences in radiological findings have any impact on clinical management.
Materials and Methods: A total of 50 consecutive patients with suspected urolithiasis underwent computerized tomography and ultrasound. Two radiologists reviewed each study independently in blinded fashion. When a difference in findings was detected, 8 pediatric urologists reviewed the case. Clinical management was based on the results of each radiological test independently. Statistical analysis was performed using Fisher's exact test.
Results: Compared to computerized tomography ultrasound had 76% sensitivity and 100% specificity. In 8 patients stone(s) seen on computerized tomography was not seen on ultrasound. The average size of missed stones was 2.3 mm. In 7 patients computerized tomography showed stones bilaterally but stone was seen on only 1 side on ultrasound. When evaluating the clinical impact, the ultrasound/computerized tomography discrepancy did not result in any significant change in clinical management except in 4 cases. In these cases ultrasound findings suggested that additional imaging was required and, thus, stone(s) in the distal ureter would have been identified on subsequent imaging.
Conclusions: Although computerized tomography is more sensitive for detecting urolithiasis than ultrasound, the difference in usefulness between the 2 radiological tests may not be clinically significant. Given concerns for the potentially harmful cumulative long-term effect of radiation, ultrasound should be considered the first imaging test in children with suspected urolithiasis.