Utility of hematuria testing in patients with suspected renal colic: correlation with unenhanced helical CT results

Objectives. To determine the utility of hematuria testing in a large series of patients with suspected renal colic using unenhanced helical computed tomography (CT) as the reference standard.

Methods. A retrospective review of the CT reports of all patients who underwent unenhanced helical CT for suspected renal colic at one institution during a 3.5-year period and who also underwent a formal microscopic urinalysis within 24 hours of the CT study was conducted. The sensitivity, specificity, positive predictive value, and negative predictive value of the presence of any blood on the urinalysis for renal colic were calculated.

Results. Urolithiasis was present in 587 (62%) of the 950 patients, and 363 patients had negative examinations for renal colic, including 69 with significant alternative diagnoses in the latter group. Of the urinalyses, 492 were true-positive, 174 were true-negative, 189 were false-positive, and 95 were false-negative, yielding a sensitivity, specificity, positive predictive value, and negative predictive value of 84%, 48%, 72%, and 65%, respectively. Forty-six percent of the urinalysis results were negative for blood in the subset of patients with significant alternative diagnoses.

Conclusions. The sensitivity of hematuria on microscopic urinalysis for renal colic using unenhanced CT as the reference standard was 84%, and the specificity and negative predictive value was low. The presence or absence of blood on urinalysis cannot be used to reliably determine which patients actually have ureteral stones.