Hematuria Testing in Patients with Suspected Urinary Stone Disease: Correlation with Contrast Enhanced Multidetector Computed Tomography Results

ABSTRACT

PURPOSE: Our aim was to determine the efficacy of hematuria testing in suspected urinary stone disease using contrast enhanced multidetector computed tomography (MDCT) as the reference standard. METHODS: Records of all patients who presented to the emergency department with suspicion of urinary stone that undergone MDCT during a 2-year period were reviewed. The sensitivity, specificity, positive predictive value, and negative predictive value of the positive hematuria on the urinalysis for renal colic were calculated. The rates of incidence of negative hematuria were obtained. In addition, significant alternative CT findings requiring immediate or deferred treatment were classified. RESULTS: A total of 492 enhanced MDCTs were performed. Urinary stone had been identified in 414(84.1%) of the 492 patients, and 78 patients had a negative stone, including 33 (6.7%) with clinically significant alternative diagnoses in the latter group. Microscopic urinalysis had a sensitivity, specificity, positive predictive value, and negative predictive value of 89.4%, 41.1, 88.9%, and 42.1%, respectively. The combination of microscopic urinalysis and Urine Dipstick test (UDT) yielded a sensitivity, specificity, positive predictive value, and negative predictive value of 96.9%, 28.2%, 87.5%, 62.9%, respectively. The incidence of negative hematuria for microscopic urinalysis, UDT, and the combination were 10.6%, 4.4%, 3.1%, respectively. CONCLUSION: The presence or absence of blood on urinalysis alone cannot be used to reliably determine which patients actually have urinary stone. Therefore, patients presenting with an episode of clinically suspected urinary stone should undergo CT scanning because it enhances diagnostic certainty by identifying alternative significant diagnoses not suspected on clinical grounds alone.