Nonenhanced helical CT and US in the emergency evaluation of patients withrenal colic: Prospective comparison

PURPOSE: To compare nonenhanced helical computed tomography (CT) with ultra sonography (US) for the depiction of urolithiasis. MATERIALS AND METHODS: During 9 months, 45 patients (mean age, 44 years; me an weight, 92.5 kg) prospectively underwent both nonenhanced helical CT (5- mm collimation; pitch of 1.5) and US of the kidneys, ureters, and bladder. US evaluation included a careful search for ureteral calculi. Presence of c alculi and obstruction and incidental diagnoses were recorded. Clinical, su rgical, and/or imaging follow-up data were obtained in all patients. The Mc Nemar test was used to compare groups. RESULTS: Diagnoses included 23 ureteral calculi and one each of renal cell carcinoma, appendicitis, ureteropelvic junction obstruction, renal subcapsu lar hematoma, cholelithiasis, medullary calcinosis, and myelolipoma. CT dep icted 22 of 23 ureteral calculi (sensitivity, 96%). US depicted 14 of 23 ur eteral calculi (sensitivity, 61%). Differences in sensitivity were statisti cally significant (P = .02). Specificity for each technique was 100%. When modalities were compared for the detection of any clinically relevant abnor mality (eg, unilateral hydronephrosis and/or urolithiasis in patients with an obstructing calculus), sensitivities of US and CT increased to 92% and 1 00%, respectively. One case of appendicitis was missed at US, whereas medul lary calcinosis and myelolipoma were missed at CT. CONCLUSION: Nonenhanced CT has a higher sensitivity for the detection of ur eteral calculi compared with US.