Radiologic investigation of renal colic: Unenhanced helical CT compared with excretory urography

OBJECTIVE. Our aim was to compare unenhanced helical CT and excretory urogr aphy in the assessment of patients with renal colic. SUBJECTS AND METHODS. Fifty-three of 70 consecutive patients with acute sig ns of renal colic were prospectively examined with unenhanced helical CT, w hich was followed immediately by excretory urography. Two radiologists who were unaware of the findings independently interpreted these examinations t o determine the presence or absence of ureteral obstruction On all CT scans that had positive findings for ureteral stones or obstruction, we looked f or secondary signs of obstruction (perinephric or periureteral fat strandin g, ureteral wall edema, ureteral dilatation, and blurring of renal sinus fa t), RESULTS. A stone was recovered in 45 of the 53 patients, nine before and 36 after imaging, The latter 36 patients had their stones identified on CT, w hereas only 24 patients had their stones identified on excretory urography. Eight patients without stone disease had normal ureters on both CT and exc retory urography. Of the 45 patients who had stone disease, 26 had ureteral dilatation on both CT and excretory urography, and 36 patients who recover ed a stone after CT had secondary signs of obstruction. Of the nine patient s who recovered a stone before CT, three had secondary signs of obstruction . Two patients had periureteral fat stranding, ureteral wall edema, and ren al sinus fat blurring. One patient had only ureteral wall edema. CONCLUSION. Compared with excretory urography, unenhanced helical CT is bet ter for identifying ureteral stones in patients with acute ureterolithiasis . Secondary CT signs of obstruction, including renal sinus fat blurring, we re frequently present even when the stone was eliminated before imaging.