Low dose unenhanced helical computerized tomography for the evaluation of acute flank pain.

Purpose: Unenhanced helical computerized tomography (CT) has proved to be an excellent diagnostic tool for evaluating acute flank pain with reported 95% to 100% sensitivity, 92% to 100% specificity, 96% to 100% positive and 91% to 100% negative predictive values. The diagnostic value of a new low dose protocol was prospectively studied and compared with the results of conventional unenhanced helical CT in a previous series with an effective dose equivalent (HE) of 3.1 to 4.3 mSv. and in current literature with an estimated HE of 4.3 to 4.7 mSv.Materials and Methods: In 109 patients 18 to 86 years old with acute flank pain we performed low dose unenhanced helical CT in addition to abdominal ultrasound and urinalysis with new CT parameters (120 kV. 70 mA., 5 mm. collimation, pitch 2 and incremental reconstruction each 5 mm.) that led to a more than 50% decrease in radiation exposure to 1.50 mSv. in females and 0.98 mSv. in males. Ureteral calculi were confirmed or excluded by retrograde ureteropyelography i...