CT in ureterolithiasis with a radiation dose equal to intravenous urography: results in 209 patients

Purpose: To evaluate a low-dose, nonenhanced helical CT protocol for the diagnosis of renal colic using an effective dose equivalent of radiation not higher than that of intravenous urography. Materials and Methods: A new low-dose helical-CT protocol (120 kV; 70 mA; rotation time 0.75 s; collimation 5 mm, pitch=2) was used to examine 209 consecutive patients with symptoms of renal colic. The initial CT reports were compared with retrograde ureterography, ureteral endoscopy, stone retrieval, surgical or clinical findings. The effective radiation dose was calculated by the method published by Nagel. The prevalence of ureterolithiasis was 70%. Results: Sensitivity and specificity of the low-dose-helical CT in detecting ureteral calculi were 97.7% and 96.8%, respectively. The positive predictive value was 99.3% and negative predictive value 92.4%. The mean effective radiation dose equivalent was 0.97 mSv in male and 1.35 mSv in female patients. Conclusions: the diagnostic value of the reported CT protocol does no differ from previously published protocols. However, the effective radiation dose equivalent is at least 50% lower than stated in the published protocols. We recommend the low-dose helical CT protocol as the method of choice. (orig.)