Diagnostic Accuracy of Twinkling Artifact Sign Seen in Color Doppler Ultrasonography in Detecting Microlithiasis of Kidney

Background: Ultrasonography (US) is a safe and cost-efficient modality which is used to assess patients with urinary tract lithiasis. Objectives: In this study, we aimed to evaluate the accuracy of the twinkling artifact of color Doppler sonography in detecting renal stones smaller than 4mmin diameter. Methods: Of all patients referring to a tertiary medical center with a probable diagnosis of urolithiasis during April 2019 to September 2019, 99 patients with a renal stone smaller than 4mmin non-contrast computed tomography (CT) scan entered our study. Both gray scale and color Doppler US were performed to assess the presence of any renal stones, the accompanying posterior shadowing, and the twinkling artifact for all patients. Results: Of 99 patients with confirmed renal stone on non-contrast CT scan, 91 patients had an echogenic focus on grayscale (sensitivity = 91.9%), 70 patients had posterior shadowing sign (sensitivity = 70.7%), and 76 patients had twinkling artifact on color Doppler US. The sensitivity, specificity, positive predictive value, and negative predictive value of this imaging finding for detecting renal stones smaller than 4mmwere 76.8%, 100%, 100%, and 32.4%, respectively. Conclusions: Our study revealed that twinkling artifact on color Doppler US is a reliable sign for detecting renal stones smaller than 4 mm. However, the sensitivity of this sign could be increased in combination with gray scale findings (echogenic focus and posterior shadowing).