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

Abstract

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 4 mm in 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 4 mm in 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 4 mm were 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).

Diagnostic accuracy of Doppler twinkling artifact for identifying urolithiasis: a systematic review and meta-analysis

“…They found that the TA sign had low specificity (40%) with a high falsepositive rate due to sonographer technique and ultrasound setting, along with high echogenicity of the adjacent renal sinus and renal arterial calcifications, as did Dillman et al [31]. Moreover, the size of the stone could have an influence on the comparison between TA sign and noncontrast CT. Letafati et al [6] evaluated the accuracy of TA in detecting renal stones smaller than 4 mm and found rather low sensitivity (76.8%) but high specificity (100%); therefore, they concluded that TA was a reliable sign for detecting renal calculi smaller than 4 mm. However, this sign could be combined with echogenic focus and posterior acoustic shadow to increase the sensitivity.…”

“…Many diagnostic methods have been thought to aid in identifying urolithiasis, including plain radiography, intravenous pyelourethrography, ultrasonography (US), and computed tomography (CT) [5]. Unenhanced CT scanning is broadly considered the current gold standard for the diagnosis of urolithiasis [6]. Noncontrast CT is the most sensitive (up to 98%) and specific (96-100%) method for the detection of urinary stones [7].…”