Sonographic Twinkling Artifact for Renal Calculus Detection: Correlation with CT

Abstract

Purpose:To retrospectively correlate sonographic color Doppler twinkling artifact within the kidneys with unenhanced computed tomography (CT ) in the detection of nephrolithiasis. Materials and Methods:Institutional review board approval was obtained for this retrospective HIPAA-complaint investigation, and the informed consent requirement was waived. Sonographic imaging reports describing the presence of renal twinkling artifact between January 2008 and September 2009 were identifi ed. Subjects who did not undergo unenhanced abdominal CT within 2 weeks after sonography were excluded. Ultrasound examinations were reviewed by three radiologists working together, and presence, number, location, and size of renal twinkling artifacts were documented by consensus opinion. Sonographic fi ndings were correlated with unenhanced CT (5-mm section width, no overlap) for nephrolithiasis and other causes of twinkling artifact. The number, location, and size of renal calculi at CT were documented. Results:The presence of sonographic renal twinkling artifact, in general, had a 78% (95% confi dence interval: 0.66, 0.90) positive predictive value for nephrolithiasis anywhere in the kidneys at CT. The true-positive rate of twinkling artifact for confi rmed calculi at CT was 49% (73 of 148 twinkling foci), while the false-positive rate was 51% (75 of 148 twinkling foci). The overall sensitivity of twinkling artifact for the detection of specifi c individual renal calculi observed at CT was 55% (95% confi dence interval: 0.47, 0.64). Conclusion:While renal twinkling artifact is commonly associated with nephrolithiasis, this fi nding is relatively insensitive in routine clinical practice and has a high false-positive rate when 5-mm unenhanced CT images are used as the reference standard.q RSNA, 2011Supplemental material: http://radiology.rsna.org/lookup /suppl

Renal Relevant Radiology

“…Stones typically appear as echogenic foci within the collecting system that cast acoustic shadows, but either finding may be absent. A twinkling artifact (nonvascular color signal) on Doppler imaging has been proposed as an additional method to detect stones, but it has poor sensitivity and specificity (16).…”

The usefulness of agent emission imaging - high mechanical index ultrasound mode in the diagnosis of urolithiasis: a prospective preliminary study

“…In a study by Dillman et al (9), the false positivity of twinkling artifact compared with CT was 51% (75 of 148 twinkling foci). Winkel et al (11) also compared CT findings with sonographic and Doppler findings and reported that the addition of color Doppler to grayscale US decreased the PPV for the diagnosis of calculi from 81% to 67% due to increased false positive foci on Doppler US.…”

“…However, lower detection rates have also been reported in the literature. Dillman et al (9) reported the sensitivity of twinkling artifact to be 55% (9). Our results for color Doppler US were closer to their study, with 41.3% (95% CI, 30.3-52.8) sensitivity for detection of calculi smaller than 5 mm.…”

Bildgebende Diagnostik bei Harnsteinen

“…Liegt eine Ektasie vor, so verbessert sich die Sensitivität für eine Urolithiasis von 57 auf 81% [19]. Zwar kann ein postobstruktives Farbartefakt (Twinkling-Effekt) die Lokalisationsdiagnostik verbessern, die Sensitivität hierfür ist mit 55% aber eher schwach [7,37]. Zusätzlich weist eine Erhöhung des Resistance-Index (RI) der Aa.…”