The ultrasound 'twinkling artefact' in the diagnosis of urolithiasis: hocus or valuable point-of-care-ultrasound? A systematic review and meta-analysis.

Presentation to the emergency department with renal colic has been reported as between 6.7 and 27.9 per 1000 emergency department visits. Clinicians rely on various radiological investigations for the prompt and accurate diagnosis of urolithiasis. This review assesses the validity of the colour Doppler ultrasonographic twinkling artefact (TA) sign as a diagnostic tool for the presence of urolithiasis. A systematic search of the Cochrane Database of Systematic Reviews, Embase, PubMed, Scopus and Web of Science databases was performed (October 2018) using specific search terms. PRISMA (Preferred Reporting Items for Systematic reviews and Meta-analyses) guidelines and the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies-2) tool were applied to rank and evaluate selected studies. Twenty-two articles that included 4389 participants were assessed. The median sample size was 102.5 (interquartile range: 47-292.5) and the age range of participants was 4-91 years. Meta-analysis of the studies that provided sufficient data resulted in a pooled sensitivity and specificity for the ultrasonographic TA sign of 88.16 [95% confidence interval (CI): 87.07-89.19%] and 79.22% (95% CI: 73.41-84.26%) respectively, with an estimated summary effect of 3.84 (95% CI: 1.08-6.60, P 0.006) in log odds ratio terms. There was significant interstudy heterogeneity as suggested by an I-statistic of 94.51% (95% CI: 94.51-99.58) and an estimated τ parameter of 7.21 (SE: 7.44). Despite the suboptimal pooled sensitivity and specificity of the TA sign and the large heterogeneity between published studies, the current body of evidence suggests that the colour Doppler ultrasonographic TA sign may be useful as a complementary tool in the diagnostic workup of patients with suspected urolithiasis.