Purpose: A positive whirlpool sign (WS) is defined as the presence of a spiral-like pattern when the spermatic cord is assessed during ultrasonography (US), using standard, high-resolution ultrasonography (HRUS) and/or color Doppler sonography (CDS), in the presence of testicular torsion. The objective of this review was to assess the validity and accuracy of this sign by performing a comprehensive systematic literature review and meta-analysis.
Methods: In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines, a comprehensive literature search was performed (August, 2017), using the following databases: BMJ Best Practice, Cochrane Library, Embase, PubMed, Scopus, and Web of Science. Selected studies were further assessed for relevance and quality using the Oxford 2010 Critical Appraisal Skills Program (CASP).
Results: Of the studies assessed, a total of 723 participants were included, with a mean of 72.3 (SD 71.9) participants. Of the participants, 226 (31.3%) were diagnosed with testicular torsion (TT). Meta-analysis of the studies that provided sufficient data resulted in a pooled sensitivity and specificity of the WS of 0.73 (95% CI, 0.65-0.79) and 0.99 (95% CI, 0.92-0.99), respectively. Removal of all neonates increased the pooled sensitivity to 0.92 (95% CI, 0.70-0.98) while the pooled specificity remained almost unchanged at 0.99 (95% CI, 0.95-1.00). The estimated summary effect of all studies with sufficient data was 4.34 (95% CI, 1.01-7.67; n = 394; p = 0.001). A large degree of heterogeneity was suggested by an I2 statistic of 88.27% (95% CI, 68.60-98.68%). Removal of neonatal subjects increased the estimated summary effect to 5.32 (95% CI, 1.59-9.05; n = 375; p = 0.001).
Conclusion: The WS, when correctly diagnosed, may be viewed as a very definitive sign for TT in the pediatric and adult populations. However, its role in neonates is limited.
Keywords: Acute scrotum; Emergency ultrasound; Scrotal pain; Testicular torsion; Testis torsion; Whirlpool sign.