Diagnostic accuracy of different ultrasound signs for detecting adnexal torsion: systematic review and meta-analysis

Objective. To evaluate the diagnostic accuracy of different ultrasound signs for diagnosing adnexal torsion (AT), using surgery as the reference standard. Methods. A search was performed in PubMed/MEDLINE, CINAHL, Scopus, Cochrane, ClinicalTrials.gov and Web of Science databases (January 1990 to November 2021) for studies evaluating the presence of ovarian edema, an adnexal mass, Doppler flow findings and the whirlpool sign as ultrasound signs (index tests) for detecting AT, using surgical findings as reference standard. The Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool was used to evaluate the quality of the studies. Pooled sensitivity, specificity, positive and negative likelihood ratios were calculated separately, and the post-test probability of AT following a positive or negative test also was determined. Results. The search identified 1267 citations after excluding duplicates. Twenty studies were ultimately included in the qualitative and quantitative syntheses. Ten studies, comprising 983 patients, analyzed ovarian edema. Eleven studies, comprising 1295 patients, analyzed the presence of adnexal mass. Fifteen studies, comprising 2212 patients, analyzed the Doppler flow. Finally, seven studies, comprising 654 patients, analyzed whirlpool sign. Overall, quality was considered as moderate or good for most studies. However, there is a high risk of bias in Patient Selection and Index text (except for whirlpool sign) in a significant proportion of studies. Pooled sensitivity, specificity and positive and negative likelihood ratios of each ultrasound sign were 58%, 86%,4.0 and 0.49 for ovarian edema, 69%, 43%, 1.3 and 0.67 for adnexal mass, 65%, 92%, 8.0 and 0.38 for whirlpool sign, 53%, 95%, 11.0 and 0.49 for Doppler findings and 55%, 69%, 1.7 and 0.66 for pelvic fluid. Heterogeneity was high for all them. Conclusion. Diagnostic accuracy of the presence of an adnexal mass or pelvic fluid as ultrasound signs for suspecting an adnexal torsion is moderate, while the presence of ovarian edema, whirlpool sign and decreased or absent Doppler flow show good specificity