Decreased attenuation difference between non-contrast and portal-venous phases of CT predicts the ultrasonography-unspecified adnexal torsion.

OBJECTIVES

To evaluate the value of contrast-enhanced CT in diagnosing ultrasonography-unspecified adnexal torsion (AT).

METHODS

Surgically confirmed patients with painful pelvic masses (n = 165) were retrospectively collected from two institutes. Two senior radiologists independently reviewed the CT images and determined the Hounsfield unit difference between non-contrast vs portal venous phases (ΔHU) in both derivation and validation samples. The cutoff value, sensitivity, specificity, predictivity, and reproducibility of the ΔHU and other visually assessed CT signs were analyzed and compared using the receiver-operating characteristic curve, multivariable regression, and inter-rater agreement assays, respectively.

RESULTS

Women with twisted (n = 73 [47 ± 19 years]) or untwisted (n = 92 [40 ± 15 years]) adnexal lesions were reviewed. The ΔHU ≤ 17.5 HU (AUC: 0.91 [95% CI: 0.86, 0.96]; sensitivity: 95% [95% CI: 87, 98]; and specificity: 88% [95% CI: 80, 94]) was the independent predictor of AT (OR: 137 [95% CI: 39, 481], p < 0.001). After training in ΔHU measurement, the agreement between two junior residents and the consensus increased from fair (resident-1: 0.29 [95% CI: 0.17, 0.41]; resident-2: 0.24 [95% CI: 0.1, 0.39]) to substantial (resident-1: 0.75 [95% CI: 0.65, 0.85]; resident-2: 0.72 [95% CI: 0.62, 0.83]). The post-training diagnostic accuracy (both residents: 81% [95% CI: 74, 87]) was higher than the pre-training accuracy (resident-1: 67% [95% CI: 59, 74], p = 0.007; resident-2: 66% [95% CI: 58, 73], p = 0.002).

CONCLUSION

The sign of ΔHU ≤ 17.5 HU in contrast-enhanced CT can be used to predict the ultrasonography-unspecified AT.

CRITICAL RELEVANCE STATEMENT

The decreased attenuation difference between non-contrast vs portal venous phases, a quantitative measurement-based CT sign, highlights the value of using contrast-enhanced CT as a second-line imaging approach after an equivocal ultrasonographic examination to diagnose AT in emergency settings.

KEY POINTS

The value of contrast-enhanced CT in diagnosing ultrasonography-unspecified AT is underestimated. The ΔHU ≤ 17.5 HU is the only predictor to diagnose the ultrasonography-unspecified AT. Contrast-enhanced CT can be used as a second-line imaging approach after an equivocal ultrasonographic examination.