Whirlpool sign of adnexal torsion on CT: where can we find it?

Background Whirlpool sign on computed tomography (CT) is pathognomic of adnexal torsion. Purpose To evaluate the visibility and common location of the whirlpool sign in adnexal torsion on CT. Material and Methods This retrospective study included 143 consecutive patients who underwent preoperative CT imaging and subsequent surgically confirmed as adnexal torsion. Two readers independently recorded the presence and location of whirlpool sign in adnexal torsion on CT. Patients with and without whirlpool sign were compared with regard to the size of the adnexal mass and the degree of torsion. Results Whirlpool sign was detected in 60 (42.0%) patients on the transverse CT plane and 79 (55.2%) patients on the coronal CT plane of 143 patients. The sign was significantly better detected on the coronal CT plane than on the transverse CT plane (P = 0.03). The most common location of the sign included the posterolateral aspect of the adnexal mass on the transverse CT plane (25/60, 41.7%, P = 0.04) and the upper-lateral aspect of the adnexal mass on the coronal CT plane (45/79, 60.0%, P < 0.001). The size of the adnexal mass with whirlpool sign was significantly larger than the mass without whirlpool sign on the transverse CT plane (median 9.6 vs. 8.6 cm, P = 0.03). No significant difference in the degree of torsion was found between patients with and without whirlpool sign on CT (P = 0.56-0.62). Conclusion Whirlpool sign of adnexal torsion is well detected at the upper-lateral aspect of adnexal mass on the coronal CT plane.