The whirlpool sign or whirl sign of ovarian torsion is characterized by the appearance of a twisted ovarian pedicle, which can be seen on ultrasound, CT, and MRI 1,2.
Terminology
The term whirlpool sign is used in other contexts: see whirlpool sign (disambiguation).
Radiographic features
It appears as a twisting of the thickened vascular pedicle of the enlarged ovary. It can be detected on ultrasound (usually the first imaging examination suspected), confirming the diagnosis along with the other suggestive imaging features and clinical presentation 3.
MRI
The whirlpool sign is demonstrated on axial T2 and T1 C+ fat sat sequences 4. A swollen and heterogeneous appearance of the ovarian tissue may be also seen, with increased T2 signal intensity 2.