Ovarian torsion is caused by partial or complete rotation of the ovary on its mesenteric pedicle. This results first in compromise of the lymphatic and venous drainage, causing congestion and edema of the ovarian parenchyma and eventually leading to loss of the arterial perfusion and infarction. The condition is a surgical emergency much like a testicular torsion. Torsions may occur in normal or abnormal (ie ovarian cyst, dermoid) ovaries. This condition usually occurs in children and younger woman who have more mobile adnexa.

The imaging findings of ovarian torsion are variable. However, any abnormal ovary on ultrasound in the proper clinical setting should suggest the diagnosis. The sonographic findings depend on the degree of vascular compromise and whether an adnexal mass is present. The ovary is usually enlarged. Multiple enlarged cortical follicles in a big ovary with the proper history-acute lower quadrant pain (same side as the abnormal ovary), nausea, vomiting, mildly elevated WBC-is considered a specific sign. Color and spectral Doppler examination may show absent flow in the affected ovary. However this is neither a specific nor sensitive sign. Torsed ovaries may have Doppler flow, and normal ovaries may not show flow on Doppler interrogation. (Rumack, Diagnostic Ultrasound p.550)