Adnexal torsion

Torsion is defined as the twisting by at least one complete turn of the adnexa, ovary, or (rarely) the tube only around the infundibulo-pelvic and tubo-ovarian ligament, resulting in ischemia. It occurs more frequently on the right side (70%), perhaps because of a longer tubo-ovarian ligament on the right. Approximately 15% of ovarian torsions occur in children. An increase in weight of the adnexa is the primary risk factor for torsion, particularly with dermoid cysts and other mobile ovarian masses. Ovarian cancer or endometriomas seldom cause torsion because of lack of mobility of these lesions. The incidence of ovarian torsion increases during pregnancy, and ovarian stimulation is an additional risk factor.

An adnexal mass in a patient with pain should prompt consideration of adnexal torsion as a diagnosis. The typical appearance of a torsed ovary is a large, edematous ovary with multiple, small, peripherally placed follicles and heterogeneous texture of the ovarian stroma. The ovary may be very large and tender during the scan. If color Doppler reveals no blood flow in the ovary, then the diagnosis of torsion can be made confidently. The presence of flow, however, cannot be used to rule out adnexal torsion. Blood flow to the ovary may be intermittent or diminished because venous flow may be obliterated, but arterial flow may still be present. The ovary also has a dual blood supply, which may confound the Doppler findings. Doppler interrogation of the twisted vascular pedicle may reveal a spiral appearance of the vessels, referred to as the “whirlpool” sign. A positive whirlpool sign has a high positive predictive value for diagnosing torsion and should be part of the evaluation in a symptomatic patient.