Findings: There is marked enlargement of the left ovary, which measures 8x6x5 cm in diameter (Fig.1). Within the center of the ovary, a homogenous mass measuring 5x5x4 cm is identified (Fig. 2). Of note, despite multiple attempts, no Doppler flow could be identified in the ovary (Fig. 3).

Diagnosis: Ovarian torsion, with central hemorrhagic cyst. At surgery, the ovary was enlarged, edematous, and black. There was a 720 degree torsion of the ovary. A unilateral salpingo-oophorectomy was performed.

Discussion: Ovarian torsion is an important yet notoriously difficult diagnosis. It can mimic a number of gynecologic and non-gynecologic conditions, appendicitis being one of the most important. Unfortunately, the diagnosis is suspected in only 35% of ultimately proven cases.

A number of radiographic appearances have been described. In one series of pubertal and prepubertal females, unilateral ovarian enlargement was seen in all patients. The most common finding was a solid mass with peripheral cysts seen in 65% of patients. 30% presented with complex masses with multiple cysts and septations. 30% had evidence of free fluid. While a lack of demonstrable blood flow to the ovary by Doppler evaluation is supposed to be pathognomonic, this was seen in only 20% of these patients. In a study looking at an adult population, all patients with ovarian torsion had a unilaterally enlarged ovary. In this population, a majority had evidence of underlying pathology, with 4/13 demonstrating ovarian neoplasms.

Unlike this patient, ovarian flow is often maintained in ovarian torsion. While venous flow is first compromised, causing swelling and edema, arterial flow will be maintained until late in the clinical course. The ovary's dual blood supply (ovarian and uterine artery), is also felt to be responsible for maintenance of flow despite the presence of ovarian torsion.

References:
Stark, J, Siegel M, Ovarian torsion in prepubertal and pubertal girls sonographic findings.
AJR 163:1479-1482.

Helvie,MA Silver, TM Ovarian Torsion:sonographic evaluation. J.Clin Ultrasound 17:327-332.

Rosado, WM, Traubert, MA, Gosnink BB, Pretorius, DH Ovarian Torsion: Case Report
AJR, 1992, 159:1251-1253.

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