Imaging description

Ultrasound is the initial study of choice for the evaluation of suspected ovarian torsion, due to its ability to evaluate the structure and size of the adnexa without ionizing radiation, and its ability to evaluate vascular flow.

It is erroneous to assume that the presence of Doppler flow excludes ovarian torsion and the absence of flow confirms torsion; evaluation is more complex and subtle than this simple binary approach would suggest.

Overall, there are quite variable data supporting the accuracy of ultrasound for the preoperative diagnosis of ovarian torsion: correct preoperative diagnostic rates have been reported to be as low as 23–66% of cases [1]. Absence of both arterial and venous flow in an enlarged ovary is highly suggestive of ovarian torsion, with a sensitivity approaching 100% and a specificity of 97% [2], while normal flow in a normal-sized and normal-appearing ovary is extremely unlikely to represent torsion. However, arterial or venous flow may occur in an ovary that has undergone torsion. In one series of 199 patients who presented with adnexal pain, 29 of whom had surgically proven ovarian torsion, the absence of Doppler flow in the ovarian artery was noted in only 22 (76%), although there was abnormal (non-continuous) or absent flow in the ovarian vein in 29 (100%) [2]. Our local experience demonstrates the presence of normal arterial and continuous venous flow does not entirely exclude torsion. An enlarged ovary with clinical symptoms of torsion may in fact have undergone torsion, either currently, or intermittently in the past, even if Doppler flow is demonstrated (Figure 74.1) [1, 3]. Other signs such as visible coiling of the ovarian pedicle (the “whirlpool sign”) have been reported to reliably predict ovarian torsion [4].