It always is important to interrogate the opposite ovary, because torsion usually is unilateral, and flow in the contralateral ovary usually is detectable (Fig. 9). Occasionally, however, in prepubertal girls 20 and in postmenopausal women,55 no Doppler signal is recorded in the normal ovary as well, despite the correct setting of the equipment, because of insufficient color Doppler sensitivity.
Fig. 9. Right adnexal torsion in a 32-year-old woman. The right ovary (arrowheads) is enlarged with peripheral follicular cysts, and no vascularization is observed at color Doppler interrogation. The left ovary (curved arrows) presents with a follicular cyst (asterisk) and normal color Doppler vascularity. U, uterus.
Diagnosis of adnexal torsion at color Doppler ultrasonography is not as simple as documenting the presence or absence of flow.15,56 In fact, although the lack of intraovarian arterial or venous flow is highly indicative of adnexal torsion (Fig. 10), several investigations show that flows, either pathologic or normal, can be recorded in a considerable percentage of patients who have surgically proved torsion.18,57 Several possible explanations have been advocated to explain this finding.18 First, torsion can be intermittent, and the patient might have been examined during detorsion. Second, torsion may be incomplete. Third, torsion could have been investigated in earlier phases, in which only venous and lymphatic occlusion have occurred. Fourth, persistent adnexal flow might be related to the dual ovarian arterial blood supply from the aorta and from the ovarian branches of the uterine arteries.55 Occlusion of only one system might account for the visualization of some arterial flows in the torsed ovary that are not evenly distributed throughout the parenchyma or sufficient to maintain normal oxygenation and perfusion.58
Fig. 10. Adnexal torsion presenting with lack of vascularization at color Doppler ultrasonography. (A) Right adnexal torsion of a previously normal ovary (arrowheads). (B) Right adnexal torsion on a follicular cyst (asterisk) in a patient who had a spontaneous abortion. The right ovarian parenchyma (arrowheads) shows a crescent configuration and no vascularization. The uterine cavity (U) is filled with fluid.