In a woman with acute pelvic pain and suspected adnexal torsion, what is the study of choice, and what are the imaging findings of adnexal torsion?
Adnexal torsion occurs when the adnexa and its vascular pedicle twist, resulting in ischemic injury to the ovary and/or fallopian tube. In the majority of cases, a predisposing ipsilateral functional cyst or neoplasm (most commonly mature teratoma) is present. When adnexal torsion is suspected, US is the initial study of choice. Common sonographic findings are an adnexal mass, an enlarged ovary, and pelvic fluid. The affected ovary may also demonstrate peripherally located follicles and may have an atypical location such as above the uterine fundus or adjacent to the contralateral ovary. Color Doppler US can demonstrate a “whirlpool” sign created by a twisted pedicle. Spectral Doppler US may demonstrate compromised blood flow depending on the extent of vascular obstruction ( Figure 38-8A ). On CT and MRI, an adnexal mass, an enlarged ovary, and simple or hemorrhagic pelvic fluid are commonly visualized ( Figure 38-8B ). Decreased or absent contrast enhancement of the ovary, visualization of a twisted vascular pedicle, fallopian tube wall thickening, deviation of the uterus toward the involved side, or atypical location of the adnexa to the contralateral pelvis or midline may also be seen. Hemorrhage within the ovary, fallopian tube, or pelvic peritoneal space when present has high attenuation on CT and high T1-weighted signal intensity on MRI.