Investigation of Choice in Ovarian Torsion
Combined transabdominal and transvaginal pelvic ultrasound with color and spectral Doppler is the investigation of choice for suspected ovarian torsion. 1, 2
Why Ultrasound is First-Line
Ultrasound is universally recommended as the initial imaging modality by the American College of Radiology because it provides the highest diagnostic accuracy when both approaches are used together, achieving 96% overall accuracy for adnexal torsion. 2 The combination is essential because:
- Transvaginal ultrasound offers superior resolution (83.3% sensitivity) for detecting subtle ovarian pathology, peripheral follicles, and the whirlpool sign 2
- Transabdominal ultrasound provides a larger field of view to assess adnexa positioned high in the pelvis and evaluate free pelvic fluid 2
- Both techniques are complementary and should be performed together as a single examination 3, 1
Critical Ultrasound Findings to Document
The systematic ultrasound evaluation must include 1, 2:
- Ovarian size: Unilateral enlargement >4 cm or volume >20 cm³ (present in 74% of cases) 2
- Peripheral follicles: "String of pearls" pattern along the ovarian periphery 2
- Whirlpool sign: Twisted vascular pedicle with 90% sensitivity in surgically confirmed cases 1, 2
- Doppler flow assessment: Abnormal or absent ovarian venous flow has 100% sensitivity and 97% specificity 1, 2
- Free pelvic fluid: Often present in torsion 4, 5
Critical Pitfall: Normal Arterial Flow Does NOT Rule Out Torsion
Normal arterial blood flow on Doppler does not exclude ovarian torsion because torsion can be intermittent or partial, and venous obstruction occurs before arterial compromise. 1, 6 Venous flow abnormalities are more sensitive than arterial findings. 1 The presence of central arterial flow may actually suggest the ovary is still viable and salvageable. 4, 7
When to Use Second-Line Imaging
MRI (Preferred Second-Line)
If ultrasound is nondiagnostic or equivocal but clinical suspicion remains high, MRI is the preferred second-line modality with 80-85% sensitivity and no radiation exposure. 1, 6, 2 MRI findings include:
CT Abdomen/Pelvis with IV Contrast
CT may be used when MRI is unavailable or when non-gynecologic pathology is in the differential, with 74-95% sensitivity and 80-90% specificity. 6, 2 CT findings include:
- Asymmetrically enlarged, featureless, hypoenhancing ovary 1, 8
- Twisted vascular pedicle (whirlpool sign) 1, 8
- Deviation of uterus to the affected side 4, 8, 5
- Engorged vessels on the twisted side 1
- Smooth wall thickening of adnexal cystic mass 4
Important note: A negative contrast-enhanced CT has 100% negative predictive value for ovarian torsion, making additional Doppler ultrasound unnecessary after a negative CT. 9
Clinical Context
Ovarian torsion is a gynecological emergency requiring immediate ultrasound in the Emergency Department, followed by urgent gynecologic consultation for surgical management. 1 The condition typically presents as severe, constant pain that fluctuates in intensity but rarely resolves without intervention. 1, 6 It can mimic appendicitis, renal colic, or urinary tract infection, leading to diagnostic delays. 6, 8