What are the diagnostic imaging modalities for ovarian torsion?

From the Guidelines

Transvaginal ultrasound with color Doppler is the first-line imaging modality for diagnosing ovarian torsion, with a sensitivity of 83.3% and a specificity of 100% for ovarian tissue edema, and should be performed promptly when ovarian torsion is suspected. This recommendation is based on the most recent and highest quality study available, which reported a pooled sensitivity of 79% and a pooled specificity of 76% for the diagnosis of adnexal torsion using ultrasound 1. Ultrasound findings suggestive of torsion include an enlarged ovary (>4 cm), peripherally displaced follicles, free fluid in the pouch of Douglas, and abnormal ovarian position. Color Doppler may show absent or decreased blood flow to the affected ovary, though normal blood flow does not exclude torsion as it can be present in partial or intermittent torsion.

Some key points to consider when using ultrasound for diagnosing ovarian torsion include:

• The sensitivity and specificity of ultrasound findings, such as ovarian tissue edema, absence of intraovarian vascularity, and absence of arterial flow, can vary, with reported values of 21% and 100%, 52% and 91%, and 76% and 99%, respectively 1.
• A unilaterally enlarged ovary with central afollicular stroma and multiple uniform 8 to 12 mm peripheral follicles can be a sign of torsion, found in up to 74% of cases, and ovarian enlargement is defined as a maximal ovarian dimension of >4 cm or volume >20 cm3 in a premenopausal patient 1.
• If ultrasound results are inconclusive but clinical suspicion remains high, CT scan or MRI can be considered as second-line options, with CT showing a twisted vascular pedicle, ovarian enlargement, or surrounding inflammatory changes, and MRI offering better soft tissue resolution and detecting hemorrhage within the ovary 1.

However, imaging should never delay surgical intervention when clinical suspicion is high, as ovarian torsion is primarily a clinical diagnosis, and negative imaging in the presence of strong clinical features should still prompt consideration for diagnostic laparoscopy, which remains both diagnostic and therapeutic. The use of CT or MRI as a primary imaging modality is not recommended, as they may not provide additional diagnostic information and may delay treatment, with reported sensitivities and specificities of 74% to 95% and 80% to 90% for CT, and 80% to 85% for MRI 1.

From the Research

Diagnostic Imaging for Ovarian Torsion

• Ovarian torsion is a surgical emergency that requires prompt diagnosis and treatment, and imaging plays a crucial role in its diagnosis 2, 3.
• The first-line imaging modality for evaluating ovarian torsion is ultrasonography, but MRI and CT can also be used, especially in cases with equivocal or non-diagnostic ultrasound findings 2, 3, 4.

Imaging Modalities

• Ultrasonography: Ultrasound features of ovarian torsion are well-known and include ovarian enlargement, adnexal mass, twisting of the vascular pedicle, and decreased adnexal enhancement 2, 3, 5.
• Computed Tomography (CT): CT is not typically used as the first-line imaging modality for ovarian torsion due to radiation concerns, but it can be useful in emergency settings where CT is already being used to evaluate abdominal pain 2, 3.
• Magnetic Resonance Imaging (MRI): MRI is helpful in cases where the diagnosis remains unclear and provides excellent soft tissue contrast without ionizing radiation, making it particularly useful in young or pregnant patients 3, 4, 6.

Key Imaging Findings

• Ovarian enlargement and twisted ovarian pedicle are key findings in ovarian torsion on MRI and CT 2, 3, 6.
• Other findings include adnexal mass, ovarian hemorrhage, abnormal ovarian enhancement, and ipsilateral deviation of the uterus 3, 6.
• Awareness of these imaging features can help radiologists recognize ovarian torsion and differentiate it from other benign or malignant ovarian lesions 6.

Comparison of Imaging Modalities

• A meta-analysis found that B-mode ultrasound had high sensitivity and specificity for diagnosing ovarian torsion, while Doppler ultrasound was highly specific but lacked sensitivity, and CT was the least sensitive test 5.
• Rapid, free-breathing non-contrast MRI has been shown to be a rapid and feasible imaging modality for evaluating ovarian torsion in the emergency department 4.