Can ultrasound reliably diagnose intermittent ovarian torsion?

Ultrasound Diagnosis of Intermittent Ovarian Torsion

Ultrasound can identify intermittent ovarian torsion, but normal Doppler flow does not rule out the diagnosis, making it essential to evaluate multiple sonographic features rather than relying on blood flow assessment alone. 1, 2

Key Ultrasound Findings in Intermittent Torsion

• Unilaterally enlarged ovary (>4 cm or volume >20 cm³) is the most consistent finding in ovarian torsion, including intermittent cases 1, 3
• Peripheral follicular distribution (found in up to 74% of cases) is a significant indicator of torsion that may persist even during intermittent symptoms 1
• The "whirlpool sign" representing the twisted vascular pedicle has 90% sensitivity in confirmed adnexal torsion and should be specifically sought in suspected intermittent cases 1
• Abnormal or absent venous flow has 100% sensitivity and 97% specificity for torsion, but may normalize during intermittent episodes 1, 4

Diagnostic Pitfalls in Intermittent Torsion

• Normal Doppler flow does not exclude ovarian torsion - studies show 61% of right ovarian torsions and 27% of left ovarian torsions had normal Doppler flow despite confirmed torsion 2
• Reliance on Doppler findings alone can delay diagnosis by an average of 59 hours compared to 5.3 hours when abnormal flow is detected 4
• Intermittent torsion may show transient normalization of blood flow between episodes, making timing of ultrasound critical 1, 2
• The presence of an ovarian cyst significantly increases torsion risk and should raise suspicion even with normal Doppler findings 2

Multimodal Approach for Intermittent Torsion

• When ultrasound findings are inconclusive but clinical suspicion remains high, MRI provides 80-85% sensitivity for torsion 5, 1
• MRI findings of intermittent torsion include enlarged ovary with stromal edema, surrounding fluid, and potentially subtle enhancement abnormalities 5, 6
• CT may show an enlarged, featureless, hypoenhancing ovary with swirling of vascular pedicle in cases where ultrasound is inconclusive 5, 1
• Machine learning algorithms combining multiple sonographic features (medialization, peripheral follicles, volume ratios, and Doppler flow) achieve 95% sensitivity and 92% specificity for torsion diagnosis, outperforming any single feature 7

Best Practices for Ultrasound Assessment

• Compare ovarian volumes bilaterally - torsed ovaries are typically 12 times larger than the contralateral normal ovary 3
• A volume ratio >20 between the affected and normal ovary strongly suggests the presence of an underlying ovarian mass (90% predictive) 3
• Evaluate for ipsilateral deviation of the uterus toward the affected side, which occurs in many torsion cases 6
• Document ovarian position relative to midline, as medialization of the ovary has moderate diagnostic value (AUC 0.76) 7

Clinical Integration of Imaging Findings

• Ultrasound sensitivity for ovarian torsion is approximately 70% with specificity of 87%, requiring integration with clinical presentation 2
• The American College of Radiology notes that ovarian torsion pain typically presents as severe, constant pain that may fluctuate in intensity but rarely completely resolves without intervention 1
• Transvaginal ultrasound combined with transabdominal views provides the most comprehensive assessment for suspected torsion 5
• Repeated ultrasound during symptomatic episodes may capture intermittent torsion that was missed during asymptomatic periods 1, 4