Critical pitfall: Normal Doppler flow does NOT exclude ovarian torsion. Intermittent torsion or partial torsion can preserve some flow. Clinical presentation + enlarged ovary + peripheral follicles = high suspicion regardless of Doppler. This is a surgical emergency — diagnostic laparoscopy if clinical suspicion is high. Delay causes ovarian infarction and loss.
Ultrasound Findings
- Enlarged ovary (>4 cm, often >5 cm)
- Peripheral follicles displaced to periphery (hallmark — "string of pearls")
- Ovary displaced from normal position (may be midline or contralateral)
- Absent or decreased Doppler flow
- Free pelvic fluid
- Associated adnexal mass (dermoid, cystadenoma) in ~50–60% of cases
- Thickened edematous stroma
Pearls
- Right > left (sigmoid colon limits left ovarian mobility)
- Associated ovarian mass in ~50–60% of cases — teratoma, cystadenoma most common
- Pediatric patients: torsion can occur with normal ovaries
- MRI if equivocal US — T2 hyperintense edematous stroma, absent enhancement in late/infarcted torsion
- Doppler twisting of vascular pedicle ("whirlpool sign") is specific but not always present
Reporting Checklist
- Side: right / left
- Ovarian volume: L × W × H × 0.523 (mL); abnormal if >20cc or asymmetrically enlarged
- Doppler flow: absent / reduced / asymmetric vs contralateral
- Whirlpool sign of vascular pedicle: present / absent
- Free pelvic fluid: present / absent; simple / complex / hemorrhagic; amount
- Underlying ovarian lesion: size (cm), morphology
- Uterine deviation toward affected side: present / absent
- Contralateral ovary: normal / abnormal (volume and flow)
References
Shadinger LL et al. Preoperative sonographic and clinical characteristics as predictors of ovarian torsion. J Ultrasound Med. 2008;27(1):7–13.
Radiopaedia — Adnexal torsion