A 24-year-old woman presents with sudden-onset severe right lower quadrant pain, nausea, and vomiting. Transvaginal ultrasound shows a markedly enlarged right ovary (7 × 6 cm) with peripheral follicles and heterogeneous edematous stroma. Color Doppler demonstrates absent venous flow within the ovary. On transverse imaging, the structure marked **B** is identified. Which of the following best describes the pathophysiological significance of this finding in ovarian torsion?

Question

Accepted Answer

D. Represents the twisted vascular pedicle and is highly specific for ovarian torsion, indicating mechanical compromise of the infundibulopelvic and utero-ovarian ligaments. ## Why the first option is right

The whirlpool sign (marked **B**) is the pathognomonic finding in ovarian torsion — it represents the twisted vascular pedicle (infundibulopelvic and utero-ovarian ligaments) seen on transverse color Doppler imaging. This sign is highly specific for torsion and directly indicates mechanical vascular compromise. The twisting of the pedicle is the anatomical basis for the cascade of venous/lymphatic compression → edema → hemorrhagic infarction → necrosis. In this case, the absent venous flow and enlarged edematous ovary are direct consequences of this pedicle twisting. Recognition of the whirlpool sign mandates emergency surgical detorsion to prevent irreversible ovarian damage (ACOG Practice Bulletin; ESUR Imaging Guidelines).

## Why each distractor is wrong

- **Second option**: While arterial flow may be paradoxically preserved longest due to the thick muscular walls and dual blood supply, the whirlpool sign indicates active mechanical torsion requiring EMERGENCY surgery, not delayed intervention. Waiting for arterial insufficiency to develop risks ovarian necrosis and loss of fertility.
- **Third option**: The whirlpool sign is a vascular finding specific to torsion (twisting of the pedicle), not a consequence of rupture or peritoneal inflammation. A ruptured cyst would show free fluid but not the characteristic twisted pedicle appearance.
- **Fourth option**: Ovarian hyperstimulation syndrome presents with bilateral ovarian enlargement and intact blood flow on Doppler. The whirlpool sign and absent venous flow are pathognomonic for torsion, not hyperstimulation, and require surgical intervention, not conservative management.

**High-Yield:** The whirlpool sign (twisted vascular pedicle on transverse Doppler) is the most specific ultrasound finding for ovarian torsion and mandates emergency laparoscopic detorsion regardless of ovarian appearance — >90% of even cyanotic ovaries recover function if detorsed promptly.

[cite: ACOG Practice Bulletin; ESUR Imaging Guidelines]

Answer

A. Indicates primary arterial insufficiency with preserved venous return, allowing time for delayed surgical intervention

Answer

B. Reflects secondary peritoneal inflammation from a ruptured ovarian cyst rather than vascular compromise

Answer

C. Demonstrates ovarian hyperstimulation syndrome with intact dual blood supply, requiring conservative management

Explanation

Why the first option is right

Why each distractor is wrong

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