The diagnosis is the pedicle and the ovarian morphology — not the flow. Preserved arterial flow does NOT exclude torsion.
Orient first
- Torsion is a MECHANICAL diagnosis. The ovary twists on its vascular pedicle; veins have thin walls and collapse first, arteries have thick walls and may keep flowing for hours. So the sequence of failure is venous → stromal oedema → arterial.
- That sequence is why flow is the LAST thing to trust and the ovary itself is the first. The dual blood supply (ovarian and uterine arteries) makes preserved arterial flow common in proven torsion.
- A torted ovary is typically enlarged and oedematous, and its follicles get pushed to the periphery by the swollen central stroma — the "string of pearls" arrangement.
Acquire the study
- Transabdominal first with a full bladder for the overview and to find a high-lying ovary, then transvaginal for detail if appropriate for the patient.
- Set colour Doppler for LOW flow before concluding anything: drop the PRF/scale, lower the wall filter, raise colour gain until noise just appears then back off. A machine set for arterial flow will show absent venous flow in a normal ovary.
- Interrogate arterial and venous flow SEPARATELY with spectral Doppler, and document both. "Flow present" without saying which is uninterpretable.
- Compare with the opposite ovary in the same settings — the asymmetry is more reliable than any absolute figure.
The manoeuvre
- Measure both ovaries and compare volumes. Unilateral enlargement with oedematous stroma is the core finding.
- Look for peripherally displaced follicles around an oedematous central stroma.
- Hunt for the WHIRLPOOL SIGN — the twisted vascular pedicle, seen as concentric rings on grey-scale or a spiral of colour, between the uterus and the ovary. This is the specific sign; look for it deliberately rather than hoping it appears.
- Note the ovarian POSITION — a torted ovary is often pulled toward the midline, above the uterine fundus.
- Assess arterial flow and venous flow separately, and say which is absent.
- Look for a LEAD POINT: a cyst or mass the ovary has twisted on. Its absence does not exclude torsion, especially in children.
- Note free pelvic fluid and any fat stranding.
What confirms it
- An enlarged oedematous ovary with peripherally displaced follicles PLUS a whirlpool sign is diagnostic.
- Absent venous flow with preserved arterial flow in an enlarged tender ovary is torsion until proven otherwise.
What licenses you to exclude it
- ⚠️ PRESERVED ARTERIAL FLOW DOES NOT EXCLUDE TORSION, and this is the single most common way the diagnosis is missed. If the morphology says torsion, report torsion and say that flow does not exclude it.
- A normal-sized ovary with normal stroma, normal follicular distribution and symmetrical flow makes torsion unlikely — but if clinical suspicion is high, say that surgical assessment outranks the scan.
The classic misread
- Reporting "flow present, torsion excluded" — the error this entry exists to prevent.
- Judging flow on a machine set up for arterial signal, so normal venous flow is invisible everywhere.
- Treating a haemorrhagic cyst as the answer and stopping — it is a common LEAD POINT for torsion.
- Applying mass descriptors (margin, echogenicity, posterior features) instead of pedicle and stromal morphology. Torsion is not a mass.