Ovarian Torsion
- Ovarian torsion is the ovary twisting on its blood-supply stalk, choking off its own circulation — a true surgical emergency where the clock matters.
- The single most useful sign is an enlarged, edematous ovary, often shoved toward the midline. An ovary that's much bigger than its partner is guilty until proven innocent.
- A mass or cyst is the usual troublemaker — it's the weight on the end of the rope that lets the ovary swing and twist.
- Doppler is reassuring when it shows flow, but treacherous when it doesn't. Present arterial flow does NOT rule out torsion. The diagnosis is gray-scale first, color second.
- A peripherally-displaced "string of pearls" of follicles around a swollen ovary is a classic gray-scale tell.
Imagine a hanging plant in a basket, suspended by a couple of twisted cords. Now hang a bowling ball off one side of the basket. It starts to swing, the cords wind around each other, and eventually they pinch tight — and anything trying to flow through those cords is in trouble. That, more or less, is ovarian torsion: the ovary twists around the vascular pedicle it hangs from, and it starts strangling its own blood supply.
This is a don't-miss because a torsed ovary is on a timer. Twist long enough and the ovary dies. Salvage is possible, especially with prompt surgery — which is exactly why a radiologist's job here is to raise the alarm fast and not get lulled into false reassurance.
What does the twisting
The ovary normally sits fairly snug. To torse, it usually needs a reason to become a swinging weight — most commonly a cyst or mass acting like that bowling ball. So when you find an enlarged ovary with a functional cyst or a dermoid on it and the patient has acute, severe, often sudden one-sided pelvic pain (frequently with nausea and vomiting), torsion belongs at the top of your worry list.
A caveat that catches people: in children and young women, ovaries can torse with no underlying mass at all because their ligaments are more lax. So "the ovary looks normal except it's huge" is still very much torsion until proven otherwise.
The finding that actually matters
Forget the fancy stuff for a second. The bread-and-butter sign of torsion is a unilaterally enlarged, edematous ovary. When the venous drainage gets pinched first (veins are floppy and collapse before stiff little arteries do), blood keeps arriving but can't leave, so the ovary engorges and swells — like a sponge that soaks up water but can't be wrung out.
A few specific tells on that swollen ovary:
- Peripherally displaced follicles — the engorged central stroma pushes the little follicles out to the rim, giving a "string of pearls" look around the edge.
- The ovary often migrates toward the midline or sits abnormally high, dragged by its twisted stalk.
- You may catch the twisted pedicle itself: a "whirlpool sign," swirling vessels coiled like a cinnamon roll. When you see it, it's gold.
The Doppler trap (read this twice)
Here's where good clinicians get burned. Everyone wants color Doppler to be the answer — flow present, ovary alive, go home. It is not that simple.
Normal arterial flow does NOT exclude torsion. The ovary has a dual blood supply (ovarian and uterine arteries), torsion can be intermittent or partial, and stiff arteries resist collapse longer than veins. So you can have a genuinely torsing ovary that still shows arterial signal. Treat absent flow as alarming, but never treat present flow as a clearance.
What Doppler can add: absent or markedly reduced flow is a worrisome, often later finding, and loss of the normal venous waveform can come earlier. But the decision to call torsion leans on the gray-scale picture — the big edematous ovary — with Doppler as a supporting actor, not the star.
If you anchor on a reassuring Doppler and sign off a swollen, painful, asymmetric ovary as "flow present, no torsion," you can send a salvageable ovary to necrosis. When gray-scale screams torsion and the surgeon is worried, the ovary wins the argument — not the color box.
How not to miss it
The discipline is simple: compare the two ovaries, every time. Torsion is loud when you put the swollen ovary next to its normal twin and the size difference smacks you in the face. Measure both. An ovary several times the volume of its partner in the setting of acute pain is a red flag regardless of what the color box says.
Then walk the checklist: Is there a mass or cyst dragging it? Are follicles shoved to the rim? Is the ovary in a weird midline or high position? Any whirlpool? Free fluid in the pelvis is common but nonspecific.
Torsion can wax and wane. A patient whose pain comes in severe waves and whose ovary looks abnormally big may be intermittently torsing and detorsing — don't let a quiet moment (or a moment of restored flow) talk you out of it.
Finally, keep the company it travels in straight. Acute one-sided female pelvic pain has a short, sharp differential, and you don't want to pin everything on the ovary.
| Diagnosis | What points to it instead of torsion |
|---|---|
| Ectopic pregnancy | Positive pregnancy test, empty uterus, adnexal ring or tubal mass. |
| Appendicitis | Right-lower-quadrant pain migrating from the periumbilical region, normal ovaries. |
| Hemorrhagic cyst rupture | Sudden pain, free fluid, but a normal-sized ovary with a collapsing cyst. |
The takeaway, if you keep one thing: torsion is a gray-scale diagnosis of an enlarged, edematous, asymmetric ovary in a patient with acute pain — and present Doppler flow has never, not once, earned the right to overrule that picture.