The Adnexal Mass — First Look on Ultrasound
Most ovarian cysts are found by chance during routine pelvic imaging.
- ~10%: Lifetime incidence (women affected)
- >70%: Found incidentally (on routine TVUS)
- <1%: Malignancy risk (simple cyst, premenopausal)
- TVUS: First-line imaging (transvaginal ultrasound)
Why cysts are found by accident
Pelvic pain or routine screening often reveals a silent cyst.
The differential diagnosis question
Is it a normal cycle event, or a true pathologic growth?
Why ultrasound comes first
TVUS is cheap, fast, and radiation-free for first triage.
Sonographic Feature Assessment — Reading the Cyst Wall
Structured criteria turn a fuzzy image into a reproducible risk score.
- 10: IOTA simple rules (B-rules & M-rules)
- 3 mm: Septation cutoff (thin vs thick wall)
- ≥3 mm: Papillary projection (suspicious feature)
- 1–4: Color score (internal vascularity grade)
Septations
Thin, few septa favor benign; thick, many favor pathologic.
Echogenicity pattern
Anechoic, ground-glass, or heterogeneous each point differently.
Wall and vascularity
Smooth thin wall with low flow favors a benign cyst.
Functional Cyst Pattern — Follicular and Luteal Origin
Simple, thin-walled, anechoic cysts almost always resolve on their own.
- <3 cm: Follicular cyst size (normal follicle range)
- 6–8 wk: Resolution time (spontaneous regression)
- <5 cm: Corpus luteum cyst (may bleed internally)
- 6–12 wk: Repeat scan interval (confirms resolution)
Follicular cysts
An unruptured follicle keeps growing past ovulation.
Corpus luteum cysts
The post-ovulation structure fills with fluid or blood.
Expectant management
Watchful waiting with a follow-up scan is usually enough.
Pathologic Cyst Pattern — Endometrioma and Dermoid
Complex internal texture signals a lesion that will not resolve alone.
- Ground-glass: Endometrioma sign (homogeneous low-level echoes)
- Tip of iceberg: Dermoid sign (fat, hair, calcification)
- 17–44%: Endometrioma rate (of endometriosis patients)
- <2%: Dermoid malignant change (rare, older patients)
Endometrioma
Old blood produces a hazy, uniform ground-glass fill.
Dermoid cyst
Fat, hair, and teeth create bright, jumbled echoes.
Why these need intervention
Complex cysts rarely regress and often need surgery.
Torsion Risk Evaluation — Size, Pedicle, and Danger
A large or heavy cyst can rotate the ovary and cut off its blood supply.
- >5 cm: Risk rises sharply (diameter threshold)
- 2.7%: Torsion incidence (of gynecologic emergencies)
- Doppler: Whirlpool sign (twisted vascular pedicle)
- <8 h: Salvage window (to save the ovary)
Size as the driver
Bigger cysts add weight that favors ovarian rotation.
The whirlpool sign
Doppler shows swirling flow around a twisted pedicle.
Time-critical surgery
Fast detorsion preserves ovarian tissue and fertility.