Adnexal Masses in Pregnancy
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Direct answer
Adnexal masses complicating pregnancy are most often physiological corpus luteum cysts, but neoplasms must be excluded on ultrasound morphology before reassurance. Simple cysts are usually observed because most resolve spontaneously, while torsion or suspicious features prompt surgery. Elective ovary-sparing cystectomy is best timed in the second trimester, when miscarriage risk has settled and the uterus has not yet crowded the pelvis.
What you must remember
- Commonest mass: the corpus luteum cyst, a functional cyst that supports progesterone production until the placenta takes over at around 10 to 12 weeks.
- Ring of fire: peripheral high-velocity colour Doppler flow around a corpus luteum, which helps separate it from a neoplasm.
- Benign features: a unilocular, thin-walled cyst without solid areas, papillary projections, ascites or bilateral disease is usually followed up.
- Dermoid cyst: the commonest benign neoplasm in young women, seen in pregnancy and treated by ovary-sparing cystectomy.
- Torsion: the commonest complication, presenting as sudden pain with nausea and vomiting, and most often seen in the first trimester.
- MRI without gadolinium: preferred when ultrasound cannot characterise the mass, because gadolinium is avoided in pregnancy.
- Markers: CA-125 and hCG are confounded by pregnancy, so imaging morphology should drive the decision.
- Surgery timing: the second trimester suits elective cystectomy, while torsion or suspected malignancy needs urgent operation.
A stepwise approach from ultrasound to surgery
Management follows a fixed sequence of confirming, characterising and then choosing between observation and surgery. Each step changes the next decision.
- Confirm and measure: Transvaginal ultrasound with colour Doppler defines size, laterality, septations and any solid component. Record the greatest dimension at every review, measured in the same plane each time.
- Look for a corpus luteum: A ring of fire flow and a thin-walled unilocular appearance favour a functional cyst. Repeat the scan later in pregnancy to confirm regression, since persistence changes the plan.
- Characterise suspicious features: Solid areas, papillary projections, thick septations, ascites or bilateral masses raise suspicion of neoplasm. Use MRI without gadolinium if the picture stays unclear.
- Observe simple cysts: Repeat ultrasound at intervals, since most physiological cysts resolve by mid-pregnancy. Large masses above about 6 cm, or cysts that fail to resolve, need surgical review.
- Operate with a clear indication: Torsion and suspected malignancy need prompt surgery, and laparoscopic cystectomy is preferred for benign cysts in the second trimester. Preserve the ovary wherever safe, and send tissue for frozen section when malignancy is suspected.
Where examiners set the trap
Adnexal questions usually test whether you know when to wait and when to operate.
- Trap: Operating on every adnexal mass in the first trimester Correct: a simple corpus luteum cyst usually regresses, so repeat ultrasound unless torsion or malignant features appear.
- Trap: Attributing sudden pain to ordinary pregnancy discomfort Correct: pain with vomiting in a woman with an adnexal mass suggests torsion, and surgery should not be delayed.
- Trap: Using CA-125 to decide on surgery Correct: marker levels are unreliable in pregnancy, so ultrasound morphology drives the decision.
- Trap: Performing oophorectomy by default Correct: ovary-sparing cystectomy preserves function and is the usual choice for benign masses.
Frequently asked questions
What is the commonest adnexal mass found in early pregnancy?
The corpus luteum cyst is the commonest adnexal mass in early pregnancy, a physiological cyst that maintains progesterone until the placenta takes over. A simple corpus luteum cyst usually resolves and is followed by ultrasound rather than removed.
Which imaging is preferred to characterise an adnexal mass in pregnancy?
Transvaginal and transabdominal ultrasound with colour Doppler is the first-line investigation for an adnexal mass in pregnancy. MRI without gadolinium is preferred when ultrasound cannot characterise the mass, since gadolinium is avoided in pregnancy.
When is the best time to operate on an ovarian cyst in pregnancy?
Elective cystectomy is best performed in the second trimester, when miscarriage risk has fallen and the uterus has not yet made the pelvis difficult to access. First-trimester surgery is reserved for torsion or suspected malignancy.
Why is ovarian torsion hard to diagnose in pregnancy?
Torsion in pregnancy is hard to diagnose because its pain, nausea and vomiting overlap with normal pregnancy symptoms. Clinical suspicion therefore matters more than ultrasound, which can appear normal even when torsion is present.