4. 1st Trimester Obstetric/OB Ultrasound Protocol

Corpus Luteal Cyst

A corpus luteal cyst develops due to the growth, instead of the normal regression, of the corpus luteum. These cysts will appear very similar to a tubal ectopic pregnancy.

How can you tell the difference between the two?

Tubal Ectopic PregnancyCorpus Luteal Cyst
May find yolk sac or fetal pole
Will move independent of the ovary in response to transducer manipulationWill move with the ovary in response to transducer manipulation
Tubal ring is more echogenicTubal ring is less echogenic
Tubal ring is thickerTubal ring is thinner
Cystic fluid is more likely to be “clumpy” or have some echoesCystic fluid is more likely to be clear and anechoic
May have ring of fire signMay have ring of fire sign
Corpus Luteum Cyst with Ring of Fire and Thin Tubal Ring Ultrasound
Corpus luteal cyst. Note how the fluid and ring are less echogenic than the ectopic pregnancies shown before. Note how the tubal ring is thinner than that of an ectopic.

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