Initial Triage

Exclude first

• Normal findings, crenulated enhancing corpus luteum, asymmetric but normal-size ovary, or calcification without a noncalcified mass.
• Previously characterized by ultrasound/MRI or stable in size and appearance for 2 years or more.
• If the mass is not fully seen or characterization is limited, recommend pelvic ultrasound or dedicated pelvic MRI.

Simple-appearing cyst

• Round or oval, unilocular, fluid attenuation/signal, thin smooth wall, and no solid component or mural nodule.
• Layering hemorrhage can still be acceptable in a premenopausal patient.

Size Thresholds

Premenopausal

• Simple cyst 5 cm or smaller: no follow-up.
• Simple cyst larger than 5 cm: pelvic ultrasound in 6-12 weeks to confirm simple morphology.
• Fully characterized MRI may allow no follow-up up to about 7 cm when unequivocally simple.

Postmenopausal

• Simple cyst 3 cm or smaller: no follow-up.
• Simple cyst 3-5 cm: no follow-up if confidently simple on ultrasound or fully characterized MRI; otherwise pelvic US or MRI in 6-12 months.
• Simple cyst larger than 5 cm: pelvic ultrasound or MRI for characterization and interval follow-up.

Complex / Limited

Probably benign / limited

• Minimally complex or poorly characterized cysts without solid nodule or papillary projection use lower thresholds.
• Premenopausal: 3 cm or smaller often no follow-up; 3-5 cm pelvic US in 6-12 weeks; larger than 5 cm US or MRI.
• Postmenopausal: early postmenopause uses about 3 cm as a no-follow-up threshold; late postmenopause uses about 1 cm.

Red flags

• Thick septations, mural nodules, papillary projections, solid component, irregular/thick wall, ascites, or peritoneal disease.
• Prompt pelvic ultrasound and/or pelvic MRI; use O-RADS risk stratification and gynecologic referral when appropriate.
• Hemorrhagic-appearing cyst after menopause usually needs US or MRI characterization.

Sources

• ACR 2019 incidental adnexal findings white paper
• ACR incidental adnexal findings white paper
• SRU / O-RADS aligned guidance review
• BWH CT/MRI incidental adnexal lesion recommendations