Exclusions — algorithm does not apply:
- Normal findings: crenulated enhancing corpus luteum wall, asymmetric ovary without discrete mass
- Calcifications without associated noncalcified mass
- Previously characterized by US or MRI
- Documented stability in size and appearance for ≥2 years
Step 1 — Classify the Mass
| Category | Imaging Features | Next Step |
|---|---|---|
| Simple-appearing cyst (<10 cm) | Fluid density/signal; smooth or imperceptible wall; no solid component, septation, or internal structure | See size-based tables below |
| Other characteristic diagnosis | CT or MR features diagnostic of a specific entity (hemorrhagic cyst, dermoid, endometrioma, fibroma, para-ovarian cyst, etc.) | See Table 1 |
| Uncertain diagnosis or simple-appearing cyst ≥10 cm | Features do not allow confident classification, or cyst ≥10 cm regardless of appearance | US or MRI to characterize (promptly) |
Step 2 — Simple-Appearing Cyst: Size-Based Management
If the mass exceeds the size threshold for no follow-up, the quality of assessment on the original study determines the recommendation.
Limited assessment = low signal-to-noise ratio, artifact, lack of IV contrast, or incomplete anatomic coverage. When assessment is limited and the cyst exceeds the size threshold for no follow-up, the recommendation upgrades to US to characterize promptly rather than scheduled follow-up.
Premenopausal (or age <50 if status unknown)
| Size | Recommendation |
|---|---|
| ≤5 cm | No further imaging |
| >5 cm — limited assessment | US to characterize (promptly) |
| >5 cm — adequate but not fully characterized by MR | US follow-up in 6–12 months |
| ↳ ≤7 cm on US, confirmed simple | No further imaging |
| ↳ >7 cm on US | US follow-up in 6–12 months |
| >5 cm — fully characterized by MR | ≤7 cm: no further imaging |
| ↳ >7 cm, fully characterized by MR | US follow-up in 6–12 months |
Postmenopausal (or age ≥50 if status unknown)
| Size | Recommendation |
|---|---|
| ≤3 cm | No further imaging |
| >3 cm — limited assessment | US to characterize (promptly) |
| >3 cm — adequate but not fully characterized by MR | US follow-up in 6–12 months |
| ↳ ≤5 cm on US, confirmed simple | No further imaging |
| ↳ >5 cm on US | US follow-up in 6–12 months |
| >3 cm — fully characterized by MR | ≤5 cm: no further imaging |
| ↳ >5 cm, fully characterized by MR | US follow-up in 6–12 months |
Fully characterized by MRI: T2-weighted + pre- and postcontrast T1-weighted sequences with complete anatomic coverage in ≥2 imaging planes. When these criteria are met, the risk of mischaracterization is substantially reduced and the MR findings can substitute for US follow-up at the thresholds noted above.
Table 1 — Other Characteristic Diagnoses (CT/MRI, ACR 2020)
| Finding | Premenopausal | Postmenopausal |
|---|---|---|
| Hemorrhagic cyst ≤5 cm | No further imaging | US or MRI to characterize (promptly*) |
| Hemorrhagic cyst >5 cm | US follow-up in 2–3 months | US or MRI to characterize (promptly*) |
| Para-ovarian cyst / peritoneal inclusion cyst / simple hydrosalpinx / ovarian fibroma / uterine leiomyoma | Further imaging usually unnecessary; clinical management | Further imaging usually unnecessary; clinical management |
| Endometrioma / Dermoid | Usually managed by gynecologist; may require periodic imaging | Usually managed by gynecologist; may require periodic imaging |
| Suspected malignancy | US or MRI to characterize (promptly*) | US or MRI to characterize (promptly*) |
*"Promptly" = for further evaluation and characterization, not temporal surveillance follow-up.
Characteristic Lesion Management at US (O-RADS/SRU)
When US is performed (either for characterization or as the primary imaging modality), the following O-RADS/SRU recommendations apply to classic benign adnexal lesions, as integrated by Wang et al. (RadioGraphics 2022).
| Lesion | Premenopausal | Postmenopausal |
|---|---|---|
| Hemorrhagic cysts ≤5 cm | No further management | MRI, US specialist, or gynecologist follow-up |
| Hemorrhagic cysts >5 cm and <10 cm | US at 8–12 weeks | MRI, US specialist, or gynecologist follow-up |
| Dermoid cysts and endometriomas <10 cm | Optional follow-up US in 8–12 weeks (may help differentiate endometriomas from atypical hemorrhagic cysts that typically resolve) | MRI, US specialist, or gynecologist follow-up; if not resected, annual US surveillance + MRI for morphology changes and size |
| Simple paraovarian / paratubal cysts | No further management | Optional follow-up US in 1 year |
| Peritoneal inclusion cysts, hydrosalpinx | Refer to gynecologist | Refer to gynecologist |
Reporting Elements
The ACR recommends including four elements when reporting an incidental adnexal mass:
- Mass characteristics — simple-appearing, characteristic diagnosis, or uncertain/indeterminate
- Size — largest single diameter; three orthogonal dimensions if follow-up imaging will be recommended
- Technical considerations — note if assessment was limited (low SNR, no IV contrast, incomplete coverage); this changes the management recommendation
- Menopausal status — include if available; use age surrogate if not documented
References
Patel MD, Ascher SM, Horrow MM, et al. Management of Incidental Adnexal Findings on CT and MRI: A White Paper of the ACR Incidental Findings Committee. J Am Coll Radiol. 2020;17(11):1328–1340.
Wang PS, Schoeck OG, Horrow MM. Benign-appearing Incidental Adnexal Cysts at US, CT, and MRI: Putting the ACR, O-RADS, and SRU Guidelines All Together. RadioGraphics. 2022;42:609–624.