| Simple/follicular/corpus luteum cyst | anechoic, thin wall; corpus luteum: crenulated wall with ring of fire | physiological; O‑RADS 1–2 |
| Haemorrhagic cyst | reticular "lace‑like / fishnet" internal echoes, retracting clot (concave margins), no internal flow | resolves in 6–12 weeks |
| Endometrioma | homogeneous low‑level "ground‑glass" echoes, echogenic wall foci; MRI: T1 bright, T2 shading, T2 dark spot sign | "chocolate cyst" |
| Mature cystic teratoma (dermoid) | echogenic Rokitansky nodule (dermoid plug) with shadowing: tip‑of‑the‑iceberg sign; dot‑dash (hair) lines; fat–fluid level; fat on CT (negative HU) / MRI (fat‑sat signal loss); teeth on radiograph | commonest ovarian neoplasm in young women; torsion; malignant transformation rare |
| Hydrosalpinx | tubular, incomplete septa, cogwheel (acute) / beads on a string (chronic) | PID, TB |
| Tubo‑ovarian abscess | complex multilocular mass, thick walls, debris | PID |
| Malignant features | solid component with internal flow (papillary projections), thick irregular septa, ascites, peritoneal implants, omental cake | serous/mucinous cystadenocarcinoma; CA‑125, RMI; MRI for indeterminate masses (O‑RADS MRI); CECT for staging |
| PCOS | ≥ 20 follicles (2–9 mm) per ovary or ovarian volume ≥ 10 mL (Rotterdam/2023), peripheral string of pearls, echogenic stroma | — |
| Ovarian torsion | enlarged oedematous ovary with peripherally displaced follicles, whirlpool sign (twisted pedicle), free fluid; Doppler flow may be present (dual supply) | clinical diagnosis; often with a lead mass (dermoid) |
| Krukenberg tumour | bilateral solid ovarian masses (gastric, colorectal primary) | — |