Ovarian cyst

Ovarian cysts are commonly encountered in gynaecological imaging, and vary widely in aetiology, from physiologic, to complex benign, to neoplastic.

Small cystic ovarian structures should be considered normal ovarian follicles unless the patient is pre-pubertal, post-menopausal, pregnant, or the mean diameter is >3 cm (see the 1-2-3 rule).

Types of cysts

• physiological cysts: mean diameter ≤3 cm
  • ovarian follicle
  • corpus luteum
• functional cysts (can produce hormones):
  • follicular cysts of the ovary (oestrogen): >3 cm
  • corpus luteum cysts (progesterone)
  • theca lutein cyst: gestational trophoblastic disease
  • complications in functional cysts:
    • haemorrhage: see haemorrhagic ovarian cyst
    • enlargement
    • rupture
    • torsion
• other cysts:
  • multiple large ovarian cysts in ovarian hyperstimulation syndrome
  • post-menopausal cyst: serous inclusion cysts of the ovary
  • polycystic ovaries
  • ovarian torsion
  • ovarian cystic neosplasmsneoplasm

Radiographic features

Ultrasound is usually the first imaging modality for assessment of ovarian lesions. Simple ovarian follicular cysts:

• are anechoic
• are intraovarian or exophytic
• have an imperceptible wall
• cause posterior acoustic enhancement, which may not be as obvious with harmonic or compound imaging
• have a visible far wall

A cyst may become large enough to obscure the ovary from which it is arising.

Treatment and prognosis

• large (>3 cm) or symptomatic cysts may undergo surgical resection
• smaller asymptomatic cysts are treated conservatively
• risk of malignancy in septated ovarian cysts with no papillary projections or solid components are also considered low and are usually followed up on ultrasound ^5,6

Follow-up guidelines

As of late 2017, the most widely used guidelines is the 2010 consensus statement by the Society of Radiologists in Ultrasound ².  For simple ovarian cysts with no suspicious features on ultrasound, current follow-up guidelines are based on menopausal status and cyst size:

In women of reproductive age

• ≤3 cm
  • normal physiologic finding; at the discretion of the interpreting physician whether or not to describe them in the imaging report
  • do not need follow-up
• >3 and ≤5 cm
  • should be described in the imaging report with a statement that they are almost certainly benign
  • do not need follow-up
• >5 and ≤7 cm
  • should be described in the imaging report with a statement that they are almost certainly benign
  • increased risk of ovarian torsion ⁴
  • yearly follow-up with ultrasound recommended
• >7 cm
  • may be difficult to assess completely with ultrasound and further imaging with MR or surgical evaluation should be considered

In post-menopausal women

• ≤1 cm
  • are clinically inconsequential; at the discretion of the interpreting physician whether or not to describe them in the imaging report
  • do not need follow-up
• >1 and ≤7 cm
  • should be described in the imaging report with a statement that they are almost certainly benign
  • yearly follow-up, at least initially, with ultrasound recommended
  • some practices may opt to increase the lower size threshold for follow-up from 1 cm to as high as 3 cm
  • one may opt to continue follow-up annually or to decrease the frequency of follow-up once stability or decrease in size has been confirmed
  • cysts in the larger end of this range should still generally be followed on a regular basis
• >7 cm
  • since these may be difficult to assess completely with ultrasound, further imaging with MRI or surgical evaluation should be considered

Haemorrhagic ovarian cysts have a different follow up-up schedule than simple cysts.

See also

• fetal ovarian cyst
• paraovarian cyst
• ruptured ovarian cyst