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Women's Health

Ovarian Cysts

An ovarian cyst is a fluid-filled sac in or on the ovary; most in premenopausal women are functional and resolve spontaneously, so the clinical task is to separate these benign cysts from the minority that are complications (torsion, rupture) or malignant, using menopausal status, ultrasound morphology and CA125.

In a nutshell

Most simple ovarian cysts in premenopausal women are functional and can be observed. Assess every cyst through symptoms, pregnancy status, menopausal status and transvaginal ultrasound morphology; use CA125 and RMI I in the postmenopausal pathway, and use the current NICE ovarian-cancer symptom pathway when symptoms are persistent or suspicious. Sudden severe pain with vomiting is an emergency until torsion, rupture, haemorrhage and ectopic pregnancy are assessed.

Classic presentation

An incidental simple cyst in a premenopausal patient, or acute unilateral pelvic pain with nausea/vomiting suggesting torsion or rupture; a postmenopausal patient needs TVUS and CA125-based risk assessment.

Key points

  • Functional follicular and corpus-luteum cysts are common before the menopause and usually resolve.
  • Transvaginal ultrasound is first-line; simple unilocular morphology is reassuring, while solid, papillary, multilocular, bilateral or ascitic features are concerning.
  • In postmenopausal women, use the RCOG pathway with TVUS, CA125 and RMI I; the December 2025 update removes routine follow-up for unilateral, unilocular simple cysts 3 cm or less.
  • CA125 is non-specific and a normal value does not exclude cancer; apply current NICE age-sensitive symptom/referral thresholds.
  • Suspected torsion is a surgical emergency and normal Doppler flow does not exclude it; do not delay senior review for reassuring imaging.
  • Discuss fertility and ovarian preservation when surgery is needed, but use an oncology pathway for suspicious or high-risk masses.

First-line investigation

History, examination, pregnancy test when relevant and transvaginal ultrasound; add CA125 and RMI I for postmenopausal cysts and follow NICE NG12 for persistent cancer-suggestive symptoms.

Management

Treat acute pain as a possible cyst accident

  • Stabilise, perform pregnancy testing and involve senior gynaecology for sudden severe pain, vomiting, peritonism, collapse or suspected torsion; do not let normal Doppler flow exclude torsion.4,3,5

Characterise the cyst and risk

  • Use transvaginal ultrasound to classify morphology and use menopausal status, CA125 and RMI I in the postmenopausal pathway; follow NICE NG12 for persistent ovarian-cancer symptoms.6,4,1

Observe safe benign-appearing cysts

  • Use guideline-based interval imaging for appropriate simple cysts, including the RCOG December 2025 no-routine-follow-up rule for incidental unilateral, unilocular simple postmenopausal cysts 3 cm or less.4,1,3

Refer persistent, complex or symptomatic disease

  • Discuss persistent, enlarging, large, symptomatic or complex cysts with gynaecology; use gynaecological oncology MDT pathways for high RMI, suspicious imaging or suspected cancer, with fertility-aware surgery when benign disease is likely.4,1,6

Document surveillance and safety-netting

  • Record the responsible service, repeat-scan interval and return advice for new severe pain, vomiting, faintness, fever, bleeding, swelling or worsening symptoms; changing lesions need re-review.4,3

Exam traps

  • Do not call every postmenopausal cyst malignant: use the updated RCOG morphology, CA125 and RMI pathway; simple unilateral unilocular cysts 3 cm or less do not need routine follow-up when incidental.
  • Do not use CA125 as a screening test or as a standalone rule-in/rule-out test; benign conditions can raise it and cancer can occur with a normal result.
  • A normal Doppler scan does not exclude ovarian torsion, and torsion is a surgical diagnosis that should not wait for repeated imaging.
  • Always consider ectopic pregnancy in reproductive-potential patients with pain and an adnexal finding.
  • Do not routinely aspirate postmenopausal ovarian cysts; cyst size alone is not the whole management decision.
  • The RCOG premenopausal guideline is from 2011 and its second edition is in development, so use current local imaging and referral pathways.

Illustrations

Haemorrhagic ovarian cyst on CTAxial pelvic CT showing a large heterogeneous right adnexal cystic lesion measuring approximately 7 by 5.5 cm, consistent with a haemorrhagic ovarian cyst.James Heilman, MD, Wikimedia Commons · CC-BY-SA-3.0

Key sources

  1. RCOG Green-top Guideline No. 62, Management of Suspected Ovarian Masses in Premenopausal Women (RCOG premenopausal ovarian-mass guideline, last reviewed 2 December 2011; second edition is in development and local imaging/gynaecology pathways should be checked.)Published 2 Dec 2011
  2. RCOG patient information, Ovarian cysts before the menopause (RCOG patient information cross-check for common benign premenopausal cysts and conservative management.)Published 1 Jun 2013
  3. NHS, Ovarian cyst (Current NHS patient information covering symptoms, watchful waiting, menopause, surgery and urgent symptoms; accessed 4 August 2026.)
  4. RCOG Green-top Guideline No. 34, Ovarian Cysts in Postmenopausal Women (Current RCOG postmenopausal ovarian-cyst guideline, minor update 5 December 2025; includes CA125/TVUS, RMI I, referral and the updated no-routine-follow-up threshold for unilateral unilocular simple cysts 3 cm or less.)Published 1 Jul 2016
  5. NHS, Ectopic pregnancy (Current NHS early-pregnancy safety-netting and emergency symptom cross-check for pelvic pain, bleeding, collapse and pregnancy testing.)
  6. NICE NG12, Suspected cancer: recognition and referral (Current NICE ovarian-cancer recognition and referral guidance, last updated 15 April 2026, including age-sensitive CA125 thresholds and ultrasound referral recommendations.)Published 23 Jun 2015

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.