Health condition · Clinically reviewed
Ovarian cysts, simple, complex and functional — when to watch and when to treat.
Fluid-filled sacs in or on the ovary. Most are benign and often resolve without treatment — but complex or persistent cysts need proper assessment.
Why trust this guide
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Clinically reviewed
Written by our editorial team and reviewed by a registered UK clinician before publication.
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Sourced from guidance
Every claim is checked against RCOG, NICE or peer-reviewed sources you can see at the end.
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Current for 2026
Reflects current UK guidance on ultrasound characterisation, IOTA / ADNEX scoring and surgery.
Key facts
Ovarian cysts at a glance.
The essentials, in plain English — what a cyst is, which types are common, how they’re characterised, and when treatment is needed.
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What it is
A fluid-filled sac in or on the ovary — most are benign and often resolve without treatment.
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Most common type
Functional cysts (follicular or corpus luteum) — usually resolve spontaneously within a few cycles.
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How risk is classified
The IOTA / ADNEX model uses ultrasound features to estimate the risk of malignancy.
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Other common types
Endometrioma, dermoid (mature teratoma) and cystadenoma are the common non-functional cysts.
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First-line imaging
Transvaginal ultrasound is first-line; MRI is added when characterisation is uncertain.
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Emergency features
Ovarian torsion, cyst rupture and haemorrhage — sudden severe pelvic pain needs urgent assessment.
Why this guide matters
Reassurance where it belongs — and care where it counts.
Most ovarian cysts are benign — but a small number need urgent or specialist care. These three points shape everything else on this page.
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Most cysts are benign and quietly resolve
Functional cysts are the commonest kind and usually settle without any treatment.
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Ultrasound characterisation drives the plan
The IOTA / ADNEX model uses ultrasound features to estimate risk and decide the next step.
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Sudden severe pain is an emergency
Torsion, rupture and haemorrhage present as sudden severe pelvic pain — call 999 or go to A&E.
How the diagnosis is made
From first scan to a clear plan.
The steps a UK GP and gynaecologist will normally follow, in order — so you know what to expect and why.
Phase 1 · Recognising
History and examination to spot the pattern
Phase 2 · Confirming
Ultrasound with IOTA / ADNEX, CA-125 and MRI
Phase 3 · Managing
Watch, repeat scan or gynaecology referral
- 01
Recognising
A careful symptom history
Pain pattern, cycle timing, pressure symptoms, menstrual change and any pregnancy — all shape the next step.
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Recognising
Pelvic examination
Abdominal and, where appropriate, bimanual pelvic examination to feel for a mass or tenderness.
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Confirming
Transvaginal ultrasound + IOTA
The first-line scan — with IOTA / ADNEX scoring to estimate the risk of malignancy from ultrasound features.
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Confirming
CA-125 in context
A tumour marker used carefully — helpful in postmenopausal women or with an IOTA-M (suspicious) lesion.
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Confirming
MRI pelvis if uncertain
Dedicated pelvic MRI characterises a complex mass when ultrasound cannot — endometrioma, dermoid or cystadenoma.
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Managing
Repeat ultrasound in 6-12 weeks
Most functional cysts resolve — a follow-up scan confirms this and avoids unnecessary surgery.
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Managing
Gynaecology consultation
Persistent, complex or symptomatic cysts are reviewed by a gynaecologist to plan surgery or ongoing follow-up.
Typical timeline: weeks from first scan to a settled plan, longer when surgery is planned.
Symptoms
What ovarian cysts can feel like.
Many cysts cause no symptoms at all. When they do, it’s usually pelvic pain, pressure or a change in periods — with a small number presenting as an emergency.
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Often no symptoms
Many ovarian cysts are found incidentally on a scan for something else and cause no problems.
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Pelvic pain
Dull ache or intermittent sharp pain on one side of the lower abdomen or pelvis.
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Pressure sensation
A feeling of fullness, bloating or pressure — sometimes on the bladder or bowel.
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Menstrual disturbance
Irregular, heavier or lighter periods — especially with hormonally active cysts.
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Pregnancy-related cysts
Corpus luteum cysts are common in early pregnancy and usually resolve by the second trimester.
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Dyspareunia
Pain during sex — often deep pain on one side, worse in certain positions.
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Torsion — sudden severe
Sudden severe pelvic pain with nausea and vomiting — a surgical emergency.
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Red flag — call 999
Sudden severe pelvic pain with vomiting suggests torsion or rupture — call 999 or go to A&E.
Treatment
How ovarian cysts are treated in the UK.
A stepped plan — watch and rescan for simple cysts, surgery for persistent, complex or symptomatic ones, and specialist referral when features are suspicious.
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Watchful waiting + repeat scan
For simple functional cysts — a repeat ultrasound in 6-12 weeks usually shows resolution.
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Combined oral contraceptive
Sometimes used to prevent new functional cysts — evidence for shrinking existing cysts is limited.
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Laparoscopic cystectomy
Keyhole removal of the cyst while preserving the ovary — the standard approach for benign cysts.
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Laparoscopic oophorectomy
Removal of the whole ovary — considered for larger cysts, torsion or postmenopausal women.
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Open surgery
Laparotomy for very large cysts or where suspicious features suggest a careful, controlled removal.
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Fertility-preserving surgery
Careful cystectomy that spares as much healthy ovarian tissue as possible — important for future fertility.
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Gynae-oncology referral
Suspicious features on ultrasound or a high IOTA / ADNEX score prompt referral to a specialist centre.
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Post-op follow-up plan
A clear plan for symptom review, wound care, histology results and further imaging as needed.
What this guide is based on
The sources behind every claim on this page.
UK national guidance and specialist society standards, current at the time of last review.
Key references
Guidelines and standards we relied on.
A quiet reminder
This guide is for information, not medical advice.
Your GP or gynaecologist knows your history and can tell you which parts apply to you. If in doubt, seek assessment — especially with any red-flag features.
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Royal College of Obstetricians and Gynaecologists (RCOG). Green-top Guideline 62 — management of suspected ovarian masses in premenopausal women.
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NICE CKS. Ovarian cysts.
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IOTA / ADNEX model — International Ovarian Tumour Analysis classification of adnexal masses.
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British Gynaecological Cancer Society (BGCS) — guidelines for suspected ovarian cancer.
Red flags
When an ovarian cyst needs urgent care.
Most cysts are benign. These are the patterns that need urgent or specialist assessment — do not wait them out.
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Ovarian torsion
Sudden severe pelvic pain with nausea and vomiting — a surgical emergency, call 999 or go to A&E.
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Cyst rupture with peritoneal signs
Sudden severe pain with a rigid, tender abdomen — urgent assessment.
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Postmenopausal complex cyst
Any complex cyst after the menopause needs assessment to rule out malignancy.
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Rising CA-125
A rising CA-125 in an appropriate clinical context needs specialist review.
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Ascites
Free fluid in the abdomen alongside an ovarian mass is a red flag.
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Family history ovarian or breast
A strong family history — especially BRCA1 or BRCA2 — changes the threshold for investigation.
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Rapidly growing cyst
A cyst that grows quickly between scans deserves urgent specialist assessment.
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Fever with pelvic pain
Fever with pain may suggest a tubo-ovarian abscess — urgent assessment.
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Endometrioma in fertility work-up
An endometrioma found during fertility assessment needs a considered plan before surgery.
Living with it
Usually a short chapter, handled well with the right plan.
Four things that make the biggest difference — keeping the follow-up scan, tracking symptoms, discussing fertility early, and being under the right team.
A quiet reminder
The follow-up scan is where reassurance is earned.
A repeat ultrasound in a few weeks is the single most useful step in most cases — do not let it slip.
- 01 Follow-up
Do not skip the repeat scan
A follow-up ultrasound at 6-12 weeks is what turns a worrying finding into a reassuring one — or triggers the right next step.
- 02 Symptom diary
Track pain and cycle
A short daily note on pain, cycle day and any bleeding helps your clinician spot the pattern.
- 03 Fertility
Have the conversation early
If you may want children, discuss fertility-preserving options with your gynaecologist before any surgery is planned.
- 04 Specialist care
Get to the right team
Suspicious features or a high IOTA / ADNEX score mean gynae-oncology review, not a general gynae list.
Frequently asked
Everything we get asked about ovarian cysts.
Quick answers on diagnosis, IOTA / ADNEX scoring, surgery, fertility and emergency features.
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What is an ovarian cyst?
A fluid-filled sac in or on the ovary. Most are benign and many resolve without treatment.
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How are ovarian cysts diagnosed?
Transvaginal ultrasound is first-line, with IOTA / ADNEX scoring to estimate the risk of malignancy. MRI is added when characterisation is uncertain, and CA-125 is used carefully in context.
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What is the IOTA / ADNEX model?
A validated ultrasound-based model that uses features of an ovarian mass — with or without CA-125 — to estimate the probability that it is benign, borderline or malignant.
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Do all ovarian cysts need surgery?
No. Simple functional cysts usually resolve on their own and are followed with a repeat scan. Surgery is offered for persistent, complex, large or symptomatic cysts.
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When is an ovarian cyst an emergency?
Sudden severe pelvic pain, especially with nausea and vomiting, may signal torsion or rupture — call 999 or go to A&E.
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Will removing a cyst affect my fertility?
A carefully performed laparoscopic cystectomy aims to preserve as much healthy ovarian tissue as possible. Discuss fertility plans with your gynaecologist before surgery.