About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Functional cysts (follicular, corpus luteum): very common, usually resolve within 2–3 cycles. No treatment needed
- Pathological cysts: dermoid (teratoma — most common benign in young women), endometrioma, cystadenoma, malignant
- USS features of benignity: simple, unilocular, thin-walled, no solid components, no blood flow. IOTA simple rules help classify
- Simple cysts <5 cm in premenopausal women: conservative management with repeat USS in 12 weeks
- Ovarian torsion: sudden-onset severe unilateral pelvic pain ± nausea/vomiting. Absent/reduced Doppler flow on USS. Emergency laparoscopy for detorsion
- RMI (Risk of Malignancy Index) = USS score × menopausal score × CA-125. If >250 → refer to gynaecological oncology
Overview
Ovarian cysts are fluid-filled sacs within or on the surface of the ovary. They are extremely common, particularly in women of reproductive age, and the vast majority are benign. Functional cysts (follicular cysts and corpus luteum cysts) arise from normal ovulation and typically resolve spontaneously. Pathological cysts include dermoid cysts (mature cystic teratomas), endometriomas, serous and mucinous cystadenomas, and malignant neoplasms. Ovarian torsion occurs when the ovary (and often the fallopian tube) twists on its vascular pedicle, compromising blood supply and causing ischaemia — it is a gynaecological emergency.
Epidemiology
Ovarian cysts are found in approximately 7–10% of premenopausal women and up to 18% of postmenopausal women. Most are functional and asymptomatic. Dermoid cysts account for ~20–40% of benign ovarian neoplasms and are the most common ovarian tumour in women under 30. Ovarian torsion accounts for approximately 3% of gynaecological emergencies, with most occurring in women aged 20–40. Risk factors for torsion include ovarian cysts >5 cm, ovarian hyperstimulation (IVF), pregnancy, and long utero-ovarian ligament.
Clinical Features
Symptoms
Many ovarian cysts are asymptomatic — discovered incidentally
Unilateral pelvic or lower abdominal pain — dull ache or sharp if complicated
Menstrual irregularity
Bloating, abdominal distension (large cysts)
Sudden-onset severe unilateral pelvic pain ± nausea/vomiting (TORSION)
Acute pain after rupture — may cause peritonism
Urinary frequency or constipation (large cysts compressing adjacent structures)
Signs
Adnexal mass on bimanual examination
Adnexal tenderness (cyst complication or torsion)
Peritonism (cyst rupture or torsion with necrosis)
Torsion: extreme unilateral tenderness, guarding. Intermittent pain (torsion-detorsion cycles)
Investigations
First-line
Pelvic USS (TVUSS)First-line imaging. Assess size, laterality, internal structure (simple vs complex), solid components, septations. IOTA simple rules help classify benign vs malignant
Pregnancy testExclude ectopic pregnancy — always in any woman of reproductive age with pelvic pain
Second-line
CA-125Tumour marker — raised in epithelial ovarian cancer. Also elevated in endometriosis, PID, menstruation, pregnancy. Most useful in postmenopausal women
Doppler USSFor suspected torsion — absent or reduced blood flow to ovary. Note: normal Doppler does NOT exclude torsion
RMI (Risk of Malignancy Index)USS score × menopausal score × CA-125. RMI >250 → refer to gynaecological oncology centre
Specialist
MRI pelvisIf USS indeterminate — excellent soft tissue characterisation. Helps differentiate benign from malignant
CT abdomen/pelvisIf malignancy suspected — staging, lymphadenopathy, omental deposits
1
Simple cysts — premenopausal
- <5 cm: no follow-up required — almost always functional, will resolve
- 5–7 cm: repeat USS in 12 weeks to confirm resolution
- >7 cm: consider MRI or surgical evaluation
2
Simple cysts — postmenopausal
- <5 cm with normal CA-125: conservative management with serial USS (4-monthly for 1 year)
- ≥5 cm or complex features or raised CA-125: refer to gynaecological oncology
3
Complex or persistent cysts
- Calculate RMI. If >250: 2-week wait referral to specialist gynaecological oncology centre
- Dermoid cysts: elective laparoscopic cystectomy (risk of torsion and slow growth)
- Endometriomas: manage as part of endometriosis (see endometriosis page)
- If benign on imaging and RMI: laparoscopic cystectomy (preserve ovary) or oophorectomy
4
Ovarian torsion — emergency
- Suspect in any woman with sudden-onset severe unilateral pelvic pain
- Emergency laparoscopy: DETORSION is the goal — preserve the ovary whenever possible
- If ovary is still viable after detorsion (even if appears dusky): leave in situ — most recover
- Oophorectomy only if clearly necrotic or if suspicious of malignancy
- Fix ovary (oophoropexy) to reduce recurrence risk
Complications
- Torsion: Surgical emergency — loss of ovary if not treated promptly
- Rupture: Acute peritonitis. Haemoperitoneum if corpus luteum or endometrioma ruptures
- Haemorrhage into cyst: Pain, enlargement
- Malignant transformation: Rare in functional and dermoid cysts. Higher risk in postmenopausal and complex cysts
- Infection: Tubo-ovarian abscess (in context of PID)
UKMLA Exam Tips
- 1Simple cysts <5 cm in premenopausal women = no follow-up needed. They resolve spontaneously
- 2Ovarian torsion: sudden severe pain + nausea + adnexal tenderness. Emergency laparoscopy for DETORSION
- 3Dermoid cyst (teratoma) = most common benign tumour in young women. Contains hair, teeth, fat (calcification on X-ray)
- 4Normal Doppler does NOT exclude torsion — clinical suspicion is key
- 5Postmenopausal cyst + raised CA-125 + complex features = suspect malignancy → RMI >250 → 2WW referral
- 6Always do a pregnancy test first — ectopic pregnancy can mimic ovarian cyst complications
practicetest your knowledge on ovarian cysts and ovarian torsionApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — obstetrics and beyond.
open q-bank