Ovarian Cysts — Symptoms, Causes & Treatment | MyMedicPlus

Ovarian cysts are fluid-filled or semi-solid sacs that develop on or within one or both ovaries — ranging from simple, thin-walled unilocular fluid collections to complex structures containing solid components, septations, or mixed tissue elements. They are among the most common gynaecological findings, detected in up to 18% of women overall and in nearly all pre-menopausal women at some point in their reproductive lifetime. The vast majority of ovarian cysts in women of reproductive age are functional (physiological), arising from the normal ovulatory cycle: follicular cysts form when the dominant follicle fails to rupture and ovulate, instead continuing to grow (typically 2-8cm), and corpus luteum cysts form when the post-ovulatory corpus luteum accumulates fluid or blood rather than regressing — both types resolve spontaneously within 1-3 menstrual cycles without intervention. Non-functional cyst types include dermoid cysts (mature cystic teratomas — the most common ovarian germ cell tumour, containing skin, hair, teeth, and sebaceous material from pluripotent germ cells), endometriomas (ovarian endometriosis — 'chocolate cysts' containing old blood from ectopic endometrial tissue), cystadenomas (serous or mucinous epithelial neoplasms), and malignant ovarian tumours. Distinguishing benign functional cysts from neoplastic or malignant cysts is the central clinical task, guided by age, ultrasound characteristics, menopausal status, and CA-125.

Functional (physiological) cysts are the most common type and arise from the normal ovarian follicular cycle: follicular cysts form when the dominant Graafian follicle fails to ovulate and continues growing (typically 2-8cm); corpus luteum cysts develop when the post-ovulatory corpus luteum fills with blood or fluid rather than involuting — both resolve spontaneously within 1-3 menstrual cycles without intervention and require no treatment. Polycystic ovary syndrome (PCOS): produces multiple small antral follicles (each typically 2-9mm) from chronic anovulation due to LH-driven androgen excess and insulin resistance — these are not true cysts but arrested follicles; true simple ovarian cysts are also more common in PCOS. Endometriomas: result from ovarian endometriosis — endometrial glands and stroma implant on the ovarian surface, forming an encapsulated cyst filled with 'chocolate' coloured old blood; associated with infertility (destroys surrounding ovarian cortex), dysmenorrhoea, and dyspareunia. Dermoid cysts (mature cystic teratomas): arise from pluripotent germ cells containing ectodermal tissue (skin, hair, teeth, sebaceous glands) — the most common ovarian tumour in women under 30, accounting for 20% of all ovarian tumours; benign in 97-98% of cases; rupture releases sebaceous material causing severe chemical peritonitis. Cystadenomas: epithelial neoplasms — serous cystadenomas (thin-walled, unilocular or multilocular — most common ovarian epithelial tumour; may reach 30cm); mucinous cystadenomas (multilocular, large, containing mucinous fluid — can grow enormous). Risk factors for malignant ovarian lesions requiring urgent specialist assessment: postmenopausal status, age above 50, nulliparity, personal or family history of ovarian or BRCA-related cancer, and complex ultrasound features (solid areas, papillary projections, thick septations, bilateral lesions).

The majority of ovarian cysts — particularly functional follicular and corpus luteum cysts — are entirely asymptomatic and discovered incidentally on pelvic ultrasound performed for other indications (e.g., assessment of pelvic pain, routine gynaecological review, early pregnancy scan). When symptoms do occur, they are typically related to cyst size, type, or complications. Chronic symptoms: dull, aching lower abdominal or pelvic pain or pressure, often unilateral, which may be cyclical (related to the menstrual cycle — notably dysmenorrhoea from endometriomas); pelvic bloating and a sensation of fullness; urinary frequency from bladder compression by a large cyst; dyspareunia (pain during intercourse — particularly deep); and abnormal uterine bleeding (intermenstrual or irregular periods) from hormonal cysts or endometriomas. Large cysts (above 10cm) may cause visible abdominal distension. Hormonal effects: functional follicular cysts may produce oestrogen causing irregular bleeding; corpus luteum cysts may produce progesterone extending the luteal phase and mimicking early pregnancy symptoms; rare granulosa cell tumours or theca cell tumours produce oestrogen causing post-menopausal bleeding, endometrial hyperplasia, or precocious puberty. Acute emergency presentations from ovarian cyst complications: sudden-onset severe unilateral lower abdominal or pelvic pain radiating to the inner thigh, associated with nausea, vomiting, and haemodynamic compromise (pallor, tachycardia, low blood pressure) — this combination indicates either ovarian torsion or significant haemorrhagic cyst rupture, both of which are surgical emergencies requiring immediate hospital assessment.

Transvaginal ultrasound (TVS) is the gold standard first-line investigation for ovarian cyst characterisation — far superior to transabdominal ultrasound for ovarian visualisation; TVS assesses cyst diameter, wall thickness, internal architecture (unilocular smooth vs multilocular), presence and thickness of septations, solid components, papillary projections, internal echogenicity (simple anechoic fluid vs complex heterogeneous content), and vascularity using colour Doppler (vascularised solid areas raise malignancy concern). IOTA (International Ovarian Tumour Analysis) classification system: Simple Rules using 5 malignant (M) features (irregular solid tumour, ascites, multilocular-solid tumour with irregular solid parts, at least 4 papillary structures, very strong blood flow) and 5 benign (B) features (simple unilocular cyst, presence of solid components with largest less than 7mm, acoustic shadowing, smooth multilocular cyst less than 100mm, no detectable blood flow) — provides greater accuracy than experienced clinicians when rules apply. Risk of Malignancy Index (RMI = CA-125 x ultrasound score x menopausal status score): RMI above 200 is high risk — requires urgent referral to a gynaecological oncology MDT; RMI 25-200 is intermediate risk. Serum CA-125: elevated in over 80% of advanced ovarian cancer but low specificity in premenopausal women (also raised in endometriosis, fibroids, pelvic inflammatory disease, and any cause of peritoneal irritation); most useful and informative in postmenopausal women. Additional biomarkers: HE4 (human epididymis protein 4) combined with CA-125 in the ROMA algorithm (Risk of Ovarian Malignancy Algorithm) improves specificity. MRI pelvis: provides superior soft tissue characterisation for complex or indeterminate ultrasound findings — particularly useful for differentiating dermoid cysts (T1 fat signal) from endometriomas (T1 shading), and for staging suspected malignancy. Tumour markers for non-epithelial tumours: AFP and beta-hCG for germ cell tumours (dysgerminoma, endodermal sinus tumour) in young women; inhibin and AMH for granulosa cell tumours.

Management is guided by cyst characteristics (simple vs complex), size, menopausal status, malignancy risk stratification, and symptoms. Conservative management (watchful waiting): simple unilocular cysts below 5cm (NICE guidance, RCOG Green-top Guideline 62) in premenopausal women — repeat transvaginal ultrasound at 8-12 weeks to confirm resolution; 80-90% of functional cysts resolve spontaneously within 1-3 cycles; no pharmacological treatment is required during watchful waiting. In postmenopausal women, simple unilocular cysts below 5cm with normal CA-125 can be monitored with 6-monthly TVS for up to 2 years (RCOG guidance). Combined oral contraceptive pill (COCP): suppresses the hypothalamic-pituitary-ovarian axis, reducing the development of new functional follicular cysts — does not shrink or hasten resolution of existing cysts (contrary to a common misconception), but used for menstrual regulation and pain management in women with recurrent functional cysts or dysmenorrhoea. Endometrioma management: GnRH agonists or the COCP/progestogen for pain management; laparoscopic cystectomy for endometriomas above 4cm prior to IVF (reduces cyst-related complications during egg collection, though cystectomy itself reduces ovarian reserve — a carefully balanced decision). Surgical indications: cysts above 5-7cm that are persistent beyond 3 months or growing; complex cysts with internal solid areas, papillary projections, thick septations, or increased vascularity on Doppler; ovarian torsion (emergency laparoscopic detorsion within hours, avoiding oophorectomy unless necrotic — most torsed ovaries recover if detorsed early); ruptured haemorrhagic cyst with haemoperitoneum and haemodynamic instability (laparoscopic washout and haemostasis); symptomatic dermoid cysts (spillage of cyst contents causes chemical peritonitis — careful laparoscopic enucleation with contained removal); and any postmenopausal complex cyst with elevated CA-125 or high RMI. Laparoscopic cystectomy (removing cyst wall while preserving normal ovarian cortex) is preferred over oophorectomy to preserve ovarian reserve; laparotomy for large tumours or suspected malignancy. Bilateral salpingo-oophorectomy for confirmed ovarian malignancy.

Ovarian torsion: twisting of the ovary on its infundibulopelvic and utero-ovarian ligament pedicle causes venous and lymphatic obstruction followed by arterial ischaemia — presents with sudden severe unilateral lower abdominal and pelvic pain (often colicky), nausea, vomiting, and low-grade fever; the right ovary is more commonly affected. Requires emergency laparoscopic detorsion within hours to preserve ovarian function — ovaries can recover even after prolonged torsion appearing dusky or necrotic, and oophorectomy should be avoided unless clearly non-viable. Haemorrhagic cyst rupture: most commonly from a corpus luteum cyst in the late luteal phase — sudden-onset severe pelvic pain with peritoneal irritation; haemoperitoneum can cause haemodynamic compromise requiring emergency surgical haemostasis in unstable patients; most resolve conservatively with analgesia and monitoring. Chemical peritonitis: rupture of a dermoid cyst releases sebaceous material causing intense chemical peritonitis requiring laparoscopic peritoneal lavage. Endometrioma impact on fertility: bilateral endometriomas progressively destroy surrounding ovarian cortex through local inflammatory reaction and oxidative stress, reducing antral follicle count and AMH (anti-Müllerian hormone — the ovarian reserve marker); repeat laparoscopic cystectomy for recurrent endometriomas carries significant cumulative ovarian reserve loss — balancing surgical and expectant management with IVF in women with reduced reserve is a complex specialist decision. Ovarian cancer: a minority of complex ovarian masses prove malignant, with the risk rising substantially with age, postmenopausal status, and complex morphological features on ultrasound.

Prevention of functional cysts: combined oral contraceptive pills suppress pituitary gonadotrophin secretion, preventing ovarian follicle stimulation and reducing new functional cyst formation — recommended in women with recurrent functional cysts causing significant symptoms. Endometriosis management: early and effective medical management of endometriosis (combined OCP, progestogens, GnRH agonists with add-back) and timely surgical treatment of endometriosis reduces endometrioma development and recurrence; however, endometriomas recur in 30-40% within 5 years after cystectomy, requiring ongoing medical suppression. BRCA1/BRCA2 genetic screening and risk management: women with BRCA1 mutations face a 39-46% lifetime risk of ovarian cancer; BRCA2 carriers 10-27%; risk-reducing salpingo-oophorectomy (RRSO) is recommended at age 35-40 for BRCA1 and 40-45 for BRCA2 carriers after completion of childbearing — reducing ovarian cancer risk by 80% and breast cancer risk by 50%. Annual surveillance (transvaginal ultrasound plus CA-125) is recommended for BRCA carriers who defer RRSO, though screening sensitivity for early ovarian cancer detection remains imperfect. All postmenopausal women with any newly discovered ovarian cyst require specialist gynaecological assessment — the post-menopausal ovary is normally quiescent, making any cyst structurally abnormal and warranting malignancy risk stratification using the IOTA classification system, RMI, or CA-125.

Go to A&E immediately for: sudden severe one-sided lower abdominal or pelvic pain, especially with nausea and vomiting — this may indicate ovarian torsion (twisting of the ovary cutting off its blood supply), a surgical emergency requiring laparoscopic detorsion within hours to save the ovary; or significant internal bleeding from a ruptured hemorrhagic cyst causing shoulder-tip pain (diaphragm irritation) and haemodynamic instability. See your GP within 1–2 weeks if: you have new-onset persistent pelvic pain or bloating; pain during intercourse or pain with urination; a pelvic cyst has been found incidentally on ultrasound and you have not been given follow-up instructions. All postmenopausal women with any ovarian cyst found on imaging — even a simple-looking one — should be referred urgently to gynaecology for specialist assessment, CA-125 measurement, and IOTA scoring: the risk of malignancy is meaningfully higher in this group. If you carry a BRCA1 or BRCA2 gene variant, ask your gynaecologist about the timing of risk-reducing salpingo-oophorectomy — this is typically recommended between age 35–40 for BRCA1 and 40–45 for BRCA2 carriers after childbearing is complete.