Endometriotic Ovarian Cyst

An endometriotic ovarian cyst (endometrioma, chocolate cyst) is an ovarian cyst filled with old blood and lined by endometrial tissue.

• It is a marker of moderate to severe endometriosis and is often bilateral.
• It causes pelvic pain and infertility and reduces ovarian reserve.
• Treatment depends on symptoms, size and fertility wishes.

Dysmenorrhoea, chronic pelvic pain, deep dyspareunia, painful defaecation or urination during menses, infertility; some women are asymptomatic.

• Fixed adnexal mass, tender nodules in the pouch of Douglas, retroverted uterus.
• Differential diagnosis: haemorrhagic cyst, dermoid cyst, cystadenoma, tubo-ovarian abscess, ovarian cancer, ectopic pregnancy, pelvic inflammatory disease.
• Complications: rupture, infection, torsion, adhesions, infertility, reduced ovarian reserve and, rarely, malignant change.

Diagnosis is by ultrasound, with MRI for complex cysts and deep disease.

• Transvaginal ultrasound: unilocular cyst with homogeneous low-level (ground-glass) echoes, 2 to 10 cm, with no flow in the contents.
• MRI to characterise complex cysts and map deep disease.
• CA-125 (often mildly raised) and anti-Müllerian hormone for ovarian reserve.
• Pregnancy test; full blood count.
• Histology after removal; laparoscopy for diagnosis and treatment.

Control pain and suppress disease hormonally, and operate for large cysts, uncontrolled pain or diagnostic doubt.

• Supportive: heat to the lower abdomen; pelvic floor physiotherapy; counselling on fertility and pain control.
• Pharmacological: naproxen 500 mg oral 12-hourly with food (maximum 1 g in 24 hours) or ibuprofen 400 mg oral 8-hourly with food (maximum 1.2 g in 24 hours) during pain. Hormonal suppression: dienogest 2 mg oral daily for 6 to 12 months; or a combined oral contraceptive with ethinylestradiol 30 micrograms taken continuously; or norethisterone acetate 5 mg oral daily, increased to 15 mg daily if bleeding occurs. Refractory disease: leuprorelin 3.75 mg IM every 4 weeks for up to 6 months with norethisterone acetate 5 mg oral daily as add-back.
• Procedures: laparoscopic cystectomy (stripping of the cyst wall) for cysts above 4 cm, for pain not controlled by drugs or for diagnostic doubt; ablation for smaller cysts. Give hormonal suppression after surgery until pregnancy is wanted. In women with infertility, refer for in vitro fertilisation; surgery may lower ovarian reserve.
• Special groups: in women wishing pregnancy avoid long courses of hormonal suppression and refer early for assisted reproduction. In postmenopausal women remove the cyst to exclude cancer. Avoid oestrogen-containing pills in migraine with aura, smoking above age 35 or thromboembolism.
• Red flags: rapid growth, solid areas with flow, postmenopausal cyst, fever (infection), sudden severe pain.
• Follow-up: review at 3 months and then every 6 months; ultrasound yearly; fertility review within 6 months after surgery.