Simple Ovarian Cyst

A simple ovarian cyst is a unilocular, thin-walled, anechoic ovarian cyst without solid parts, septa or internal flow on ultrasound. It is almost always benign.

• It occurs in reproductive-age and postmenopausal women.
• Most are functional in premenopausal women and serous cystadenomas in postmenopausal women.
• Cancer is very rare in simple cysts.

Usually found incidentally; pelvic ache, pressure, bloating, dyspareunia, and acute pain if rupture or torsion occurs.

• A mobile, smooth, non-tender adnexal swelling.
• Differential diagnosis: follicular cyst, paraovarian cyst, hydrosalpinx, peritoneal inclusion cyst, cystadenoma, endometrioma, ovarian cancer, pedunculated fibroid.
• Complications: rupture, torsion, haemorrhage and rarely malignancy.

Diagnosis is by transvaginal ultrasound, with CA-125 in postmenopausal women.

• Transvaginal ultrasound: anechoic, thin-walled, unilocular cyst; measure the mean diameter.
• Pregnancy test in reproductive-age women.
• CA-125 in postmenopausal women (normal below 35 units/mL) and a risk of malignancy index; an elevated result or complex features need specialist review.
• MRI for cysts above 7 cm or unclear features.

Reassure and follow up by size and menopausal status, with surgery for larger cysts or suspicious features.

• Supportive: reassure; advise on symptoms of torsion or rupture.
• Pharmacological: paracetamol 1 g oral 6-hourly (maximum 4 g in 24 hours) and ibuprofen 400 mg oral 8-hourly with food (maximum 1.2 g in 24 hours) for pain.
• Procedures: premenopausal women: cysts below 5 cm need no follow-up; 5 to 7 cm: yearly ultrasound; above 7 cm: MRI or surgery. Postmenopausal women: cysts below 5 cm with normal CA-125 need repeat ultrasound at 4 months and then yearly for 1 to 2 years; larger cysts or raised CA-125 need laparoscopic cystectomy or oophorectomy, with intact removal in a bag. Needle aspiration is not advised because it refills and may spill malignant cells.
• Special groups: in pregnancy observe, with surgery for torsion or rupture only, and avoid ibuprofen from 28 weeks. In girls under 16 years, check for growth and puberty changes.
• Red flags: growth, new septa or solid parts, raised CA-125, ascites, pain with vomiting, postmenopausal bleeding.
• Follow-up: yearly ultrasound for premenopausal cysts of 5 to 7 cm, and ultrasound at 4 months then yearly for postmenopausal cysts; discharge after a stable cyst for 1 to 2 years.