How should a 45 mm left ovarian simple cyst (unilocular, anechoic, thin‑walled on transvaginal ultrasound) in a reproductive‑age woman with 48 hours of nausea and dull pelvic pain be managed?

Management of 45mm Simple Ovarian Cyst with Acute Symptoms

This 45mm unilocular, anechoic, thin-walled ovarian cyst should be managed conservatively with symptomatic treatment and follow-up ultrasound in 8-12 weeks, as it represents a benign functional cyst (O-RADS 3) with extremely low malignancy risk (<1-10%). 1

Immediate Clinical Assessment

Confirm the cyst characteristics meet simple/functional criteria:

• Wall thickness <3mm (thin-walled confirms benign) 1
• Completely anechoic (no internal echoes or debris) 1
• Unilocular (single compartment, no septations) 1
• Absent internal vascularity on color Doppler 1, 2

Rule out surgical emergencies requiring immediate intervention:

• Ovarian torsion: Check for absent or abnormal venous flow on Doppler, ovarian enlargement >4cm, peripheral follicle pattern, or severe unilateral pain 3
• Rupture with hemoperitoneum: Assess for peritoneal signs, hemodynamic instability, or significant free fluid 2
• Infection/TOA: Evaluate for fever, bilateral adnexal involvement, or thick-walled complex masses 3

If any of these features are present, immediate gynecology consultation and possible laparoscopy are indicated. 2

Risk Stratification Using O-RADS Classification

This cyst falls into O-RADS 3 (Low Risk, 1-10% malignancy) because:

• Size 5-10cm in a reproductive-age woman 1
• Unilocular smooth morphology 1
• Simple features (anechoic, thin-walled) 1

Key point: Simple cysts regardless of size carry near-zero cancer risk (<0.5 per 10,000 women over 3 years), and size alone does not indicate malignancy in truly simple cysts. 1 However, cysts ≥10cm warrant more aggressive evaluation even when appearing benign. 1

Conservative Management Protocol

Symptomatic treatment for the current episode:

• NSAIDs for pain management 2
• Antiemetics for nausea as needed 2
• Monitor hemoglobin if rupture is suspected 2

No surgical intervention is indicated because:

• Most functional cysts resolve spontaneously, even when >5cm 1, 2
• Operating on functional cysts is unnecessary and should be avoided 1
• 23-27% of simple cysts disappear spontaneously within 3-36 months 4, 5

Follow-Up Imaging Strategy

Schedule repeat transvaginal ultrasound in 8-12 weeks (ideally during proliferative phase after menstruation): 1, 2

At follow-up, three outcomes are possible:

1. Cyst resolved: No further imaging needed 1

2. Cyst stable or decreased: Continue annual surveillance if patient desires, though not strictly required for simple cysts 1

3. Cyst persists, enlarges, or develops concerning features: Refer to gynecology or obtain pelvic MRI with contrast 1, 2

When to Escalate Care

Refer to gynecology if:

• Cyst persists or enlarges at 8-12 week follow-up 1, 2
• Development of solid components, septations ≥3mm, or papillary projections 1
• Abnormal Doppler flow (color score ≥4) develops 1
• Patient develops worsening symptoms or acute abdomen 2

Refer directly to gynecologic oncology if:

• High vascularity (color score 4) in any solid component 1
• ≥4 papillary projections (O-RADS 5, ≥50% malignancy risk) 1
• Irregular solid components develop 1

This is critical because only 33% of ovarian cancers are appropriately referred initially, yet oncologist involvement is the second most important prognostic factor after stage. 1

Critical Pitfalls to Avoid

Do NOT perform:

• Fine-needle aspiration (absolutely contraindicated—risk of disseminating malignant cells if misdiagnosed) 6, 2
• Immediate surgery for a stable patient with simple cyst features 1, 2
• CT or PET/CT for cyst characterization (ultrasound is superior) 1
• Routine CA-125 testing (performs worse than ultrasound alone and is elevated in only ~50% of early ovarian cancers) 6

Do NOT assume malignancy based on:

• Size alone in a truly simple cyst 1
• Acute symptoms (functional cysts commonly cause pain and nausea) 2

Additional Considerations for Reproductive-Age Women

Confirm color Doppler was performed to differentiate hemorrhagic content from solid components—peripheral vascularity only (no internal flow) confirms benign hemorrhagic cyst. 1, 2

If hemorrhagic features are present (reticular pattern, retracting clot with concave margins), this represents O-RADS 2 (<1% malignancy) and requires only 8-12 week follow-up if ≤5cm, or immediate follow-up if >5cm. 1, 2