When is a CT (Computed Tomography) scan urgently ordered in obstetrics and gynecology?

Urgent CT Scan Indications in Obstetrics and Gynecology

CT scans should be urgently ordered in obstetrics and gynecology when life-threatening conditions are suspected, conventional medical treatment has been unsuccessful, or when ultrasound and MRI are inconclusive or unavailable. 1, 2

Major Trauma

• Polytrauma assessment in pregnant patients with high-velocity (>35 mph) motor vehicle collisions, rollover accidents, ejections, motorcycle trauma, or falls from >15 feet 1
• Suspected intra-abdominal hemorrhage in hemodynamically stable patients 1, 2
• Unstable pelvic fractures (vertical shear and AP compression injuries) associated with higher rates of active hemorrhage 1

Postpartum Hemorrhage (PPH)

• Persistent hemorrhage after empiric embolization 1
• Failed conventional medical treatment (oxytocin) for PPH 1, 2
• Suspected vascular complications such as:
  • Pseudoaneurysm formation 1
  • Arteriovenous malformations 1
  • Supra-umbilical and perivaginal space hematomas 1

Gynecologic Emergencies

• Suspected ovarian vein thrombosis in the setting of negative β-hCG 1
• Suspected adnexal torsion when ultrasound is inconclusive 1
  • CT shows 74-95% sensitivity and 80-90% specificity for adnexal torsion 1
• Suspected tubo-ovarian abscess (TOA) when ultrasound is inconclusive 1
  • CT findings include thick-walled fluid density in adnexal location, septations, indistinct borders, and gas bubbles 1

Surgical Complications

• Postoperative complications after gynecological surgery 1, 2
• Suspected uterine perforation or rupture 3
• Suspected abscess formation 2, 3

Other Critical Conditions

• HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets) 3
• Pulmonary thromboembolism when CT pulmonary angiography is the standard of care 3
• Suspected appendicitis after inconclusive ultrasound 2
• Small bowel obstruction after initial evaluation with conventional radiography 2
• Mesenteric ischemia (CT angiography preferred) 2

Important Considerations and Caveats

• Radiation safety in pregnancy: CT should be avoided when possible in pregnant patients, with ultrasound and MRI preferred 2
• Radiation threshold: Fetal radiation exposure should be kept below 50 mGy to minimize risks 2, 4
• Cancer risk: Fetal exposure >50 mGy is associated with doubled risk of childhood cancer 2
• Contrast considerations: Use iodinated contrast only when absolutely necessary in pregnancy 2
• Multiphasic CT advantage: Has 97% accuracy for detecting active extravasation in hemorrhage 1, 2
• CT limitations: Poor sensitivity for detecting myometrial invasion in endometrial cancer (58-61% vs. 88-89% for MRI) 2

When a life-threatening diagnosis is suspected and time is critical, the benefits of CT imaging outweigh the risks, particularly when other imaging modalities are inconclusive or unavailable 1, 2.