What are the indications for urgent computed tomography (CT) scans in obstetrics and gynecology (OB/GYN)?

Urgent CT Scan Indications in Obstetrics and Gynecology

CT scans in obstetrics and gynecology are primarily indicated for life-threatening conditions, failed conventional medical treatment, or when ultrasound and MRI are inconclusive or unavailable. 1

Primary Indications for Urgent CT Scans

Obstetric Emergencies

• Postpartum Hemorrhage (PPH)

  • Persistent hemorrhage after empiric embolization 2
  • Failed conventional medical treatment for PPH 1
  • Suspected vascular complications (pseudoaneurysm, arteriovenous malformations) 2, 1
  • Multiphasic CT has 97% accuracy for detecting active extravasation in hemorrhage 1

• Trauma in Pregnancy

  • Polytrauma assessment in pregnant patients with high-velocity trauma 1
  • Suspected intra-abdominal hemorrhage 1
  • Unstable pelvic fractures 1

• Postpartum Complications

  • Suspected uterine dehiscence or rupture 2
  • Subfascial or perivaginal space hematomas 2
  • Ovarian vein thrombosis 2, 1
  • Parametrial abscess or infected hematoma 2

Gynecologic Emergencies

• Adnexal Emergencies

  • Adnexal torsion when ultrasound is inconclusive (74-95% sensitivity, 80-90% specificity) 2, 1
  • Tubo-ovarian abscess (TOA) with thick-walled fluid density in adnexal location 2, 1
  • Ruptured ectopic pregnancy with hemodynamic instability when ultrasound is inconclusive 3

• Pelvic Inflammatory Disease (PID)

  • PID with suspected complications 1
  • Pyosalpinx (tubular cystic lesion with multiple satellite lesions) 2

• Non-specific Presentations

  • Poorly localized pain with suspected gynecologic and non-gynecologic etiologies 1
  • Nonspecific clinical presentation with broad differential diagnosis 1
  • Equivocal or nondiagnostic ultrasound evaluation 1

Imaging Protocol Considerations

Contrast Enhancement

• CT with IV contrast is recommended for most urgent indications 2
• Contrast-enhanced CT has higher sensitivity (89% vs 70%) than ultrasound for urgent diagnoses 1
• Multiphasic CT (including non-contrast, arterial, and portal venous phases) has excellent accuracy (97%) for detection of active extravasation 2

Radiation Safety in Pregnancy

• Avoid CT scans in pregnancy whenever possible 1
• Use non-ionizing imaging modalities (ultrasound and MRI) as preferred alternatives 1
• When CT is necessary in pregnancy:
  • Cumulative ionizing radiation exposure should be less than 50 mGy 1
  • Use proper abdominal shielding to minimize fetal exposure 1
  • Iodinated contrast should be used only when absolutely necessary 1

Clinical Decision Algorithm

1. First-line imaging: Transvaginal/transabdominal ultrasound for all suspected gynecologic or obstetric conditions 2, 1

2. Consider urgent CT when:

   • Patient is hemodynamically unstable
   • Widespread disease is suspected
   • Non-gynecologic etiology is suspected
   • Ultrasound is inconclusive
   • MRI is unavailable or contraindicated

3. For pregnant patients:

   • Ultrasound → MRI without gadolinium → CT (only if absolutely necessary)
   • Maternal well-being takes priority in life-threatening situations 1

Common Pitfalls and Caveats

• CT cannot reliably distinguish vascular uterine abnormalities from normal postpartum changes 1
• Hypodense edema at cesarean incision site can be misinterpreted as dehiscence in the first postpartum week 2, 1
• CT has limited accuracy for adnexal mass characterization compared to ultrasound or MRI 1
• RPOC (retained products of conception) can be difficult to differentiate from blood products even on multiphase CT 2
• CT findings of endometritis are nonspecific (thickened heterogeneous endometrium with fluid, gas, and debris) 2

By following these guidelines, clinicians can appropriately utilize CT scanning in urgent obstetric and gynecologic conditions while minimizing unnecessary radiation exposure and optimizing diagnostic accuracy.