What is the best imaging modality to assess a hematoma in the pelvis?

Best Imaging Modality for Assessing Pelvic Hematoma

CT or CTA of the abdomen and pelvis is the most appropriate initial imaging modality for assessing a hematoma in the pelvis due to its speed, high spatial resolution, and ability to detect active bleeding. 1

Initial Imaging Selection Algorithm

CT Without Contrast (Non-contrast CT)

• Appropriate for expeditiously confirming or excluding bleeding 1
• Particularly useful in patients with compromised renal function 1
• Can determine relative acuity of hematoma based on attenuation values:
  • High/mixed attenuation indicates acute to subacute bleeding (85-370 HU) 2
  • Low attenuation suggests subacute to chronic blood products (40-70 HU) 2
• Can identify "sentinel clot" suggesting area of bleeding even without active extravasation 1

CT Angiography (CTA)

• Superior choice when active bleeding is clinically suspected 1
• Provides exact location of hematoma plus vascular information 1
• More sensitive than conventional angiography for detecting active bleeding 1
  • Can detect bleeding rates as low as 0.3 mL/min (vs. 0.5-1.0 mL/min for conventional angiography) 1
• Shows active extravasation in 78.9-84.2% of cases with active bleeding 1
• Provides valuable preoperative information for potential intervention 1

Advantages of CT/CTA for Pelvic Hematoma

• Rapid acquisition - critical in potentially unstable patients 1
• High spatial resolution for detailed anatomic assessment 1
• Ability to scan large areas to identify bleeding source and cause (e.g., pelvic fracture, vascular injury) 1
• Excellent for follow-up of known hematomas to assess for rebleeding or complications 1
• Can distinguish between active hemorrhage and clotted blood through attenuation measurements 2

Alternative Imaging Modalities and Limitations

Angiography

• Best reserved for hemodynamically unstable patients with high suspicion for active bleeding 1
• Advantage: allows simultaneous diagnosis and treatment via embolization 1
• Disadvantage: invasive with risks of access site complications and infection 1
• Less sensitive than CTA for detecting low-volume active bleeding 1

MRI/MRA

• Not recommended for initial assessment of suspected pelvic hematoma 1
• Limitations include:
  • Lengthy examination time inappropriate for acute setting 1
  • May delay diagnosis and treatment in emergency situations 1
  • Contraindicated with certain implanted devices 1
• May be useful for follow-up or when underlying neoplasm is suspected 1
• Can characterize blood products by age (acute vs. chronic) 1

Ultrasound

• Limited role in pelvic hematoma assessment 1
• Advantages include portability and lack of radiation 1
• Major limitations:
  • Difficult visualization of retroperitoneal structures 1
  • Limited acoustic windows in critical care settings 1
  • Poor sensitivity for small volume bleeding 1
  • Cannot reliably determine if bleeding is active 1

Common Pitfalls to Avoid

• Absence of visible hematoma on CT does not exclude active bleeding - 83% of patients with no visible pelvic hematoma still had active bleeding at angiography 3
• Absence of contrast blush on CT does not rule out active bleeding - 71% of patients without CT blush had positive findings at angiography 3
• Relying on non-contrast CT alone when active bleeding is suspected - contrast-enhanced studies are more sensitive for detecting active extravasation 4
• Delaying appropriate imaging in unstable patients - rapid diagnosis is essential for reducing morbidity and mortality 5

Special Considerations

• In pregnant patients with vaginal bleeding, ultrasound should be performed before any digital examination 6
• For trauma patients, CT can accurately show anatomic location of bleeding and guide surgical or angiographic intervention 2
• Multi-detector CT (MDCT) provides excellent diagnostic information for both small pelvic fractures and associated vascular injuries 5