What is the ultrasonic appearance of a hematoma (hematoma)?

Ultrasound Appearance of Hematomas

Hematomas demonstrate variable and evolving ultrasound appearances that depend primarily on their age, with acute hematomas initially appearing hypoechoic and progressively becoming more echogenic over time, though the specific echotexture does not reliably predict the age of the hematoma. 1, 2

Acute Hematomas (First Few Days)

• Initially hypoechoic to anechoic in the first hours to days after formation 1, 3
• Acute intracerebral hematomas become hyperechogenic within 16-23 seconds after formation (average 22 seconds), reaching full echogenicity between 40-213 seconds 3
• Spherical or ovoid shape within the abdomen, or lentiform shape within the pleural space or abdominal wall 1
• May contain variable amounts of internal echoes during the first month 1
• The hyperechogenicity is independent of clotting mechanism and related to blood stasis 3

Subacute to Chronic Hematomas (Days to Weeks)

• Gradually become more anechoic over time, typically after the first month 1
• Organizing hematomas appear as well-defined hypoechoic heterogeneous masses with surrounding increased echogenicity in the subcutaneous fat layer 4
• Generally decrease in size with time 1
• Usually have irregular walls 1
• Old, anechoic hematomas may contain gelatinous material that cannot be aspirated 1

Key Diagnostic Features

Echotexture Patterns

• Hypoechoic: Most common appearance, easier to aspirate (OR 3.77, p=0.010) 2
• Complex/heterogeneous: Mixed echogenicity with variable internal architecture 2
• Echogenic: Can occur in acute or organizing hematomas 1, 2
• The sonographic appearance is not specific and an abscess may have similar appearance 1

Important Clinical Considerations

The age of a hematoma cannot be reliably predicted from its ultrasound appearance (OR 1.03 per week, p=0.547), meaning older hematomas do not necessarily appear different from newer ones 2. This is a critical pitfall to avoid when attempting to date hematomas based on imaging alone.

Doppler Characteristics

• Color and spectral Doppler can help differentiate hematomas from vascular lesions 5
• Hematomas should show no internal vascularity on color Doppler imaging 5
• Hemorrhagic regions within other lesions (such as hepatic adenomas) are avascular and show no enhancement in any phase 5

Differential Diagnosis Pitfalls

• Organizing hematomas and thrombi can mimic benign-looking soft tissue tumors and should be considered in the differential diagnosis of superficial soft tissue masses 4
• In postpartum patients, hematomas may demonstrate variable T1 and T2 signal characteristics on MRI depending on time since delivery, with low T2 signal rim after >2 weeks due to hemosiderin deposition 5
• Small (<4 cm) subfascial and bladder flap hematomas may not be clinically significant in postpartum patients 5

Practical Aspiration Guidance

• Ultrasound-guided aspiration is safe and effective regardless of hematoma age or appearance 2
• Hypoechoic hematomas are significantly easier to aspirate than complex, heterogeneous, or echogenic hematomas 2
• Neither the appearance nor age of a hematoma should dissuade attempted aspiration if clinically indicated 2
• No instances of infection were reported in a cohort of 148 patients undergoing ultrasound-guided hematoma aspiration, with all patients reporting symptomatic relief 2