What is a hematoma?

What is a Hematoma

A hematoma is a collection of blood outside of blood vessels that accumulates in tissue spaces, organs, or body cavities due to vessel damage or rupture.

Basic Definition and Pathophysiology

A hematoma represents an abnormal accumulation of blood that has leaked from damaged blood vessels into surrounding tissues, creating a localized swelling or mass 1. Unlike simple bruising, hematomas involve sufficient blood volume to create a discrete collection that may persist or expand over time 2.

Key Anatomical and Clinical Features

Location-Specific Characteristics

Intracranial hematomas include several distinct types based on anatomical compartments:

• Subdural hematomas occur between the dura mater and arachnoid membrane, often appearing as encapsulated collections of blood and fluid on the brain surface 3, 4
• Subgaleal hematomas accumulate in the loose areolar tissue layer between the skull periosteum and galea aponeurotica, extending from orbital ridges anteriorly to the nuchal line posteriorly 5
• Hemorrhagic stroke represents intraparenchymal, intraventricular, or subarachnoid hemorrhage causing acute neurological dysfunction lasting >24 hours 6

Spinal hematomas can be epidural, subdural, or subarachnoid, typically presenting with intense, knife-like pain ("coup de poignard") at the hemorrhage site, potentially followed by a pain-free interval before progressive paralysis develops 7.

Soft tissue hematomas of the extremities occur in approximately 33 per 10,000 individuals annually, most commonly following trauma or surgical procedures 1.

Temporal Classification

• Acute hematomas present with sudden onset and appear as high-density lesions on CT imaging within the first week 6, 8
• Chronic hematomas develop over weeks to months, with chronic subdural hematomas most often occurring in patients aged 60 and older with brain atrophy 4
• Chronic expanding hematomas represent an unusual variant that slowly enlarges over time, sometimes mimicking soft-tissue neoplasms 2

Clinical Presentation

Symptoms Requiring Immediate Attention

Hematomas causing mass effect or neurological compromise present with:

• Acute or subacute onset headache 6
• Epileptic seizures 6
• Impaired consciousness 6
• New or worsened focal neurological deficits referable to the anatomical location 6
• Intense localized pain particularly with spinal hematomas 7

Physical Examination Findings

• Visible swelling in soft tissue hematomas 1
• Posterolateral extension pattern in subgaleal hemorrhages due to gravity and lack of anatomical barriers 5
• Progressive neurological deterioration below the affected spinal level in spinal hematomas 7

Diagnostic Approach

First-Line Imaging

CT head without IV contrast is the gold standard initial test for suspected intracranial hemorrhage, rated 9/9 (usually appropriate) by the American College of Radiology 8. CT demonstrates acute blood as high-density areas with Hounsfield values consistent with hemorrhage 6, 8.

Timing Considerations

• Perform imaging as soon as possible after symptom onset, ideally within 1 week to reliably demonstrate acute hemorrhage 6, 8
• CT should be obtained within 3 hours of symptom onset when hematoma expansion is suspected, as 28-38% of patients show expansion of greater than one-third on follow-up 8

Advanced Imaging

• MRI with gradient echo (GRE) or susceptibility-weighted imaging (SWI) is equally sensitive to CT for acute hemorrhage detection and superior for characterizing hemorrhage age 8
• Follow-up imaging at 24 hours, 7-10 days, 30 days, and 90 days is recommended after initial diagnosis 8

Pathophysiological Mechanisms

Chronic Hematoma Development

Chronic subdural hematomas involve complex processes beyond simple trauma 3:

• Angiogenesis creates fragile blood vessels within characteristic membrane walls 3
• Fibrinolytic processes prevent clot formation, resulting in continued hemorrhage 3
• Inflammatory responses stimulate ongoing membrane growth and fluid accumulation 3, 4

Tissue Damage Mechanisms

Blood accumulation causes tissue injury through:

• Increased tissue pressure leading to necrosis of overlying skin 1
• Cellular and biochemical changes resulting in tissue ischemia even without elevated pressure 1

Common Pitfalls and Clinical Caveats

Diagnostic Errors to Avoid

• Never rely on clinical features alone to differentiate hemorrhage from ischemia—neuroimaging is mandatory 8
• Do not confuse subgaleal hemorrhage with other cranial hemorrhages that have more restricted anatomical boundaries 5
• Subarachnoid spinal hematomas may present with symptoms mimicking cerebral hemorrhage, including meningitis symptoms, altered consciousness, and seizures 7
• Subdural hematomas are intracranial hemorrhagic events but not strokes according to ACC/AHA definitions 6

Management Considerations

• Prompt recognition and operative evacuation of extremity hematomas prevents significant complications from tissue necrosis 1
• Surgical decompression is the treatment of choice for spinal hematomas, with outcomes directly related to preoperative symptom severity and time to surgery 7
• Complete recovery occurs in 39.6% of spinal hematoma patients, with better outcomes when surgery is performed quickly 7

Risk Factor Assessment

• Anticoagulant therapy alone probably does not trigger hemorrhage—there must be an additional vulnerable site and increased venous pressure 7
• Warfarin-related hemorrhages carry increased risk of hematoma expansion, morbidity, and mortality 8
• Brain atrophy in elderly patients predisposes to chronic subdural hematoma from minor trauma due to tearing of bridging veins 4