Does subcutaneous emphysema without an obvious pneumothorax indicate the presence of a pneumothorax?

Subcutaneous Emphysema and Pneumothorax

Subcutaneous emphysema without an obvious pneumothorax on plain chest radiograph does not definitively rule out pneumothorax, and CT scanning should be performed when subcutaneous emphysema obscures the plain chest radiograph. 1

Understanding the Relationship

The development of subcutaneous emphysema associated with pneumothorax requires an air-filled space to be brought into communication with subcutaneous tissues. 1 This mechanism inherently suggests that a pneumothorax or air leak exists somewhere, even if not immediately visible on standard imaging.

Key Clinical Scenarios

The presence of subcutaneous emphysema indicates one of several possibilities:

• A pneumothorax exists but is obscured by the subcutaneous air on plain radiography, making CT scanning essential for definitive diagnosis 1
• A small or occult pneumothorax that may not be visible on standard PA chest radiograph but can be detected with lateral or lateral decubitus views 1
• A pneumothorax that has partially resolved but left residual subcutaneous air tracking through tissue planes 1

Diagnostic Algorithm

When subcutaneous emphysema is present without obvious pneumothorax on PA chest radiograph:

1. Obtain lateral chest or lateral decubitus radiograph if clinical suspicion remains high, as these views provide added diagnostic information in up to 14% of cases 1

2. Proceed directly to CT scanning when the plain chest radiograph is obscured by surgical emphysema, as this is the definitive recommendation 1

3. CT scanning is also indicated when differentiating pneumothorax from complex bullous lung disease, which is critical to avoid dangerous aspiration attempts 1, 2

Critical Clinical Considerations

Subcutaneous emphysema indicates severe chest wall injury and the presence of an air leak, even if pneumothorax is not immediately visible. 3 The absence of an obvious pneumothorax on initial imaging does not exclude its presence, particularly when:

• Extensive subcutaneous emphysema can obscure underlying pneumothorax on plain films 1
• Delayed presentations are possible, with patients deteriorating rapidly even 24 hours after initial injury 3
• Subcutaneous emphysema itself rarely occurs without an underlying source of air leak from the pleural space or airways 1, 4

Management Implications

The presence of subcutaneous emphysema warrants aggressive investigation for pneumothorax because:

• Even if initially stable, patients can rapidly deteriorate with airway compromise 3
• Treatment of any underlying pneumothorax is critical, as subcutaneous emphysema can worsen with malpositioned, kinked, blocked, or clamped chest tubes 1
• A small tube in the presence of a large air leak may cause progressive subcutaneous emphysema 1

Life-Threatening Complications

While subcutaneous emphysema is generally of cosmetic importance only and subsides after a few days, it can occasionally cause acute airway obstruction or thoracic compression leading to respiratory compromise. 1 In these life-threatening situations, treatment options include tracheostomy, skin incision decompression, and insertion of large bore modified subcutaneous chest drains 1

Bottom line: Subcutaneous emphysema without obvious pneumothorax on plain radiograph mandates further investigation with CT scanning to definitively exclude or confirm pneumothorax, as the presence of subcutaneous air strongly suggests an underlying air leak from the pleural space. 1