In a patient with a gunshot wound to the right chest causing pneumothorax who has had a chest tube placed and now presents with subcutaneous emphysema (crepitus) extending to the neck and tachypnea, what imaging test should be performed next to further evaluate for tracheobronchial, mediastinal, vascular, or esophageal injury?

CT Chest with IV Contrast (CT Angiography)

In a patient with gunshot wound to the chest, pneumothorax, chest tube placement, and now presenting with subcutaneous emphysema extending to the neck and tachypnea, you should immediately obtain a contrast-enhanced CT chest (CT angiography) to evaluate for tracheobronchial injury, esophageal perforation, and vascular injuries. 1

Rationale for CT with Contrast

The combination of persistent subcutaneous emphysema extending to the neck despite chest tube placement, along with tachypnea, strongly suggests either:

• Tracheobronchial injury (most likely given the extensive air dissection)
• Esophageal perforation (high mortality if missed)
• Inadequate chest tube drainage or ongoing air leak

CT scan is the best tool for detailed visualization of the trachea and bronchi, and to assess associated injuries, particularly those to the great vessels and esophagus 1. In penetrating chest trauma, contrast-enhanced CT offers up to 99% negative predictive value and successfully excludes the need for surgery in patients with nonsignificant findings 2.

Why CT Over Other Modalities

• Ultrasound is NOT accurate in the presence of subcutaneous emphysema 1, making it unreliable in this specific scenario despite its general utility in chest trauma
• Chest X-ray alone is insufficient - it may show indirect signs but cannot definitively identify the source or extent of injury 1
• CT provides comprehensive evaluation of bullet trajectory, mediastinal structures, vascular injuries (pseudoaneurysms, active bleeding), and can detect esophageal injury with 95% sensitivity and 91% specificity when performed as CT esophagography 3

Follow-up Bronchoscopy

After CT imaging, bronchoscopy remains the gold standard for diagnosing specific tracheal and bronchial injuries, providing direct airway visualization 1. The 2025 WSES-AAST guidelines emphasize this two-step approach: CT first for anatomic mapping, then bronchoscopy for definitive diagnosis and characterization of airway injuries.

Critical Pitfalls to Avoid

1. Do not delay imaging for bronchoscopy first - CT provides the roadmap and identifies associated injuries that may alter surgical approach
2. Do not assume the chest tube resolved the problem - persistent/worsening subcutaneous emphysema indicates ongoing air leak from an uncontrolled source
3. Consider esophageal injury - in penetrating trauma with pneumomediastinum, contrast CT-scan or esophagoscopy is strongly recommended 1. Esophageal injuries have 10-20% mortality, and delay in treatment is the most important survival predictor 3

Specific Injuries to Evaluate

The CT should specifically assess for:

• Tracheobronchial disruption (most traumatic injuries occur within 2.5 cm of the carina) 4
• Esophageal perforation (look for paraesophageal collections, mediastinal air, pleural effusions) 3
• Vascular injuries in the "cardiac box" region (pseudoaneurysms, active extravasation, intimal flaps) 2
• Diaphragmatic injury (CT is the most reliable tool for this) 1

If the patient becomes hemodynamically unstable before CT can be obtained, proceed directly to the operating room with intraoperative bronchoscopy and esophagoscopy 3.