What are the causes of hemothorax?

Causes of Hemothorax

Hemothorax is primarily caused by trauma (both blunt and penetrating), with other significant causes including iatrogenic injuries, malignancy, and vascular abnormalities. Understanding these causes is essential for proper diagnosis and management to reduce morbidity and mortality.

Traumatic Causes

Blunt Trauma

• Rib fractures - especially between the 3rd and 9th ribs, which can lacerate intercostal vessels or lung parenchyma 1
• Lung lacerations - severe lung tissue damage causing significant bleeding 1
• Cardiac injury - rupture of cardiac chambers (most commonly right ventricle due to its anterior location) 1
• Great vessel injuries - tears or ruptures of major thoracic vessels
• Diaphragmatic injury - with or without obvious diaphragm rupture 2
• Inferior phrenic artery damage - can cause hemothorax even without diaphragm rupture 2

Penetrating Trauma

• Stab wounds to the chest
• Gunshot wounds affecting thoracic structures
• Impalement injuries

Iatrogenic Causes

• Surgical complications - especially following:
  • Esophageal resections (up to 4% complication rate) 1
  • Lung cancer resections 1
  • Cardiovascular surgeries 1
  • Spinal surgeries 1
• Thoracentesis complications - vessel trauma during the procedure 1
• Central line placement - inadvertent arterial puncture
• Thoracic interventional procedures

Spontaneous/Non-traumatic Causes

Malignancy-Related (18% of non-traumatic cases) 1

• Lymphoma - most common malignant cause (75% of malignant cases) 1
• Metastatic carcinoma - can invade pleural space or erode blood vessels

Vascular Causes

• Aortic dissection - rupture into pleural space
• Arteriovenous malformations
• Coagulopathies - including anticoagulant use 3
• Pulmonary infarction - can lead to bleeding into pleural space

Chylothorax-Related (blood-tinged chyle)

• Thoracic duct disruption - from trauma or surgery
• Lymphatic obstruction - from malignancy or inflammation

Other Medical Conditions

• Tuberculosis - can cause both hemothorax and chylothorax 1
• Sarcoidosis 1
• Lymphangioleiomyomatosis 1
• Cirrhosis - with portal hypertension 1
• Venous thrombosis - especially central veins 1
• Catamenial hemothorax - associated with thoracic endometriosis

Diagnostic Approach

1. Initial imaging:

   • Chest radiography - first-line but has limited sensitivity (54-62.5%) 1
   • Chest CT with IV contrast - gold standard for non-invasive assessment (can identify source of bleeding) 1
   • Point-of-care ultrasound - useful for rapid assessment (sensitivity 60%, specificity 98%) 1, 4

2. Laboratory evaluation:

   • Thoracentesis with fluid analysis - to confirm hemothorax and rule out chylothorax
   • If chylothorax suspected, check triglyceride and cholesterol levels 1

Management Considerations

• Small occult hemothoraces (<300 mL or <1.5 cm pleural stripe) may be managed conservatively with observation 5
• Larger hemothoraces typically require tube thoracostomy 4
• Massive hemothorax (>1,500 mL initial drainage or >200 mL/hour ongoing drainage) requires surgical exploration 3
• Retained hemothorax may require fibrinolytic therapy or surgical intervention to prevent complications like empyema and fibrothorax 4

Pitfalls to Avoid

1. Missing delayed hemothorax - can develop up to 2 weeks after minor trauma in 7.4-11.8% of patients 1
2. Overlooking cardiac injuries - hemothorax can result from cardiac rupture with pleuropericardial laceration 1
3. Confusing chylothorax with hemothorax - both can appear bloody; triglyceride analysis is essential for differentiation 1
4. Assuming diaphragm rupture is necessary - vascular damage from pressure trauma can cause hemothorax without diaphragm rupture 2
5. Delaying intervention for massive hemothorax - can lead to hemodynamic compromise and increased mortality

Understanding the diverse causes of hemothorax allows for prompt diagnosis and appropriate management, ultimately improving patient outcomes by reducing morbidity and mortality.