What is the most likely cause of a massive hemothorax?

Causes of Massive Hemothorax

The most common cause of massive hemothorax is injury to the intercostal artery, which is located along the inferior border of each rib and is vulnerable during chest trauma. 1

Definition and Major Causes

Massive hemothorax is defined as the accumulation of blood in the pleural space that threatens life through asphyxiation, exsanguination, or rapid hemodynamic compromise. It is typically quantified as at least 200 mL of blood in 24 hours or 1,500-2,000 mL of blood accumulation in the pleural space 1.

The primary causes of massive hemothorax, in order of frequency, are:

1. Intercostal artery injury - Most common cause 1

   • Can occur from trauma, procedures, or spontaneously
   • Located along the inferior border of each rib, making them vulnerable during chest trauma
   • Documented as a complication of thoracentesis 2

2. Hilar vessel injury - Second most common cause 1

   • Involves major pulmonary vessels at the hilum
   • Often associated with severe trauma or iatrogenic injury
   • Carries high mortality due to rapid blood loss

3. Other causes:

   • Pulmonary artery branches 1
   • Internal thoracic artery (rare) 3
   • Transverse cervical artery (rare) 4
   • Lung parenchymal injury (less common source of massive bleeding)
   • Coagulopathy or hypercoagulable states 1

Clinical Presentation

Patients with massive hemothorax typically present with:

• Chest pain
• Shortness of breath
• Shock symptoms in severe cases
• Attenuated or absent breath sounds on the affected side
• Percussion dullness 1

Diagnostic Approach

The diagnosis of massive hemothorax relies on:

• Chest radiography
• Ultrasound (can be valuable for early detection) 2
• CT scan to identify the specific source of bleeding when the patient is stable 1

Management

Immediate management includes:

• Tube thoracostomy (chest tube placement) in the 4th/5th intercostal space in the midaxillary line
• Volume resuscitation and blood product replacement
• Consideration for surgical intervention or angiographic embolization for ongoing bleeding 1

Special Considerations

• Trauma is the primary cause of hemothorax, while cancer is the primary cause of chylothorax 5
• Most patients with hemothorax can be treated with chest tube drainage alone 5
• Unusual causes like cough-induced rib fractures with intercostal artery tear can lead to massive hemothorax 6
• Video-assisted thoracoscopy may play an increasing role in surgical treatment 5

In conclusion, when considering the options provided in the question (subcostal artery, hilar vessel, or lung parenchyma), the intercostal artery (not subcostal) is the most common cause of massive hemothorax, followed by hilar vessel injury, with lung parenchymal injury being a less common source of massive bleeding.