A 28-year-old man is brought to the trauma centre following a stab wound to the left hemithorax. On arrival, he is haemodynamically stable with a respiratory rate of 24/min and oxygen saturation of 94% on room air. Chest X-ray shows a moderate-sized left-sided collection with an air-fluid level. What is the most common cause of haemothorax in penetrating chest trauma?

Explanation

## Haemothorax in Penetrating Chest Trauma — Most Common Cause **Key Point:** Intercostal vessel injury is the most common cause of haemothorax in penetrating chest trauma, accounting for approximately 75–80% of cases. These vessels run in the neurovascular bundle along the inferior aspect of each rib. ### Anatomical Basis of Intercostal Vessel Injury **High-Yield:** The intercostal vessels (artery, vein, and nerve) run in a groove on the inferior surface of each rib in the neurovascular bundle. Penetrating trauma (stab, gunshot) that traverses the rib cage commonly lacerates these vessels. ### Comparison of Haemothorax Causes | Cause | Frequency | Mechanism | Bleeding Pattern | Prognosis | | --- | --- | --- | --- | --- | | **Intercostal vessels** | 75–80% (most common) | Rib laceration, penetrating wound | Moderate, self-limited if small | Usually self-limited; may require tube thoracostomy | | Pulmonary parenchymal | 10–15% | Lung laceration from rib fragments or penetrating injury | Variable; often mixed with pneumothorax | Usually self-limited; rarely requires thoracotomy | | Cardiac/great vessels | 5–10% (life-threatening) | Penetrating injury to mediastinum | Massive, rapidly fatal | High mortality; requires emergency thoracotomy | | Diaphragmatic | Rare | Penetrating injury below 5th intercostal space | Depends on associated organ injury | Depends on associated injuries | ### Why Intercostal Vessels Are Most Common 1. **Anatomical exposure:** Every penetrating wound that crosses the rib cage has high probability of hitting intercostal vessels 2. **Predictable location:** Vessels run in a fixed groove on each rib 3. **Moderate bleeding:** Intercostal vessel injury produces haemothorax that is often self-limited (bleeding stops due to tamponade or vessel retraction) 4. **Survivable:** Unlike great vessel injury, intercostal bleeding rarely causes immediate exsanguination **Clinical Pearl:** A haemodynamically stable patient with moderate haemothorax (as in this case) is typical of intercostal vessel injury. Massive haemothorax (>1500 mL on initial drainage or >200 mL/hour ongoing) suggests great vessel injury and mandates emergency thoracotomy. ### Management Algorithm ```mermaid flowchart TD A[Penetrating chest trauma with haemothorax]:::outcome --> B{Haemodynamic status?}:::decision B -->|Stable| C[Chest tube insertion]:::action B -->|Unstable/Massive| D[Emergency thoracotomy]:::urgent C --> E{Bleeding rate?}:::decision E -->|< 200 mL/hr| F[Observe, manage conservatively]:::action E -->|> 200 mL/hr| G[Consider thoracotomy]:::action F --> H[Most likely intercostal vessel]:::outcome G --> I[Rule out great vessel injury]:::outcome ``` **Mnemonic:** **MASSIVE** haemothorax = **M**ediastinal injury (great vessels); **A**cute = **S**table with **S**mall-moderate bleed = **I**ntercostal vessels; **V**ery **E** = Emergency thoracotomy needed. [cite:ATLS 10e Ch 4; Sabiston Textbook of Surgery 21e Ch 19]