Pleural effusion and pneumothorax
- Lesion
Fluid, pus, blood, chyle or air can collect between the pleural layers. Each one has its own causes and compresses the lung.
What it is
The pleural space normally holds a thin film of fluid. Effusions are inflammatory (exudates: pleuritis, empyema, hemorrhagic pleuritis) or noninflammatory (hydrothorax transudates, hemothorax, chylothorax). Air in the space is pneumothorax, spontaneous or traumatic. Most pleural disease is secondary to disease of the lung or elsewhere; malignant effusions are common.
Structure
- Fibrinous pleuritis: shaggy fibrin on the pleura (friction rub), later organised into fibrous adhesions.
- Empyema: creamy pus with neutrophils, walled off by granulation tissue and fibrosis.
- Malignant effusion: tumour cells in cytology of the fluid (lung, breast, ovary, lymphoma most often).
- Spontaneous pneumothorax: small thin-walled apical blebs with pleural inflammation and eosinophils at the rupture site.
Step by step
- Transudates form when hydrostatic pressure rises or oncotic pressure falls with intact pleura.
- Exudates form when inflammation or tumour makes pleural capillaries leaky or blocks lymphatic drainage.
- Bacteria reaching the space convert a parapneumonic effusion into empyema.
- Air enters through a ruptured bleb or a chest wound and the lung recoils away from the chest wall.
- If a flap valve lets air in but not out, pressure rises with each breath: tension pneumothorax compresses the heart and great veins.
- Any large collection compresses the lung (compression atelectasis).
What is in the pleural space
| Collection | Content | Main causes |
|---|---|---|
| Hydrothorax | Transudate | Heart failure, cirrhosis, nephrotic syndrome |
| Serofibrinous pleuritis | Exudate with fibrin | Pneumonia, TB, infarct, lupus, RA |
| Empyema | Pus | Spread from bacterial pneumonia or abscess |
| Hemothorax | Blood | Trauma, ruptured aortic aneurysm |
| Chylothorax | Milky lymph | Thoracic duct trauma, tumour |
| Pneumothorax | Air | Ruptured blebs, emphysema, trauma |
Clinical notes
- Pleuritic pain and dyspnoea; dullness for fluid, hyperresonance and absent breath sounds for air.
- Light's criteria on the fluid separate transudate from exudate.
- Tension pneumothorax: hypotension, tracheal deviation away from the affected side; needs immediate decompression.
Test yourself
Think of the answer, then tap the question to see it.
What usually causes spontaneous pneumothorax in a young adult?
Rupture of small apical subpleural blebs, often in tall young men.
What is chylothorax and what causes it?
Milky lymph in the pleural space from thoracic duct injury or obstruction of lymphatics, often by tumour.
Why is tension pneumothorax life-threatening?
A flap-valve leak lets air in but not out; rising pressure collapses the lung and shifts the mediastinum, impairing venous return to the heart.
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Pleural Disorders (MedlinePlus, US National Library of Medicine, 2025); Collapsed Lung (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.