Pleural effusion
Description
- Abnormal fluid accumulation in the pleural space
- Normal volume ~10 mL; ~0.2 mL/kg/h turnover, cleared by parietal lymphatic stomata
- Lymphatic reserve capacity is ~20x normal - an effusion requires either massive production or blocked drainage
Mechanisms
| Mechanism | Type | Example |
|---|---|---|
| inc hydrostatic pressure | Transudate | Heart failure |
| dec oncotic pressure | Transudate | Nephrotic, cirrhosis, malnutrition |
| inc capillary permeability | Exudate | Infection, malignancy, inflammation |
| dec lymphatic drainage | Exudate | Malignancy, mediastinal fibrosis |
| Transdiaphragmatic movement | Transudate | Hepatic hydrothorax, peritoneal dialysis |
| Thoracic duct disruption | Chylothorax | Lymphoma, surgery, trauma |
Named effusions
- Empyema - frank pus, or organisms on Gram stain/culture
- Complicated parapneumonic - sterile but loculated/acidotic; requires drainage
- Chylothorax - triglycerides >1.24 mmol/L (110 mg/dL) +/- chylomicrons; milky, not clearing on centrifugation
- Pseudochylothorax - cholesterol >5.18 mmol/L, cholesterol crystals; chronic (TB, RA)
- Haemothorax - pleural fluid Hct >50% of blood Hct
- Trapped lung - visceral pleural peel prevents re-expansion; markedly negative pleural pressure
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