Exudative - high protein content (>30g/L) Transudative - lower protein (<30g/L)
Transudate tame - fluids leak from intact vessels so low protein
Exudates extreme - from pathological capillaries so high protein
Light’s criteria
| Transudative | Exudative | |
|---|---|---|
| Mechanism | Capillary hydrostatic pressure | Capillary permeability |
| Protein (pleural/serum) | <0.5 | >0.5 |
| LDH | <0.6 or Pleural LDH < 2/3 upper limit of normal serum LDH | >0.6 or Pleural LDH > 2/3 upper limit of normal serum LDH |
| Common Causes | Hypoalbuminaemia (Cirrhosis, Nephrotic syndrome) Congestive Heart Failure Constrictive Pericarditis | Autoimmune disease (inflammatory) Oesophageal rupture Infection (TB, fungal, empyema) Palignancy Pancreatitis Post-CABG |
Causes/Factors
Pleural effusion can result from various underlying causes, including:
Exudative - related to inflammation
- Cancer
- Infection
- RA
Transudative - fluid moving into the pleural space
- Congestive Heart Failure
- Hypoalbuminaemia
- Hypothyroidism
- Meigs syndrome
Presentation
- Shortness of breath
- Dullness to percussion
- Reduced breath sounds
- Tracheal deviation away from the effusion
Diagnostic Tests
- CXR: blunting of costophrenic angle, fluid in lung fissures, meniscus, mass effect
- USS and CT can detect smaller effusions, estimate volume and may identify cause
- Pleural fluid analysis requires a sample taken by aspiration or chest drain. This helps establish the underlying cause by measuring the protein content, LDH, cell count, pH, glucose and microbiology testing.
Management
- Conservative management for small effusions. Treat underlying problem instead
- Pleural aspiration - needle through the chest wall, temporary relief
- Chest drain may be used but can reoccur when taken out.
Complications/Red Flags
Untreated or unmanaged pleural effusion can lead to serious complications, such as:
- Lung Collapse: Severe effusions can compress the lung, causing it to collapse (atelectasis).
- Empyema: Accumulation of pus within the pleural space due to bacterial infection.
- Respiratory Failure: Severe effusion can lead to difficulty breathing and reduced Oxygen levels.