Transudate tame - fluids leak from intact vessels so low protein
Exudates extreme - from pathological capillaries so high protein
Light’s Criteria
How to determine what type of effusion it is:
| 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 |
Transudate effusion
- Low capillary oncotic pressure/high hydrostatic pressure
- Low protein & lactate dehydrogenase
Exudate effusion
- Pathological capillaries leak too much → high protein