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