Pleural Effusion

• Presence of fluid in the pleural space
• 2 types
  • Transudate (protein conc < 25 g/L)
  • Exudate (protein conc > 35 g/L)
    
    

    Light's Criteria

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    • If the protein concentration falls between 25 and 35 g/L → use Light’s criteria to decide whether exudate or transudate
    • Pleural fluid protein: serum protein ratio > 0.5 → favouring exudate
    • Pleural fluid LDH: serum LDH ration > 0.6 → favouring exudate


• Transudate causes:
  • Increased venous pressure: cardiac failure, constrictive pericarditis, fluid overload
  • Hypoproteinaemia: cirrhosis, nephrotic syndrome, malabsorption
  • Also seen in hypothyroidism and Meig’s syndrome (ovarian fibroma)
• Exudate causes:
  • Increased vascular permeability: pneumonia, TB, pulmonary infarction, rheumatoid arthritis, SLE, cancer

Signs and symptoms

• Symptoms: may be asymptomatic, can present with dyspnoea, pleuritic chest pain
• Signs: decreased lung expansion, stony dullness to percussion, decreased air entry, tracheal deviation (in large effusions). Signs associated with the cause including peripheral oedema (heart failure, cirrhosis), lymphadenopathy (cancer), coarse crackles (pneumonia) etc.

Investigation

• CXR: blunting of the costo-phrenic angles
• Ultrasound: helpful to guide drainage
• Aspiration: with 21G needle inserted 1-2 intercostal spaces below the upper border of the effusion → send for biochemistry, cytology, bacteriology and immunology (e.g. rheumatoid factor, ANA) if indicated.
• Pleural biopsy: if pleural fluid analysis inconclusive may obtain a biopsy via CT-guided means

Management

• Treat the underlying cause e.g., IV antibiotics for pneumonia
• If symptomatic: drainage with intercostal chest drain (drain slowly 0.5-1.5 L/day)
• Pleurodesis: helpful with recurrent effusions
• Intra-pleural urokinase, alteplase or dornase alfa: helps break the septae and pockets of empyema
• Surgery if resistant to above measures

Reference: Oxford Handbook of Clinical Medicine (10th Edition)