Pleural effusion

Background

• Exudative
  • Active fluid secretion or leakage w/ high protein content
• Transudative
  • Imbalance between hydrostatic (e.g. CHF) and oncotic (e.g. nephrotic syndrome)
  • Fluid has low protein content

Diagnosis

Detection of exudative pleural effusion

• 99% Sn, 65-85% Sp
  • Pleural fluid/serum protein ratio >0.5 OR
  • Pleural fluid/serum LDH ratio >0.6 OR
  • Pleural fluid LDH > two thirds of upper limit for serum LDH

Exudative Effusion Tests

• Gram stain and culture
• Cell count
  • Neutrophil predominance: parapneumonic, pulmonary embolism, pancreatitis
  • Lymphocytic predominance: cancer, tuberculosis, postcardiac surgery
• Glucose
  • Low glucose seen in parapneumonic, malignant, TB, and RA
• ABG (pH)
  • Normal pleural fluid pH = 7.64;
  • In parapneumonic effusions, <7.10 predicts development of empyema or persistence and indicates need for thoracostomy tube drainage
• Amylase: Elevated in pleural effusions due to pancreatitis or esophageal rupture
• TB
• India ink
• Cytology

Work-Up

Thoracentesis

DDx

Common

1. CHF
2. Cancer
3. PNA w/ parapneumonic effusion

Less Common

1. PE
2. Cirrhosis
3. Nephrotic syndrome
4. Viral, fungal, or parasitic infection
5. SLE, RA
6. Uremia
7. Pancreatitis
8. Amiodarone

See Also

Thoracentesis