Pleural Effusion

Pathophysiology

  • Systemic factors (eg, ↑ PCWP, ↓ oncotic pressure) → transudative effusion
  • Local factors (ie, Δ pleural surface permeability) → exudative effusion

Transudates

  • Congestive heart failure (40%): 80% bilateral, ± cardiomegaly on CXR occasionally exudative (especially after aggressive diuresis or if chronic)
  • Constrictive pericarditis (knock on exam, calcification or thickening on imaging)
  • Cirrhosis (“hepatic hydrothorax”): diaphragmatic pores allow passage of ascitic fluid often right-sided (⅔) & massive (even w/o marked ascites)
  • Nephrotic syndrome: usually small, bilateral, asymptomatic (r/o PE b/c hypercoag)
  • Other: PE (usually exudate), malignancy (lymphatic obstruction), myxedema, CAPD