Pleural Effusion

Pleural Effusion is a topic covered in the 5-Minute Emergency Consult.

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  • Normal conditions:
    • Pleural space contains 0.1–0.2 mL/kg (30 mL in an adult) of clear, low-protein fluid that facilitates movement of the pulmonary parenchyma within the thoracic space.
    • Fluid formation and reabsorption are governed by hydrostatic and oncotic forces.
    • Normally, the sum of these forces results in movement of fluid into the pleural space from the parietal surface and reabsorption at the visceral surface.
    • Lymphatics help remove any excess fluid.
  • Alteration of any of the above factors results in abnormal fluid accumulation.
  • Classification:
    • Transudative effusion:
      • An ultrafiltrate of serum, containing low protein and cells
      • Results from increase in hydrostatic pressure and/or decrease in oncotic pressure
      • Pleural surface is not involved in the primary pathologic process.
    • Exudative effusion:
      • Contains high protein and cells
      • Results from pathologic disease of the pleural surface leading to membrane permeability and/or disruption of lymphatic reabsorption


  • Transudative effusions:
    • Congestive heart failure (CHF)
    • Peritoneal dialysis
    • Cirrhosis with ascites
    • Pulmonary embolism
    • Acute atelectasis
    • Nephrotic syndrome
    • Myxedema
    • Hypoproteinemia
    • Superior vena cava syndrome
    • Meigs syndrome:
      • Triad of ascites, benign ovarian tumor, and pleural effusion
  • Exudative effusions:
    • Pulmonary or pleural infection:
      • Bacterial, viral, fungal, tuberculosis (TB), parasitic
    • Primary lung cancer
    • Mesothelioma
    • Metastasis (often from breast cancer, ovarian cancer, or lymphoma)
    • Pericarditis
    • Pulmonary embolism
  • Intra-abdominal disorders:
    • Pancreatitis, hepatitis, cholecystitis
    • Subdiaphragmatic abscess
    • Esophageal rupture
    • Peritonitis
    • Meigs syndrome
  • Rheumatologic disease:
    • Systemic lupus erythematosus
    • Rheumatoid arthritis
    • Sarcoidosis
  • Trauma:
    • Hemothorax
    • Chylothorax
  • Drugs:
    • Drug-induced lupus
    • Nitrofurantoin, methysergide, dantrolene, amiodarone, bromocriptine
    • Crack cocaine

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