Pleural Effusion

Basics

Description

  • Normal conditions:
    • Pleural space contains about 0.25 mL/kg 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 from the parietal pleural capillaries, into the pleural space, where it is resorbed by visceral surface lymphatics
  • The rate of entry of fluid and its resorption are normally equal but become deranged in effusion accumulation. Classification:
    • Transudative effusion:
      • An ultrafiltrate of serum, containing low protein and cell concentration
      • Results from increase in hydrostatic pressure and/or decrease in oncotic pressure
      • Pleural surface is not involved in the primary pathologic process
      • Bilateral effusions are most commonly transudates
    • Exudative effusion:
      • Contains high protein and cell concentrations
      • Results from pathologic disease of the pleural surface leading to membrane permeability and/or disruption of lymphatic reabsorption

Etiology

  • Transudates:
    • 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
  • Exudates:
    • 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
    • Asbestosis
  • Intra-abdominal disorders:
    • Pancreatitis, hepatitis, cholecystitis
    • Subdiaphragmatic abscess
    • Esophageal rupture
    • Peritonitis
    • Meigs syndrome
  • Rheumatologic disease:
    • Systemic lupus erythematosus
    • Rheumatoid arthritis
    • Sarcoidosis
    • Vasculitis
  • Trauma:
    • Hemothorax
    • Chylothorax
  • Vascular:
    • Rupture of thoracic aortic aneurysm
    • Aortic dissection
  • Iatrogenic:
    • Drug-induced lupus
    • Nitrofurantoin, methysergide, dantrolene, amiodarone, bromocriptine, chemotherapy agents (interleukin-2, methotrexate, others)
    • Misplaced central line or nasogastric tube
    • Following radiotherapy to thoracic neoplasm
    • Postcardiothoracic surgery

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