Pleural Effusion

Definition | Classification | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Referral

Definition

Pleural effusion is the abnormal accumulation of fluid in the pleural space, leading to impaired lung expansion and breathlessness.

Classification

Pleural effusions are classified into:

  • Transudative effusion: caused by systemic factors altering pleural fluid balance (e.g., heart failure, cirrhosis).
  • Exudative effusion: due to local pleural inflammation and increased capillary permeability (e.g., pneumonia, malignancy).

Aetiology

Common causes of pleural effusion include:

1. Transudative Causes:

  • Heart failure (most common cause).
  • Liver cirrhosis (hepatic hydrothorax).
  • Nephrotic syndrome (low protein levels causing fluid shift).
  • Hypoalbuminaemia (e.g., chronic illness, malnutrition).

2. Exudative Causes:

  • Pneumonia (parapneumonic effusion).
  • Malignancy (lung cancer, mesothelioma, metastases).
  • Tuberculosis.
  • Pulmonary embolism (infarcted lung tissue causing pleural inflammation).
  • Autoimmune diseases (e.g., rheumatoid arthritis, lupus).

Pathophysiology

Pleural effusion results from an imbalance in fluid production and drainage within the pleural space:

  • Transudates: caused by increased hydrostatic pressure or decreased oncotic pressure, leading to passive fluid leakage.
  • Exudates: due to increased vascular permeability from infection, malignancy, or inflammation.
  • Large effusions can cause lung compression, leading to breathlessness and hypoxaemia.

Risk factors

  • Chronic heart failure.
  • History of malignancy.
  • Recent pneumonia or lung infection.
  • Chronic kidney or liver disease.
  • Exposure to asbestos (risk of mesothelioma).

Signs and symptoms

  • Progressive breathlessness.
  • Pleuritic chest pain (inflammatory causes).
  • Cough (typically dry and non-productive).
  • Reduced or absent breath sounds on the affected side.
  • Stony dullness to percussion.
  • Reduced chest expansion on the affected side.

Investigations

  • Chest X-ray:
    • Blunting of the costophrenic angle (small effusion).
    • Meniscus sign (fluid level in the pleural space).
    • Complete white-out of a lung if large effusion.
  • Thoracic ultrasound: To assess fluid volume and guide aspiration.
  • Diagnostic pleural aspiration:
    • Determines transudate vs. exudate using Light’s criteria:
    • Effusion is exudative if at least one of the following is true:
      • Pleural protein/serum protein ratio >0.5.
      • Pleural LDH/serum LDH ratio >0.6.
      • Pleural LDH >⅔ of upper normal limit of serum LDH.
  • Further tests on pleural fluid (if exudative):
    • pH and glucose (low in infection and malignancy).
    • Cytology (for malignancy detection).
    • AFB and TB culture if tuberculosis is suspected.
  • CT thorax: Indicated if malignancy or tuberculosis is suspected.

Management

1. Treat Underlying Cause:

  • Heart failure → diuretics (e.g., furosemide 40 mg OD) and fluid restriction.
  • Pneumonia → antibiotics based on severity and likely pathogen.

2. Therapeutic Aspiration:

  • Indicated for large effusions causing significant breathlessness.
  • Performed under ultrasound guidance.
  • Drain up to 1.5L at a time to avoid re-expansion pulmonary oedema.

3. Chest Drain Insertion:

  • Indicated if:
    • Large symptomatic effusion.
    • Empyema (infected pleural fluid).
    • Pneumothorax co-exists with the effusion.

4. Pleurodesis (for recurrent effusions):

  • Used in malignant pleural effusions.
  • Involves instilling sterile talc or other agents into the pleural space to induce adhesion.

5. Surgery (if indicated):

  • Video-assisted thoracoscopic surgery (VATS) for recurrent or undiagnosed effusions.
  • Decortication in empyema if fibrinous adhesions develop.

Referral

Refer to secondary care in the following scenarios:

  • Respiratory specialist: for pleural effusion is recurrent or unexplained.
  • Thoracic surgery: for surgical intervention (e.g., pleurodesis, decortication) is required.
  • Hospital admission:
    • Severe breathlessness or hypoxaemia.
    • Empyema requiring chest drain and IV antibiotics.
    • Large or rapidly accumulating effusion requiring urgent drainage.
 
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