Pleural Effusion

 

• Background

  Definition

  • Small amount of fluid is usually present in the pleural space for lubrication.
  • Pleural effusion results from excess production of this fluid. Less commonly, it is due to reduced clearance e.g. in lymphatic obstruction due to TB or cancer.

  Transudative and exudative causes

  Transudative effusions are usually bilateral and due to organ failure:

  • Commoner: LVF, cirrhosis, nephrotic syndrome.
  • Rare: Meigs' syndrome, hypothyroidism.

  Exudative effusions are usually unilateral and are due to the 4 Inf's:

  • Infection: pneumonia, TB.
  • Infiltration (cancer): lung, breast, lymphoma, malignant mesothelioma.
  • Infarction: PE, MI.
  • Inflammation: RA, SLE.

• Signs and symptoms

  Symptoms:

  • SOB
  • Cough
  • Pleuritic chest pain.

  Signs:

  • Dull percussion.
  • ↓Breath sounds.
  • ↓Expansion
  • Mediastinal shift if large.
  • Signs of the cause e.g. clubbing in lung cancer, ↑JVP in HF.

• Investigations

  CXR

  • 1st line test which usually makes the diagnosis.
  • PA view is usually sufficient, though very small effusions may need a lateral view.
  • Findings: opacification with fluid level, usually in lower hemithorax.

  Pleural aspiration

  Indications:

  • Unilateral effusions which clinically are not thought to be transudative.
  • Not routinely recommended for bilateral effusions which are thought to be transudative e.g. LVF, hypoalbuminaemia.

  Transudative or exudative:

  • Transudative < 30 g/L protein < exudative (eggs are high in protein).

  Light's criteria:

  • For 25-35 g/L protein, compare pleural fluid to serum protein and LDH to determine if transudative or exudative.
  • Fluid:serum protein ratio: transudative < 0.5 < exudative.
  • Fluid:serum LDH ratio: transudative < 0.6 < exudative.

  Other tests and findings:

  • On initial aspiration: pus (empyema), white-coloured lymph (chylothorax), blood (haemothorax).
  • ↓pH (<7.2) and ↓glucose (<3.3) suggests infection, inflammation, or cancer.
  • MC+S: infection = empyema.
  • Cytology: cancer (60% sensitive).
  • Triglycerides: ↑ in chylothorax.
  • Amylase: ↑ in pancreatitis, a rare cause of exudative effusion.

  Other investigations

  • FBC and CRP to look for underlying infection.
  • LFT and U&E to look for liver or kidney failure.
  • Consider BNP and/or echo for heart failure.

• Management

  Unilateral effusions:

  • Treat underlying cause. May require further investigations such as bronchoscopy, CT, or pleural biopsy.
  • May require therapeutic aspiration or chest drain if symptomatic.
  • Chest drain should be placed if there are signs of pleural infection: cloudy fluid or pH <7.2
  • Without treating the underlying cause it is likely to recur if aspirated/drained. Such patients may require an indwelling pleural catheter (IPC) or pleurodesis.

  Bilateral effusions:

  • Treat underlying cause.
  • Diagnostic aspiration only if there is diagnostic uncertainty or a poor response to treatment.