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Pleural Empyema

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Overview

An empyema is a collection of pus within a pre-existing anatomical cavity. Pleural empyema is the collection of pus within the pleural cavity. An empyema is different to a lung abscess, as lung abscesses are collections of pus in newly-formed cavities.

A pleural empyema can develop following an infection of the lung.

Risk Factors

Presentation

Patients tend to have a subacute onset of symptoms, usually around 2 weeks. Patients who fail to respond to antibiotics or deteriorate on a background of pneumonia should raise suspicion of an empyema. Features are:

  • Recent pneumonia
  • Fevers and rigours
  • Pleuritic chest pain
  • Productive cough
  • Dyspnoea
  • Constitutional symptoms – fatigue, weight loss, night sweats, anorexia, malaise
  • Examination may show:
    • Dullness to percussion
    • Reduced breath sounds
  • Patients may have signs of sepsis:
    • Tachypnoea
    • Tachycardia
    • Hypotension

Differential Diagnoses

Pneumonia

  • There may be no way to differentiate them clinically
  • Chest x-ray shows consolidation but no effusion

Lung abscess

  • There may be no way to differentiate them clinically
  • Chest x-ray shows a cavitating lung lesion with an air-fluid level

Pleural effusion

  • There may be no way to differentiate them clinically
  • Chest x-rays show effusions with a clear fluid level

Investigations

All patients

  • Blood cultures:
    • Ideally should be performed before giving antibiotics, but do not delay treatment
    • Identifies causative pathogen
  • White cell count:
    • Usually raised due to infection
  • C-reactive protein (CRP):
    • Usually raised due to infection
  • Chest x-ray:
    • May show blunting or blurring or the costophrenic angle on the affected side
    • May show an effusion on the affected side
  • Thoracic ultrasound:
    • Useful for guiding thoracentesis and more specific than x-rays for detecting an empyema
    • The empyema may be echogenic, loculated, or septated
  • Thoracentesis and fluid analysis:
    • If there is pus present, an empyema can be diagnosed
    • Pleural fluid findings may be:
      • pH: <7.2
      • Protein: >30 g/dL
      • Glucose: reduced (<3.3 mmol/L)
      • Lactate dehydrogenase (LDH): raised
      • Cytology and white cell differential: polymorphonuclear cells present

Diagnosis

Diagnosis is based on clinical features and investigations. The presence of pus in the pleural cavity fluid is diagnostic of an empyema.

Management

All patients

  • 1st-line: broad-spectrum IV antibiotics and sepsis six + chest drain insertion
  • Surgery may be needed in some cases

Complications

Prognosis

  • Prognosis depends on the presence of comorbidities and whether the patient is immunocompromised or not

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