Empyema

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

Definition

Empyema is a collection of pus within the pleural space, often as a complication of pneumonia, surgery, or chest trauma. It requires urgent treatment with antibiotics and drainage.

Aetiology

Empyema typically develops due to bacterial infection of the pleural fluid. Common causes include:

  • Pneumonia (parapneumonic effusion): the most common cause, where infection spreads to the pleura.
  • Post-surgical infection: such as thoracic surgery (e.g., lobectomy, pneumonectomy).
  • Post-traumatic infection: after a penetrating chest injuries or rib fractures.
  • Oesophageal rupture: can lead to empyema due to leaked gastric contents.
  • Haematogenous spread: rarely, bacteria can spread via the bloodstream.

Pathophysiology

Empyema progresses through three stages:

  • Exudative stage: inflammation causes protein-rich fluid accumulation in the pleural space.
  • Fibrinopurulent stage: bacterial infection leads to pus formation and fibrin deposits, causing loculated pockets.
  • Organising stage: fibrous tissue forms around the pus, restricting lung expansion.

Risk factors

  • Pneumonia (especially in immunocompromised patients).
  • Chronic lung disease (e.g., COPD, bronchiectasis).
  • Recent thoracic surgery or trauma.
  • Diabetes mellitus.
  • Immunosuppression (e.g., chemotherapy, HIV).

Signs and symptoms

Symptoms:

  • Persistent fever despite antibiotic treatment.
  • Pleuritic chest pain (sharp pain worsened by breathing).
  • Shortness of breath.
  • Productive cough (may be purulent or foul-smelling).
  • Weight loss and malaise.

Signs:

  • Reduced breath sounds on the affected side.
  • Stony dullness to percussion.
  • Decreased chest expansion.
  • Signs of sepsis (e.g., tachycardia, hypotension).

Investigations

  • Chest X-ray:
    • Shows pleural effusion (loss of costophrenic angle).
    • May show loculated fluid collections.
  • Thoracic ultrasound:
    • Detects fluid and guides aspiration.
  • Diagnostic pleural aspiration:
    • Fluid analysis determines if the effusion is exudative.
    • Positive findings in empyema:
      • pH <7.2: suggestive of an infection.
      • Glucose <3.3 mmol/L: caused by bacterial metabolism.
      • High lactate dehydrogenase (LDH): could indicates pleural inflammation.
      • Presence of pus or organisms: this confirms empyema.
  • Microbiological tests:
    • Pleural fluid culture (to identify causative bacteria).
    • Blood cultures if sepsis is suspected.
  • CT Thorax:
    • Defines the extent of empyema.
    • Distinguishes between free-flowing and loculated fluid.

Management

1. Antibiotic Therapy:

  • Start empirical IV antibiotics immediately (follow local guidelines).
  • First-line: Co-amoxiclav or piperacillin/tazobactam.
  • Penicillin allergy: Ceftriaxone + Metronidazole.
  • Adjust based on culture results.
  • Treatment duration: 2–4 weeks.

2. Pleural Drainage:

  • Indicated for all empyemas.
  • Insert a small-bore chest drain under ultrasound guidance.
  • Flush with saline to prevent blockage.

3. Fibrinolytic Therapy (if loculated):

  • Intrapleural fibrinolytics (e.g., alteplase + DNase) break down fibrin adhesions.
  • Consider if drainage is incomplete despite antibiotics.

4. Surgery (if necessary):

  • Video-assisted thoracoscopic surgery (VATS) for persistent effusions.
  • Decortication if the lung remains trapped by fibrous adhesions.

Referral

  • Respiratory specialist: requested when empyema is suspected but not resolving.
  • Thoracic surgery: performed if drainage is unsuccessful or requires surgical intervention.
  • Hospital admission:
    • Severe empyema with respiratory distress.
    • Sepsis or haemodynamic instability.
    • Large loculated effusions requiring intervention.
 
RespiratorymypanotesEmpyema