Empyema Thoracis

Empyema thoracis is pus in the pleural space, defined as frankly purulent pleural fluid, positive Gram stain or culture, or pleural fluid pH under 7.2 with glucose under 40 mg/dL and LDH over 1000 IU/L in an infected setting.

• Usually complicates pneumonia (parapneumonic effusion, 40% of hospitalised pneumonia, 5 to 10% progress to empyema); also post surgical, trauma, oesophageal rupture, subdiaphragmatic abscess, bronchial obstruction, lung abscess.
• Stages (Light/ATS): exudative (simple, free flowing), fibrinopurulent (loculated, fibrin deposition), organising (pleural peel, fibrosis).
• Organisms: Streptococcus pneumoniae, Streptococcus milleri (anginosus) group, Staphylococcus aureus (including MRSA), anaerobes (Fusobacterium, Bacteroides, Prevotella), Gram negatives (Klebsiella, Pseudomonas, E. coli), Mycobacterium tuberculosis, Actinomyces; hospital acquired infections polymicrobial.
• Risk factors: alcohol misuse, diabetes, aspiration, immunosuppression, IV drug use, poor dentition; RAPID score for mortality.
• Mortality 10 to 20% (up to 40% in older/comorbid); complications include sepsis, fibrothorax, bronchopleural fistula, empyema necessitans.

• Fever, pleuritic chest pain, cough, dyspnoea, night sweats, malaise, weight loss in indolent anaerobic disease.
• Reduced breath sounds, stony dull percussion, bronchial breathing above effusion.
• Persistent fever or sepsis despite appropriate antibiotics for pneumonia.
• Foul smelling sputum in anaerobic infection; empyema necessitans (mass on chest wall).

• Chest radiograph (effusion, D shaped opacity), thoracic ultrasound (septations, echogenic fluid, guides aspiration), contrast enhanced CT (split pleura sign, pleural enhancement, loculations, bronchopleural fistula).
• Diagnostic thoracentesis: pus, pH under 7.2 (or under 7.0), glucose under 40 mg/dL, LDH over 1000, positive Gram stain/culture (inoculate blood culture bottles to increase yield); cytology; AFB and TB culture; pleural biomarkers.
• Blood cultures, CBC, CRP, procalcitonin; sputum cultures; pneumococcal and Legionella urine antigens; HIV; sinus/dental assessment.
• Underlying causes: bronchoscopy for obstruction (tumour, foreign body); CT abdomen for subphrenic abscess; contrast swallow for oesophageal perforation.

• Early antibiotics covering Streptococcus, Staphylococcus, anaerobes, based on culture:
  • Community acquired: ceftriaxone 2 g daily plus metronidazole 500 mg every 8 hours, or ampicillin sulbactam 3 g every 6 hours, or piperacillin tazobactam 4.5 g every 6 to 8 hours; amoxicillin clavulanate orally on step down.
  • Add vancomycin 15 to 20 mg/kg every 8 to 12 hours or linezolid 600 mg every 12 hours if MRSA risk.
  • Hospital acquired: broaden to meropenem 1 g every 8 hours or cefepime plus metronidazole.
  • Duration 2 to 6 weeks (IV then oral), guided by clinical response, CRP and imaging.
• Drainage is essential: image guided small bore chest tube (12 to 14 Fr, flushed with 20 to 30 mL saline every 6 to 8 hours) for free flowing or early loculated empyema; large bore (24 to 28 Fr) in thick pus.
• Intrapleural fibrinolytic therapy: alteplase 10 mg with dornase alfa 5 mg intrapleural twice daily for 3 days (MIST 2 trial: improves drainage, reduces surgical referral and hospital stay); each dose instilled, clamped for 1 hour.
• Early VATS debridement (within 3 to 7 days) for failure of medical drainage (persistent sepsis or residual collection after 5 to 7 days), loculated organising empyema; open decortication for chronic empyema with trapped lung (3 to 6 months); thoracoplasty, open window thoracostomy (Eloesser flap) for chronic cavity or bronchopleural fistula.
• Supportive: nutrition, analgesia, thromboprophylaxis (enoxaparin 40 mg daily), physiotherapy, glycaemic control, treat alcohol dependence.
• Tuberculous empyema: anti-tuberculosis therapy (isoniazid, rifampicin, pyrazinamide, ethambutol) with drainage and decortication.
• Follow up chest imaging at 4 to 6 weeks; residual pleural thickening often resolves.