Empyema
Collection of pus in the pleural space, most commonly as a complication of pneumonia. Requires chest drain insertion and antibiotics. Pleural fluid pH <7.2 is a key indicator for drainage.
Key Facts
Definition: infected pleural fluid collection — frank pus, positive Gram stain/culture, or pH <7.2 in context of infection Most common cause: complication of parapneumonic effusion (~40% of pneumonias develop effusion; ~5% progress to empyema) Organisms: Streptococcus (most common CAP-related), Staphylococcus, anaerobes, Gram-negatives (hospital-acquired) BTS guideline: pleural fluid pH <7.2 mandates chest drain insertion Antibiotics: co-amoxiclav 1.2g IV TDS or piperacillin-tazobactam 4.5g IV TDS (cover anaerobes) Intrapleural fibrinolytics: alteplase 10mg + DNase 5mg BD for 3 days improves drainage of loculated empyema (MIST2 trial) VATS decortication: for failed medical/fibrinolytic therapy or organised empyema Mortality: ~15-20% overall; higher in elderly, immunocompromised, and hospital-acquired
Overview
Key Facts
Empyema thoracis is the accumulation of pus within the pleural space. It most commonly develops as a complication of bacterial pneumonia (parapneumonic empyema) and requires prompt drainage alongside appropriate antibiotic therapy.
Epidemiology
- ~65,000 parapneumonic effusions per year in the UK; ~5% progress to empyema
- Incidence increasing, particularly in older adults
- Mortality: ~15-20% overall
- More common in males, elderly, immunocompromised, and those with comorbidities (diabetes, alcohol misuse)
Aetiology
Parapneumonic (most common):
- S. pneumoniae, S. milleri group, Staphylococcus aureus
- Anaerobes (Bacteroides, Fusobacterium, Peptostreptococcus)
- Gram-negative bacilli (Klebsiella, E. coli — hospital-acquired)
Other causes:
- Post-surgical (thoracic, oesophageal surgery)
- Trauma
- Oesophageal rupture (Boerhaave syndrome)
- Subdiaphragmatic spread (hepatic abscess, subphrenic abscess)
- Haematogenous spread (rare)
Pathophysiology
Three stages:
- Exudative stage (1-7 days): sterile parapneumonic effusion; free-flowing fluid; pH >7.2
- Fibrinopurulent stage (7-14 days): bacterial invasion; fibrin deposition → loculations; pH <7.2, low glucose, high LDH
- Organising stage (>14 days): fibroblast ingrowth → thick pleural peel (cortex) trapping the lung; requires surgical decortication
Clinical Presentation
Typical Presentation
- Ongoing or recurrent fever despite antibiotics for pneumonia
- Persistent or worsening pleuritic chest pain
- Breathlessness
- Malaise, sweats, weight loss
- Failure to improve on appropriate pneumonia antibiotics
Clinical Signs
- Signs of pleural effusion: stony dull percussion, reduced breath sounds
- Pyrexia (may be swinging/spiking)
- Tachycardia
- Signs of sepsis in severe cases
- Reduced air entry at base
Red Flags
- Persistent fever >48-72 hours despite appropriate antibiotics
- Rapidly re-accumulating effusion
- Loculated effusion on USS/CT
- Sepsis (NEWS2 ≥5)
- Pleural fluid pH <7.2 with pneumonia
Differential Diagnosis
| Diagnosis | Key Features | Investigation |
|---|---|---|
| Simple parapneumonic effusion | pH >7.2, clear fluid, responds to antibiotics alone | Pleural fluid analysis |
| Malignant effusion | Weight loss, bloodstained fluid, pleural nodularity | Cytology, CT, biopsy |
| TB pleuritis | Lymphocytic effusion, high ADA, granulomas | Biopsy, TB culture |
| Lung abscess | Cavitating lesion, air-fluid level, foul sputum | CT chest |
| Subdiaphragmatic abscess | Post-surgical, liver abscess, diaphragm elevation | CT abdomen |
| Haemothorax | Trauma, bloody fluid, dropping Hb | CXR, USS, Hct of fluid |
Diagnosis / Investigation
Bedside
- Thoracic USS: essential — identifies effusion, loculations, guides aspiration; more sensitive than CXR
- Pulse oximetry: baseline
Bloods
- FBC: leucocytosis
- CRP: markedly elevated
- U&Es: renal function
- Blood cultures x2: before antibiotics
- Albumin: nutritional status
- Lactate: if sepsis
Pleural Fluid Analysis
- Appearance: turbid/purulent (frank pus is diagnostic)
- pH: <7.2 mandates drainage (measure in blood gas analyser)
- Glucose: <2.2 mmol/L supports empyema
- LDH: markedly elevated (>1000 IU/L)
- Protein: exudative (>35 g/L)
- MC&S: identify causative organism (positive in ~60%)
- Gram stain: rapid identification
Imaging
- CXR: pleural effusion, consolidation, air-fluid level (if bronchopleural fistula)
- CT chest (contrast-enhanced): split pleura sign (enhancing visceral and parietal pleura separated by fluid), loculations, guide intervention
- Thoracic USS: loculations, septations, guide drain placement
Special Tests
- CT-guided drain placement: for complex/loculated collections
- Pleural fluid cytology: exclude malignancy if atypical
Management
Non-pharmacological
- Nutritional support (often catabolic)
- Chest physiotherapy
- VTE prophylaxis
Pharmacological
Antibiotics:
- Co-amoxiclav 1.2g IV TDS (aerobic + anaerobic cover) — first-line
- Or piperacillin-tazobactam 4.5g IV TDS if severe/hospital-acquired
- If penicillin allergic: meropenem 1g IV TDS or clindamycin 600mg IV QDS + ciprofloxacin
- Duration: minimum 3 weeks (often 4-6 weeks); guided by clinical/radiological response
- Switch to oral when improving: co-amoxiclav 625mg TDS or clindamycin 300mg QDS
Intrapleural fibrinolytics (MIST2 trial):
- Alteplase (tPA) 10mg + DNase (dornase alfa) 5mg in 30mL saline via chest drain
- Instil BD for 3 days (6 doses total), clamp drain for 1 hour between doses
- Significantly improves drainage, reduces need for surgery, and reduces hospital stay
Surgical/Interventional
- Chest drain insertion: USS-guided, small bore (10-14Fr) Seldinger technique or large bore (24-28Fr) for thick pus
- Daily drain assessment: output, air leak, CXR
- VATS decortication: if failed medical/fibrinolytic management (persistent sepsis, loculated collection, organised empyema)
- Open thoracotomy and decortication: if VATS not possible
- Open window thoracostomy (Eloesser flap): for chronic empyema in patients unfit for decortication
Referral Criteria
- Early thoracic surgery referral if loculated empyema or failed drain/fibrinolytics
- Radiology for CT-guided drainage if complex collection
- Respiratory/infectious diseases for complex cases or unusual organisms
Prognosis
- Overall mortality: ~15-20%
- Higher in elderly, immunocompromised, hospital-acquired, and delayed treatment
- S. aureus and Gram-negative empyema carry higher mortality (~30%)
- Early drainage + antibiotics: good outcomes with complete resolution
- MIST2 fibrinolytic protocol reduces surgical referral from ~44% to ~16%
- VATS decortication success rate: ~80-90%
- Chronic empyema/trapped lung: may require prolonged treatment
- Full functional recovery expected in most patients with appropriate treatment
Other Relevant Information
Empyema Staging (American Thoracic Society)
| Stage | Features | Management |
|---|---|---|
| I (Exudative) | Free-flowing, pH >7.2, sterile | Antibiotics ± aspiration |
| II (Fibrinopurulent) | Loculated, pH <7.2, +ve cultures | Drain + antibiotics ± fibrinolytics |
| III (Organising) | Thick peel, trapped lung | Surgical decortication |
MIST2 Trial Summary
| Treatment | Referral for Surgery | Hospital Stay |
|---|---|---|
| tPA + DNase | 4% | Reduced |
| tPA alone | 18% | No benefit |
| DNase alone | 39% | Increased |
| Placebo | 16% | Baseline |
Pleural Fluid Analysis in Empyema
| Parameter | Empyema |
|---|---|
| Appearance | Turbid/purulent |
| pH | <7.2 |
| Glucose | <2.2 mmol/L |
| LDH | >1000 IU/L |
| Culture | Positive ~60% |