Management of Pleural Abscess (Empyema Thoracis)

Pathological Staging (BTS Classification)

• Bailey & Love's Short Practice of Surgery, 28th Ed.

CT Imaging: Empyema vs. Lung Abscess

Step 1 - Initial Resuscitation and Assessment

• Hospitalize all patients with suspected pleural infection
• Blood cultures before antibiotics (positive in ~15% of cases)
• Pleural fluid sampling - diagnostic thoracentesis is mandatory
  • pH <7.2, glucose <3.4 mmol/L, LDH >1000 IU/L, or frank pus = drainage indicated
• Thoracic ultrasonography in all cases - detects loculations/septations more accurately than CT, guides tube placement, reduces iatrogenic injury
• Contrast-enhanced CT - reserved for persistent collections despite chest tube drainage, suspected airway obstruction, or if surgery is being planned. NOT needed routinely.
• Nutritional support - a cornerstone identified by the 1918 U.S. Army Empyema Commission that remains unchanged today
• Murray & Nadel's Textbook of Respiratory Medicine, 2-Volume

Step 2 - Antibiotic Therapy

Empiric Regimens

• Cover aerobic organisms (Streptococcus milleri group, S. pneumoniae, Staphylococcus aureus) AND anaerobes
• Amoxicillin-clavulanate OR penicillin + metronidazole
• If penicillin-allergic: clindamycin or moxifloxacin

• Broader Gram-negative and MRSA coverage needed
• Piperacillin-tazobactam + vancomycin (or linezolid) as empiric choice
• Anti-MRSA coverage should be routine

• Mandates anaerobic coverage (amoxicillin-clavulanate or clindamycin or metronidazole)

Duration

• Typically 6 weeks of antibiotics total (oral step-down once clinically improving)
• Infectious disease consultation is recommended given the complexity and duration
• Antibiotics are a complement to drainage, not a substitute
• Fischer's Mastery of Surgery, 8th Ed.; Murray & Nadel's Textbook of Respiratory Medicine

Intrapleural Antibiotics

• Routine intrapleural antibiotics are not recommended - systemic therapy achieves adequate pleural levels; local instillation has no proven benefit and can cause pain and chemical pleuritis.

Step 3 - Pleural Drainage

When to Drain

• Frank pus (empyema)
• Pleural fluid pH <7.2
• Positive Gram stain or culture
• Glucose <3.4 mmol/L
• Fibrinopurulent or organising phase clinically

Chest Tube Size

• Small-bore tube (12-14 French) via Seldinger technique is the first-line approach for most patients - equivalent efficacy to large-bore tubes with significantly less pain during insertion and while in situ
• The MIST trial (n=405) showed no difference in death or surgical referral between small- and large-bore tubes, but large-bore tubes caused significantly more pain
• Large-bore drains are reserved for complex, thick empyemas not draining adequately

Tube Positioning

• Under ultrasound guidance, into the largest locule in a dependent position
• Regular saline flushes (30 mL every 6 hours via three-way stopcock) to prevent tube occlusion
• Murray & Nadel's Textbook of Respiratory Medicine, 2-Volume

Step 4 - Intrapleural Enzyme Therapy (IET)

The MIST2 Regimen (Standard of Care)

• Tissue plasminogen activator (tPA) 10 mg + DNase 5 mg instilled twice daily for 3 days
• tPA breaks down fibrin clots; DNase reduces pus viscosity by degrading extracellular DNA
• The MIST2 RCT (n=210) showed this combination significantly reduced pleural opacity on CXR, reduced surgical referral rates, and reduced hospital stay
• Neither agent alone is as effective as the combination - streptokinase (MIST1 trial, n=454) showed no benefit over placebo when used alone

Contraindications to IET

• Recent (<1 week) cardiothoracic surgery
• Known broncho-pleural fistula (risk of systemic fibrinolysis)
• Active significant haemoptysis
• Murray & Nadel's Textbook of Respiratory Medicine, 2-Volume; Fischer's Mastery of Surgery, 8th Ed.

Step 5 - Surgical Intervention

• Persistent pleural sepsis despite chest tube drainage + IET for 3-5 days
• Highly loculated, multilocular empyema not amenable to tube drainage
• Organizing phase with lung entrapment (thick fibrous peel preventing lung re-expansion)
• CT shows complex empyema or trapped lung

Surgical Options (Escalating Invasiveness)

• Operation of choice for most patients requiring surgery
• Allows debridement, division of septations, lavage, and decortication under direct vision with minimal access
• Superior cosmesis, less pain, faster recovery than open surgery
• The MIST-3 trial (2023 RCT) showed early VATS reduced length of stay to 7 days vs. 10 days for standard care, supporting early surgical escalation when needed

• Reserved for advanced organising phase where the thick fibrous peel trapping the lung cannot be removed by VATS
• Fowler's decortication - formal peeling of the visceral pleural peel to allow lung re-expansion
• Higher morbidity but may be the only option for a completely trapped lung

• For patients who are too debilitated for major surgery (high anaesthetic risk)
• A permanent window into the pleural space allowing daily dressing changes and gradual healing by secondary intention
• Also used for specific situations: fungal empyema (Aspergillus) - open drainage with gauze impregnated with amphotericin B
• Bailey & Love's Surgery, 28th Ed.; Murray & Nadel's Textbook of Respiratory Medicine; Washington Manual of Medical Therapeutics

• Rarely used today
• Involves resection of ribs to allow the chest wall to collapse onto the pleural cavity, obliterating the space
• Historical role in TB empyema; now used in refractory cases where lung cannot re-expand and other approaches have failed

Special Situations

Tuberculous Empyema

• Anti-TB chemotherapy for at least 6 months is the backbone
• Drainage if frank pus is present
• Decortication may be needed for trapped lung; risk of bronchopleural fistula is higher

Fungal Empyema (Aspergillus)

• Closed chest tube drainage mandatory
• Systemic antifungal therapy: initial 2-4 weeks of amphotericin B, then longer-term azole (total at least 6 months)
• Lung resection is usually necessary as infection destroys underlying lung
• For patients unfit for surgery: Eloesser flap + topical amphotericin B-impregnated gauze packing

Post-traumatic / Post-surgical Empyema

• Broad empiric antibiotic coverage (including Gram-negative organisms)
• Image-guided drain placement for loculated collections
• Early VATS for retained hemothorax converting to empyema

Bronchopleural Fistula Complicating Empyema

• Closed drainage (to prevent contamination of the contralateral lung)
• Bronchoscopic identification of fistula site
• Surgical repair (VATS or open) usually required

Management Algorithm Summary

Suspected Pleural Infection
        |
        v
Ultrasound + Diagnostic Thoracentesis
        |
   _____|_____
   |         |
Simple     Complicated/Empyema
Effusion   (pH<7.2, pus, +culture)
   |         |
Antibiotics  Chest Tube (small-bore, US-guided)
alone        + Antibiotics (6 weeks)
             |
         Draining adequately?
           YES → Continue, remove when <50mL/day
           NO (after 3-5 days)
             |
        Add tPA + DNase (IET × 3 days)
             |
         Draining adequately?
           YES → Continue to resolution
           NO
             |
        VATS (operation of choice)
             |
         Dense organising peel?
           YES → Open decortication
           NO → VATS decortication
             |
        Unfit for major surgery?
           YES → Eloesser flap (open drainage)

Key Evidence Milestones

Outcome Predictors

• Age >65
• Hospital-acquired infection
• Low serum albumin / malnutrition
• Anaerobic/Gram-negative organisms
• Delay in diagnosis or drainage
• Organism: S. aureus or Gram-negative bacilli carry worse outcomes than streptococcal infections

• Murray & Nadel's Textbook of Respiratory Medicine, 2-Volume (Chapter 109: Bacterial Pleural Empyema)
• Bailey & Love's Short Practice of Surgery, 28th Edition (Chapter 60: Pleural Infection and Empyema)
• Fischer's Mastery of Surgery, 8th Edition (Empyema/Fibrinolytics)
• The Washington Manual of Medical Therapeutics (Surgical Management)
• Bedawi EO et al. MIST-3 RCT. Am J Respir Crit Care Med. 2023. PMID 37820359