Empyema Thoracis
Definition And Epidemiology
- Collection of pus in pleural cavity associated with underlying lung infection.
- Late stage of complicated parapneumonic effusion (CPPE) characterized by grossly purulent fluid with or without bacterial organisms.
- Occurs in 5-10% of children with bacterial pneumonia.
- Complicates up to 86% of necrotizing pneumonia cases.
- Most frequently encountered in infants and preschool children.
Etiology
Pathogens vary based on immune status and age. Empyema in children below two years is nearly always Staphylococcal in etiology.
| Host Status | Common Pathogens |
|---|---|
| Immunocompetent | - Streptococcus pneumoniae - Staphylococcus aureus (MSSA and MRSA) - Streptococcus pyogenes - Haemophilus influenzae (rare post-vaccination) |
| Immunocompromised | - Gram-negative organisms (Pseudomonas aeruginosa, Klebsiella) - Fungi - Mycobacterium tuberculosis (rare) |
Pathogenesis And Staging
Empyema development represents a continuum divided into three distinct phases.
| Stage | Timeline | Pleural Fluid Characteristics | Pathological Features |
|---|---|---|---|
| Stage I (Exudative) | Days 1-3 |
- Thin fluid - pH > 7.3 - Glucose > 60 mg/dL - LDH < 1,000 IU/L - Gram stain/Culture: Negative |
- Minimal cellular response - Free-flowing fluid - Fibrinous exudate formation |
| Stage II (Fibrinopurulent) | Days 4-14 |
- Purulent, viscous fluid - pH < 7.2 - Glucose < 40 mg/dL - LDH > 1,000 IU/L - Gram stain/Culture: Positive |
- High polymorphonuclear leukocyte count - Fibrin deposition - Loculations and septations form - Parietal pleura thickening |
| Stage III (Organizational) | >14 Days | - Reorganization of fluid | - Fibroblast proliferation - Solid fibrous peel/thick membrane formation - Entraps lung, prevents expansion |
Clinical Presentation
Suspect empyema upon failure to respond 48 hours post-initiation of appropriate antibiotic therapy for pneumonia.
General Symptoms
- High-grade fever, malaise, loss of appetite.
- Toxic appearance, irritability.
Respiratory Signs
- Breathlessness, cough, chest pain.
- Splinting hemithorax (lying on affected side for temporary analgesia).
- Respiratory distress, retractions.
Physical Examination Findings
- Reduced chest movement and expansion.
- Dullness to percussion.
- Reduced or absent breath sounds.
- Decreased vocal resonance.
- Scoliosis on affected side.
- Pulsatile swelling over chest (Empyema necessitans).
Complications
Untreated or severe empyema leads to localized and systemic sequelae.
Local Complications
- Atelectatic lung.
- Bronchopleural fistula.
- Pyopneumothorax.
- Empyema necessitans (pus dissects through chest wall).
- Purulent pericarditis.
- Pulmonary abscesses.
- Peritonitis (diaphragmatic extension).
- Rib osteomyelitis.
Systemic Complications
- Septicemia (common in H. influenzae and pneumococcal infections).
- Meningitis.
- Suppurative arthritis.
- Septic osteomyelitis.
Diagnostic Evaluation
Pleural Fluid Investigations
Thoracentesis essential for definitive diagnosis.
- Biochemistry: pH < 7.2, Lactate Dehydrogenase (LDH) > 1,000 U/L, Glucose < 40 mg/dL, High proteins.
- Cellularity: Markedly elevated White Blood Cell (WBC) count, predominantly polymorphonuclear leukocytes.
- Microbiology: Gram stain, bacterial culture, Polymerase Chain Reaction (PCR).
Imaging Modalities
- Chest X-Ray: Uniform opacity of hemithorax. Mediastinal shift to opposite side. Obliteration of costophrenic angle.
- Ultrasonography (USG): Identifies fluid nature (loculated vs. free-flowing). Detects septations. Quantifies volume. Guides optimal thoracentesis site. Serial monitoring tool.
- Contrast-Enhanced Computed Tomography (CECT) Chest: Identifies underlying lung parenchymal necrosis/abscess. Measures pleural thickness. Identifies mediastinal fluid collection and adenopathy. Crucial for surgical planning. Note: Cannot reliably identify septations.
Blood Investigations
- Complete Blood Count: Leukocytosis.
- Inflammatory Markers: C-Reactive Protein (CRP) trend monitoring.
- Metabolic Panel: Electrolytes (assess for Syndrome of Inappropriate Antidiuretic Hormone Secretion - SIADH), total proteins, albumin.
- Blood Culture: Typically low positivity, but necessary.
Management Principles
Stage-Based Treatment Strategy
| Disease Stage | Therapeutic Intervention |
|---|---|
| Stage I (Exudative) | - Antibiotics - Clinical monitoring - Intercostal Drainage (ICD) if increasing fluid or no improvement |
| Stage II (Fibrinopurulent) | - Antibiotics - ICD - Fibrinolytics OR Video-Assisted Thoracoscopic Surgery (VATS) |
| Stage III (Organizational) | - VATS OR Mini-thoracotomy/Decortication |
Antimicrobial Therapy
- Initial Empirical: Intravenous Ceftriaxone + Cloxacillin (covers S. pneumoniae and S. aureus).
- MRSA/Hemodynamic Instability: Add Vancomycin or Linezolid.
- Associated Soft Tissue Involvement: Add Clindamycin.
- Duration: Total 2-4 weeks. Transition from intravenous to oral route based on clinical improvement and decreasing inflammatory marker trend.
Specific Interventions
Fibrinolytic Therapy
- Indications: Loculations/septations noted on USG. Most effective early in course (first 7-10 days), though utility beyond 14 days reported.
- Agents & Dosing:
- Streptokinase: <1 year: 10,000 units/kg. >1 year: 20,000 units/kg. Dissolve in 50 mL Normal Saline. 4-hour dwell time (infusion over 1 hour). Administer 3 consecutive days (4-6 doses superior to 3).
- Urokinase: 40,000 units in 40 mL saline.
- Tissue Plasminogen Activator (tPA): 4 mg in 20-40 mL saline.
Surgical Intervention
- Indications: Sepsis/infected fluid uncontrolled by antibiotics + ICD. Significant respiratory compromise secondary to thickened pleura. Decreasing ICD output coupled with clinical deterioration and persistent effusion on imaging.
- Options:
- Video-Assisted Thoracoscopic Surgery (VATS): Preferred at centers with minimally invasive expertise. Shorter postoperative stay, reduced reintervention need.
- Mini-Thoracotomy / Decortication: Required for thick inelastic peel preventing lung expansion.
Supportive Management
- Respiratory Support: Oxygen supplementation (nasal prongs, High-Flow Nasal Cannula [HFNC], Non-Invasive Ventilation [NIV]) based on distress severity.
- Symptom Control: Paracetamol for fever, analgesics for ICD-related pain.
- Physiotherapy: Incentive spirometry and deep breathing exercises improve ICD drainage.
- Contraindications: No role for chest physiotherapy or inhaled bronchodilators.
- Outcomes: Good long-term clinical and pulmonary function outcomes regardless of medical or surgical intervention.