What are the diagnostic criteria and treatment options for empyema?

Diagnostic Criteria and Treatment of Empyema

Empyema is defined as pus in the pleural space, requiring prompt diagnosis and treatment with chest tube drainage, antibiotics, and possible surgical intervention if medical management fails. 1

Diagnostic Criteria

Clinical Presentation

• Empyema should be suspected in patients with pneumonia who are failing to respond to appropriate antibiotic therapy 1
• Common symptoms include fever, chest pain, and breathlessness 1

Diagnostic Imaging

• Initial evaluation should include chest radiography to detect pleural effusion 2
• Posteroanterior and lateral views have significantly greater sensitivity (83.9%) compared to single-view AP radiographs (67.3%) for detecting pleural effusions 2
• Ultrasound is the preferred imaging modality to:
  • Confirm presence of pleural fluid 1
  • Differentiate free from loculated pleural fluid 2
  • Guide thoracentesis or chest drain placement 2
• CT scanning with contrast enhancement is indicated in complicated cases to:
  • Delineate loculated pleural fluid 1
  • Detect airway or parenchymal lung abnormalities 1
  • Identify the "split pleura" sign (enhancing pleural tissue visible on both visceral and parietal surfaces) 2

Laboratory Diagnosis

• Diagnostic thoracentesis should be performed in all patients with suspected pleural infection 1
• Empyema is diagnosed based on one or more of the following criteria:
  • Presence of frank pus on aspiration 1
  • Positive pleural fluid Gram stain or culture 3
  • Pleural fluid pH <7.2 with radiographic features of empyema 3
• Additional pleural fluid tests include:
  • Biochemical analysis: pH, glucose, LDH 1
  • Microbiology: Gram stain, aerobic and anaerobic cultures 1, 2
• Blood cultures should be performed in all patients with suspected empyema 1, 2

Classification of Parapneumonic Effusions

• Simple parapneumonic effusion:
  • Clear fluid
  • pH >7.2
  • LDH <1000 IU/l
  • Glucose >2.2 mmol/l
  • No organisms on culture or Gram stain 1
• Complicated parapneumonic effusion:
  • Clear fluid or cloudy/turbid
  • pH <7.2
  • LDH >1000 IU/l
  • Glucose <2.2 mmol/l
  • May be positive Gram stain/culture 1
• Empyema:
  • Frank pus
  • May be positive Gram stain/culture 1

Treatment Options

Antibiotics

• Empirical antibiotic therapy must be initiated immediately after diagnosis 1
• Potentially nephrotoxic antibiotics (i.e., aminoglycosides) should be avoided 1
• Recommended regimens:
  • Third-generation cephalosporins (e.g., cefotaxime) 1
  • Amoxicillin/clavulanic acid (initially intravenous, then oral) 1
  • Ciprofloxacin (initially intravenous, then oral) for switch therapy 1

Chest Tube Drainage

• Indicated for:
  • All cases of empyema (frank pus) 1
  • Complicated parapneumonic effusions (pH <7.2) 1
• Ultrasound guidance is recommended for drain placement 1, 2
• Chest tubes should be connected to a unidirectional flow drainage system 1
• The drain should be removed once there is clinical resolution 1

Intrapleural Fibrinolytics

• Recommended for complicated parapneumonic effusions or empyema with loculations 1, 4
• Urokinase is the most studied fibrinolytic in children 1
• Fibrinolytics shorten hospital stay 1
• Should be considered when drainage is inadequate despite proper chest tube placement 4

Surgical Management

• Indications for surgical consultation:
  • Failure of chest tube drainage, antibiotics, and fibrinolytics 1
  • Persistent sepsis with persistent pleural collection 1
  • Organized empyema in a symptomatic patient 1
• Surgical options include:
  • Video-assisted thoracoscopic surgery (VATS) for early intervention 4, 5
  • Decortication for patients with reexpandable underlying lung 6
  • Open thoracotomy for complicated or chronic empyema 4, 6
  • Open-window thoracostomy for patients not eligible for radical treatment 6

Management Algorithm

1. Confirm diagnosis with imaging and thoracentesis
2. Start appropriate antibiotics immediately
3. Insert chest tube for drainage if empyema or complicated parapneumonic effusion
4. Consider intrapleural fibrinolytics if loculations present
5. Consult thoracic surgery if no improvement after 5-7 days of medical management 1

Special Considerations

Spontaneous Bacterial Pleural Empyema

• Uncommon complication in patients with cirrhosis and hydrothorax 1
• Diagnosis based on pleural fluid analysis showing:
  • Positive pleural fluid culture and >250 neutrophils/mm³, or
  • Negative pleural fluid culture and >500 neutrophils/mm³ in absence of pneumonia 1
• Requires antibiotic therapy similar to spontaneous bacterial peritonitis 1

Complications and Prognosis

• Mortality rates typically range from 7-33%, but may exceed 50% in elderly patients or those with significant comorbidity 7
• The Streptococcus milleri group has emerged as the most common causative pathogen in community-acquired empyema 3
• Anaerobes may be present in up to 76% of cases and are more common following possible aspiration pneumonia 1