Empyema and lung abscess

empyema

• Causes
  • Bacterial pneumonia (56%), post-chest surgery (22%), trauma (4%), oesophageal perforation (4%), complication of thoracocentesis (4%), extension from subdiaphragmatic infection (3%) and other (7% – osteomyelitis, haemothorax, chylothorax or hydrothorax infection)
• Predisposing factors
  • Aspiration pneumonia and conditions leading to this
  • Respiratory disease impairing mucociliary transport
  • Immunocompromise
  • Malignancy
  • Alcoholism

empyema

• When to suspect?
  • Pneumonia symptoms not improving with therapy
  • May be insidious with weight loss, anaemia and night sweats
  • Decreased breath sounds, dullness to percussion, decreased tactile fremitus, friction rub
  • Pain
• Diagnosis
  • Aspiration of grossly purulent material and at least one of:
    • Positive gram stain or culture
    • Glucose <2.2mmol/L
    • pH <7.1
    • LDH >1000
    • In countries where TB is a common cause, NPV of adenosine deaminase is 99.9% to exclude this

empyema

• Three stages
  • Exudative (<48 hours; amenable to chest tube drainage)
  • Fibrinopurulent (fibrin stranding leads to loculations; successful drainage with a single tube is unlikely)
  • Organisational (takes weeks with more extensive fibrosis and restricts lung expansion)
• Treatment
  • Treat pneumonia, CCF, ascites
  • NSAIDs or opioids for pain
  • Definitive treatment is drainage and antibiotics
    • Targets presumptive underlying pneumonia, lung abscess or bronchiectasis
    • PipTaz or meropenem +- vancomycin for MRSA if at risk (Tintinalli)
    • Ceftriaxone + Metronidazole (MetroSouth)
    • Tailor antibiotics to culture results

empyema

• Surgical treatment
  • Exudate empyema – Chest tube tuboracostomy
  • Fibrinopurulent stage – Fibrinolytic agents in consult with specialists (streptokinase, urokinase, deoxyribonuclease and alteplase +- VATS for loculations
  • Organisational stage – Surgical removal of fibrous peel

Lung abscess

• Introduction
  • Localised necrosis of lung parenchyma caused by suppurative microbial infection
  • Initial infection usually aspirational
  • May also result from haematogenous spread or lung infarct
  • Less common causes include penetrating lung trauma, fungal or parasitic infections, primary or metastatic neoplasma, Wegener’s or sarcoidosis
• 80% are primary (otherwise well individuals) with 10-15% mortality
• Secondary lung abscesses (malignancy, immunosuppression, extrapulmonary infection or sepsis, complication of surgery) with 50% mortality
• >1 month = Chronic
• Mortality rate for community-acquired (anaerobic) lung abscess is considerably lower than for hospital-acquired (aerobic) lung abscess

Lung abscess

• Pathophysiology
  • 7-14 days for aspiration pneumonia to develop into lung abscess
  • Aerobic bacteria found more commonly in immunosuppressed patients
    • S. aureus, E. coli, Klebsiella, Pseudomonas, S. pyogenes, Burkholderia pseudomallei, H. influenaze, Legionella, Nocardia, Actinomyces and rarely S. pneumoniae
  • Anaerobic
    • Pigmented Prevotella, Porphyromonas, Bacteroides, Fusobacterium and Peptostreptococcus species
  • Haematogenous spread tend to be multilobular and risk factors include IVDU, endocarditis, triscupid valve endocarditis
  • Jugular vein thrombophlebitis (Lemierre’s syndrome) can complicate tonsillitis and spread to lungs with Fusobacterium necrophorum bacterial seeding
• Typically basal segments of lower lobes or posterior segments of upper lobes (sites of aspiration)
• If anterior lung, neoplasm often underpins the infection
• Cancer is associated with 8-18% of all lung abscess; rising to 30% in those over 45yo

Lung abscess

• Presentation
  • Indolent pneumonia symptoms + weight loss and night sweats for 2 weeks or more
  • Haemoptysis in 25%
• Diagnosis
  • Dense consolidation with air-fluid level inside of a cavity lesion
  • Multiple abscess should suggest haematogenous spread or Lemierre’s disease
• DDx of cavity lesions
  • Infected bullae, pleural fluid collection with bronchopleural fistula and hiatus hernia
  • TB
  • Fungal – Coccidioidomycosis, Histoplasmosis, Blastomycosis, Aspergillosis, Cryptococcus
  • Parasitic – Echinococcus, Amebiasis
  • Neoplastic – Bronchogenic carcinoma (SCC or adenocarcinoma), metastatic cancer, lymphoma, Hodgkin’s
  • Wegener’s, sarcoidosis

Lung abscess

• Treatment
  • Medical management for most as most will drain via tracheobronchial tree (as evidenced by air-fluid line)
  • Cef + Metronidazole +- Vanc if MRSA suspected
  • Surgical image-guided percutaneous draiange or thoracotomy with pulmonary resection for non-draining lung abscess
  • Risk factors for poor outcomes include aerobic infection (hospital-acquired), large cavity, advanced age, debilitation, immunosuppression, malignancy, malnutrition and sepsis
  • Risk factors for failed medical management include bronchial obstruction, non-bacterial abscess, large cavity size and concomitant empyema

Lung abscess

• Disposition
  • Admit all with new lung abscess
  • After resolution of symptoms, can discharge on oral Ab’s for 4- 8 weeks
  • CXR findings lag behind clinical progress and take 2 months to resolve
• Complications
  • Empyema
  • Massive haemoptysis
  • Contamination of uninvolved lung
  • Failure to resolve
  • 10% require surgical intervention

Differentiating on CXR

• Favors empyema
  • Air-fluid level at side of previous pleural effusion
  • A cavity with air-fluid level that tapers at pleural border
  • Air fluid level that crosses fissures
  • Air-fluid level that extends to lateral chest wall
• Favors lung abscess
  • Cavity  with air-fluid level
  • Most common sites of aspiration-induced abscess are posterior RUL and superior segments of RLL and LLL
  • Lung abscess secondary to parenchymal disease, lung cancer, opportunistic infection or septicaemia can occur anywhere

Last Updated on October 28, 2020 by Andrew Crofton