Lung Abscess
Article status: Temporary high-yield summary
- This article will be fully reviewed, expanded, and referenced in due course
- Current content focuses on core principles and exam-relevant concepts
Definition
A lung abscess is a local collection of pus within the lung parenchyma, resulting in cavity formation.
Aetiology
Most commonly caused by anaerobic bacteria (e.g. Fusobacterium species, Prevotella species)
Less commonly aerobic bacteria (e.g. Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginoisa)
Some important predisposing risk factors include:
- COPD
- Sedative use
- Alcohol abuse
- Poor dental status
Clinical Features
Lung abscess typically has a subacute to chronic presentation:
- Cough
- Purulent, foul-smelling sputum
- Haemoptysis
- Constitutional symptoms
- Malaise and fatigue are often prominent
- Fever (but can be low-grade / absent)
- Weight loss
Investigation and Diagnosis
Imaging
1st line: chest X-ray
- Classic finding: well-demarcated, thick-walled cavity with an air-fluid level
- But tends to miss the diagnosis in early stages
Imaging of choice: CT chest with IV contrast
- Demonstrates thick-enhancing wall with central necrosis
Microbiology Tests
Sputum culture is important to identify the organism and guide antimicrobial treatment
- However, there is a high false +ve rate from oral flora contamination
Management
Corestone of management: prolonged course of antibiotics (that covers both anaerobes and aerobes)
Percutaneous / endoscopic drainage is indicated if there is:
- Failure to respond to antibiotics after 1-2 weeks, or
- Clinical deterioration despite antibiotics