- Definition – severe, localised suppurative infection in the lung, with necrotic cavity formation (>2cm)
- Usually surrounded by a fibrous reaction, forming the abscess wall
- Multiple small abscesses are called necrotising pneumonia
Etiology
Causative organisms
- Anaerobes – peptostreptococcus, bacteroides
- Aerobes – S.aureus, S.pyogenes, H.influenza, K.pneumoniae, S.pneumoniae
- Others – TB, fungal, E. histolytica
Precipitating factors
- Foreign body inhalation
- Bacteraemia seeding in the lungs
- Complication of severe pneumonia – MC due to staph/klebsiella
- Extension of Hepatic abscess
- Penetrating trauma
Risk factors
- Alcohol/drug misuse
- General anaesthesia
- Diabetes mellitus
- Impaired consciousness – leading to aspiration
- Cystic fibrosis
- Severe periodontal disease
Clinical features
Symptoms
- Insidious onset (more acute if it follows pneumonia)
- Spiking temp, rigors, night sweats
- Cough ± sputum
- Pleuritic chest pain
- Breathlessness
Signs
- Tachypnea + tachycardia
- Dehydration
- If consolidation present – dullness to percussion + bronchial breathing
- Clubbing – chronic cases
Diagnosis
- FBC – neutrophilia
- Renal function, liver functional tests
- ↑ESR + CRP
- Sputum examination
- CXR – shows walled cavity with a fluid level
- CT thorax
- Fibre-optic bronchoscopy
Treatment
- Supportive – analgesia, oxygen, fluids, postural drainage
- Antibiotics – penicillin/cephalosporin + clindamycin; metronidazole
- Higher concentrations usually needed as abscess wall forms resistance
- Surgery – chest tube drain
Complications
- Empyema, bronchopleural fistula, distant haematogenous spread – e.g. brain abscess