Lung Abscess

Clinical Description

A lung abscess is defined as necrosis of the pulmonary parenchyma and formation of cavities containing necrotic tissue or purulent fluid, usually caused by microbial infection.

Causative organisms: Aerobic bacteria (e.g., staphylococcus aureus, streptococcus pyogens, streptococcus pneumonia, Klebsiella pneumonia, Pseudomonas aeruginosa, Haemophilus influenza, Nocardia species), anaerobic bacteria (e.g., Bacteroides species, Fusobacterium species, Pepto streptococcus species), Mycobacterium species (e.g., MTB, NTM), Fungal organisms (e.g., Aspergillus, Cryptococcus, Histoplasma, Blastomyces and Coccidioides species).

Risk factors:

• Most common is aspiration of infected orophangeal secretions e.g., in semi- conscious/unconscious alcoholics, epileptics, stroke, anaesthetised or dental disease patients.
• Foreign body aspiration e.g., inhaled peanut, dentures, fish bone
• Inadequately treated bacterial pneumonia especially, gram negative bacteria like

Klebsiella pneumoniae, and beta-haemolytic streptococci, Staphylococcus aureus causing multiple lung abscesses.

• Penetrative lung injury
• Partial obstruction of an airway by tumour or lymph node.
• Septic emboli from other infected areas of the body e.g., right sided bacterial endocarditis
• Bronchiectasis
• Infected bullae in chronic lung disease

Signs and Symptoms

• Fever with swinging temperatures
• Cough
• Productive of copious amounts of purulent foul-smelling sputum
• Haemoptysis
• Chest pain
• Breathlessness
• Fatigue
• Anorexia
• Night sweats
• Weight loss
• Fever
• Tachycardia
• Tachypnoea
• Finger clubbing
• Chest wall tenderness
• Dull percussion note
• Diminished breath sounds or bronchial breath sounds with increased vocal resonance or amphoric breath sound.

COMPLICATIONS OF LUNG ABSCESS:

• Rupture into pleural space causing empyema
• Bronchopleural fistula
• Pleural cutaneous fistula
• Respiratory failure

Investigations

• Full blood count
• Urea, Creatinine and Electrolytes
• Blood culture
• Sputum gram stain, culture and sensitivity, ZN stain, GeneXpert MTB/RIF
• Chest X-ray

Treatment

• Treat underlying infection
• Treat predisposing conditions
• Ensure at least 4 weeks of antibiotics

Non-pharmacological

• Chest physiotherapy: aid postural drainage of sputum
• Improve nutritional status
• Ensure adequate fluid intake

Pharmacological

• Amoxicillin-Clavulanic acid IV 1.2g 8 hourly or oral 1g 12
• Alternative - Ceftriaxone IV 2g daily plus Metronidazole 500mg IV 8 hourly
• Or Cloxacillin or flucloxacillin 500mg 6 hourly IV or orally
• Adjust treatment as per microbiological sputum results