10.) Lung Abscess

Question 1

Define

Answer 1

Lung abscess is a localised collection of pus within the lung tissue often resulting from bacterial infection

Question 2

Most common causes

Answer 2

Aspiration of oropharyngeal secretions, especially anaerobic bacteria (e.g. Bacteroides, Fusobacterium, Peptostreptococcus).

Question 3

Etiology-based Classification

Answer 3

• Anaerobic ( lives withouth oxygen ) → aspiration (most common)

•	Aerobic → Staph aureus, Klebsiella, Pseudomonas

•	Fungal → immunocompromised patients

•	Tuberculous abscess → rare, secondary to TB

Question 4

Aspiration vs Non-aspiration

Answer 4

• Aspiration: usually affects posterior segments of upper lobes or superior segments of lower lobes

•	Non-aspiration: can occur anywhere, often in immunocompromised patients

Question 5

Simple vs Complex Abscess

Answer 5

• Simple: single, thin-walled, responsive to treatment

•	Complex: multiple, thick-walled, may need surgery or drainage

Question 6

Symptoms

Answer 6

Fever
• Productive cough (foul-smelling or purulent sputum)
• Hemoptysis
• Chest pain
• Weight loss, night sweats (chronic cases)

Question 7

Diagnosis

Answer 7

Chest X-ray: cavitary lesion with air-fluid level

Pleural fluid ?

•	CT chest: better detail to confirm diagnosis and rule out mass

•	Sputum culture: for identifying organism (aerobic/anaerobic)

•	Bronchoscopy: may be needed if no response to treatment or to rule out obstruction

Question 8

Treatment

Answer 8

B-Lactamase inhibitors

Co amoxiclav 1.2g iv every 8 hours and clindamycin 600mg/8 hours

Consider metronidazole for anaerobes

1-2 weeks iv followed by oral antibiotics 2-6 weeks

Drainage

Surgery if above 6cm

Question 9

Complications

Answer 9

Haemorrhage ( erosion of blood vessels as the abscess extends into the lung parenchyma )