Localised inflammation and necrosis (destruction) of lung tissue leading to pus formation

Cause

• Aspiration of infected material from upper airway

• Infection of lungs with pus forming organisms: eg. Klebsiella pneumoniae, Staphylococcus aureus

• Septic pulmonary emboli

• Secondary infection of pulmonary infact

• Direct extension of liver abscess through the diaphragm

• Complicating bronchogenic carcinoma

Predisposing factors to aspiration

• Altered consciousness from various causes: eg. alcoholism, epilepsy, general anaesthesia, excessive sedation, cerebrovascular accident

• Bronchial obstruction

• Intestinal obstruction

Clinical features

• Onset is acute or chronic
• Malaise, loss of appetite
• Cough with purulent sputum, foul smelling breath
• Sweating with chills and fever
• Chest pain indicates pleurisy
• Finger clubbing

Complications

• Pus in the pleural cavity (empyema)
• Coughing out blood (haemoptysis)
• Septic emboli to various parts of the body: eg. brain (causing brain abscess)
• Bronchiectasis (pus in the bronchi)

Differential diagnosis

• Bronchogenic carcinoma
• Bronchiectasis
• Primary empyema communicating with a bronchus
• TB of the lungs
• Liver abscess communicating into the lung

Investigations

X-ray: chest

- Early stages: signs of consolidation

- Later stages: a cavity with a fluid level

Sputum: for microscopy and culture

Management
HC4

benzylpenicillin 1-2 MU IV or IM every 4-6 hours child: 50,000-100,000 IU/kg per dose (max: 2MU)

plus metronidazole 500mg IV every 8-12 hours for child: 12.5mg/kg per dose

Once improvement occurs, change to oral medication to complete a 10-14 day course:

metronidazole 400mg every 12 hours
child: 10mg/kg per dose

plus phenoxymethylpenicillin
500-750mg every 6 hours
child: 10-20mg/kg per dose

Postural drainage - surgical drainage is rarely necessary

Prevention

• Early detection and treatment of pneumonia

• Avoid situations which lead to aspiration