Lung abscess classification

Lung abscess is defined as an infection of lung resulting in necrosis of lung parenchyma. It can be classified into three categories based on the duration of symptoms, etiology, and mode of spread as acute or chronic, primary or secondary and bronchogenic or hematogenic.

• Acute: If the duration of symptoms is less than 4-6 weeks before presenting to medical care.^[1]
• Chronic: If the symptoms persist for more than 6 weeks.

• Primary: When the abscess develops after lung infection in previously healthy persons or in patients prone to aspiration. ^[2]
• Secondary: Abscess formation in patients due to complications of a co-existing lung disease such as post obstructive process (bronchial obstruction due to tumor, foreign body or enlarged lymphnodes) and systemic process resulting in decreased immune response like HIV, and patients on immunosuppressants and corticosteroids.

Bronchiogenic: Abscess formation is due to aspiration and inhalation.^[1]

• Aspiration of oropharyngeal secretions.
• Bronchial obstruction by a tumor.
• Foreign body, congenital malformations, and enlarged lymph nodes.

Hematogenic: Abscess formation due to dissemination of causative agents from other infected sites

• Infective endocarditis.
• Abdominal sepsis.
• Septic thromboembolism.