Lung Abscess: Etiology, Gross and Microscopic Appearance, and Complications

Etiology of Lung Abscess: Causes and Risk Factors

A lung abscess is a localized collection of pus within the lung parenchyma caused by microbial infection. It is typically a result of aspiration pneumonia, necrotizing pneumonia, or septic embolism.

Causes

• Aspiration of oropharyngeal secretions
• Bacterial infections (Staphylococcus aureus, Streptococcus species, Klebsiella pneumoniae)
• Parasitic infections (Entamoeba histolytica)
• Fungal infections (Aspergillus, Cryptococcus)

Risk Factors

• Immunocompromised states
• Alcoholism and substance abuse
• Neurological disorders leading to aspiration
• Chronic obstructive pulmonary disease (COPD)

Gross and Microscopic Appearance

Gross Pathology

On gross examination, lung abscesses appear as well-demarcated cavities filled with pus. The surrounding lung tissue may show signs of necrosis and consolidation.

Microscopic Pathology

Histological examination reveals liquefactive necrosis, neutrophilic infiltration, fibrin deposition, and bacterial colonies.

Complications

• Bronchopleural fistula formation
• Sepsis and multi-organ failure
• Chronic lung abscess with fibrosis
• Empyema (pus collection in the pleural cavity)