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

Introduction

A lung abscess is a necrotic infection within the lung parenchyma, typically caused by bacterial invasion. These infections result in localized tissue destruction, leading to serious pulmonary complications.

Etiology

Common causes of lung abscess include:

• Aspiration pneumonia
• Bacterial infections (e.g., Streptococcus, Staphylococcus)
• Post-obstructive pneumonia due to malignancy
• Immunocompromised states

Gross Appearance

On gross examination, lung abscesses appear as cavitated lesions with necrotic debris and purulent exudate. The cavity may contain air-fluid levels seen on imaging.

Microscopic Appearance

Histological examination shows extensive neutrophilic infiltration, necrotic debris, and fibrosis around the cavity. Bacterial colonies may be present in the necrotic tissue.

Complications

Clinical Consequences

• Pulmonary Hemorrhage: Erosion into nearby vessels may cause bleeding.
• Bronchopleural Fistula: Formation of an abnormal communication between the bronchi and pleural cavity.
• Empyema: Spread of infection leading to pus accumulation in the pleural space.
• Sepsis: Systemic infection due to bacteremia.

Sequelae

Long-term consequences include pulmonary fibrosis, recurrent infections, and chronic respiratory failure.

Conclusion

Understanding lung abscesses is essential for early diagnosis and management to prevent severe complications. Timely intervention can significantly improve patient outcomes.