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- The term lung abscess refers to a microbial infection of the lung that results in necrosis of pulmonary parenchyma typically forming a single walled-off cavity >2 cm in diameter (1).
- Necrotizing pneumonia and lung gangrene, which are on the same clinical spectrum, are usually in multiple areas of the lung caused by a virulent pathogen.
- In the age of antibiotics, this is a very uncommon infection, and the exact incidence is unknown.
- Typically affects middle-aged men with predisposition to aspiration especially alcoholics (2)
Etiology and Pathophysiology
- Most commonly, oral bacteria from the gingival crevice are aspirated which lead to inflammation and eventual liquefactive necrosis with abscess formation (2).
- Less commonly, septic emboli from endocarditis and others
- Because microbiologic growth is scant from sputum and invasive specimen procurement is rarely pursued, treatment is empiric.
- Immunocompetent hosts: anaerobic bacteria and micro-aerophilic streptococci, occasionally Staphylococcus aureus especially MRSA
- Immunocompromised: pseudomonas and gram-negative rods in addition to those mentioned above. Attention should also be paid to the possibility of atypical organisms like fungi, Nocardia, Rhodococcus, TB, and Actinomyces.
- Rarely, amebic liver abscesses can rupture through the diaphragm and cause lung abscess; consider if there is history of prolonged stay in an endemic region.
No known genetic pattern
- Aspiration risk factors
- Alcohol intoxication (loss of consciousness)
- Heroin and other CNS depressant drugs
- General anesthesia with surgery
- Dysphagia from muscular dysfunction either local or systemic
- Tracheal/nasogastric tube and severe GERD
- Airway obstruction
- External compression from lymph nodes
- Endobronchial foreign bodies
- Immune compromise
- Malignancy and chemotherapy
- HIV infection
- Chronic steroid use
- Cystic fibrosis
- Treatment of predisposing diseases
- Aspiration precautions
- Treatment of periodontal diseases