Lung abscess
Lung abscess is a necrotic, pus-filled cavity in the lung parenchyma, most often from aspiration of oropharyngeal anaerobes in a patient with impaired airway protection, diagnosed by a cavity with an air-fluid level on imaging and treated with prolonged anaerobe-covering antibiotics plus postural drainage.
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What this article covers
- Overview
A necrotic cavity, not a diffuse infiltrate: lung abscess is a circumscribed collection of pus within the lung parenchyma that leads to cavity formation, with an air-fluid level on chest radiography…
- Epidemiology
Concentrated in patients with impaired airway defenses: the classic patient has altered consciousness (alcohol intoxication, seizure, anesthesia, stroke), poor dental hygiene, or a swallowing disorder permitting large-volume aspiration.
- Risk factors
Impaired level of consciousness: alcohol intoxication or use disorder, general anesthesia, seizure disorder, stroke, and drug overdose predispose to large-volume oropharyngeal aspiration.
- Pathophysiology
Aspiration deposits a polymicrobial inoculum into a dependent segment: oropharyngeal secretions settle by gravity into the posterior upper lobe or superior lower lobe, the most dependent regions when supine or reclined.
- Clinical features
Subacute, indolent onset over days to weeks: fever, productive cough, and malaise develop gradually, in contrast to the abrupt onset of aspiration pneumonitis.
- Differential diagnosis
Cavitary lung cancer: irregular, thick-walled cavity with weight loss out of proportion to infection and no response to antibiotics; bronchoscopy with biopsy distinguishes it.
- Diagnosis
The diagnosis is established by a cavity with an air-fluid level on chest imaging in a compatible clinical setting: a circumscribed, thick-walled cavity greater than 2 cm, typically in a dependent…
- Management
Start empiric IV antibiotics covering oral anaerobes and streptococci as soon as the diagnosis is suspected: give ampicillin-sulbactam 3 g IV every 6 hours first-line.
- Complications
Empyema from pleural rupture: the most common serious complication; needs its own chest tube drainage plus continued antibiotics.
- Prognosis
Mortality up to 20% despite antibiotic therapy.
- Prevention
Position at-risk patients to limit aspiration volume: head of bed at 30 degrees or higher, lateral or semi-recumbent positioning, for patients with impaired consciousness, sedation, or active seizure.
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