Lung Abscess

A lung abscess is characterized as a localized collection of pus or necrotic tissue within the lung parenchyma, resulting in a cavity. Once a bronchopulmonary fistula develops, this cavity often exhibits an air-fluid level. Lung abscesses belong to the broader category of lung infections, including lung gangrene and necrotizing pneumonia, with the latter marked by multiple abscess formations. Lung abscesses are typically categorized based on duration as either an acute abscess, which resolves in less than 6 weeks, or a chronic abscess, which persists for more than 6 weeks. A lung abscess may also be classified according to the underlying etiology. Primary lung abscess results from oropharyngeal secretion aspiration. Aspiration of oropharyngeal secretions may be secondary to various conditions, including dental or periodontal infections, sinusitis, altered states of consciousness, swallowing disorders, gastroesophageal reflux disease, frequent vomiting, necrotizing pneumonia, or immunocompromised individuals. Secondary lung abscesses arise from pulmonary conditions, including bronchial obstructions (eg, tumors, foreign bodies, or enlarged lymph nodes), existing lung conditions (eg, bronchiectasis, bullous emphysema, cystic fibrosis, infected pulmonary infarcts, or lung contusions). A lung abscess may also be classified according to the pathophysiologic mechanism of spread from extrapulmonary sites, which can be hematogenous (eg, abdominal sepsis, infective endocarditis, infected catheters, or septic thromboembolisms) or direct (eg, bronchoesophageal fistulas or subphrenic abscesses). Early symptoms mimic pneumonia, including fever, chills, cough, night sweats, and chest pain, with a productive cough developing as a hallmark sign. Diagnostic imaging, including computed tomography (CT) scans and thoracic ultrasounds, is essential for characterizing lung abscesses. Furthermore, additional diagnostic studies (eg, sputum examination and bronchoscopy) are crucial for identifying the causative agents and differentiating lung abscesses from other conditions eg, cavitary tuberculosis and lung carcinoma. Complications can include pyopneumothorax or pleural empyema, especially in immunocompromised patients. Management often begins with empiric antibiotic therapy targeting a broad range of organisms, with adjustments made based on specific pathogens identified. Poor prognostic factors include old age, severe comorbidities, and immunosuppression. Surgical or percutaneous interventions may be necessary for abscesses larger than 6 cm or when medical therapy fails. Treatment duration is generally around 3 weeks, with a switch to oral antibiotics once the patient stabilizes.