pulmonary abscess

Pulmonary abscess

Pulmonary abscess is a collection of puswithin the lung parenchyma with confined cavitation that results from a pulmonary infection.

The three bacterial causes of pulmonary abscesses are:

  • Staphylococcus aureus in IV drug users with endocarditis.
  • Klebsiella pneumoniae in obtunded alcoholics.
  • Anaerobic oral flora in patients with aspiration pneumonia.

Bacteria from the oropharynx implicated in pulmonary abscesses from aspiration include:

  • Bacteroides
  • Fusobacterium
  • Peptococcus

Pulmonary abscesses due to septic embolization should always be considered in patients with endocarditis and multiple cavitary pulmonary infiltrates.

Suspect pulmonary abscess in a patient who is at risk for aspiration who presents with:

  • Productive cough
  • Poor dentition
  • Spiking fevers

Patients with pulmonary abscesses will often be predisposed to aspiration pneumonia due to** impaired epiglottic function** and therefore inadequate airway protection. Commonly tested scenarios include:

  • Obtunded alcoholic
  • Patient with seizure disorder
  • Advanced dementia

Foul smelling sputum in a patient with aspiration is indicative of anaerobic infection.

Lung abscesses appear as solitary, cavitating lesions with an air-fluid level and surrounding infiltrateon CXR.

This patient has a lung abscess, most likely as a result of aspiration, and should be treated with antibiotics to reduce the risk of rupture into the airway or pleural space. Empiric therapy should cover anaerobes and microaerophilic streptococci (choice D is correct) because most lung abscesses develop as a complication of aspiration and are typically polymicrobial and indolent in nature. Risk factors that predispose to the development of lung abscesses due to aspiration include impaired swallowing, poor airway clearance, and reduced consciousness. Lung abscesses may also form as a consequence of septic embolization, direct extension of an empyema, endobronchial obstruction from a foreign body or tumor, or superinfection of damaged lung tissue (eg, contusion or infarct). Treatment is usually continued for several weeks or until symptoms are improved and chest imaging is resolved.

A small percentage of patients fail antimicrobial therapy and require procedural intervention. Percutaneous catheter drainage or transbronchoscopic catheter drainage may be considered for patients who do not respond to antibiotic therapy, depending on the location of the abscess (peripheral/abutting the pleura vs central), but should not be attempted prior to antibiotic therapy (choices A, B, and C are incorrect). Surgical intervention is rarely indicated for patients who fail to improve with antibiotic therapy or develop a complication during treatment (eg, bronchopleural fistula). Mortality with surgical intervention is as high as 15% to 20%, and surgery should not be considered before a prolonged trial of antibiotic therapy.1

Footnotes

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