Lung Abscess

• • Localized collection of pus

  • Acute: < 6 wks

  • Chronic: > 6 wks

Primary

• • Aspiration of oropharyngeal contents

  • Acute necrotizing pneumonia (Staph, Klebsiella)

  • Chronic pneumonia due to fungi, TB

  • Opportunistic infection in immunocompromised person

Secondary

• • Bronchial obstruction (cancer, foreign body)

  • Cavitating pulmonary lesions (cancer)

  • Direct extension (amebiasis, subphrenic abscess)

  • Hematogenous dissemination

Epidemiology

• • Increased incidence with AIDS, transplantation, and chemotherapy

  • Pathogens typically found in cultures include:

  • -Staphylococcus

    -Streptococcus

    -Klebsiella

    -E coli

    -Pseudomonas

    -Clostridium

    -Bacteroides

  • Pathogens found in immunocompromised patients:

  • -Candida

    -Legionella

    - Pneumocystis carinii

Symptoms and Signs

• • Cough, fever, dyspnea, pleuritic chest pain

  • Malaise, weight loss if chronic

  • On exam: Clubbing; signs of pleural effusion; cachexia; and rarely, draining chest wound (empyema necessitatis)

Laboratory Findings

• • Elevated WBC, with left shift

  • Positive sputum culture

Imaging Findings

• • Chest film: Area of intense consolidation or rounded density; with or without air-fluid level

  • CT scan: Helpful in cases of suspected bronchial obstruction

• • Evaluate for primary structural diseases of lungs, including cancer

• • WBC, sputum culture

  • Chest x-ray and chest CT scan

  • Bronchoscopy in patients with unexplained reason for lung abscess

  • Fine-needle aspiration (FNA) of abscess cavity identifies pathogens in 94% of cases

  • -Bronchoalveolar lavage (BAL) identifies organism in only 3%

  • FNA important to identify unusual organisms in immunocompromised patients

• • Antibiotics mainstay of treatment

  • Penicillin and clindamycin commonly used

  • Trimethoprim-sulfamethoxazole, pentamidine, erythromycin, or amphotericin B often indicated in immunocompromised patients

  • Continue antibiotics until complete resolution (3-6 mos)

  • Chest physiotherapy, bronchoscopy with drainage may be necessary

Surgery

Indications

• • Poor response to above medical regimen, percutaneous drainage

  • Tense abscess (mediastinal shift, shift of diaphragm, etc)

  • Evidence of contralateral lung contamination

  • Signs of sepsis after 72 hrs of antibiotic therapy

  • Abscess size > 4 cm or enlarging

  • Rising fluid level

  • Persistent ventilatory dependency

Complications

• • Rupture into bronchus

  • Rupture into pleural space resulting in pyopneumothorax

  • Massive hemoptysis

Prognosis

• • Percutaneous drainage: 1.5% mortality, 10% morbidity

  • Overall mortality rate: 5-20%

  • Medical therapy success: 75-88%

  • Operative patients: Cured 90% of time, 1% mortality

  • Mortality in immunocompromised patients: 28%

References