Lung Abscess

Aka: Lung Abscess, Pulmonary Abscess

1. Definitions
   1. Lung Abscess
      1. Localized lung cavity filled with pus
      2. Product of lung necrosis
      3. Cavity is often surrounded by infection
2. Causes: Organisms
   1. See Pneumonia Causes
   2. Oral Flora due to aspiration (most common, typically polymicrobial, anaerobic)
      1. Peptostreptococcus
      2. Prevotella
      3. Bacteroides
      4. Fusobacterium
   3. Pneumonia Complications
      1. Staphylococcal Pneumonia (Staphylococcus aureus)
      2. Gram Negative Pneumonia (e.g. KlebsiellaPneumoniae)
      3. Streptococcus Pyogenes
      4. HaemophilusInfluenzae Type B
   4. Other organisms
      1. Mycobacterium tuberculosis
      2. Nontuberculous Mycobacteria
      3. Fungal infection (e.g. Nocardia, Actinomyces)
      4. Atypical infections in travelers or Immigrants (e.g. Entamoeba histolytica, Echinococcus)
3. Causes: Mechanisms
   1. Oropharyngeal Aspiration
      1. Dental Infections
      2. Sinus infections
      3. Altered Level of Consciousness (e.g. Intoxication, Alcoholism, Seizures)
      4. Gastroesophageal Reflux disease
      5. Frequent Vomiting
      6. Endotracheal Intubation
      7. Tracheostomy
   2. Hematologic Spread
      1. Infective Endocarditis
      2. IV Drug Abuse
      3. Central Line-Associated Bloodstream Infection
      4. Septic Thromboembolism
   3. Acute Lung Disorders
      1. Necrotizing Pneumonia
      2. Bronchial obstruction (e.g. foreign body, tumor)
      3. Lung Infarction (secondarily infected)
      4. Lung Contusion
   4. Chronic Lung Disorders
      1. Bronchiectasis
      2. Cystic Fibrosis
      3. Bullous Emphysema
      4. Congenital malformation
      5. Bronchoesophageal Fistula
4. Risk Factors
   1. Elderly
   2. Aspiration History (e.g. Cerebrovascular Accident, bulbar dysfunction)
   3. Dental Infections
   4. Alcoholism
   5. Intravenous Drug Abuse
   6. Diabetes Mellitus
   7. Seizure Disorder
   8. Malnutrition
   9. Chronic Immunosuppression (e.g. Corticosteroids, HIV Infection, Chemotherapy, post-transplant)
5. Symptoms
   1. Fever
   2. Chills
   3. Night Sweats
   4. Productive cough of foul Sputum
   5. Dyspnea
   6. Fatigue
   7. Weight loss
   8. Pleuritic Chest Pain
   9. Hemoptysis
6. Signs
   1. Localized dullness over involved lung
   2. Bronchial breath sounds or absent breath sounds
   3. FingernailClubbing
7. Differential Diagnosis
   1. Foreign Body Aspiration
   2. Pulmonary Infarction (cavitary)
   3. Lung Cancer
   4. Tuberculosis
   5. Pleural Empyema
   6. Infected Emphysematous bulla
   7. Alveolar Hydatid Disease (Echinococcus)
   8. Hiatal Hernia
   9. Granulomatosis with Polyangiitis (previously known as Wegener's Granulomatosis)
8. Imaging
   1. Chest XRay
      1. Solitary cavitary lesion with air-fluid level
      2. Lesion surrounded by pneumonitis
   2. CT Chest
      1. Better defines infiltrates and cavitary lesions
      2. Explores differential diagnosis in refractory Lung Abscess
   3. Echocardiogram
      1. Consider in cases of suspected hematologic spread
9. Labs
   1. Sputum examination
      1. Microscopy
         1. Gram Stain
         2. Mycobacterial stains
         3. Fungal stains
      2. Sputum layers on standing
   2. Cultures
      1. Blood Cultures
      2. Sputum Cultures (often not helpful)
   3. Complete Blood Count
      1. Leukocytosis
10. Diagnosis
    1. Bronchoscopy if proximal obstructing tumor is suspected
11. Management: Antibiotics
    1. Initial Empiric Management (start with IV)
       1. Ampicillin-Sulbactam (Unasyn) 3 g IV every 6 hours
       2. Alternative options for Penicillin Allergy
          1. Clindamycin 600 mg IV every 8 hours or
          2. Moxifloxacin 400 mg IV every 24 hours or
          3. Levofloxacin 750 mg IV every 24 hours AND Metronidazole 500 mg IV every 8 hours
       3. Alternatives for suspected drug-resistant Gram Negative organisms
          1. Imipenem 1 g IV every 6 hours or
          2. Meropenem 1 g IV every 8 hours
    2. Symptom, Sign and Lab Improvement by 3 to 4 days (fever may persist 7-10 days)
       1. Adjust antibiotics as needed based on culture results
       2. Transition to oral antibiotics (plan 3 to 4 week outpatient course)
          1. Augmentin 875 mg orally twice daily
          2. Clindamycin 300 mg orally every 6 hours or
          3. Moxifloxacin 400 mg orally daily or
          4. Levofloxacin 750 mg orally daily AND Metronidazole 500 mg orally every 8 hours
    3. Failure to Improve or Worsening Despite IV Antibiotics at 3 to 4 days
       1. Adjust antibiotics as needed based on culture results
       2. Consider drug resistant Bacteria
       3. Consider atypical infection (e.g. Fungal Lung Infection, Mycobacteria)
       4. Consider differential diagnosis (see above)
       5. Obtain CT Chest
       6. Consider flexible bronchoscopy to obtain lesion sample and evaluate for airway obstructiuon or foreign body
       7. Consider abscess drainage (e.g. Intervention Radiology or transbronchial catheter)
12. Course
    1. Day 3 to 4
       1. Expect symptom, Vital Sign and lab (e.g. CBC) improvement on antibiotics
    2. Day 7 to 10
       1. Fever typically resolves by this time on antibiotics
    3. Day 21 to 50
       1. Abscess cavity typically closes by this time on antibiotics
13. Complications
    1. Respiratory Failure
    2. Pleural fibrosis
    3. Bronchopleural Fistula
    4. Pleurocutaneous Fistula
14. Resources
    1. Bhanusivakumar (2022) Lung Abscess, StatPearls, Treasure Island
       1. https://www.ncbi.nlm.nih.gov/books/NBK555920/
15. References
    1. Klompas in Calderwood (2022) UpToDate, accessed 4/24/2022
    2. Kuhajda (2015) Ann Transl Med 3(13):183 +PMID: 26366400 [PubMed]