Lung abscesses represent necrosis and cavitation of the lung due to microbial infection. They are typically marked by a single cavity greater than 2cm in diameter. Primary lung abscesses usually arise from aspiration of oral bacteria and affect the lower lobes. Secondary abscesses occur in the context of an underlying condition like obstruction or immunosuppression. Treatment involves antibiotics targeting anaerobic bacteria for several weeks and sometimes drainage for large abscesses. Complications include persistent cysts, recurrence, and life-threatening bleeding or aspiration.

1. - Dr Rahul Arya
- Assistant Professor
- Department of Medicine

2. • Lung abscess represents necrosis and cavitation of the lung following
microbial infection.
• Lung abscesses can be single or multiple but usually are marked by a
single dominant cavity >2 cm in diameter.

3. ETIOLOGY
• Primary (~80% of cases) or Secondary.
• Primary lung abscesses usually arise from aspiration, are often
caused principally by anaerobic bacteria, and occur in the absence of
an underlying pulmonary or systemic condition.
• Secondary lung abscesses arise in the setting of an underlying
condition, such as a post-obstructive process (e.g., a bronchial foreign
body or tumor) or a systemic process (e.g., HIV infection or another
immunocompromising condition).

4. • Lung abscesses can also be characterized as acute (<4–6 weeks in
duration) or chronic (~40% of cases).

5. EPIDEMIOLOGY
• Middle-aged men are more commonly affected.
• The major risk factor for primary lung abscesses is aspiration.
• Colonization of the gingival crevices by anaerobic bacteria or
microaerophilic streptococci combined with a risk of aspiration, is
important in the development of lung abscesses.

6. PATHOGENESIS
Primary Lung Abscesses
• It originate when chiefly anaerobic bacteria in the gingival crevices
are aspirated into the lung parenchyma in a susceptible host.
• Pneumonitis develops initially then, over a period of 7–14 days, the
anaerobic bacteria produce parenchymal necrosis and cavitation.

7. PATHOGENESIS
Secondary Lung Abscesses
• It depends on the predisposing factor.
• In cases of bronchial obstruction from malignancy or a foreign body,
the obstructing lesion prevents clearance of oropharyngeal
secretions, leading to abscess development.
• With underlying systemic conditions (e.g., immunosuppression after
bone marrow or solid organ transplantation), impaired host defense
mechanisms lead to increased susceptibility to development of lung
abscesses caused by opportunistic organisms.

8. PATHOLOGY AND MICROBIOLOGY-
Primary Lung Abscesses
• In primary lung abscesses, the dependent segments (posterior upper
lobes and superior lower lobes) are the most commonly involved.
• The right lung is affected more commonly than the left because the
right mainstem bronchus is less angulated.
• The microbiology of primary lung abscesses is often polymicrobial,
primarily including anaerobic organisms as well as microaerophilic
streptococci.

9. PATHOLOGY AND MICROBIOLOGY-
Secondary Lung Abscesses
• The microbiology of secondary lung abscesses can encompass quite a
broad bacterial spectrum, with infection by Pseudomonas aeruginosa
and other gram-negative rods.

10. CLINICAL MANIFESTATIONS
• Fevers
• Cough
• Sputum production
• Chest pain
• Night sweats, fatigue, and anemia is often observed with anaerobic lung abscesses.
• Discolored phlegm and foul-tasting or foul-smelling sputum.
• Infection with non-anaerobic organisms, such as S. aureus, may present with a more
fulminant course characterized by high fevers and rapid progression.

11. PHYSICAL EXAMINATION
• Fever
• Poor dentition, and/or gingival disease.
• Amphoric and/or cavernous breath
sounds on lung auscultation.
• Digital clubbing.

12. DIFFERENTIAL DIAGNOSIS
• Lung infarction
• Malignancy
• Vasculitides (e.g., granulomatosis with polyangiitis)
• Lung cysts or bullae containing fluid
• Septic emboli (e.g., from tricuspid valve endocarditis).

13. INVESTIGATIONS

14. • CHEST X-RAY:- Thick-walled
cavity with an air-fluid level.

15. • CT THORAX:-
- Better definition and may
provide earlier evidence of
cavitation.
- CT may also yield additional
information regarding a possible
underlying cause of lung abscess,
such as malignancy.

16. • SPUTUM EXAMINATION
• BRONCHOSCOPY WITH BRONCHOALVEOLAR LAVAGE

17. TREATMENT
• Clindamycin (600 mg IV three times daily; then, with the
disappearance of fever and clinical improvement, 300 mg PO four
times daily)
• IV-administered β-lactam/β-lactamase combination, followed—once
the patient’s condition is stable—by orally administered amoxicillin-
clavulanate.
• This therapy should be continued until imaging demonstrates that the
lung abscess has cleared or regressed to a small scar.

18. • Treatment duration may range from 3–4 weeks to as long as 14
weeks.
• Metronidazole is not effective as a single agent: it covers anaerobic
organisms but not the microaerophilic streptococci that are often
components of the mixed flora of primary lung abscesses.

19. • An abscess >6–8 cm in diameter is less likely to respond to antibiotic
therapy without additional interventions.
• In theses patients surgical resection and percutaneous drainage of the
abscess can be done.

20. COMPLICATIONS
• Persistent cystic changes (pneumatoceles) or bronchiectasis.
• Recurrence of abscesses despite appropriate therapy
• Extension to the pleural space with development of empyema
• Life-threatening hemoptysis
• Massive aspiration of lung abscess contents.

21. PROGNOSIS
• Mortality rates for primary abscesses- 2% and for Secondary
abscesses- 75% .
• Poor prognostic factors include an age >60, the presence of aerobic
bacteria, sepsis at presentation, symptom duration of >8 weeks, and
abscess size >6 cm.

22. PREVENTION
• Airway protection
• Oral hygiene
• Minimized sedation with elevation of the head of the bed for patients at
risk for aspiration.
• Prophylaxis against certain pathogens in at-risk patients (e.g., recipients of
bone marrow or solid organ transplants or patients whose immune systems
are significantly compromised by HIV infection) may be undertaken.