Lung Abscess - Paediatrics - Lecture Slides, Slides of Pediatrics

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Lung Abscess

Background

Definition:

Necrosis of the pulmonary tissue & formation of

cavities containing necrotic debris or fluid

caused by microbial infection.

The formation of multiple small (< 2 cm)

abscesses is occasionally referred to as

necrotizing pneumonia or lung gangrene.

In the early post-antibiotic period, sulfonamides didn’t improve the out-come of patients with lung abscess until the penicillin's & tetracycline's were available.

Although resectional surgery was often considered a treatment option in the past, the role of surgery has greatly diminished over time coz most patients with un-complicated lung abscess eventually respond to prolonged antibiotic therapy.

Lung abscesses can be classified based on the duration & the likely etiology.

Acute abscesses are less than 4-6 wks old, whereas chronic abscesses are of longer duration.

Primary abscess is infectious in origin, caused by aspiration or pneumonia in the healthy host.

Pathophysiology

Lung abscess arises as a complication of aspiration pneumonia caused by mouth anaerobes.

A bacterial inoculums from the gingival crevice reaches the lower airways, & infection is initiated coz the bacteria aren’t cleared by the patient’s host defense mechanism.

Abscesses generally develop in the right lung and involve the posterior segment of the right upper lobe, the superior segment of the lower lobe, or both. This is due to gravitation of the infectious material from the oropharynx into these dependent areas.

Other mechanisms for lung abscess formation

include :

Septic emboli to the lung ,caused by:

1) Bacteremia.

2) Tricuspid valve endocarditis.

Microbiology

Anaerobes are recovered in up to 89% of the patients, 46% of patients with lung abscess had only a mixture of anaerobes isolated from sputum cultures while 43% of patients had a mixture of anaerobes & aerobes.

The most common anaerobes are Peptosretococcus, Bacteroids , Fusobacterium species & Microaerophilic streptococcus.

Non-bacterial pathogens may also cause lung abscesses.

Theses micro-organisms include:

1. Parasites [ Paragonimus , Entamoeba ].
2. Fungi [ Aspergillus , Cryptococcus , Histoplasma , Blastomyces , Coccidioides ].
3. Mycobacterium.

History

Anaerobic infection:

1. Patients often present with indolent symptoms that evolve over a period of weeks to months.

2. The usual symptoms are fever , cough with sputum production , night sweats , anorexia & weight loss.

3. The expectorated sputum characteristically is foul smelling & bad tasting.

4. Patients may develop hemoptysis or pleurisy.

Physical

Patients may have low-grade fever in anaerobic infections & temperature > 38.5 C in other infections.

Generally, evidence of gingival disease is present.

Clinical findings of consolidation may be present: [decreased breath sounds, dullness to percussion, bronchial breath sounds, course inspiratory crackles].

Evidence of pleural friction rub signs of associated pleural effusion, empyema & pyo-pneumothorax may be present. Signs include :

[dullness to percussion, contralateral mediastinal shifting & absent breath sounds over the effusion].

Digital clubbing may develop rapidly.

Factors contributing to lung abscess

Oral cavity disease Periodontal disease Gingivitis

Altered consciousness[ inability to protect their airways coz of an absent gag reflex] Alcoholism Coma Drug abuse Anesthesia Seizures

Immunocompromised host Steroid chemotherapy Malnutrition Multiple trauma

Esophageal disease Achalasia Reflux disease Depressed cough and gag reflex Esophageal obstruction