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CHAPTER 47

Lung Abscess

Jonathan Karperlowsky

Introduction right-sided endocarditis, long-term lines, or, rarely, in children with
A lung abscess is a cavity in the lung parenchyma that contains purulent haematogenous spread from thrombophlebitis. S. aureus septicaemia
material resulting from pulmonary infection. This chapter focuses on may frequently result in this mechanism of lung abscess formation.
pyogenic lung abscesses and does not consider other causes of pulmo- Clinical Presentation
nary cavitations with or without air fluid levels, such as tuberculosis The differentiation of pneumonia and lung abscess on purely clinical
or a complicated hydatid cyst. The role of surgery in lung abscesses is grounds is difficult. Fever and cough predominate but are not universal.
limited, with the vast majority being treated with antimicrobials and Other findings include chest pain, anorexia, productive sputum, mal-
percutaneous techniques.
aise, haemoptysis, chills, and halitosis. Signs of lung abscess are varied,
Demographics but may include tachypnoea, dullness, bronchial breathing, amphoric
Lung abscesses in previously well children are uncommon and are breathing, and crepitations over the affected area.
usually the complication of a virulent necrotising pneumonia. The inci- Investigations
dence would thus depend on the burden of respiratory disease. This is
Radiology typically shows a cavity with an air fluid level; this needs
in contrast to children at risk for lung abscesses, which would include
to be differentiated from a pneumatocoele, complicated hydatid, or
children with impaired immunity (e.g., human immunodeficiency
pyopneumothorax. Occasionally, to further delineate the anatomy, to
virus (HIV) or cystic fibrosis), an underlying anatomical abnormality
exclude an underlying abnormality, or to facilitate percutaneous inter-
(e.g., congenital cystic adenomatoid malformation or bronchopulmo-
vention, a computed tomography (CT) scan must be done. Ultrasound
nary sequestration), or at risk for aspiration (e.g., neurodevelopmental
can be used if the abscess abuts the hemidiaphragm or chest wall, thus
anomalies or cerebral palsy).
creating an acoustic window to enable visualisation.
Pathophysiology and Pathology Bacteriology, sputum, or pus, if intervention is performed, is
A pulmonary abscess develops when a localised infection within the invaluable in guiding antibiotic therapy. Ideally, this intervention
parenchyma becomes necrotic, with subsequent cavitation. Several should occur prior to commencement of antibiotic therapy. This may be
mechanisms exist for this process. The first is an unchecked infec- done in the older child by using an induced sputum and in the younger
tion secondary to impaired immunity, clearance of the organism, or child by bronchoscopy, if safe facilities exist.
virulence of the organism. Patients with impaired cellular or humoral Management
immunity, which may be congenital or acquired, are unable to eradicate The mainstay of therapy involves prolonged antimicrobials. The exact
the infection, leading to breakdown. Nutritional deficiency can be a duration and route of administration have not clearly been delineated
significant cofactor in Africa. Inadequate clearance may be secondary in the literature. It would seem that it would be prudent to begin with
to a congenital cystic pulmonary lesion, an inhaled foreign body or intravenous antibiotics until signs and symptoms have settled, follow-
bronchial narrowing. The latter, especially in the African setting, may ing which the remainder of the 4–6 week course may be given orally.
occur secondary to tuberculosis (TB) lymphadenitis with a superad- Drainage of the lesion can usually be achieved by using physiotherapy
ded infection. Cystic fibrosis also will lead to inadequate clearance, with postural drainage and percussion. In children unable to adequately
potentially leading to a lung abscess. Infection with a virulent organism, expectorate, bronchoscopy can be a useful adjunct.
typically anaerobes, Staphylococcus aureus, streptococcal species, and Antimicrobials should ideally be microbiologically directed, but
Klebsiella, can cause a lung abscess. Delay in antimicrobial therapy empiric antibiotics with a B-lactam is usually adequate in the absence
in treating pneumonia is often causative in a lung abscess because the thereof. If there is consideration of coliforms, an aminoglycoside may
infection remains unchecked for a prolonged period. Unfortunately, in be added, and if aspiration or anaerobes are considered to be causative,
Africa, due to difficult health access, easily treated conditions may lead the addition of metronidazole or clindamycin is warranted. The
to significant morbidity, and mortality. latter makes an excellent single agent provided coliforms have been
Second, pulmonary aspiration is a central contributing factor to excluded. For primary abscesses, staph, strep, and coliforms should be
lung abscess formation in many children. Aspiration usually occurs considered; for secondary abscesses, it is important to cover anaerobes.
in children with a neurological deficit, particularly cerebral palsy. A significant morbidity is associated with surgery, such as empyema
Any acquired depressed level of consciousness, such as trauma and air leaks, with mortalities of 5–10% having been reported. The
or postanaesthesia, would also place a child at risk. Children with need for surgery has further been minimised by percutaneous drains
incoordinate swallowing or muscle weakness are a second group of where interventional radiology is available. Thus, in most instances,
patients who frequently aspirate. Last are children with oesophageal surgical intervention should be reserved for underlying congenital
abnormalities, including dysmotility, achalasia, and unrecognised anomalies and treatment failures. This would include large chronic
trachea-oesophageal fistulas. abscesses, significant haemoptysis, bronchial stenosis, bronchiectasis,
A final mechanism involves patients who develop a lung abscess or massive necrosis.
secondary to septic emboli. This may be seen in children with