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Viral Chest Infection


KEY FACTS

Terminology

  • Viral infection may involve airways &/or lung parenchyma

  • Bronchiolitis: Acute inflammation & necrosis of epithelial cells lining small airways with ↑ mucus production

    • Classically < 2 years of age

  • Other terms: Viral pneumonia, lower respiratory tract infection, peribronchial pneumonia

Imaging

  • Primary goal of chest radiography: Differentiate viral airway infection from bacterial pneumonia

    • 92% negative predictive value for bacterial pneumonia

  • Best imaging clues for viral airway infection

    • ↑ peribronchial markings with radiating linear rope-like or “dirty” perihilar opacities & “doughnuts” of thickened bronchial walls (viewed in cross section)

    • Hyperinflation: Depression of hemidiaphragms with downward sloping on lateral view; ↑ AP chest diameter on lateral view; ± convex bulging of lungs between ribs

    • Subsegmental atelectasis, possibly multifocal

    • Lack of focal/lobar consolidation or pleural effusion

  • Best imaging clues for viral parenchymal involvement

    • Interstitial, nodular, or patchy ground-glass opacities

Clinical Issues

  • Viruses cause majority of chest infections in preschool children; most frequent causative virus differs by age

  • Presents with rhinorrhea, cough, tachypnea, wheezing, rales, ↑ respiratory effort (grunting, nasal flaring, intercostal/subcostal retractions)

    • Difficult to differentiate bacterial from viral parenchymal infection based on physical exam or laboratory tests

  • Treatment

    • Antibiotics for concomitant bacterial infection

    • No utility for albuterol or steroids

    • Hospitalization if hypoxemia or respiratory distress

    • Antiviral therapy for influenza cases

AP radiograph in a wheezing child shows typical findings of viral airways disease. There are mildly increased perihilar markings with an increased number of “doughnuts” (thickened bronchial walls viewed in cross section)
. The lungs show convex bulging between the ribs
, typical of hyperinflation.

AP radiograph shows viral airways disease with increased perihilar markings of bronchial wall edema
. There is no focal lung consolidation or pleural effusion.

AP radiograph in a wheezing child shows hyperinflated lungs with increased rope-like perihilar markings, consistent with viral airways disease. There is no focal lung consolidation.

Lateral radiograph in the same patient shows marked hyperinflation with flattening of the hemidiaphragms
(much more evident than on the corresponding frontal view) & widening of the AP diameter of the chest. Also note the increased markings radiating from the hila.

TERMINOLOGY

Definitions

  • Bronchiolitis (as defined by AAP): Viral lower respiratory tract infection in infants with “acute inflammation, edema, & necrosis of epithelial cells lining small airways,” & ↑ mucus production

  • Lower respiratory tract infection may describe findings identical to bronchiolitis in patients ≥ 2 years old but may also refer to any infection of lower airways & parenchyma

  • Viral pneumonia may refer to viral infection of lung parenchyma ± airways infection

  • Lower airways disease includes viral airways infection as well as asthma

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