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Round Pneumonia


KEY FACTS

Terminology

  • Bacterial lung infection with very round, well-defined appearance on chest radiography; simulates mass lesion

  • Majority seen in patients < 8 years of age

Imaging

  • Well-circumscribed round opacity ± air bronchograms

  • Most common posteriorly in lower lobe superior segments

  • No mass effect on or invasion of adjacent tissues

    • No mediastinal or vascular distortion

    • No splaying or erosion of ribs

  • Margins of round lung “mass” classically create acute angles with mediastinum or chest wall but can be obtuse

Top Differential Diagnoses

  • Bronchogenic cyst

  • Neuroblastoma

  • Congenital pulmonary airway malformation

  • Bronchopulmonary sequestration

Pathology

  • Collateral pathways of air circulation in lung not well developed until ∼ 8 years of age

    • Channels of Lambert, pores of Kohn

  • Spread of bacterial infection through lung therefore hindered in young children, predisposing to round appearance

  • Typically occurs with Streptococcus pneumoniae infection

Diagnostic Checklist

  • Round lung opacity in child < 8 years of age → strongly consider round pneumonia

  • With classic symptoms of pneumonia (cough, fever) in this age range, other masses do not need to be excluded

  • If any doubt of diagnosis, consider

    • Targeted US or CT through lesion

    • Follow-up radiograph after completion of antibiotic course

      • –

        Resolution of “mass” excludes other etiologies

AP radiograph in a young child with cough & fever shows a round, mildly lobulated, well-circumscribed density
in the medial aspect of the right lower lobe.

Lateral radiograph in the same patient confirms that the round “mass”
is located posteriorly in the right lower lobe. Note that the lesion makes acute angles with the posterior chest wall, consistent with a pulmonary origin. These findings are typical of a round pneumonia.

Abdominal radiograph of a 7-year-old boy with fever & vomiting shows a round opacity
projecting over the right hemidiaphragm, suggesting a right lower lobe round pneumonia.

Subsequent chest radiograph in the same patient clearly demonstrates a lobulated, well-circumscribed right lower lobe opacity
, consistent with a round pneumonia. Note that the adjacent ribs are normal.

TERMINOLOGY

Definitions

  • Bacterial lung infection with very round, well-defined appearance on chest radiography; simulates mass lesion

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