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Parapneumonic Effusion and Empyema


KEY FACTS

Terminology

  • Pleural effusions classified as transudative or exudative

  • Parapneumonic effusions are exudative secondary to adjacent lung infection & ↑ capillary permeability

Imaging

  • Upright chest radiograph

    • Flattened & elevated hemidiaphragm, lateral shift of diaphragm apex, gastric bubble > 1.5 cm from diaphragm secondary to subpulmonic fluid

    • Blunted posterior costophrenic angle (∼ 50 mL)

    • Blunted lateral costophrenic angle (∼ 200 mL)

    • Hemidiaphragm inversion (> 2,000 mL)

  • Supine chest radiograph may require up to 500 mL

    • Homogeneous vs. gradation of hazy/dense opacification of hemithorax ± pleural cap, mass effect

  • CECT: Parietal pleural enhancement & thickening, thickening of extrapleural space, & chest wall edema seen with both transudative & exudative effusions in children

  • US: Effusion appears anechoic, echoic, or mixed with floating/swirling/undulating echoes

    • Floating fibrin strands attached to pleural surface, septations, &/or pleural rind/thickening; immobile lung suggests entrapment by pleural rind

    • Loculation: Nonshifting fluid with position change

  • Imaging recommendations

    • US if pleural disease suspected on chest radiograph

    • CECT if persistent/progressive illness despite treatment

Clinical Issues

  • Treatment

    • Antibiotics

    • Chest tube drainage if effusion of large volume, loculated, or with worsening/persistent symptoms

    • If empyema: Chest tube + tissue plasminogen activator; video-assisted thoracoscopic surgery if no clinical improvement & pleural disease persists on imaging

  • Majority of children make complete clinical recovery

PA radiograph of a child with a right pneumonia shows opacification of the majority of the right hemithorax with mediastinal shift to the left.

Sagittal US of the right hemithorax in the same patient shows a large pleural effusion
with internal debris & multiple echogenic septa
, consistent with a fibrinopurulent parapneumonic effusion.

Axial CECT in the same patient shows the large pleural effusion compressing the right lung
. While the rind of enhancement
suggests complexity, the septations demonstrated on the previous US are not visualized on this CT examination.

Longitudinal US of the right lung in a patient with pneumonia shows a right pleural effusion
with multiple areas of echogenic debris & septations. Note the consolidated, echogenic lung
. The liver
is shown inferiorly.

TERMINOLOGY

Definitions

  • Pleural effusions classified as transudative or exudative

    • Transudative: Due to hydrostatic & oncotic imbalances

    • Exudative: Due to ↑ capillary permeability

  • Parapneumonic effusions are exudative

    • Stages of progression: Exudative (simple) → fibrinopurulent (complicated) → organized

    • Empyema is fibrinopurulent parapneumonic effusion

IMAGING

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