Brian C. Allen, MD

Tan-Lucien H. Mohammed, MD, FCCP

Frontal radiograph shows a subtle diffuse increased reticular pattern in an asthmatic patient.

Axial HRCT shows a mosaic attenuation pattern consistent with air-trapping image.


Abbreviations and Synonyms

  • Reactive airway disease


  • Intermittent reversible obstruction to air flow in lungs due to hyperreactivity and inflammation

  • Status asthmaticus: Medical emergency in which asthmatic attack is refractory to bronchodilator therapy


General Features

  • Best diagnostic clue

    • Air-trapping on expiratory scans

    • Bronchial wall thickening

  • Patient position/location

    • Segmental and distal bronchi

    • Nonuniform distribution through both lungs

CT Findings

  • More sensitive than chest radiography but not usually indicated

    • Used to assess for complications such as allergic bronchopulmonary aspergillosis, presence of emphysema in smokers, or to identify asthma mimics

  • Heterogeneous distribution of bronchial and lung parenchymal findings typical

  • Airways

    • Mainly small and medium-sized bronchi

    • Bronchial wall thickening (50-90%)

      • Degree of thickening correlates with severity of disease and airflow obstruction

      • Will improve with treatment

    • Bronchial artery ratio (normal approximately 1:1)

      • 75% of asthmatics (35% of bronchi) have bronchial artery ratio > 1 (but < 1.5)

    • Bronchial dilatation (30%)

      • Subsegmental bronchi larger than adjacent artery or nontapering airway morphology (typically cylindrical)

      • Bronchiectasis consider: APBA, irreversible airway remodeling, artifactual (from hypoxic vasoconstriction), or physiologic (from ventilation at large lung volumes)

    • Centrilobular micronodules or branching opacities (10-20%)

      • Finding most likely to be seen in patients with near-fatal asthma

  • Lung parenchyma

    • Decreased lung attenuation (50%)

    • Air-trapping (total volume > 1 segment) 50%

    • Mosaic lung attenuation

      • Degree of mosaic attenuation correlates with degree of asthma

    • Emphysema rare

      • Debatable whether secondary to asthma, usually only seen in those who smoke

Radiographic Findings

Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Asthma

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