title: Expiratory air trapping on thoracic computed tomography. A diagnostic subclassification.
abstract: BACKGROUND
  Multiple causes for air trapping as identified by expiratory computed tomography (CT) have been reported, but a unified evaluation schema has never been proposed.
  
  
  OBJECTIVE
  It was our purpose to identify imaging features that would help distinguish etiologies of mosaic air trapping.
  
  
  METHODS
  Cases with the term "air trapping" in the radiology report in 2010 were identified by searching the Radiology Information System of an academic tertiary care center and associated community hospital. Medical records and CT examinations were reviewed for the causes of air trapping.
  
  
  RESULTS
  Causes for moderate to severe air trapping could be identified in 201 of 230 (87.4%) cases and could be subdivided into those associated with bronchiectasis (76 of 201, 38%), those associated with interstitial lung disease (62 of 201, 31%), those associated with tree-in-bud opacities (5 of 201, 2%), and those with air trapping alone (58 of 201, 29%). When found with bronchiectasis, nontuberculous mycobacteria, cystic fibrosis, idiopathic bronchiectasis, and transplant-related bronchiolitis obliterans were the most common causes of air trapping. When found with interstitial lung disease, sarcoidosis, hypersensitivity pneumonitis, or unspecified interstitial lung disease were the most common cause of air trapping. When found in isolation, chronic bronchitis, asthma, bronchiolitis obliterans, and unspecified small airways disease were the most common causes of air trapping. Unusual conditions causing isolated air trapping included vasculitis and diffuse idiopathic neuroendocrine cell hyperplasia.
  
  
  CONCLUSIONS
  A variety of conditions can cause air trapping. Associated imaging findings can narrow the differential diagnosis.
authors: 1 Department of Radiology, and.
authors: Wallace T
authors: WT
authors: Miller
authors: Jonathan
authors: J
authors: Chatzkel
authors: Michael G
authors: MG
authors: Hewitt
mesh_terms: D001249:Asthma / Q000000981:diagnostic imaging* / Q000503:physiopathology; D001987:Bronchiectasis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D001989:Bronchiolitis Obliterans; D003550:Cystic Fibrosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D003937:Diagnosis, Differential; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000503:physiopathology; D012372:ROC Curve; D015203:Reproducibility of Results; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: air trapping; asthma; bronchiolitis obliterans; chronic bronchitis; computed tomography