title: Air trapping in Wegener's granulomatosis: an additional finding on expiratory chest HRCT.
abstract: OBJECTIVE
  This study was undertaken to assess the presence and extent of air trapping (AT) on high-resolution computed tomography (HRCT) in patients with Wegener's granulomatosis (WG) and to correlate the finding with the inspiratory pattern and bronchial/bronchiolar involvement.
  
  
  METHODS
  Twenty-one patients (7 M/14 F) with WG underwent inspiratory and expiratory HRCT. Images were evaluated for the presence and extent of AT and for airway involvement (bronchi/bronchioles); the predominant HRCT pattern was also documented. The attenuation difference was measured between the areas of AT on expiration and the same areas on inspiration in order to verify the finding of AT. The extent of AT was calculated by visual scoring and correlated with the predominant inspiratory patterns and bronchial/bronchiolar involvement.
  
  
  RESULTS
  AT was found in seven patients (33.3%) and its extent ranged between 3% and 70% (mean 15.8±7). Two patients showed no lesions on inspiratory HRCT, and the only finding was AT on expiration. The attenuation difference between areas of AT on expiration and the same areas on inspiration ranged between 32 and 89 HU. Inspiratory HRCT was pathological in 19 patients (90.4%), and the principal lung patterns were nodular, cavitary or noncavitary (n=7, 38.9%); ground-glass opacities (n=5, 26.3%); masses (n=3, 15.8%); fibrotic (n=3, 15.8%); and consolidation with air bronchogram (n=1, 5.3%). Bronchial and bronchiolar involvement was found in 14 and five patients, respectively. No statistically significant correlation was found between AT extent and the findings on inspiration. In addition, there were no specific patterns that caused higher or lower scores of AT. Moreover, when bronchial or bronchiolar involvement was absent, the mean AT score was statistically significantly higher.
  
  
  CONCLUSIONS
  Areas of AT represent a new and indirect HRCT finding--and in rare cases the only finding--of pulmonary WG. The nonsignificant correlation between AT extent and inspiratory findings may suggest AT as an additional HRCT finding in patients with WG.
authors.affiliation: Department of Radiology, University Hospital of Heraklion, Medical School of Crete, 71110 Stavrakia, Heraklion, Crete, Greece. emagkanas@gmail.com
authors.forename: E
authors.initials: E
authors.lastname: Magkanas
authors.forename: E
authors.initials: E
authors.lastname: Detorakis
authors.forename: I
authors.initials: I
authors.lastname: Nikolakopoulos
authors.forename: S
authors.initials: S
authors.lastname: Gourtsoyianni
authors.forename: M
authors.initials: M
authors.lastname: Linardakis
authors.forename: P
authors.initials: P
authors.lastname: Sidiropoulos
authors.forename: D
authors.initials: D
authors.lastname: Boumpas
authors.forename: N
authors.initials: N
authors.lastname: Gourtsoyiannis
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000388:Air; D001987:Bronchiectasis / Q000000981:diagnostic imaging*; D005260:Female; D014890:Granulomatosis with Polyangiitis / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*