Air-trapping in extrinsic allergic alveolitis on computed tomography.

AIM

To document the phenomenon and distribution of air-trapping on computed tomography in patients with sub-acute extrinsic allergic alveolitis (EAA).

PATIENTS AND METHODS

A retrospective analysis of high resolution CT scans was performed on 20 patients with proven EAA. All patients had inspiratory scans and 12 patients had expiratory scans. These were assessed for the presence and distribution of: air-trapping, ground-glass opacification and nodularity.

RESULTS

Areas of decreased attenuation consistent with small airways disease was demonstrated in 15/20 patients on inspiratory scans, and confirmed to be areas of air-trapping in 11/12 patients on expiratory scans. Additional areas of air-trapping were identified in 5/11 patients on expiratory scans. 18/20 patients had found-glass opacification and 14/20 patients demonstrated a nodular patter.

CONCLUSION

Air-trapping is a common finding in sub-acute extrinsic allergic alveolitis on CT and its detection is enhanced by performing expiratory scans.