AIR-TRAPPING IN EXTRINSIC ALLERGIC ALVEOLITIS ON COMPUTED-TOMOGRAPHY

Aim To document the phenomenon and distribution of air-trapping on com puted tomography in patients with sub-acute extrinsic allergic alveoli tis (EAA). Patients and methods: A retrospective analysis of high reso lution CT scans,vas performed on 20 patients with proven EAA. All pati ents had inspiratory scans and 12 patients had expiratory scans. These were assessed for the presence and distribution of: air-trapping, gro und-glass opacification and nodularity. Results: Areas of decreased at tenuation consistent with small airways disease mas demonstrated in 15 /20 patients on inspiratory scans, and confirmed to be areas of air-tr apping 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 enhanc ed by performing expiratory scans.