RT Journal Article SR Electronic T1 Structural differences in airways during chronic rejection after lung transplantation: A (micro)-CT analysis JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP 1855 VO 40 IS Suppl 56 A1 Stijn Verleden A1 Stijn Willems A1 David Ruttens A1 Robin Vos A1 John McDonough A1 Annemie Vaneylen A1 Erik Verbeken A1 Johny Verschakelen A1 Dirk Van Raemdonck A1 Benoït Rondelet A1 Christiane Knoop A1 Marc Decramer A1 James Hogg A1 Geert Verleden A1 Bart Vanaudenaerde YR 2012 UL http://erj.ersjournals.com/content/40/Suppl_56/1855.abstract AB Chronic rejection is a major problem after lung transplantation (Tx) and is accepted to be a small airway disease. Recently a distinction between an obstructive (fBOS) and restrictive phenotype (RAS) has been made. We aimed to investigate structural differences.Human explant lungs from 5 fBOS and 3 RAS patients were collected during reTx, were air-inflated to TLC, frozen solid in liquid nitrogen vapor and frozen specimens were examined by HRCT. Unused donor lung (n=1) served as control. The lungs were kept frozen while cut in 2cm slices and cylinders of 1.4cm diameter were removed. These were fixed at -20°C in a solution of acetone/1% gluteraldehyde and warmed to 25°C, dried and scanned with microCT (skyscan1172, Belgium).HRCT images showed that RAS lungs displayed a lower number of airways starting at generation 5. In patients with fBOS >50% of the airways get obstructed at generation 6 (figure 1), mainly in airways <2mm (82%). MicroCT analysis shows a lower number of terminal bronchioles in RAS patients (2/ml of tissue vs 4.5/ml in fBOS and 5/ml in control, p<0.0001) and a lower average cross-sectional area of remaining terminal bronchioles (110mm² vs 178 in fBOS vs 175 in control).In conclusion: in RAS lungs, both airways>1mm and terminal bronchioles shrink and/or disappear while in fBOS lungs, the airways become obstructed. There was no difference in terminal bronchioles between fBOS and normal lung.