The importance of central airway dilatation in patients with bronchiolitis obliterans

BACKGROUND: Bronchiolitis obliterans (BO) is a clinical syndrome characterised by progressive small airway obstruction, causing significant morbidity and mortality. Central airway dilatation is one of its radiological characteristics, but little is known about the clinical and pathological associations between airway dilatation and BO. METHODS: This retrospective study consecutively included patients who underwent lung transplantation due to BO at Kyoto University Hospital from 2009 to 2019. Demographic and histopathological findings of the resected lungs were compared between patients with and without airway dilatation measured by chest computed tomography (CT) at registration for lung transplantation. RESULTS: Of a total of 38 included patients (median age, 30 years), 34 (89%) had a history of hematopoietic stem-cell transplantation, and 22 (58%) had airway dilatation based on CT. Patients with airway dilatation had a higher frequency of Pseudomonas aeruginosa isolation with greater residual volume than those without airway dilatation. Quantitative CT analysis revealed an increase in lung volume to predictive total lung capacity and a percentage of low attenuation volume <−950 HU at inspiration in association with the extent of airway dilatation. Airway dilatation on CT was associated with an increased number of bronchioles with concentric narrowing of the lumen and thickening of the subepithelium of the walls on histology. CONCLUSIONS: In patients with BO, airway dilatation may reflect increased residual volume or air trapping and pathological extent of obstructive bronchioles, accompanied by a risk of Pseudomonas aeruginosa isolation. More attention should be paid to the development of airway dilatation in the management of BO.