Tubular Y-shaped nonenhancing lesion in the apicoposterior segment of the left upper lobe, a finding consistent with mucus impaction of the S1-2 bronchus (bronchocele). Surrounding fibrotic changes. Decreased attenuation is seen around fibrotic changes, a finding indicative of associated air trapping. These CT features are diagnostic of bronchial atresia.
Large zone of decreased attenuation is seen in lateral basal segment of left lower lobe with dilated bronchus in central area with no connection to main bronchial tree. This finding is due to bronchial atresia and air trapping.