Abnormal bronchus morphology Traction bronchiectasis 2020-04-25T12:55:04Z Distortion of the bronchial airways due to mechanical traction on the bronchi resulting from fibrosis of the surrounding lung parenchyma. CT findings represent irregular bronchial dilatation caused by surrounding retractile pulmonary fibrosis. Dilated airways are usually identifiable as such but may be seen as cysts. The juxtaposition of numerous cystic airways may make the distinction from pure fibrotic honeycombing difficult. Also the differentation to peribronchovascular interstitial thickening can be difficult, but they can be distinguished on the basis of symptoms or pulmonary function abnormalities. In addition, patients with traction bronchiectasis have abnormal thick-walled and dilated bronchi that often appear much larger than the adjacent pulmonary artery branches, with a bronchoarterial ratio exceeding 1. This results in the appearance of an additional finding, the signet ring sign (HP:0032175).