Diagnostic imaging in adult non-cystic fibrosis bronchiectasis

Radiology plays a key role in the diagnosis of bronchiectasis, defined as permanent dilatation of the bronchial lumen. Volumetric thin-section multidetector computed tomography is an excellent noninvasive modality to evaluate bronchiectasis. Bronchiectasis is categorised by morphological appearance. Cylindrical bronchiectasis has a smooth tubular configuration and is the most common form. Varicose bronchiectasis has irregular contours with alternating dilating and contracting lumen. Cystic bronchiectasis is the most severe form and exhibits saccular dilatation of bronchi. Bronchial dilatation is the hallmark of bronchiectasis and is evaluated in relation to the accompanying pulmonary artery. A broncho–arterial ratio exceeding 1:1 should be considered abnormal. Normal bronchi are narrower in diameter the further they are from the lung hila. Lack of normal bronchial tapering over 2 cm in length, distal from an airway bifurcation, is the most sensitive sign of bronchiectasis. Findings commonly associated with bronchiectasis include bronchial wall thickening, mucus plugging and tree-in-bud opacities. Bronchiectasis results from a myriad of conditions, with post-infectious bronchiectasis being the most common. Imaging can sometimes discern the cause of bronchiectasis. However, in most cases it is nonspecific or only suggestive of aetiology. While morphological types are nonspecific, the distribution of abnormality offers clues to aetiology. KEY POINTS: Bronchiectasis is a chronic progressive condition with significant disease burden and frequent exacerbations, for which the diagnosis relies on cross-sectional imaging. The major imaging findings include bronchial dilatation, bronchial contour abnormalities and visualisation of the normally invisible peripheral airways. Bronchiectasis is the end result of various conditions, including immunodeficiencies, mucociliary disorders and infections. Imaging is often nonspecific with regard to aetiology but can be suggestive. Distribution of abnormality in the lung offers helpful clues for establishing aetiology. EDUCATIONAL AIMS: To review the cross-sectional imaging appearance of bronchiectasis and the common associated findings. To get a sense of how radiology can aid in establishing the aetiology of bronchiectasis.