Respiratory Tract

• local irreversible dilatation of bronchi
• cause of haemoptysis, chronic sputum

• Bronchial obstruction
• Bronchial wall damage
• Parenchymal fibrosis

3 pathological subtypes

• cylindrical - uniform airway dilatation
• varicose - nonuniform
• serpiginous
• cystic

• thickened bronchial walls - single or tramlines
• dilated bronchi can fill with mucous or pus - tubular, ovoid
• cystic - multiple thin walled ring shadows with air fluid levels

HRCT

• dilated bronchi +/- wall thickening
• lack of tapering of bronchial lamina
• signet ring sign (internal bronchial diameter greater than adjacent pulmonary artery
• varicose - beaded appearance
• cystic - string of cysts

Associated bronchiolitis

• small centrilobular nodular and linear branching = tree in bud

MDCT with thin collimation currently technique of choice

Cystic fibrosis and ABPA - bilateral upper lobe distribution

TB - unilateral upper lobe

childhood viral - lower lobe distribution

CT not very good at diagnosing specific aetiologies of bronchiectasis.