Table 2

Examples of other common causes of dilated bronchi

Other causes of dilated bronchiHow to differentiate from bronchiectasis
Normal ageing
High altitude
Clinical context is key
Bronchial dilatation tends to be generalised and mild (broncho–arterial ratio <1.5:1)
No associated imaging findings of airway disease or inflammation
Regional hypoxiaBronchial dilatation usually mild
Bronchi may actually be normal in diameter but have increased broncho–arterial ratio due to small pulmonary artery secondary to hypoxic vasoconstriction
BronchopneumoniaAcute clinical symptoms
Comparison to prior studies
May require re-imaging