Table 1

Differential diagnosis of unilateral hyperlucent lung

Anatomical siteRadiological and supportive findingsAbnormalities
1.Technical issueHyperlucency on the side to which patient is rotatedRotation
2.Chest wallNormal vasculature of hyperlucent sidePoland syndrome (hypoplasia of pectoralis muscle)
3.Pleural spacesThin sharp pleural line with no vascular markings peripheral to itPneumothorax
4.Parenchymal defectObstructive hyperinflation: hyperlucent lung with spreading and narrowing of pulmonary vessels
Characteristic appearance: at full expiration normal lung volume decreases whereas the diseased side volumes remain fairly similar
Compensatory hyperinflation: small or normal sized hyperlucent lung, spreading of the vascular markings and displacement of the ipsilateral hilum with normal decrease in volume of lung in the expiratory films
Congenital lobar emphysema
Swyer–James–MacLeod syndrome
Unilateral bullous emphysema or cystic lung diseases
5.Vascular defect: congenitalHyperlucent lung, a small hilum, poor vascularisation, and ipsilateral shift of the mediastinum
Normal reduction in lung size on expiration
Aplasia of a pulmonary artery (its proximal interruption) and pulmonary hypoplasia
Vascular defect: acquiredUnilateral hyperlucent lung with no evidence of air trapping on both inspiratory and expiratory radiographs
Normal sized lung and the ipsilateral hilum is normal size/ enlarged
Pulmonary thromboembolism, fibrosing mediastinitis, sequelae of mediastinal irradiation
6.Airway defectAbnormally large affected side even in expiratory film
Obstruction in spirometry
Unilateral obstruction: bronchial atresia, extrinsic and intrinsic causes of bronchial compression (such as a foreign body), endobronchial tumours