Differential diagnosis of unilateral hyperlucent lung
| Anatomical site | Radiological and supportive findings | Abnormalities | |
| 1. | Technical issue | Hyperlucency on the side to which patient is rotated | Rotation |
| 2. | Chest wall | Normal vasculature of hyperlucent side | Poland syndrome (hypoplasia of pectoralis muscle) Mastectomy |
| 3. | Pleural spaces | Thin sharp pleural line with no vascular markings peripheral to it | Pneumothorax |
| 4. | Parenchymal defect | Obstructive 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 Atelectasis/lobectomy |
| 5. | Vascular defect: congenital | Hyperlucent 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: acquired | Unilateral 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 defect | Abnormally 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 |