If a hilum is displaced, ask yourself if it has been pushed or pulled
The hila consist of vessels, bronchi and lymph nodes. On a chest X-ray, abnormalities of these structures are represented by a change in position, size and/or density.
Hilar enlargement may be unilateral or bilateral, symmetrical or asymmetrical. In combination with clinical information, each of these patterns is often helpful in reaching a diagnosis. Bilateral, symmetrical hilar enlargement should raise the suspicion of sarcoidosis, particularly if there is evidence of paratracheal enlargement, or lung parenchymal shadowing.
If a hilum has moved, you should try to determine if it has been pushed or pulled, just like you would for the trachea. Ask yourself if there is a lung abnormality that has reduced volume of one hemithorax (pulled), or if there has been increase in volume or pressure of the other hemithorax (pushed).