Signs of positive mass effect on the right include:
- shift of the mediastinum and trachea (blue) to the left
- leftward bowing of the azygo-oesophageal recess (yellow)
- splaying of the ribs on the right (red)
On the lateral film one knows that the affected side is the right because:
- the aortic arch is visible (orange)
- the visible hemidiaphragm and pleural surface (green) abuts the posterior border of the heart (IVC)
- gastric air bubble (purple) abuts the visible hemidiaphragm
Note that the film has been obtained with the right side against the film (opposite to normal) and thus it is the left hemidiaphragm which is magnified.