Discussion
This radiograph demonstrates several findings:
First, this is a COPD patient with very few lung markings seen in the right upper lobe due to severe emphysema.
Second, this patient has undergone endobronchial valve placement leading to complete lobar atelectasis in the left upper lobe. The valves themselves are visible projecting over the left hilum. There is expected volume loss in the left hemithorax, with increased opacity in the left lung due to superimposition of the collapsed left upper lobe and aerated left lower lobe.
Third, a named sign is demonstrated: The luftsichel sign (German for “air crescent”), which is seen as a crescentic lucency in the paramedian left upper lung and indicates left upper lobe collapse. The lucency is created by a portion of the aerated left lower lobe that insinuates itself between the mediastinal wall and the collapsed upper lobe.
Fourth, there is an incidentally noted small hiatal hernia seen as a rounded opacity projecting just to the left of midline at the level of the diaphragm. Diaphragmatic eventration is also noted.