#Answer: You were correct! Atelectasis from mucus plugging of R mainstem bronchus. This patient had severe oropharyngeal dysphagia. The position of the trachea is crucial in formulating a differential for a unilateral lung white-out. Here it is pulled towards the white out, indicating a resorptive atelectasis (also with pulmonary hypoplasia and intubation of bronchus). A pleural space process (effusion, hemothorax) will push the trachea away, while it will remain largely central in a primarily parenchymal (pneumonia, edema) and pleural/chest wall (mesothelioma, tumor) pathology.

Image and write-up credit: Arjun Gupta

A man in his 60’s admitted for myeloma chemotherapy develops acute onset shortness of breath. CXR 12 hours prior (Fig 1) and now (Fig 2) are presented.