21 month old male with wheezing and cough for 6 hours. Otherwise in usual state of health prior to lunch this afternoon. No history of reactive airway disease. 
What is the diagnosis?
Aspirated foreign body (in this case an apple was pulled from the right mainstem bronchus upon bronchoscopy). Notice the hyperinflation of the right lung field, which is asymmetric to the left. The foreign body can act as a ball-valve trapping air on exhalation and producing a hyperinflated lung. This can uncommonly lead to pneumothorax.
If clinically concerned for aspiration make sure to obtain expiratory films, again to evaluate for asymmetry of lung fields. Alternatively, in patients who are not cooperative with expiratory films you may obtain films in the lateral decubitus position – when laying on one’s side the dependent lung should be asymmetrically smaller than the opposing lung. If the lung fields are symmetrical this may be a sign of air trapping in the dependent lung. When ordering decub films you should obtain both left and right. You may consider CT. Definitive study and therapy is bronchoscopy.
