How is a suspected aspirated foreign body evaluated?
A nonradiopaque aspirated foreign body in a mainstem bronchus may produce a ball-valve effect, trapping air unilaterally in the lung and creating a large lucent lung compared with the contralateral normal side. These findings may be subtle, but if suspected, expiratory radiographs may make them more obvious because the unaffected lung would lose volume, whereas the affected lung would not. Decubitus radiographs may also exaggerate this difference and are helpful if the patient cannot sit upright, with the unaffected lung losing volume when it is in the dependent position. Pulmonary air trapping may also be shown by fluoroscopy.