Aspirated foreign bodies, particularly organic material, can cause pneumonia, lung abscess and empyema.
Given the risks of retained aspirated foreign bodies and the small, albeit known risks of bronch (laryngeal lacerations, pneumomediastinum, pneumothorax, etc), a negative bronchoscopic evaluation rate of 10-15% is acceptable.
Hence, the decision to bronch or not lies in the pre-test (bronch) probability of retained foreign body which can be assessed by the usual means (history, physical, chest x-ray [expiratory, decubitus]) as well as admission for short period of observation and/or expert consultation. CT and MRI are generally not part of the evaluation given the young age of the patients, time and expense involved and the need for sedation in a patient with potential pulmonary compromise.
Source
Taussig: Pediatric Respiratory Medicine, 2nd ed.