An inhaled foreign body (FB) in a child can be easily missed if the diagnosis is not considered, particularly if a history of choking or coughing is not forthcoming, or the episode of aspiration is unwitnessed. Once the diagnosis is suspected a chest radiograph (CXR) is invariably requested. This may provide clues to the diagnosis but a normal CXR does not rule out FB aspiration. Radio-opaque foreign bodies are easily localised, usually within a major airway. However, it can be difficult to identify the radiographic signs associated with an inhaled FB that is not radio-opaque—for example, food or small plastic objects. The presence of an intraluminal FB within the trachea or a bronchus often results in secondary changes in the associated lung or pulmonary lobe. One of the most important signs to identify is obstructive emphysema, or overinflation of the lung or lobe distal to the airway obstruction.

Laryngeal or tracheal FBs can be life threatening if the obstruction is not rapidly cleared, and these children do not usually require imaging in order to make the diagnosis. More commonly, aspirated FBs lodge in either a main or lobar bronchus. There should be no delay in recognising the need for intervention in a symptomatic child. But it is important to remember that organic material such as nuts or beans may swell in the airway, and the inflammatory response to an airway FB may …