Imaging description

The imaging hallmark of foreign body aspiration is static lung volume that persists over the respiratory cycle [1]. A unilateral hyperlucent lung is often identified but not required (Figure 90.1). In most pediatric patients this is evaluated with bilateral decubitus views in addition to the conventional frontal and lateral projections. Normally the dependent lung should become more opaque with atelectasis on decubitus imaging. In the setting of aspiration, the affected lung either remains lucent on the ipsilateral decubitus view, or does not increase in opacity to the same extent as the contralateral lung due to partial bronchial obstruction.

In older and more compliant patients, expiratory views may be performed in lieu of decubitus projections. Expiration may reveal persistent lucency in the setting of aspiration, while the normal lung should become more opaque.

The majority of foreign bodies are radiolucent [2]. In some cases there is interruption of the air-filled bronchus at the level of the aspirated foreign body, known as the interrupted bronchus sign (Figure 90.2) [3].

Importance

Suspicion of foreign body aspiration on radiographs should prompt an urgent bronchoscopy for retrieval. Delay in diagnosis may result in bronchial rupture, bronchopulmonary fistula, prolonged hospitalization, and chronic or recurrent pulmonary infection [4].