Conventional Radiography in the Evaluation of Foreign Body Aspiration
ABSTRACT & COMMENTARY
Synopsis: In children with proven airway foreign body aspiration, chest radiographs are frequently normal. Children with a history of choking or who have small particles in their mouths and are noted to subsequently have raspy respirations, wheezing, or coughing should undergo bronchoscopy regardless of radiographic findings.
Source: Zerella JT, et al. Foreign body aspiration in children: Value of radiography and complications of bronchoscopy. J Pediatr Surg 1998;33:1651-1654.
Zerella and associates, surgeons at the phoenix children’s Hospital, reviewed the records of 293 children seen over a 10-year period who underwent bronchoscopy for suspected airway foreign body aspiration. A total of 265 patients were proven at bronchoscopy to have foreign body aspiration. A history of a choking episode was obtained from 86% (228/265) of children who had foreign bodies, but it was also present in five of the 28 children with negative bronchoscopies. The prebronchoscopy chest radiograms were considered to be normal in 42% (110/265) and atypical in nine children who had foreign bodies. There were three significant complications of bronchoscopy, only one of which required hospitalization.
Zerella et al conclude that in children with foreign body airway obstruction, chest radiograms are frequently normal or display findings atypical for published characteristic abnormalities. A history of a choking spell is of great importance in determining the need for bronchoscopy. In experienced hands, the risk of bronchoscopy is small—1% in this series.
COMMENT BY MARC S. KELLER, MD
A widely mistaken view adopted by pediatricians who evaluate children suspected of foreign body aspiration is that the purpose of radiographic studies is to rule out this possibility. Such a viewpoint shows a lack of understanding of what these images can accomplish. The use of radiography and fluoroscopy in these children allows detection of foreign bodies in several ways. The most direct, but rarest, finding is that of a radiopaque foreign body seen within the airways. Another manifestation is the presence of a localized parenchymal lung infiltrate from either inflammation or bronchial occlusion within a small area of lung. While this finding implies localized involvement, it does not exclude the possibility of other mobile material within the airway. The radiographic finding of one large lung and one smaller lung is probably the most well-known and sought after finding but, by itself, does not actually diagnose which lung is the abnormal one, as two main pathophysiologies may cause this finding. A ball valve mechanism may result from a foreign body lodged in a mainstem bronchus, allowing the distal lung to hyperinflate in inspiration but not empty in expiration, a situation known as obstructive emphysema. Conversely, a mainstem bronchus may be totally blocked by a wedged foreign body, resulting in distal lung collapse. The purpose, therefore, of either chest fluoroscopy or decubitus views of the chest is to see how patterns of inflation and deflation are disturbed. The decubitus series gives, in two exposures, similar information, since the dependent lung will normally exhibit obligate deflation.
None of the above techniques allows the exclusion of the possibility of either mobile nonobstructive foreign material or of lodged nonobstructive material. The presence of "normal" results should not dissuade the airway surgeon from bronchoscopy when the history and the physical examination call for it.
While I am not as yet advocating the use of routine CT scanning for this purpose, its direct cross-sectional depiction of the airways represents the most sensitive available diagnostic imaging for foreign body detection, as the images rely on direct findings of intraluminal material.
When radiographic studies obtained prior to bronchoscopy are abnormal, both the surgeon and the anesthesiologist will know prior to the procedure if an entire lung is affected and on which side the most prominent aeration disturbance is located. Radiographs after the procedure are helpful to evaluate for complications of the procedure, such as atelectasis or airblock, and to confirm that any preprocedural lesions, such as localized pneumonia, are resolving. (Dr. Keller is Professor of Diagnostic Imaging and Pediatrics and Chief of Pediatric Radiology at the Yale-New Haven Children’s Hospital.)
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