In the initial management of stridor, laboratory and radiographic data are often low-yield. Rapid viral antigen testing, heterophile antibody testing, and bacterial cultures may identify specific organisms in cases of infection; however, results from these tests rarely alter initial management. Most causes of stridor are determined clinically; however, imaging studies can be helpful in establishing a definitive diagnosis in specific instances, or when the diagnosis or response to treatment is unclear or unexpected.2
X-ray is often the quickest and most readily available imaging modality in the ED. In cases of significant obstruction in an unstable child, an x-ray can be obtained without the child leaving the ED. While croup should be diagnosed clinically and does not require an x-ray for diagnosis, a soft-tissue neck x-ray may be obtained to help assess for other possible diagnoses such as epiglottitis, neck mass, retropharyngeal abscess, or foreign body. The classic x-ray finding in croup is a “steeple” sign caused by narrowing of the subglottic area. However, a negative x-ray does not rule out the diagnosis, as about half of children with a diagnosis of croup have a normal neck x-ray.34,35 Similarly, the steeple sign is not pathognomonic of croup and, thus, does not unequivocally prove its presence. Epiglottitis has a classic lateral x-ray finding of an enlarged, thickened epiglottis called the “thumbprint” sign.30,36 (See Figure 2.) Maintain a high level of suspicion for epiglottis in a child presenting with drooling, agitation, and no cough. However, given the relatively low incidence of epiglottitis in cases of stridor, radiographs are often obtained to confirm the diagnosis in a stable child.37 Among children with bacterial tracheitis, a lateral neck x-ray may show nonspecific subglottic narrowing or irregularities of the anterior wall known as the “candle dripping” sign.28
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