Imaging description

Initial imaging evaluation for retropharyngeal abscess consists of a lateral radiograph of the cervical soft tissues. In the setting of either retropharyngeal abscess or cellulitis, there is usually marked thickening of the prevertebral soft tissues. The degree of thickening typically exceeds 50% of the anterior-posterior (AP) diameter of the adjacent vertebral body (Figure 94.1) [1]. In severe cases there may be anterior displacement of the airway and/or loss of normal cervical lordosis due to soft tissue expansion. Identification of soft tissue gas is the only method to distinguish abscess from cellulitis alone on radiography. Sensitivity and specificity of lateral neck radiography for retropharyngeal abscess has been reported to be 80% and 100%, respectively [2].

Pseudothickening of the cervical soft tissues results from neck flexion, expiration, or swallowing during radiography. This entity is particularly common in infants and young children, where the neck is short [3]. There is apparent widening of the pre-vertebral soft tissues that mimics abscess or cellulitis (Figure 94.2).