Prompt treatment of an infant or child with a suspected esophageal foreign body is crucial because of the potential for severe complications. Radiographic evaluation of the esophageal foreign body is warranted in symptomatic and asymptomatic patients. Ingestions that are witnessed are generally managed without problems. Conversely, diagnosis of nonwitnessed ingestions can often be difficult and delayed. This delay in diagnosis can result in severe morbidity and mortality. [1, 2, 3, 4, 5, 6, 7, 8, 9] See the images below.
See Foreign Bodies: Curious Findings, a Critical Images slideshow, to help identify various foreign objects and determine appropriate interventions and treatment options.
The radiographic evaluation begins with the acquisition of anteroposterior and lateral chest, lateral neck, and supine abdominal radiographs to complete the examination from the nasopharynx to the rectum.
If a child is referred from an outside institution, a repeat chest radiograph can be obtained to reconfirm the presence of the foreign body in the esophagus or confirm its passage beyond the esophagus, obviating a retrieval procedure.
If the presence of a nonradiopaque object is suspected after the initial series of radiographs is obtained, contrast-enhanced esophagography is indicated to rule out a radiolucent foreign body. Further evaluation with cross-sectional imaging may be required to determine the presence and extent of mediastinitis versus mediastinal abscess formation. [4, 10]
Limitations of techniques
The major limitation of the initial plain radiographic evaluation is the potential failure to visualize the nonradiopaque foreign body. Small esophageal foreign bodies may also be difficult to visualize on plain radiographs alone. Additional evaluation is required when the suspected foreign body is not radiopaque or when the presence of a retained object is highly suspected. The initial radiographic evaluation also can cause underestimation of the extent or degree of involvement, such as the amount of edema with foreign bodies that are retained for long periods.
The initial plain radiographic series is crucial in the diagnosis of an esophageal foreign body, because the location and characteristics of the esophageal foreign body direct treatment. The most common site of foreign body lodgment is the upper esophagus at the level of the thoracic inlet. 
On the frontal chest radiograph, an opaque foreign body is depicted at the midclavicular level. A coin in the esophagus is depicted in the coronal plane of a frontal image because of the inherent configuration of the esophagus. If the coin is in the sagittal plane of the frontal image, the foreign body most likely is in the trachea. The orientation is generally caused by the incomplete circumferential cartilaginous rings along the posterior aspect of the trachea that allow the coin to protrude posteriorly. (See the images below.) [12, 13]
The second most common site for esophageal foreign body retention is the level of the carina and aortic arch because of normal physiologic narrowing in the mid esophagus at this level. The third location is the distal esophagus slightly above the gastroesophageal junction. On the frontal chest radiograph, this location is approximately 3 vertebral body levels above the gastric air bubble. If a radiopaque foreign body is seen at another level, an underlying stricture should be suspected, and further investigation with contrast-enhanced esophagography is indicated.
The characteristics of the object (eg, radiopaque or radiolucent and sharp or blunt) and the number of retained items affect the choice of retrieval method. Additional plain radiographic findings may include soft-tissue masses; these may represent inflammatory changes and possibly indicate a more chronic process.
Tracheal displacement or compression suggests mediastinal inflammation and airway compromise (see the images below). An air-fluid level suggests mediastinal abscess formation, whereas a pneumomediastinum may indicate an esophageal perforation.
If the presence of a nonradiopaque foreign body is suspected, contrast-enhanced esophagography is indicated. Positive findings on the esophagram include irregularity of the contrast medium column or esophageal mucosa, as well as deviation in the expected course of the esophagus. Underlying stricture formation, with or without proximal esophageal dilatation or diverticula formation caused by chronic esophageal perforation, also may be present.
Foreign bodies that migrate outside the esophagus into the mediastinum or soft tissues usually cause respiratory symptoms. Complete foreign body migration outside the esophagus is occult on esophagoscopic images, but it may be depicted on chest radiographs.
Contrast-enhanced computed tomography (CT) scanning is indicated for the assessment of a suspected esophageal foreign body when the plain radiographic findings are negative, the contrast-enhanced esophagographic findings are positive, or the presence of an esophageal foreign body is highly suspected.
CT can aid in characterizing the nature of the foreign body, as well as the presence and extent of surrounding disease such as mediastinitis or abscess formation. Also, small foreign bodies that cannot be visualized with a standard radiologic examination can be evaluated with CT. Chicken and fish bones lodged in the hypopharynx and cervical esophagus are difficult to evaluate on plain radiographs. CT is also valuable in the assessment of complications of foreign body removal. (See the image below.) [14, 15, 16, 17]
CT was found to be a useful method for identification of esophageal fish bone foreign bodies, and the authors of the study suggested that CT be considered a first-choice technique for the diagnosis of esophageal fish bone foreign body. In 88 patients studied with a history of fish bone impaction, 66 patients were discovered to have a fish bone foreign body in the esophagus by CT, as compared to 30 patients by plain radiography. 
Multidetector computed tomography (MDCT) has been found to be useful for the evaluation of pharyngeal and upper esophageal foreign bodies. In one study, the sensitivity of MDCT for the detection of foreign bodies was 100%, which was superior to that of plain radiography (51.7%). 
Magnetic Resonance Imaging
Although magnetic resonance imaging (MRI) is the preferred cross-sectional imaging tool for evaluating the full extent of cervicothoracic masses and the relationships between neurovascular structures, it is not the initial imaging method of choice for the workup for a retained foreign body or traumatic lesion. However, MRIs can readily demonstrate the extent of a mediastinal inflammatory abscess or granuloma formation.