Radiological Techniques of Examination

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An empty esophagus is not visible on plain radiographs or CT. However, the esophagus is not uncommonly outlined by air in a child that is crying and swallowing large amounts of air (Fig. 2.1). An air-filled esophagus is also frequently seen in neonates ventilated with continuous positive airway pressure (CPAP), as well as in those with tracheo-esophageal fistula, esophageal stricture and achalasia (Fig. 2.2). In children with developmental delay, air in the esophagus is a common finding, and is usually secondary to reflux.

Despite the current emphasis on the superb diagnostic possibilities of CT and MR, the conventional barium examination still remains the most important modality for evaluating patients with dyspha-gia, gastroesophageal reflux and other symptoms referable to the esophagus (Levine and Rubesin 2005). The barium swallow, or esophagram, provides anatomic and functional information about the esophagus along its entire course. Radiation safety and dose reduction are important factors to consider for pediatric imaging, and fluoroscopy time must be carefully monitored. Dose reduction is achieved with low-dose pulsed fluoroscopy. "Last image hold" on the monitor helps to reduce fluoroscopy exposure. Because fine mucosal detail is not the main object in routine esophagrams, image capture from the disc provides sufficient information without additional radiation.

Barium suspension is the most frequently used contrast medium. Children above 6 months of age who are reluctant to drink barium may be encouraged by adding additional flavoring to the barium. Any commercially available chocolate syrup or instant drinking chocolate powder renders the barium more palatable without altering its radiographic characteristics. It is advisable to check for allergies and to be aware that some commercial flavoring preparations contain allergenic products.

Noraml Lateral Chesty Xray Oedophagus
Fig. 2.1a,b. Air outlining a normal esophagus. AP (a) and lateral chest (b) radiographs of a crying infant with an air-filled esophagus (arrow)
Fig. 2.2. Air-filled esophagus. Esophageal malposition of the endotracheal tube with resultant gaseous gastric and esophageal distention and right upper lobe atelectasis

Some children find chilled barium more palatable. Barium must not be used if either esophageal perforation or massive aspiration is suspected. Such patients are best studied with water-soluble low osmolar non-ionic contrast media. Gastrografin, due to its high osmolality, should never be used in infants or in any patients lacking adequate airway protection. Its use must be restricted to older, stable and neurologically unimpaired patients.

Children who are to undergo barium swallow examinations must be fasting. A child who is not hungry will simply refuse to drink barium. The duration of fasting depends on the child's age, and should be no longer than the child's routine time between feeds. Premature infants should fast 2-3 h, and infants up to 3 months fast 3-4 h. Children above 2 years can fast up to 6 h. To minimize parental and patient discomfort, fasting children are best scheduled for examinations early in the morning. Older children and adolescents will be most comfortable swallowing barium in the erect position. Infants and younger children are examined recumbent, and require immobilization. Effective immobilization decreases fluoroscopy time, and ensures clear and diagnostic images. Safe and convenient immobilization is accomplished with a device such as the Octagon board (Octostop, Laval, Qc, Canada) which enables immobilization, as well as rotation of the child into any position, including true lateral and oblique. This device facilitates positioning with the infant's arms above the neck so that the esophagus is not obscured during fluoroscopy. Barium can be very conveniently administered with the modified Poznanski technique using an 8-F feeding tube inserted through the end hole of a nipple and injected via syringe (Kuhns and Poznanski 1972; Poznanski 1969). The side holes of the feeding tube are further from the tip, so the tube must be advanced all the way through the nipple and the protruding 1-cm cut so that the tube is almost flush with the nipple in order to prevent gagging. When the nipple is loosely attached to the face with paper tape, this "hands free" technique ensures that no hand or bottle obscures the mouth or pharynx during the examination and also decreases exposure to the radiologist. Barium is injected at a rate that is easily judged by observing a few trial sips of contrast medium prior to commencing fluoroscopy. This rate of administration of barium should be maintained to prevent aspiration. Older children may be fed from a cup or they may drink through a straw if they are examined in the upright position. When evaluating for gastroesophageal reflux, the volume of barium administered should be the same as that of a normal feed. If the child refuses to drink sufficient barium, the volume can be augmented with milk or juice after the anatomy to the level of the duodenojejunal flexure has been evaluated.

Swallowing begins in the mouth when chewed food or liquid reach the back of the tongue which then elevates and propels the oral contents posteriorly to the pharynx while the soft palate elevates to occlude the nasopharynx. The larynx and hyoid bone are seen to elevate as the oropharynx contracts, propelling the bolus distally while the epi

Fig. 2.3. Normal mucosal folds. Parallel linear mucosal in an infant's empty esophagus

glottis closes to protect the airway. The oral and pharyngeal phases of swallowing are evaluated in the lateral position to avoid overlap with the skull and spine. Peristalsis begins in the cervical esophagus, and the bolus passes inferiorly with a smooth primary stripping wave (Schlesinger and ParkeR 2004). Distal to the cervical esophagus, the esophagus is evaluated in the oblique position and true lateral, thus projecting the esophagus off the spine and avoiding overlap. Gravity helps the esophagus to clear, and infants with poor esophageal motility may benefit by tilting the fluoroscopy table into a more upright position. The distended esophagus has a smooth and regular outline. In its collapsed state, the mucosal folds appear as parallel, longitudinal lines 1-2 mm thick (Fig. 2.3). The esophagram in children should always include the stomach and the duodenum to the level of the duodenojejunal flexure to observe gastric emptying and to document normal bowel rotation. Cross-sectional imaging has limited application in evaluation of the esophagus, but is invaluable in cases with extrinsic compressive masses and vascular rings.

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