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Radiological Findings

The chest radiograph and esophagram demonstrate extrinsic esophageal impressions and tracheomala-cia, as well as the side of the aortic arch. A right sided aortic arch in a child with respiratory symptoms is suggestive of a double aortic arch. The next examination is often a barium esophagram. A normal esophagram will clearly rule out the presence of a vascular ring. Symptomatic vascular rings caused by double aortic arches with bilateral arch patency cause significant narrowing and anterior bowing of the trachea, which are apparent on the lateral chest radiograph and barium esophagram. On the frontal projection, right and left indentations assume an "S" configuration. The barium esophagram is helpful to determine which component of a double aortic arch is larger. Barium swallow can show the right arch and a posterior esophageal impression (Fig. 2.16). This type of arch is usually associated with congenital heart disease. Advantages of the barium swallow include its ready availability, that f k

Fig. 2.16. Anomalous left pulmonary artery. CT with intravenous contrast medium shows the anomalous left pulmonary artery originating from the right main pulmonary artery, passing posterior to the trachea between the airway and the esophagus (arrowhead)

it does not require sedation, an important feature for children who have airway compromise, and that it can show extrinsic compression by an atretic vascular segment not delineated by CT or MRI (Woods et al. 2001).

Over the last decade, however, the diagnosis of esophageal rings has changed from barium swallow and angiography to cross-sectional imaging (Figs. 2.17 and 2.18). CT angiography and MRI are optimal for more precise pre-operative delineation of the anatomy of the vascular ring (Hernanz-Schulman 2005). CT is more quickly performed, and can often be done without sedation. CT angi-ography can be completed in 20-30 s, whereas MR often requires sedation or immobilization for studies that can take as long as 45 min. The advantage of CT is visualization of the lungs and bronchi, and the diagnostic yield is even enhanced with multiplanar reformations. High-resolution 3D FISP (fast imaging with steady precession) MRA will accurately define vascular rings. This bright blood technique differentiates between vascular and non-vascular structures with higher spatial resolution than spin-echo (Greil et al. 2005). The choice of imaging modality varies with institutional preferences.

Fig. 2.17. Double aortic arch. Barium esophagram with double extrinsic impressions on the barium column. The dominant right arch (R) is higher than the smaller left arch (L)

Fig. 2.17. Double aortic arch. Barium esophagram with double extrinsic impressions on the barium column. The dominant right arch (R) is higher than the smaller left arch (L)

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