Page 508 - Clinical Small Animal Internal Medicine

476 Section 6 Gastrointestinal Disease

(a) (b) Figure 48.4 Moderate generalized
VetBooks.ir dog. Left lateral (a) and dorsoventral (b)
dilation of the esophagus with gas in a
radiographs of the thorax. The ventral wall
of the dilated esophagus is summating
with the dorsal wall of the trachea
resulting in a “tracheal stripe sign” (arrow)
in the lateral radiograph. The borders of
the dilated esophagus (arrowheads) show
in the dorsoventral view a characteristic
V‐shape.

deviation of the trachea and cardiac silhouette may be anomaly, reported in 95% of dogs with vascular ring
noted. When the esophagus is fluid filled, a wide soft tis­ anomaly. In patients with persistent right aortic arch, the
sue attenuating area can be seen in the dorsal aspect of aorta is formed by the right instead of the left fourth aor­
the thorax. In the VD or DV view of megaesophagus, the tic arch. The left ligamentum arteriosum, connecting
esophagus is usually located on or to the right of midline. between the abnormally positioned aorta and the pul­
A fluid‐ or gas‐filled, dilated esophagus typically shows a monary artery, creates a vascular ring anomaly around
V‐shape narrowing from cranially to caudally on a VD or the trachea and esophagus. Approximately one‐third of
DV radiograph, with the narrowest area at the level of the these dogs also have an aberrant left subclavian artery,
esophageal hiatus at the diaphragm. A contrast esopha­ which, in combination with the persistent right aortic
gram is recommended if it is not possible to differentiate arch, can contribute to an additional partial ring forma­
between generalized and focal esophageal dilation. tion, resulting in focal dilation of the esophagus.
In the cat, vascular ring anomalies occur less frequently
than in the dog and reported vascular anomalies include
Vascular Ring Anomalies
a persistent right aortic arch with right or left ligamentum
Vascular ring anomalies are the most common reason arteriosum, double aortic arch or aortic coarctation. If, in
for focal dilation of the esophagus in the cranial medi­ addition to the aforementioned imaging changes, a tra­
astinum. Other, less common causes for focal esophageal cheal stenosis and/or malformation of the tracheal rings
dilation include bronchoesophageal fistulae, neoplasia is present, a double aortic arch should be considered.
or strictures secondary to trauma of the esophagus. In Contrast‐enhanced CT angiography will help to more
addition to regurgitation, patients with vascular ring accurately define and outline the vascular anomaly
anomalies are often smaller than their littermates, have responsible for the focal dilation of the esophagus and
an overall low body condition and can have a history of can therefore help to improve surgical planning.
regurgitation of solid food when weaning.
Vascular ring anomalies are developmental abnormali­
ties of the primordial aortic arches resulting in a com­ Esophageal Foreign Bodies
plete or partial circle of tissue around the trachea and the Esophageal foreign bodies occur commonly in dogs, but
esophagus, causing compression of the encircled struc­ are less commonly noted in cats. Esophageal foreign bod­
tures. Most commonly, a focal dilation of the esophagus ies are most commonly found in the caudal esophagus and
cranial to the base of the heart is noted on imaging stud­ are often located between the heart base and the dia­
ies. Additionally, a marked focal leftward shift of the phragm. However, esophageal foreign bodies in the mid‐
trachea is noted on DV or VD radiographs. A ventral mediastinum dorsal to the heart, in the cranial mediastinum
deviation of the esophagus can be noted on lateral radio­ cranial to the heart as well as just caudal of the pharynx
graphs (Figure 48.5). In the dog, the persistent right aor­ have also been reported. Esophageal obstruction second­
tic arch is the most commonly encountered vascular ary to foreign bodies can lead to perforation (Figure 48.6).