Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

108 Small Animal Radiolo g y and Ultrasono graphy
Fig. 2-81 A 6-year-old male
Doberman Pinscher with a 2-week
history of epistaxis. A, Thoracic
radiographs were obtained before
the dog was anesthetized for aspiration
and flushing of the nasal passages.
B, The second radiograph was
obtained after anesthesia. Marked
thickening of the tracheal wall is evident
(arrows) when B is compared
with A. This is due to accumulation
of exudate in the trachea. This
resulted from the nasal cavity and
frontal sinus irrigation. Diagnosis:
Tracheitis.
A
B
one indistinct or poorly defined margin at the point of tracheal attachment.
Superimposed soft-tissue masses have less distinct margins if surrounded by fat and have
all sides visible if surrounded by air (i.e., on the outside of the animal). If an intraluminal
lesion is not identified on both lateral and ventrodorsal radiographs, the radiograph
that showed the lesion should be repeated and should be centered on the region of interest
to confirm the location of the mass. Ultrasonography has little value in evaluation of
tracheal abnormalities.
T R AC H E A L F O R E I G N B O D I E S
Dense tracheal foreign objects are detected easily; small tissue-dense objects are more easily
overlooked. Larger tracheal foreign bodies may lodge at the tracheal bifurcation. 200
Smaller foreign bodies usually pass into and obstruct an individual bronchus, the right
caudal being the most commonly involved. 201 This may lead to local inflammation and
bronchial thickening. Ideally, the foreign object should be identified on at least two radiographs,
preferably at right angles to each other. When this is not possible, two similarly
positioned radiographs, with one centered on the lesion, are preferred. The sharp, distinct
margins resulting from the air surrounding the tracheal foreign body may not always be
observed.
Radiographic studies using barium or water-soluble iodine-containing contrast agents
have been used for tracheal evaluation. 202,203 However, these are rarely necessary if the
patient is well positioned and properly exposed survey radiographs are obtained.
Tracheoscopy usually is preferable to contrast radiographic studies.
T R AC H E A L D I S P L AC E M E N T
The trachea is an easily identified landmark when evaluating intrathoracic masses. When displaced,
the tracheal position indicates the origin of the mass. Ventral displacement of the cranial
thoracic trachea may occur secondary to esophageal enlargement, periesophageal masses,
or other dorsal mediastinal masses. Dorsal tracheal displacement occurs in association with
masses arising within the mediastinum ventral to the trachea, from right atrial enlargement or