Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Two The Thorax 175
Fig. 2-156 A 5-year-old male
Greyhound had exercise intolerance,
cardiomegaly, and pulmonary nodules.
The two-dimensional echocardiogram
revealed a moderate volume
of pericardial effusion (PE) and a
mass (M) attached to the pericardial
sac. Diagnosis: Hemangiosarcoma.
Ultrasonography will distinguish readily between pericardial fluid and abdominal viscera
within the pericardial sac.
ABNORMALITIES OF THE AORTA
A N E U RY S M
Aortic abnormalities, other than those associated with congenital cardiac disease (e.g.,
PDA, aortic stenosis) or vascular ring anomalies, are uncommon. Aneurysmal dilation in
the descending aorta, as in patent ductus, or aortic arch, as in aortic stenosis, may be
observed in those cases. Aneurysmal dilations of the descending aorta may occur secondary
to Spirocerca lupi infestation in dogs and have been observed as an incidental finding
in asymptomatic dogs. 484,485 In these cases, an enlarged aortic shadow will be visible, especially
on the lateral radiograph. Because of the migration of these parasites in the aortic
regional vessels, nonbridging, nonspondylitic, almost palisading bony reaction may be seen
on the ventral aspect of the regional vertebrae (Fig. 2-158).
C OA R C TAT I O N O F T H E AO RTA
Coarctation of the aorta is narrowing, usually severe, of the aortic lumen. It has been
reported rarely in dogs. 486-488 The lesion will be evident radiographically as a poststenotic
aneurysmal dilation. An angiographic study may be required to establish the diagnosis.
Echocardiography rarely will be helpful, because the lesion is likely to be located away from
the heart and lack a sonographic window. Transposition of great vessels affecting the aortic
arch has been reported also. 489
T U M O R
Aortic body tumors originate from the baroreceptor tissue within the aortic arch. 490-495 A
localized dorsal deviation of the trachea cranial to the bifurcation may be evident when the
mass becomes large (Fig. 2-159). This usually is an abrupt deviation, initially dorsally and
then ventrally, near the ascending aorta. On the dorsoventral or ventrodorsal view, the trachea
may be displaced abruptly to the right as it passes the aortic arch. Aortic body tumors
may extend dorsal to the trachea. The mass also may be apparent cranial to the cardiac silhouette
ventral to the trachea (Fig. 2-160). Invasion of the cranial thoracic vertebral bodies
may occur. Pericardial effusion may accompany aortic body tumors. Flexion of the head
and neck will produce dorsal deviation of the trachea in the cranial mediastinum cranial