Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Two The Thorax 179
Echocardiography frequently will reveal the presence of an aortic body tumor. They are
most common between the aorta and pulmonary artery. The right parasternal short-axis
view of the cardiac base is the most common view used to identify these masses (Fig. 2-161).
C A L C I F I C AT I O N
Calcification of the aorta is rare. It has been observed in association with lymphosarcoma,
renal secondary hyperparathyroidism, atherosclerosis, and Cushing’s disease. 496,497 Thin,
linear calcification will be seen extending along the margins of the aorta (Fig. 2-162). The
aortic valves may be involved.
ABNORMALITIES OF THE CAUDAL VENA CAVA
Isolated abnormalities of the caudal vena cava are rare. 271,498,499 Although most right heart
diseases eventually will cause the caudal vena cava to dilate, its size varies normally with
cardiac cycle and phase of respiration. Invasion of the caudal vena cava by masses
extending from the right atrium, liver, kidney, or adrenal glands, or masses of Dirofilaria
may alter the shape of the vena cava. Diaphragmatic abnormalities also may alter the shape
of the caudal vena cava. The size of the caval foramen may be altered after repair of a
diaphragmatic hernia.
P E R I P H E R A L A RT E R I O V E N O U S C O N N E C T I O N S
On occasion, connections between the arterial and venous systems develop. 500,501 These
create prominent disturbances in circulatory dynamics and can lead to congestive heart
failure as well as to problems such as mass lesions. They can be the result of a congenital
anomaly, focal trauma, neoplasia, and previous surgery. Because these are effectively high
pressure–to–low pressure shunts outside the heart, vascular noise (bruit) often can be
detected. These can occur anywhere including the lung, parenchymal abdominal organs,
and musculoskeletal system. Masses of unknown origin when identified in the presence of
systemic circulatory disturbances should foster consideration of a peripheral arteriovenous
fistula.
PULMONARY ABNORMALITIES
The first step in evaluating the lung on a thoracic radiograph is to be certain that the
technical quality of the radiograph is adequate. Next, evaluate the overall pulmonary
Fig. 2-161 A 7-year-old male Samoyed with exercise intolerance. A
right parasternal short-axis view at the level of the aorta revealed a
mass (m-arrows) between the aorta (ao) and pulmonary artery.
Diagnosis: Aortic body tumor.