Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Two The Thorax 129
Fig. 2-102 A 6-year-old female
mixed breed dog with a history of
poor exercise tolerance, lethargy, and
abdominal distention. The cardiac
silhouette is enlarged. A, On the lateral
radiograph the cranial aspect of
the cardiac silhouette is rounded and
the cardiac apex is elevated from the
sternum. B, On the ventrodorsal
radiograph the right side of the cardiac
silhouette is rounded. There is a
bulge on the left side of the cardiac
silhouette in the area of the main
pulmonary artery segment. The pulmonary
arteries are enlarged and
tortuous (arrows) on both radiographs.
There is an increase in pulmonary
interstitial density, especially
in the caudal dorsal lung lobes.
Diagnosis: Dirofilariasis.
A
B
Slight bulging in the area of the main pulmonary artery may be observed in normal
dogs. This may be due to rotation of the heart within the thorax, exposure of the radiograph
during systole, or malpositioning of the animal.
The main pulmonary artery is seen best by echocardiography on the right parasternal
short-axis view high on the base through the pulmonic valve region. The pulmonary artery
is normally the same diameter as the valvular orifice. The right and left pulmonary arteries
normally have a smaller diameter than the main pulmonary artery.