Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Two The Thorax 61
Fig. 2-35 A pulsed wave Doppler study of the
tricuspid valve made from the right parasternal
short-axis view reveals normal E and A deflections.
The maximal velocity is 0.5 meter per
second. Diagnosis: Normal study.
A
Fig. 2-36 A 14-year-old male Yorkshire Terrier with nasal obstruction and dyspnea. The thorax is normal.
The aorta is redundant and extends cranial to the cardiac silhouette (arrows) on the lateral radiograph
(A) and also extends into the left hemithorax (arrows) on the ventrodorsal radiograph (B). This
elongation and redundancy of the aorta is seen often in normal, old dogs. There is no evidence of pulmonary
metastasis. The cardiac silhouette is of normal size and shape. Diagnosis: Normal thorax.
shorter at expiration and collapses slightly during diastole. The caudal vena cava has been
reported to be equal to or shorter than the length of T5 or T6 in dogs. 51
The caudal vena cava is identified more easily in the ventrodorsal than the dorsoventral
radiograph. It can be traced from the heart to the diaphragm along the right side of the
vertebral column. The width of the caudal vena cava in the ventrodorsal view is usually
uniform and, although a mild, even curvature is not abnormal, its margins should be
smooth, straight, and parallel.
The visibility of the caudal vena cava depends on aeration of the accessory lung lobe.
Poor margin definition may be observed on expiratory radiographs, on dorsoventral radiographs,
and in animals with accessory lung lobe infiltrates.
B