Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Two The Thorax 27
A
Fig. 2-2 A 5-year-old spayed German Shepherd dog was presented for evaluation of the thorax prior
to treatment for heartworm disease. A, In the initial ventrodorsal thoracic radiograph the cardiac silhouette
appears short. There is a prominent pulmonary knob. B, The thoracic radiograph was repeated.
The prominent pulmonary knob is again seen. The cardiac silhouette appears longer. The difference in
cardiac silhouette length is due to geometric distortion resulting from malpositioning of the dog relative
to the x-ray beam. In A the x-ray beam is incorrectly centered over the diaphragm, while in B the
x-ray beam is centered behind the scapulae. There are incidental findings of old fractured ribs on both
the right and left sides. Diagnosis: Enlarged pulmonary artery segment due to heartworm disease.
B
A
B
Fig. 2-3 A 2-year-old female Persian cat with anterior uveitis. Thoracic radiographs were obtained to
evaluate the cat for systemic involvement. A, In the initial lateral thoracic radiograph the thorax is
rotated markedly. The dorsal arches of the ribs are separated (closed arrows). The costochondral junctions
are at widely different levels (open arrows). B, An additional lateral thoracic radiograph was
obtained. The ribs are superimposed, and the costochondral junctions are at the same level. The thoracic
rotation moves the trachea closer to the thoracic spine and creates an apparent cardiomegaly.
Diagnosis: Normal thorax.