Page 317 - Small Animal Internal Medicine, 6th Edition

CHAPTER 20 Diagnostic Tests for the Lower Respiratory Tract 289

finding of arteries larger than their companion veins indi­
BOX 20.1 cates the presence of pulmonary hypertension or thrombo­
VetBooks.ir Common Lower Respiratory Tract Differential Diagnoses embolism, most commonly caused by heartworm disease—a
finding seen in both dogs and cats (Fig. 20.2). The pulmo­
for Dogs and Cats With Respiratory Signs and Normal
nary arteries often appear tortuous and truncated in such
Thoracic Radiographs
animals. Concurrent enlargement of the main pulmonary
Respiratory Distress artery and the right side of the heart may be seen in affected
Pulmonary thromboembolism dogs. Interstitial, bronchial, or alveolar infiltrates may also
Acute aspiration be present in cats and dogs with heartworm disease as a
Acute pulmonary hemorrhage result of concurrent inflammation, edema, or hemorrhage.
Acute foreign body inhalation Infection with Aelurostrongylus abstrusus can also cause pul­
monary artery enlargement.
Cough Veins larger than their companion arteries indicate the
Canine infectious respiratory disease complex presence of congestion resulting from left­sided heart failure.
Canine chronic bronchitis Pulmonary edema may also be present.
Collapsing trachea Dilation of both arteries and veins is an unusual finding,
Feline bronchitis (idiopathic) except in young animals. The finding of pulmonary overcir­
Acute foreign body inhalation
Gastroesophageal reflux* culation is suggestive of left­to­right cardiac or vascular
shunts, such as patent ductus arteriosus and ventricular
*Gastroesophageal reflux is a common cause of cough in people. septal defects.
Documentation in dogs and cats is limited, but the possibility should The finding of smaller­than­normal arteries and veins
be considered. may indicate the presence of pulmonary undercirculation or
hyperinflation. Undercirculation most often occurs in com­
bination with microcardia resulting from hypoadrenocorti­
cism or other causes of severe hypovolemia. Pulmonic

BOX 20.2
Differential Diagnoses for Dogs and Cats With Abnormal
Pulmonary Vascular Patterns on Thoracic Radiographs

Enlarged Arteries
Heartworm disease
Aelurostrongylosis (cats)
Pulmonary thromboembolism
Pulmonary hypertension

Enlarged Veins
Left-sided heart failure

Enlarged Arteries and Veins (Pulmonary Overcirculation)
Left-to-right shunts
Patent ductus arteriosus
Ventricular septal defect
Atrial septal defect
Small Arteries and Veins
Pulmonary undercirculation
Cardiovascular shock
Hypovolemia
• Severe dehydration
• Blood loss
• Hypoadrenocorticism FIG 20.2
Pulmonic valve stenosis Dilation of pulmonary arteries is apparent on this
Hyperinflation of the lungs ventrodorsal view of the thorax in a dog with heartworm
Feline bronchitis (idiopathic) disease. The artery to the left caudal lung lobe is extremely
Allergic bronchitis enlarged. Arrowheads delineate the borders of the arteries
to the left cranial and caudal lobes.