Page 354 - Small Animal Internal Medicine, 6th Edition

326 PART II Respiratory System Disorders

A bronchial pattern with increased interstitial markings (i.e., CBC, serum biochemical panel, urinalysis). Echocar-
is typically seen on thoracic radiographs, but changes are diography may reveal evidence of secondary pulmonary
VetBooks.ir often mild and difficult to distinguish from clinically insig- hypertension, including right heart enlargement (i.e., cor
pulmonale).
nificant changes associated with aging, and radiographs may
Ciliary dyskinesia, in which ciliary motion is abnormal,
be completely unremarkable. Thoracic radiographs are most
useful for identifying other causes of cough or secondary is uncommon but should be considered in young dogs with
diseases. bronchiectasis or recurrent bacterial infection. Abnormali-
Tracheal wash or bronchoalveolar lavage (BAL) fluid ties exist in all ciliated tissues, and situs inversus (i.e., lateral
should be collected at the time of the initial presentation and transposition of the abdominal and thoracic organs, such
after a persistent exacerbation of signs. Tracheal wash will that left-sided structures are found on the right and vice
usually provide a sufficient specimen in diffuse airway versa) is seen in 50% of such dogs. Dextrocardia that occurs
disease. Neutrophilic or mixed inflammation and increased in association with chronic bronchitis is extremely sugges-
amounts of mucus are usually present. The finding of degen- tive of this disease. Sperm motility can be evaluated in intact
erative neutrophils indicates the possibility of a bacterial male dogs. The finding of normal sperm motility rules out a
infection. Airway eosinophilia is suggestive of a hypersensi- diagnosis of ciliary dyskinesia. The disease is diagnosed on
tivity reaction, as can occur with allergy, parasitism, or the basis of the rate at which radioisotopes deposited at the
heartworm disease. Slides should be carefully examined for carina are cleared and the findings from electron micro-
organisms. Bacterial cultures are performed and the results scopic examination of bronchial biopsy, nasal biopsy, or
interpreted as discussed in Chapter 20. Although the role of sperm specimens.
Mycoplasma infection in these cases is not well understood,
Mycoplasma cultures or PCR are also considered. Treatment
Bronchoscopy, with specimen collection, is performed in Chronic bronchitis is managed symptomatically, with spe-
selected cases, primarily to help rule out other diseases. The cific treatment possible only for concurrent or complicating
maximal benefit of bronchoscopy is obtained early in the diseases that are identified. Each dog with chronic bronchitis
course of disease, before severe permanent damage has is presented at a different stage of the disease, with or without
occurred and while the risk of the procedure is minimal. concurrent or secondary cardiopulmonary disease (see Box
Gross abnormalities visualized by bronchoscopy include an 21.3). Hence each dog must be managed individually. Ideally,
increased amount of mucus, roughened mucosa, and hyper- medications are initiated one at a time to allow assessment
emia (Video 21.1). Major airways may collapse during expi- of the most effective combination. It will likely be necessary
ration as a result of weakened walls (Fig. 21.3), and polypoid to modify treatment over time.
mucosal proliferation may be present. Bronchial dilation
may be visualized in animals with bronchiectasis. GENERAL MANAGEMENT
Further diagnostic procedures are indicated to rule out Exacerbating factors, either possible or proven, are avoided.
other potential causes of chronic cough, and selection of Potential allergens are considered in dogs with eosinophilic
these depends on the presenting signs and results of the inflammation and trial elimination pursued (see the section
previously discussed diagnostic tests. Diagnostic tests to be on allergic bronchitis). Exposure to irritants such as smoke
considered include heartworm tests, fecal examinations for (from tobacco or fireplace) and perfumed products should
pulmonary parasites (flotation, Baermann, and sediment be avoided in all dogs. Motivated clients can take steps to
examinations), echocardiography, and systemic evaluation improve the air quality in their home through carpet, furni-
ture, and drapery cleaning; cleaning of the furnace and fre-
quent replacement of air filters; and the use of an air cleaner.
The American Lung Association has a useful Web site with
nonproprietary recommendations for improving indoor air
quality (www.lung.org). Excitement or stress can cause an
acute worsening of signs in some animals, and short-term
tranquilization with acepromazine or sedation with pheno-
barbital can be helpful in relieving the signs for short periods.
Anxiolytic drugs, such as trazadone, may be beneficial if
long-term control is needed.
It is normal for flora from the oropharynx to be aspirated
A B into the airways. Routine dental prophylaxis and teeth
brushing will help maintain a healthy oral flora and may
FIG 21.3 decrease any contributions of normal aspiration to ongoing
Bronchoscopic view of the right caudal bronchus of a dog
with chronic bronchitis and severe bronchomalacia. The airway inflammation in patients with reduced mucociliary
airways appear normal during inspiration (A) but clearance.
completely collapse during expiration, obliterating the lumen Airway hydration should be maintained to facilitate
of the airway (B). mucociliary clearance. Adequate airway hydration is best