Page 365 - Small Animal Internal Medicine, 6th Edition

CHAPTER 21 Disorders of the Trachea and Bronchi 337

immediately after stent placement and must be controlled to aeroallergens. For cats that reacted to storage mites or cock-
minimize trauma to the stent. Initially, cough results from roach antigen, discontinuation of any dry food was recom-
VetBooks.ir direct damage to the tracheal endothelium by the stent. In mended (i.e., only canned food was provided). Remission of
signs occurred in three cats given only this treatment. Immu-
addition, ongoing cough from airway inflammation may be
exacerbated by areas of mucus accumulation where the stent
signs in some of the other cats. As a preliminary study, other
does not lie perfectly against the epithelium and chronic notherapy (desensitization) appeared to reduce or eliminate
infections. Results after intraluminal stent placement are suf- treatments were also given to the study cats, and a control
ficiently encouraging that motivated clients with a dog that is population was not described.
failing medical management of tracheal collapse, particularly It is likely that some patients with allergic bronchitis are
related to ventilation, should be referred to someone expe- misdiagnosed because of difficulty in identifying specific
rienced in stent placement for consideration of this option. allergens. In dogs, long-standing allergic bronchitis may
Extraluminal stenting can also be performed with the use result in the permanent changes recognized as canine chronic
of plastic rings. This procedure provides the benefit of great bronchitis. In cats, failure to identify specific allergen(s)
durability over many years. The procedure is technically results in a diagnosis of idiopathic feline bronchitis.
more difficult than intraluminal stenting, perioperative mor- Allergic bronchitis in dogs may result in acute or chronic
bidity is high as a result of damage to laryngeal nerves or cough. Rarely, respiratory distress and wheezing occur. Phys-
other cervical structures, and only the cervical trachea is ical examination and radiographic findings reflect the pres-
readily accessible. However, good success has been reported, ence of bronchial disease, as described in the section on
even in dogs with intrathoracic collapse (Becker et al., 2012). canine chronic bronchitis. Eosinophilic inflammation is
This procedure may be worth considering, particularly in expected in tracheal wash or BAL fluid. Heartworm tests and
very young dogs that otherwise might be expected to outlive fecal examinations for pulmonary parasites are performed to
an intraluminal stent. eliminate parasitism as the cause of eosinophilic inflamma-
tion. In dogs younger than 2 years of age, bronchoscopic
Prognosis evaluation for O. osleri also should be considered (see the
In most dogs clinical signs can be controlled with conscien- following section).
tiously performed medical management, with diagnostic Allergic bronchitis in cats has the same presentation and
evaluations performed during episodes of persistent exacer- results of diagnostic testing as described for idiopathic feline
bation of signs. Animals in which severe signs develop bronchitis, with eosinophilia expected in airway specimens.
despite appropriate medical care have a guarded prognosis, Management of allergic bronchitis is initially focused on
and motivated clients should be referred for possible stent identifying and eliminating potential allergens from the
placement. The following survival data was provided in a environment (see the section on feline bronchitis). Diet trials
study of 27 dogs after intraluminal stent placement: median with novel protein and carbohydrate sources also can be
survival was 502 days; 78% of dogs survived 6 months; 60% considered. According to the preliminary study previously
of dogs survived 1 year; and 26% of dogs survive at least 2 described, a change in diet to canned food may be beneficial
years (Rosenheck et.al., 2017). Ongoing medical manage- in some cases. Such experimentation with environment and
ment is required, and the rate of serious complications from diet is possible only in patients with clinical signs that are
stents has been reported to be approximately 40% (Rosen- sufficiently mild to delay the administration of glucocorti-
heck et al., 2017; Tinga et al., 2015). coids and bronchodilators, as described in the sections on
canine chronic bronchitis and feline bronchitis (idiopathic).
Elimination trials can still be pursued once clinical signs are
ALLERGIC BRONCHITIS controlled with medications, but confirmation of a beneficial
effect will require discontinuation of the medication and, for
Allergic bronchitis is a hypersensitivity response of the a definitive diagnosis to be made, reintroduction of the aller-
airways to an allergen or allergens. The offending allergens gen. The latter may not be necessary or practical in all cases.
are presumably inhaled, although food allergens could also Specific immunotherapy for cats with artificially induced
be involved. A definitive diagnosis requires identification of allergic bronchitis has been reported. Hyposensitization
allergen(s) and resolution of signs after elimination of the regimens for cats and dogs with naturally occurring allergic
allergen(s) or successful hyposensitization. It is well docu- bronchitis hold promise, but criteria for patient selection and
mented that purposeful exposure of cats to inhaled allergens expected success rate have not been established.
can produced feline bronchitis, but large controlled clini-
cal studies describing allergic bronchitis in dogs or cats are
lacking and are complicated by the challenges of ruling out OSLERUS OSLERI
other potential etiologies of bronchitis and differentiating
allergic bronchitis from idiopathic chronic bronchitis (Trzil Etiology
and Reinero, 2014). Oslerus osleri is an uncommon parasite of young dogs,
A study by Prost (2004) presented as an abstract found usually those younger than 2 years of age. Adult worms live
that 15 of 20 cats had positive intradermal skin tests to at the carina and mainstem bronchi and cause a local,