Page 294 - Small Animal Internal Medicine, 6th Edition

266 PART II Respiratory System Disorders

88 days (95% confidence interval [CI], 65-106 days) and evaluation of the nasal cavity is indicated (see Chapters
of dogs without epistaxis was 224 days (95% CI, 54-467 13 and 14). Nasal radiographs reveal increased soft tissue
VetBooks.ir days). The overall median survival time was 95 days (range, opacity with minimal or no turbinate destruction. Classi-
cally, nasal biopsy reveals eosinophilic inflammation. It is
7-1114 days).
Radiation therapy can prolong survival and improve
response occurs, obscuring the diagnosis. There should be
quality of life in some animals and consultation with a radia- possible that with chronic disease, a mixed inflammatory
tion oncologist is recommended. The therapy is well toler- no indication in any of the diagnostic tests of an aggres-
ated by most animals, and in those that achieve remission the sive disease process, parasites or other active infection,
quality of life is usually excellent. The prognosis for a given or neoplasia.
patient is dependent upon a number of variables, including
histopathologic classification, extent of the tumor, and the Treatment
presence and location of metastatic disease. Early studies Removing the offending allergen from the animal’s environ-
of dogs treated with megavoltage radiation, with or without ment or diet is the ideal treatment for allergic rhinitis. When
prior surgical treatment, found median survival times of this is not possible, a beneficial response may be achieved
approximately 1 year. Less information is available concern- with antihistamines. Chlorpheniramine can be administered
ing prognosis in cats. A study by Theon et al. (1994) of 16 orally at a dose of 4 to 8 mg/dog q12h or 2 mg/cat q12h. The
cats with nonlymphoid neoplasia receiving radiation therapy second-generation antihistamine cetirizine may be more
showed a 1-year survival rate of 44% and a 2-year survival successful in cats. A pharmacokinetic study of this drug in
rate of 17%. Cats with nasal lymphoma treated with radiation healthy cats found a dosage of 1 mg/kg, administered orally
and chemotherapy had a median survival time of 511 days, every 24 hours, to maintain plasma concentrations similar
according to preliminary data from Arteaga et al. (2007). to those reported in people (Papich et al., 2006). Glucocor-
ticoids may be used if antihistamines are unsuccessful. Pred-
nisone is initiated at a dose of 0.25 mg/kg, orally, q12h until
ALLERGIC RHINITIS signs resolve. The dose is then tapered to the lowest effective
amount. If treatment is effective, signs will generally resolve
Etiology within a few days. Drugs are continued only as long as
Allergic rhinitis has not been well characterized in dogs or needed to control signs. Administration of steroids via face
cats. However, dermatologists provide anecdotal reports of mask using a metered dose inhaler, as described for the treat-
atopic dogs rubbing the face (possibly indicating nasal pru- ment of feline bronchitis (see Chapter 21), can also be tried.
ritus) and experiencing serous nasal discharge, in addition Although the inhalers are designed to deliver drug to the
to dermatologic signs. Allergic rhinitis is generally consid- lower airways, some drug will also be deposited within the
ered to be a hypersensitivity response within the nasal cavity nasal cavity.
and sinuses to airborne antigens. It is possible that food
allergens play a role in some patients. Other antigens are Prognosis
capable of inducing a hypersensitivity response as well, and The prognosis for dogs and cats with allergic rhinitis is excel-
thus the differential diagnoses must include parasites, other lent if the allergen can be eliminated. Otherwise, the prog-
infectious diseases, and neoplasia. nosis for control is good, but a cure is unlikely.

Clinical Features
Dogs or cats with allergic rhinitis experience sneezing and/ IDIOPATHIC RHINITIS
or serous or mucopurulent nasal discharge. Signs may be
acute or chronic. Careful questioning of the owner may Idiopathic rhinitis is a more common diagnosis in cats com-
reveal a relationship between signs and potential allergens. pared with dogs. The diagnosis cannot be made without a
For instance, signs may be worse during certain seasons, or thorough diagnostic evaluation to rule out specific diseases
after the introduction of a new brand of kitty litter or new (see Chapters 13 and 14).
perfumes, cleaning agents, furniture, or fabric in the house.
Note that worsening of signs may simply be a result of expo- FELINE CHRONIC RHINOSINUSITIS
sure to irritants, such as cigarette smoke, rather than an
actual allergic response. Debilitation of the animal is not Etiology
expected. Feline chronic rhinosinusitis has long been presumed to be
a result of viral infection with FHV or FCV (see the earlier
Diagnosis section on feline URI). Persistent viral infection has been
Identifying a historical relationship between signs and a par- implicated, but studies have failed to show an association
ticular allergen and then achieving resolution of signs after between tests indicating exposure to or infection with these
removal of the suspected agent from the animal’s environ- viruses and clinical signs. It is possible that infection with
ment support the diagnosis of allergic rhinitis. When this these viruses results in damaged mucosa that is more sus-
approach is not possible or successful, a thorough diagnostic ceptible to bacterial infection or that mounts an excessive