Page 357 - Small Animal Internal Medicine, 6th Edition

CHAPTER 21 Disorders of the Trachea and Bronchi 329

TABLE 21.2
VetBooks.ir Differential Diagnoses (Etiologic) for Cats With Presenting Signs of Bronchitis

DISTINGUISHING FEATURES COMPARED WITH IDIOPATHIC FELINE BRONCHITIS
DIAGNOSIS
Allergic bronchitis Dramatic clinical response to elimination of suspected allergen(s) from environment
or diet.
Pulmonary parasites (Aelurostrongylus Thoracic radiographs may have a nodular pattern; larvae (Aelurostrongylus) or eggs
abstrusus, Capillaria aerophila, identified in tracheal wash or BAL fluid or in the feces. See Chapter 20 for
Paragonimus kellicotti) appropriate procedures for fecal testing.
Heartworm disease Pulmonary artery enlargement may be present on thoracic radiographs; positive
heartworm antigen test or identification of adult worm(s) on echocardiography
(see Chapter 10).
Bacterial bronchitis Intracellular bacteria in tracheal wash or BAL fluid and significant growth on culture
(see Chapter 20).
Mycoplasmal bronchitis Positive PCR test or growth of Mycoplasma on specific culture of tracheal wash or
BAL fluid (presence may indicate primary infection or secondary infection, or may
be incidental).
Idiopathic pulmonary fibrosis Radiographs may show more severe infiltrates than expected in cats with idiopathic
bronchitis. CT findings may be supportive. Diagnosis requires lung biopsy (see
Chapter 22).
Carcinoma Radiographs may show more severe infiltrates than expected in cats with idiopathic
bronchitis. Cytologic or histologic identification of malignant cells in tracheal
wash or BAL fluid, lung aspirates, or lung biopsy. CT findings may be supportive.
Histologic confirmation is ideal.
Toxoplasmosis Systemic signs usually present (fever, anorexia, depression). Radiographs may show
more severe infiltrates than expected in cats with idiopathic bronchitis, possibly
with a nodular pattern. Diagnosis is confirmed by identification of organisms
(tachyzoites) in tracheal wash or BAL fluid. Rising serum antibody titers or
elevated IgM concentrations are supportive of the diagnosis (see Chapter 98).
Aspiration pneumonia Unusual in cats. History supportive of a predisposing event or condition.
Radiographs typically show an alveolar pattern, worse in the dependent (cranial
and middle) lung lobes. Neutrophilic inflammation, usually with bacteria, in
tracheal wash fluid.
Idiopathic feline bronchitis Elimination of other diseases from the differential diagnoses.

BAL, Bronchoalveolar lavage; CT, computed tomography; PCR, polymerase chain reaction.

severity of signs and responses to therapy shows this diver- BOX 21.5
sity. Different combinations of factors that result in small
airway obstruction—a consistent feature of feline bronchial Factors That Can Contribute to Small Airway
disease—are present in each animal (Box 21.5). Some of Obstruction in Cats With Bronchial Disease
these factors (e.g., bronchospasm, inflammation) are revers-
ible, and others (e.g., fibrosis, emphysema) are permanent. Bronchoconstriction
The classification proposed by Moise et al. (1989), which Bronchial smooth muscle hypertrophy
was formulated on the basis of similar pathologic processes Increased mucus production
Decreased mucus clearance
that occur in people, is recommended as a way to better Inflammatory exudate in airway lumens
define bronchial disease in individual cats for the purpose Inflammatory infiltrate in airway walls
of treatment recommendations and prognostication (Box Epithelial hyperplasia
21.6). A cat can have more than one type of bronchitis. Glandular hypertrophy
Although it is not always possible to absolutely determine Fibrosis
the type or types of bronchial disease present without per- Emphysema
forming sophisticated pulmonary function testing, routine
clinical data (i.e., history and physical examination find-
ings, thoracic radiographs, analysis of airway specimens,