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136 Bronchitis, Chronic

Bronchitis, Chronic Bonus Material Client Education
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BASIC INFORMATION
challenging to determine whether cough is
from lower airway disease or tracheal col- bronchoconstriction, as is characteristic
of feline asthma, is uncommon in dogs
Definition lapse. In many cases of mild to moderate with airway disease. Airway narrowing in
Chronic bronchitis (CB) is an inflammatory tracheal collapse, there is also a component dogs is usually due to airway exudate or
disease of the airways characterized by sterile of CB. architectural remodeling.
suppurative inflammation and cough lasting • Small-breed dogs are also predisposed to ○ Crackles (often inspiratory): often best
≥ 2 months in the absence of other identifiable mitral valve disease, which can develop appreciated after a cough (post-tussive
causes. concurrently with CB. Both disorders can crackles) and suggest concurrent pul-
cause cough. monary edema, fibrosis, or secondary
Synonyms • Chronic rhinitis in some dogs (p. 890) pneumonia
Chronic cough, canine asthma (inaccurate), • Syncope (seen with high vagal tone) • Severely affected dogs may have a marked
feline asthma (inaccurate), chronic obstructive • Pulmonary hypertension (p. 838) expiratory push, occasionally with abdominal
pulmonary disease (COPD), chronic asthmatic • Bronchomalacia muscular hypertrophy or “heave” line. Typi-
bronchitis • Emphysema (rare) cally seen with concurrent small airway
collapse/bronchomalacia
Epidemiology Clinical Presentation • Concurrent soft (grade 2 or 3) systolic apical
SPECIES, AGE, SEX DISEASE FORMS/SUBTYPES murmur is common.
• Dogs: middle aged to older • Unless there are comorbid conditions, most • Sinus arrhythmia: normal variant in dogs,
• Cats: any age, but generally older than 1 affected pets seem well other than cough. commonly seen in CB due to increased vagal
year, rare geriatric onset Coughing varies from mild/occasional to tone
frequent/severe. Cats:
GENETICS, BREED PREDISPOSITION • Mild: daily cough, minimal other signs • Cats with bronchitis typically lack the acute
• Small-breed dogs (poodles, terriers) over- • Moderate to severe: frequent and/or severe airflow limitation seen in asthmatic cats
represented cough impacts patient and owner’s quality (status asthmaticus) except in cases of chronic
• Cocker spaniels: increased risk for bronchi- of life asthmatic bronchitis.
ectasis ○ Sometimes, exercise intolerance noted • Rarely, emphysema may result in respiratory
• No clear genetic cause • In cats, bronchitis may be clinically indis- distress that is weakly responsive to
tinguishable from asthma (p. 84). Allergic bronchodilators.
RISK FACTORS asthma is defined by reversible bronchocon- • ± Crackles and wheezes on auscultation: see
• Obesity, bronchomalacia, and tracheal col- striction, eosinophilic airway inflammation, above
lapse are thought to play a role. with evidence of airway remodeling. Airway
• Exposure to irritants such as cigarette cytology (airway eosinophilia vs. neutro- Etiology and Pathophysiology
smoke is intuitively a risk. Although further philia) can help distinguish these two condi- • Causation is unknown but speculated to
studies are needed, epigenetic changes have tions. Pulmonary parasites and feline be secondary to a previous insult (often
been identified in cellular components of heartworm infection can cause a similar unknown) that sets up cycle of chronic
bronchoalveolar lavage (BAL) fluid in clinical appearance and are also characterized inflammation.
dogs exposed to environmental tobacco by eosinophilic airway lavage. • Inflammation results in airway hypertrophy/
smoke. malacia, airflow limitation, excessive mucus
• Prior infectious respiratory disease (as a HISTORY, CHIEF COMPLAINT production, and cough.
puppy or a community-acquired pneumonia) • By definition, cough is the chief complaint. • Cough precipitates further inflammation.
may trigger later bronchitis. Many dogs have a gradual, progressive • Airway hyperreactivity (bronchospasm) may
• Chronic microaspiration (e.g., laryngeal disease course. Sometimes, a historical occur in cats, although this is more com-
paralysis, gastroesophageal reflux disease) precipitating insult can be identified monly seen in asthma (p. 84).
may also contribute. (e.g., cough persists long after resolution • Asthma versus bronchitis in cats: are immu-
• ± Chronic rhinitis (expert opinion rather of infectious airway disease). Respiratory nologically distinct processes. Asthma is
than evidence based) distress is rare in the absence of comorbid presumed to be allergically mediated (T H2
• Aspirated foreign material conditions (e.g., bronchiectasis with pneu- lymphocyte driven), and bronchitis is
• Asthma: chronic allergic inflammation monia, airway collapse, congestive heart thought to be due to a previous airway insult.
leading to airway damage and CB (chronic failure). Because chronic allergic inflammation can
allergic asthma [p. 84]) • Cats may present with wheeze or cough. lead to airway damage, there is some overlap
Clients sometimes mistake cough in cats for between these two conditions (chronic
CONTAGION AND ZOONOSIS hairballs, although no trichobezoar is found asthmatic bronchitis).
Although CB is not due to infection, it is after the episode.
necessary to exclude infectious cases of chronic DIAGNOSIS
cough. PHYSICAL EXAM FINDINGS
Dogs: Diagnostic Overview
GEOGRAPHY AND SEASONALITY • Often overconditioned (body condition score The diagnosis of CB depends on recognition of
Possibly more severe in warmer/humid months, > 6/9) chronic cough and airway inflammation when
but this is not universally reported • Increased tracheal sensitivity on palpation no other cause for these can be identified. The
(inducible cough): nonspecific finding goal of diagnostic testing is to exclude other
ASSOCIATED DISORDERS • ± Wheezes or crackles on lung auscultation conditions that are more specifically treatable
• Some dogs with tracheal collapse will ○ Wheezes (often expiratory): suggest nar- (e.g., infectious tracheobronchitis [p. 987]) or
also develop CB, making it occasionally rowing of the airways. Acute reversible potentially life-threatening (e.g., congestive

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