A large number of disorders (infectious, non-infectious inflammatory, immune-mediated, neoplastic etc.) can affect the bronchopulmonary tree in dogs. A comprehensive review of each disorder is beyond the scope of this presentation. Rather we will review key clinical points about the diagnosis and management of canine chronic bronchitis and pulmonary fibrosis.

Chronic bronchitis in the dog
Definition:
Canine chronic bronchitis refers to persistent inflammation in the bronchial tree, that may involve lobar and segmental bronchi, or the smaller airways.

Etiology:
      - The vast majority of cases of chronic bronchitis in dogs are idiopathic
      - Environmental pollutants (including passive exposure to cigarette smoke) and hypersensitivity reactions are speculated but it is difficult to establish a clear link
      - Chronic or recurrent infection may contribute, and may suggest an abnormality of local innate or humoral immunity (e.g. IgA deficiency)
      - Ciliary dyskinesis is a rare congenital abnormality, that typically manifests as recurrent bacterial sinusitis, bronchitis and pneumonia
      - Proposed but unproven relationship of chronic respiratory disease to poor oral health, especially in older small breed dogs

Clinical Signs:
      - coughing
           o a hallmark of bronchitis regardless of etiology
           o usually progressive in frequency and severity
           o generally productive with expectoration (sputum swallowed) and gagging
           o often noted for years prior to presentation
           o worsens with activity / excitement and can often be elicited by tracheal palpation
      - wheezing
           o may be evident, especially on expiration
      - tachypnea
           o with advanced disease or pulmonary fibrosis
      - shortness of breath with exercise
           o severely affected dogs can become cyanotic with exertion
           o dyspnea predominantly expiratory, but can be both inspiratory and expiratory
      - cough-related syncope:
           o in severely affected dogs
      - appetite is generally unaffected and body condition score is usually normal to increased:
           o weight loss, depression and anorexia may suggest an alternative diagnosis (e.g. CHF) or secondary pneumonia (particularly in the presence of fever

Physical examination:
      - cough (especially with excitement)
      - expiratory (+/- inspiratory) dyspnea and wheezes
      - crackles in advanced cases
      - variable cardiac auscultation depending on the presence/absence of underlying heart disease (absence of a murmur and a pronounced sinus arrhythmia should allow you to rule out CHF)