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Bronchitis, Chronic (COPD) in Dogs

Chronic bronchitis, also known as chronic obstructive pulmonary disease (COPD), occurs when the mucous membranes of the bronchi (the airways that transport oxygen from the trachea to the lungs) become inflamed. Typically, this leads to a chronic cough that lasts two months or longer -- a cough that is not attributable to other causes like heart failure, neoplasia, infections, or other respiratory diseases.

Despite extensive diagnostic efforts by your veterinarian, the specific cause of the inflammation is rarely identified. In addition, toy and small dog breeds, such as the West Highland white terrier and cocker spaniel, are found to be more susceptible to COPD, although it is sometimes observed in larger breeds of dog, too.

Symptoms and Types

Other than a dry cough (a hallmark sign of COPD), other symptoms associated with the disease include:

• Gagging
• Abnormal lung sounds (i.e., wheezing, crackles, etc.)
• Inability to perform routine exercises
• Bluish discoloration of the skin and mucous membranes (cyanosis); a sign that oxygen in the blood is dangerously diminished
• Spontaneous loss of consciousness (syncope)

Causes

Chronic airway inflammation is initiated by a variety of causes.

Diagnosis

You will need to give a thorough history of your dog’s health to your veterinarian, including the onset and nature of the symptoms. He or she will then perform a complete physical examination as well as a biochemistry profile, urinalysis, and complete blood count -- the results of which are typically non-specific. In fact, COPD is rarely definitely diagnosed. In some dogs, however, polycythemia or eosinophila (allergic state in which an increased number of eosinophils concentrate in the blood) develops as a result of the disease.

Chest X-rays are helpful in determining the severity of the disease and to evaluate the extent of lung involvement. Dogs with COPD may have thickened brochi or, in severe cases, collapsed lungs. Bronchoscopy, another important diagnostic tool, is used to visualize the inside of the airways and identify abnormalities such as tumors, inflammation, and bleeding. This is done by inserting an instrument (bronchoscope) into the airways, usually through the nose or mouth. The technique can also be used to collect deep lung tissue samples, which are then sent to a laboratory for detailed examination.

Your veterinarian may also use echocardiography (ECHO) and electrocardiogram (ECG) to evaluate the heart and identify abnormalities such as heart enlargement or failure. This may even help the veterinarian rule out heartworm disease.