When presented with a dog whose primary clinical sign is coughing, a veterinarian will take a complete history from the owner and conduct a thorough physical examination. She usually will be able to elicit a cough on palpation of the trachea and may hear characteristic lung sounds, such as crackles and wheezes at the end of inspiration, when listening to the chest through a stethoscope. The veterinarian also will probably recommend thoracic radiographs (chest X-rays), which can be quite helpful in arriving at a diagnosis. Unfortunately, normal chest films do not necessarily rule out chronic as the cause of the dog’s condition. The results of routine blood work (complete blood count and serum biochemistry profile) and urinalysis are typically normal or inconclusive in dogs with bronchitis. Tests can easily be run to identify or eliminate lungworms and heartworms as the cause of the cough.
The veterinarian can obtain samples of cells from the dog’s airways through several different processes, known as bronchoalveolar lavage and transtracheal wash. Both of these procedures involve flushing the trachea and respiratory airways with a sterile solution and then aspirating the fluid out of the airways through a tube and syringe for submission to a diagnostic laboratory. Although bacterial infection is not commonly associated with bronchitis in dogs, it can happen, and the veterinarian may recommend culturing the airway sample to identify any abnormal microorganisms that are present. Bronchoscopy is another diagnostic tool. This involves inserting a wand-like instrument with a camera at its tip (an endoscope) down the dog’s throat and into its airways. This lets the doctor actually visualize the lining of the upper respiratory tract in real-time, and to take additional fluid or tissue samples if necessary. An echocardiogram may be used to rule in or out congestive heart failure as a cause of the dog’s cough.
Diagnosis of chronic bronchitis is made by eliminating other potential causes of the dog’s cough. It is called a diagnosis of exclusion.