When presented with a coughing dog, a veterinarian will perform a thorough physical examination. She will also take a complete history from the owner about the course of the dog’s condition, including the duration and severity of the cough, whether it occurs during the day or at night and whether it worsens with exercise.
A dog with a cough may be tentatively diagnosed based on the character of the cough itself. For example, a deep, dry, hacking cough that worsens with exercise or excitement is characteristic of kennel cough and typically is caused by the bacterium, Bordetella bronchiseptica. A productive, moist, bubbling cough suggests the accumulation of fluid, pus or mucous in the lungs or upper respiratory tract and may indicate that the dog has pneumonia. A weak, gagging, high-pitched cough that is followed by licking and swallowing typically is caused by a sore throat and perhaps tonsillitis. A dog that has long bouts of coughing, usually at night while lying down, may be suffering from heart disease – particularly congestive heart failure. In toy dogs, a chronic dry, harsh, “goose-honking” cough often is caused by a collapsing trachea. Dogs with a soft cough and a high fever may have contracted canine influenza, which is a fairly recently recognized disease of domestic dogs.
The attending veterinarian may recommend routine blood work, including a complete blood count and serum chemistry profile, together with a urinalysis, to assess the dog’s overall health. Analysis of a fecal sample can detect respiratory parasites (lungworms), and a heartworm test can be used if those parasites are suspected of contributing to the dog’s cough.
Other diagnostic tests for a dog with a cough include thoracic radiographs (chest X-rays), thoracic ultrasound and transtracheal wash. A transtracheal wash is a procedure where the trachea (the “wind pipe,” which connects the mouth/oral cavity to the lungs) is flushed with a sterile saline solution while the dog is sedated. The fluid is retrieved (aspirated) by suction through a tube and syringe and submitted to a laboratory for microscopic evaluation called “cytology,” and for culture to identify the presence of any microorganisms that are not part of the normal flora of a dog’s respiratory tract. A similar procedure, called a bronchoalveolar lavage, may be used to take respiratory samples, as well. Other diagnostic procedures available for dogs that are coughing are bronchoscopy, tracheoscopy and laryngoscopy. These require general anesthesia, because they involve passing a rigid or flexible endoscope into the dog’s mouth, down its throat, through its trachea and into its bronchi (large airways). The camera on the end of the instrument enables the veterinarian to see the lining of the respiratory tract, including any apparent abnormalities. Tissue biopsies can be taken with great accuracy during a bronchoscopy, and foreign bodies can also be removed.
In some specialized veterinary hospitals, computed tomography (CT scan) and/or magnetic resonance imaging (MRI) may be available.
When dogs develop a chronic cough, owners should eliminate any possible contributing factors, such as cigarette or cigar smoke, aerosol products, irritating household cleaners, dust, perfume and the like.