1st printing in AKC Gazette, May 2000 ~ Reprinted with permission from Christine Wilford, DVM

Every dog, at one time or another, develops a cough. Some coughs indicate serious problems, while others are simply annoying. Some coughs resolve without treatment, while others require medical or surgical therapy. Because a variety of heart problems and respiratory disorders can cause coughing, putting an end to the cough begins with getting the correct diagnosis.

An owner’s accurate description of coughing episodes and a complete detailed history of the onset and progression of the cough are invaluable to the veterinarian. Important observations include when and how often the cough occurs; what, if anything, initiates the cough; whether it is moist (productive) or dry (nonproductive); the intensity; and a description of the cough elicited.

Nocturnal or early morning coughing can be typical of cardiac disease. Coughing during the day develops as hearth disease progresses. In the early stages of respiratory disease, daytime coughing is more typical. Bacterial and viral infections, parasitic infections, allergic disorders and cancers frequently become severe enough to induce coughing during all hours of the day and night.

Excitement, exertion or pressure on the trachea, such as pulling on a collar or lead, elicits coughing caused by tracheal disorders, such as collapsing trachea and tracheitis, inflammation of the trachea, from kennel cough infection. Although heart disease may cause difficult breathing during exercise, coughing from heart disease often occurs at rest or after sleep.

Productive coughs sound moist, because phlegm or mucus is secreted to help clear out germs and debris from the respiratory system. After several hard coughs, the dog may spit up phlegm. Unfortunately, many dogs swallow what is brought up during coughing before presenting it for the owner or vet to see.

Although the appearance of whatever the dog spits up may be offensive to some people, examining and noting the characteristics of the fluid can lead to invaluable information to tell the vet. Knowing whether the fluid is clear, blood-tinged, yellow, green, thick, frothy or watery may hasten proper evaluation and treatment. Continuing to monitor the phlegm is helpful, since the character of the phlegm usually changes as the disease is properly treated or resists treatment.

Some owners may confuse a productive cough with vomiting, since the two acts may look similar. Occasionally, true vomiting may follow an episode of forceful, nonproductive coughing. Harsh, dry coughs can be associated with tracheal or bronchial disease and some cardiac conditions. "Honking" coughs are typical of collapsing trachea or main stem bronchi, hypoplastic (smaller than normal) trachea or tracheal injuries. Some dogs develop temporary dry coughs or honking coughs after being intubated for inhalation anesthesia, because the tube that is inserted to deliver anesthesia irritates the trachea.

Soft, moist coughs are indicative of lower respiratory (lung) disorders, such as pneumonia. Wheezing and rattling sounds are produced by obstructive lung diseases, such as chronic allergic airway disease. Pre-existing problems, such as hypoplastic trachea, may not lead to coughing until the condition becomes complicated by a second factor. For example, a dog may have a collapsing trachea but never cough until it develops an infection.

Owners may first opt for an antibiotic trial to see if the cough resolves. If it does, then the conclusion, although circumstantial, is that the cough was caused by some type of infection. These trials, without more evaluation, are only prudent in certain patients. For example, any dog with a murmur may be coughing due to heart disease and should be evaluated further.

Dogs that are middle-aged or older are at risk for chronic airway disease and cancer, so antibiotic trials may delay proper diagnosis and treatment. A good diagnostic test for respiratory disease is the chest radiograph (X-ray), which is invaluable for evaluating the positions, sizes and shapes of the trachea, lungs, airways and heart.

Once respiratory disease is confirmed, more precise information can be obtained through a procedure commonly called a transtracheal wash or aspirate. This procedure involves a very brief and light level of sedation. The vet flushes a small amount of sterile fluid through a small catheter into the dog’s trachea and immediately sucks the fluid back into the syringe.

The result is a small sample of cells from the lower airways that can be examined by a pathologist. The tracheal wash is critical in identifying types of infection and for differentiating between allergic and infectious respiratory disease.

If the vet suspects heart disease after performing a physical exam and/or the X-ray, an ultrasound of the heart is warranted. X-rays show the heart’s size, shape and position but reveal nothing about function and dysfunction. Cardiac ultrasound is the only common test that accurately identifies the nature and severity of the heart disease.