Anatomy of the Cough
What is a cough? And what does it mean? “Coughing” is defined as the expulsion of air from the lungs suddenly and noisily, often to keep the respiratory passages free of irritating material. Coughing can be a mechanism used to expel material out of the airways including particulates and fluid. Coughing can be a conscious action or the result of a reflex. Often coughing is stimulated by an irritating substance (mechanical or chemical) to the upper airways, however coughing can be caused by other diseases such as primary pulmonary and cardiac diseases. The main causes of coughing in our small animal patients include major categories as follows: inflammatory, cancerous, cardiovascular, allergic, traumatic/physical factors, parasitic, bacterial fungal. It is important to monitor coughing in your pet very closely, as this can be the first indicator of a new or worsening problem.
When trying to determine a cause for the cough, a thorough history taken by your veterinarian can often be as helpful as diagnostics performed. You may be asked some of the following questions:
- How long has your pet been coughing?
- How does the cough sound (dry, honking, wet)?
- Is the cough productive or non-productive (Does your pet cough up something)?
- Is the cough associated with time of day or activity level?
- Is the cough worse at night or during the day?
- Have you noticed anything that will stimulate your pet to cough, such as pulling on the leash or certain types of activities or places?
- Does your pet have any known allergies?
- How often does your pet cough? How many times daily?
- Has the frequency or intensity of the cough changed (increased, decreased, no change)?
- Is the timing of the cough related to when your pet eats and/or drinks?
- Has your pets cough been responsive to medications (anti-histamines, cough suppressants, diuretic medications) or changes in husbandry (using a harness instead of a collar, staying inside more often)?
Evaluation of a cough encompasses both physical examination and auscultation (listening with a stethoscope) performed by a veterinarian, as well as use of diagnostic imaging including thoracic radiography. Radiography can be utilized to assess for primary heart enlargement, enlargement of pulmonary arteries and veins, fluid build-up within (pulmonary edema) or around the lungs (pleural effusion), tracheal abnormalities, or evidence of cancer. Radiographs also have the ability to detect pneumonia or certain fungal infections, although they cannot give us information regarding the specific type of infection. Your veterinarian may recommend advanced secondary and tertiary diagnostic tests for further evaluation.
Let's focus on cardiovascular causes of coughing. Keep in mind, however, that our patients with cardiovascular disease can have other causes for coughing as well.
Main cardiovascular causes for coughing include left heart failure secondary to pulmonary edema (fluid buildup within the lungs due to a backup of fluid – see Congestive Heart Failure), cardiomegaly (enlargement of the heart, especially the left atrium with causes the trachea to be pushed up), pulmonary emboli (clot formation in the pulmonary vessels causing decreased blood flow to certain regions of the lungs), or pulmonary edema which can be secondary to a vascular cause. Pets can also cough with heartworm disease.
While no patient with heart disease reads the rule-books all the time and the following is not all-encompasing to patients with cardiac disease, often pets with cardiac disease will start to cough at night, and may progress to coughing during the day as the disease progresses. Patients who are experiencing pulmonary edema (heart failure) will often have a productive cough, and often may have a “terminal wretch”, meaning that patients seem to cough up something at the end of a coughing fit or episode.
One important thing to note is that cats often do not cough with heart disease, and more often to cough from other problems including feline asthma, certain cancers, or other primary pulmonary disease.
Treatment for coughing should be geared toward treatment of the underlying cause for the cough, whether it is aimed at the cardiovascular system, pulmonary system, or other treatment target. Only when the primary cause of the cough cannot be determined based on testing or are absolutely indicated should antitussives (cough suppressants) be considered.