By Kate Mueller, DVM
Just like people, dogs can cough for many different reasons. Sometimes, it can even be difficult to tell whether a dog is actually coughing because, just like in people, there are different types and qualities of cough in dogs. Coughing is one of the most common presenting complaints for dogs in the emergency room. When a dog presents for coughing, two of the first questions an emergency veterinarian asks themselves are: Is the dog really coughing, or is he doing something else? And, is the dog coughing but breathing normally, or is he having trouble breathing? Once we have answered those two questions, the next step is to determine the underlying cause of the cough.
To answer the first question of “is the dog really coughing,” we evaluate whether we think the dog is actually retching, rather than coughing. A dog will often retch at the end of a bout of coughing, so the two are not mutually exclusive, but there is one cause of retching that is important to immediately rule out: gastric dilatation and volvulus (GDV), or bloat. In this condition, a dog’s stomach fills up with air and then twists or flips. This is most common in large breed, deep chested dogs, and the most obvious sign is a very firm, round abdomen in conjunction with non-productive retching – trying to vomit but without producing anything. If you suspect this condition in your dog, seek veterinary care immediately as it is life-threatening and fatal if untreated.
To answer the second question of “is the dog having trouble breathing,” we focus on the physical exam. Does the dog seem calm, or are they distressed or panicked? What color are the gums and tongue? Pink gums indicate adequate oxygen delivery to tissue. Purple or blue tinged gums are referred to as cyanotic, and this would indicate that the blood is not adequately oxygenated. Similarly, pale or white gums indicate that not enough blood is being delivered to peripheral areas of the body. A dog who is having trouble breathing will sometimes extend their neck in an attempt to take in more air. Finally, the character of the dog’s breathing can be a clue to the level of difficulty. When a dog is breathing with effort, their chest will move in and out with larger excursions than normal. Often, but not always, the respiratory rate will be faster than normal (a respiratory rate of anywhere from 12 to 36 breaths per minute is normal for a dog at rest). Sometimes dogs who are breathing with increased effort will have an abdominal component to their breathing, in which the abdomen also seems to move in and out forcefully with each breath.
Most of the following described causes of coughing can progress to respiratory distress, so presence or absence of distress is not necessarily a diagnostic tool, but certainly informs the urgency of diagnostics and treatment. If any of the above signs of respiratory distress are ever observed by you at home, you should seek veterinary care for your dog as soon as possible.
There are multiple ways to break up the different causes for coughing, but one useful method is to first split them between the two main body systems housed inside the chest: pulmonary (lungs) and cardiac (heart). In dogs, the most common type of cardiac disease is chronic degenerative valve disease, and this can cause coughing in a couple of different ways. If the cough is more chronic and dry, and the dog is not in respiratory distress, it is most likely due to enlargement of the left atrium, which is one of the chambers of the heart. When this heart chamber becomes enlarged, it can press upwards on the trachea (the breathing tube) and cause a sensation that elicits coughing. Typically this cough does not lead to true respiratory distress, but it can be irritating for both the patient and owner, so these dogs can be treated with a cough suppressant if necessary. The other common way that valvular disease causes coughing is when a dog goes into heart failure. In this scenario, there is fluid in the lungs (pulmonary edema) and the dog has a wet cough and sometimes even coughs up clear or pink-tinged fluid. Pulmonary edema is a life threatening emergency that needs to be treated with injectable diuretic therapy as quickly as possible.
When coughing is not a result of heart disease, its cause likely originates in the respiratory system. Differential diagnoses for respiratory system disease causing coughing include degenerative conditions, inflammatory conditions, infections, and cancer. It can be difficult to narrow down the most likely cause of coughing; one of the clues that veterinarians use is the patient’s signalment (age, sex, and breed). For example, an older, toy breed dog with a “goose-honk” cough may have a condition known as collapsing trachea. Dogs who have recently traveled or spent time in boarding facilities will engender a higher index of suspicion for infectious causes of cough, including the bacterial infection bordetella (kennel cough) and viral influenza. A history of recent vomiting will elicit a concern for aspiration pneumonia, when fluid from the oral cavity or GI tract enters the lungs and, because it contains a large amount of bacteria, causes an infection. In older dogs of all breeds, a newly diagnosed cough can be an indication of cancer in the lungs.
If your dog is coughing, veterinary attention is always recommended. Your dog’s visit will begin with a history and physical examination, which will guide your veterinarian’s recommendations for diagnostics. In almost all cases, chest x-rays will be a helpful tool to obtain a diagnosis. Other tests that may be performed include blood work to assess systemic health, blood testing for heartworm disease, and in some cases fecal testing for lungworm infection. Treatment will be guided by the results of these diagnostic tests and, depending on underlying cause of coughing, will vary widely.