At some point, all of our dogs have likely coughed. It happened a few times and stopped, or it persists. As armchair doctors, we can find ourselves brushing it off. Naturally we don't *want* anything to be very serious, and a cough seems simple enough to brush aside. Even though stated several times on this blog, let me reiterate, before spending too much time considering your dog's cough, rely on your veterinarian for a diagnosis. If your dog is coughing, read and educate yourself, but always take your dog to the clinic for an exam. Never wait, as many conditions only worsen if untreated. Below I describe only some of the more common reasons for coughing, but it is not all-inclusive.
Some sounds our dogs make can be easily described as a "cough", but often they sound like they are gagging, and is often described by owners as "it sounds like they are trying to spit something up", because they often make a retching sound at the end. I've met many owners who didn't think their dog was coughing at all.. instead they were "gagging", and the owners brushed it off that they "had something stuck in their throat". I've also met many owners who brush off coughs because they think it's allergies or that their house was too dusty. What is key to understand about coughs, is that not all coughs are indicative of a contagious infection. While some coughing can be easily diagnosed and treated to be revealed to be just that, what's important to know about coughing is that there are many other potential reasons for it, and some quite serious.
If your dog presents to the clinic with a cough, the doctor will want to understand how long it's been going on, what "kind" of coughing it is, and other factors such as exposure to other dogs. When a doctor hears "the dog is coughing", they may immediately glance at the age and breed of the dog to already begin a working list in their minds of what is the likely culprit. How long have they been coughing? Is it worse or unchanged? What else is wrong with them which may paint a larger picture?
If your dog is a puppy or young adult, or was recently adopted from a shelter or rescue, or they go to the dog park or daycare, their first inclination may be to rule out diseases such as Bordetella or Canine Influenza. There are vaccines for both, but those are only 2 respiratory diseases in a sea of many. Dogs *of any age* can get these, but younger dogs are most at risk. There is no way to "test" to determine what kind of respiratory infection your dog has, short of a more significant procedure called a 'tracheal wash'. Doctors only tend to recommend them if they do not respond to obvious therapies, and they need to take further steps to isolate what is going on. If your puppy is around other dogs and hasn't completed their full vaccine series, they are still susceptible to infections.
Naturally dogs with pneumonia may cough. Pneumonia can be secondary to another respiratory infection that was allowed to get worse, but it can also be created by things such as "aspiration", where they accidentally breathe in something, usually when vomiting. Dogs with short airways, or "brachycephalic" dogs are more prone to aspirating, as are dogs who have seizures.
While dogs of all ages can get these infections, if they are older, especially seniors, your doctor may want to rule out more potentially serious things. When our older dogs begin to get a cough, I've experienced many owners too quick to brush it off.
If your dog is a toy breed, be aware that they can develop a condition referred to as "collapsing trachea". This is literally exactly what it sounds like. The causes are largely unknown, but there is a frequency seen in smaller, toy breed dogs. How much they are impacted can vary greatly, and typically doctors only treat the symptoms. Dogs with this condition can get an implant called a "tracheal stent", but there are risks so discuss this with your veterinarian. An x-ray can help to diagnosis this in your dog, but they can sometimes miss it if the dog isn't taking an inspiratory breath as the x-ray is taken. There is an extremely specific sound dogs with collapsing trachea make (it has a bit of a honk), and experienced doctors will "know it" the minute they hear it regardless of the x-ray.
A serious concern with symptoms such as a cough is left-sided Congestive Heart Failure. It is crucial to bear in mind that a dog of any age can have severe heart disease, and even puppies can be in heart failure if they were born with a defect. Dogs with heart disease and no failure who cough tend to be smaller breed dogs. They are coughing due to heart enlargement, and the heart grows big enough to press against the trachea and create the cough. This can happen in dogs of any size, but is infrequent in larger dogs due to their confirmation. Dogs in heart failure will cough because the heart has failed to be able to push blood through properly, and the fluid overload will back up into their lungs and create a condition called "pulmonary edema" (fluid in the lungs). If your dog goes into heart failure and gets this fluid accumulation, it will *not* go away by itself and the dog must be seen as an emergency. The fluid will continue to accumulate until treated, or they will succumb to it by essentially drowning. Not all dogs in heart failure will cough! Dogs with failure to the left side of their hearts will cough, while right-sided heart failure may create fluid in the abdomen or around the lungs instead.
Anything putting pressure on the trachea can cause coughing. So naturally, we need to rule out masses (tumors). An x-ray may diagnosis this, but sometimes the doctor may recommend further diagnostics.
Sadly, and it goes without saying, dogs with lung cancer will have changes in their breathing. Whether just labored or perhaps coughing, this can be visualized on x-ray.
Lastly, it's key to understand that our dogs cannot catch colds from us. Many owners have made the mistake of thinking that their dog caught the same bug going through their family. Dogs have their own specific infections they can only get from other dogs; not us or even our cats can transmit them.
I think it's easy for owners to consider their dogs "caught something" from the kennel, doggie day care, or the dog park. Think hard on your dogs age and environment, concurrent illnesses or heart murmurs, and consider if you are making light of something potentially more serious. For diagnostics, be prepared to partner with your veterinarian to properly diagnose your pet. Chest x-rays will always be recommended, and potentially a cardiac ultrasound, or echocardiogram, if they are concerned about heart disease.