Emergency facts (details below):
When a dog suddenly falls over or can’t use their back legs, it’s usually an emergency. You should travel to a vet.
On the way, take a video if you can. Here are some things to look for:
- Is there muscle movement? This is common in seizures or poisonings.
- Is the dog unconscious? Look for a lack of response and passing urine or faeces.
- Are the eyes moving? Vestibular disease causes nystagmus or eye flicking.
- Is the heart rhythm normal? Place your hand on the chest and try to feel it.
- How long does it last? Fainting and airway issues usually only last for seconds.
- Is recovery quick? After seizures, dogs commonly appear incoordinated for some time.
- What was the dog doing beforehand? Cardiac, respiratory and thermal problems are more common after exercise.
Cardiac arrest is an extremely uncommon cause, and therefore it is not recommended to try CPR. You will see that most causes either recover by themselves or require treatment that only a vet can give.
Now let’s dive deeper into each of these causes…
Cardiac Causes Of Collapse
Collapse would make people immediately think of the heart, and they’d mostly be right. Any heart disease can cause collapse due to fainting or syncope, which is essentially ‘blacking out’ from a lack of oxygen in the brain.
Cardiac collapse most often occurs after excitement or exercise, and might only last a few seconds each time. In our clinic, the following heart diseases are more likely to cause collapse:
- rhythm disturbances (arrhythmias such as heart block, Boxer cardiomyopathy)
- late stage mitral insufficiency
- pericardial effusion
Many causes are treatable. Read more about these in our page on heart diseases.
Shock & Bleeding
The most common cause of acute shock is bee sting in dogs.
Low blood volume or anaemia can cause collapse that looks just like cardiac disease. The best clue is very pale, almost white gums. Perhaps the one we see most is rat bait poisoning, which causes internal bleeding. Two autoimmune diseases which have similar signs are platelet deficiency and haemolytic anaemia.
Another common cause of sudden collapse due to internal bleeding is a tumour of the spleen called haemangioma or haemangiosarcoma. It is seen mostly in older large breed dogs. Spleen removal can be curative but an ultrasound exam is best done first to look for tumour spread.
Rapid fluid shifts in the body cause shock, of which by far the most common cause is any severe and sudden gastroenteritis. In these, body fluids go from the blood vessels into the gut faster than they can be replaced and the circulation collapses. The treatment is of course prompt restoration of the fluids via a drip.
Respiratory Causes Of Collapse
Any problems of the airways or lungs can cause collapse due to hypoxia. Here are some of the ones we see more often.
Brachycephalic Obstructive Airway Syndrome or BOAS occurs in dogs with short faces, like Bulldogs and Pugs. When there’s a need to breathe quickly, the soft palate that lies over the larynx in some dogs will block enough airflow to cause collapse. This can be complicated by a narrow trachea (windpipe) and small nasal openings.
If a brachycephalic breed has noisy breathing even when at rest, or gets tired easily, they almost always benefit from airway surgery. Acting proactively can save a life.
Collapsing trachea is a common cause of a honking or harsh dry cough in older small breeds. When they get hot or excited, the airflow through the flattened windpipe sometimes can’t keep up with demand and the dog might collapse for a few seconds. Treatment involves various medication combinations, weight loss, avoiding excitement, and surgery as a last resort.
Laryngeal paralysis is a similar problem mainly seen from middle age in medium and large breeds. Instead of a cough, they have harsh, raspy breathing that gets louder with exercise or temperature. Collapse most commonly occurs in warm conditions, but can be prevented by timely surgery.
Pulmonary hypertension is a rarer disease of the lungs secondary to many problems, such as heartworm, birth defects in the heart and a specific disease of West Highland White terriers. It can also happen when blood clots are formed associated with immune-mediated haemolytic anaemia, protein-losing diseases and Cushing’s disease.
Neurological Causes Of Collapse
Any poison that affects the nervous system can cause a dog to collapse. In Australia, the most common are:
Three neurotoxins found in Australian animals also deserve special mention: tick paralysis, cane toads, and snake bite, which often causes immediate collapse followed by a short-lived recovery. Other toxins are ethyl glycol in engine coolant, bromethalin in rat baits outside Australia, insecticides and herbicides.
Any injury or trauma to the brain or spinal cord can cause collapse. The best example of this is intervertebral disc disease, which is especially common in dogs like Dachshunds.
Seizures can also be a cause of collapse. Usually they’re easy to identify by paddling leg movements, jaw champing and salivation, but sometimes these aren’t obvious. That’s especially true for partial seizures where the dog remains conscious throughout.
A portosystemic shunt is an abnormal blood vessel that sends unprocessed blood from the gut directly to the brain, bypassing the liver. It can cause collapse especially not long after a meal. A shunt would be high on the list in a young adult of a susceptible breed such as the Maltese.
Low blood sugar also causes neurological signs. Collapse in a diabetic dog is most often due to a high insulin dose suppressing blood glucose levels, but we also see it with insulinoma, Addison’s disease and very young puppies not getting adequate nutrition.
The last item on the nervous system list is vestibular disease. This refers to any disorder that affects the balance organs in the inner ear and brain. These dogs have a head tilt, fast flicking in the eyes, and usually can’t stand up. The most common is Idiopathic Vestibular Syndrome, which comes on suddenly in old dogs and passes in less than a week.
As a young vet, I didn’t believe it when I first saw simple arthritis cause a dog to collapse. Why would a long-term disease known for slow worsening lead to sudden collapse? Now I understand that these dogs have been putting up with pain until they couldn’t any longer.
We see this mainly in larger breeds, and especially German Shepherds. Often they will be howling or crying and brought in on a stretcher. Good intravenous drugs (especially cortisone) can do wonders to get them up again but they really need long-term pain control to keep them going.
Of course, we should view these dogs as our own failure. To do it right would be to identify and treat their pain before it gets too much.
Let’s finish up with a common condition that’s very easy to miss: excessively high body temperature. I’ve seen it in plenty of dogs and the suspicion is always of another cause to begin with, like a seizure or heart problems. That’s because by the time they get to us the temperature is usually back to normal.
The clue is that it should happen after prolonged exercise or excitement. The outside temperature doesn’t have to be very high if a dog is generating more heat than can be dispersed. Therefore we see it most with dogs obsessed by ball-chasing, or overly excitable dogs. I saw it recently in a dog who gets hyperthermic just due to anxieties and OCD.
The trick is to realise that dogs don’t know when to stop and that you need to regulate their exercise and keep them calm.
This list is by no means complete but all the common reasons for collapse should be found here. Diagnosis will require your vet using the history you give them, taking a physical exam and choosing the right tests to confirm their suspicion. Good luck.
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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. These help topics are from a series regularly posted on email and Twitter. Subscribe via email here to never miss a story! The information provided here is not intended to be used as a substitute for going to the vet. If your pet is unwell, please seek veterinary attention.