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Dog diarrhoea: What causes it?

White shih tzu dog advice
© Unsplash

There are lots of reasons why a dog might suffer with diarrhoea. Learn about its main causes, and know what to do when the time comes. 

By Nick Whittle

Updated on the 28/11/2019, 14:38

Usually, dog diarrhoea is caused by her eating the wrong sort of food or over-eating. But in some cases the condition indicates an underlying illness both serious and potentially life-threatening. Acute diarrhoea is easily treatable and stems most often from an upset tummy. Conversely chronic diarrhoea warrants close attention to your dog’s health.

To have diarrhoea is never nice, for dogs or humans. We have the advantage of being able to mentally rule out certain causes straight away but dogs do not have the ability of self-reasoning. They will rely on us to help them through their discomfort and we must take seriously their illness if we are to help them get better.

How is the cause of dog diarrhoea diagnosed?

One of the problems of defining the causes of dog diarrhoea is the number of possible culprits. If diarrhoea has onset quite suddenly but your dog is still alert the cause may be nothing more than an upset stomach. In such cases the vet will recommend a symptomatic treatment.

If the diarrhoea seems not to be going away after a short period of time or has been continuing for a while (chronic diarrhoea) your vet will recommend further screening of your dog’s overall health.

Such tests may include:  

Endoscopy: to check for tumours, bowel disease or polyps

Surgery: to check for the above but more thoroughly 

Blood, urine and faecal tests: to check for parasites, pancreatitis and diseases of other organs 

Radiograph: to check the bowel for obstructions and abnormalities

Types of diarrhoea

The are typically two types of diarrhoea - small bowel and large bowel - each of which points to different causes.

Small bowel diarrhoea: Dogs exhibiting this type of diarrhoea usually exhibit signs of feeling poorly. Small bowel diarrhoea looks watery and is very loose. These dogs should be fed with a very bland diet, which includes carbohydrate-rich foods.

Large bowel diarrhoea: Dogs exhibiting this type of diarrhoea will seem, for all intents and purposes, bright and happy. Large bowel diarrhoea looks less watery but may contain blood. These dogs should be given food rich in fibre.

What are the causes of dog diarrhoea?
Diarrhoea can make puppies seriously ill ©Marcus Wallis. Unsplash

My dog has diarrhoea. What should I do?

Although most instances of diarrhoea should not cause us too much concern you should  contact your vet if your dog suffers with it for any longer than a couple of days.

Importantly, if you are looking after a puppy or an elderly dog you should call a vet immediately. Young dogs in particular can become dehydrated very quickly after even a short bout of diarrhoea.

You must also contact your vet sooner rather than later if your dog has some or all of these symptoms:

  • Lethargy
  • Seizures
  • Repeated vomiting
  • Increased thirst or urination

If your dog appears bright and healthy regardless of the odd bout of diarrhoea some vets advise a short 12 hour fasting followed by regular small meals of high protein meat or fish. Once the diarrhoea ceases you can then re-introduce her normal food.

It is also important for a dog with diarrhoea to take on board plenty of fluids. You can tempt her to drink more by adding a beef stock cube to her water. Bear in mind that if she is also vomiting her drinking too much water will not help.

What are the treatments of dog diarrhoea?

To treat diarrhoea the vet must first establish its cause. Usually acute diarrhoea is brought on by a parasitic or viral infection of the gut or the ingestion of a poisonous substance, but the condition can just as easily stem from your dog’s over-eating or an allergy.

Inflammatory ailments of the intestine of a dietary origin are the most common causes of diarrhoea in dogs.

In such circumstances specific medical intervention is not required and use of drugs such as antibiotics may even make matters worse. Thus, in acute and low-grade chronic diarrhoea certain non-specific treatments are recommended. These include: 

  • Adequate hydration
  • Up-to-date worming
  • Healthy diet
  • Probiotics and prebiotics included in diet
  • Mucosal protectant (a medicine that protects the stomach lining from acid)
  • Motility modifier (a medicine that slows the transit of food through the bowel)
What causes dog diarrhoea?
To have diarrhoea is never nice, for dogs or humans©James Barker. Unsplash

Chronic or ongoing diarrhoea

The treatment of the more serious kind of chronic diarrhoea involves the administration of both specific and non-specific care. Extreme cases call for more prolonged non-specific support in tandem with the application of drugs to the cause.

Non-specific treatments will be similar to those used of acute diarrhoea but will be applied for much longer and until the underlying causes of the condition are treated. They include:

  • Adequate hydration (sometimes required to be administered intravenously)
  • Digestible diet of proteinaceous meat
  • Probiotics and prebiotics included in diet (these cultures improve intestinal health; some even slow bowel transit)
  • Once the cause of the diarrhoea is established, more specific medicines can be used in an effort to improve your dog’s health.

Specific treatments include:

  • Antibiotics drugs: only to be used in extreme cases of an identified infection
  • Anti-parasitic drugs: highly effective in the removal of bowel parasites
  • Anti-inflammatory NSAIDs: effective in the reduction of pain and thought to ‘calm’ the bowel (but long-term use of NSAIDs can have an adverse effect on the gut)
  • Surgery: for the removal of tumours and diseased bowel
  • Diarrhoea is a common feature of a dog's life. Our dogs enjoy scavenging and we often feel compelled to give them our left-over scraps of food. Short bouts of diarrhoea caused by a poor diet will normally end after one or two days.

However, regardless of the length of the bout, it is worthwhile to stay vigilant when your dog is poorly: sudden and aggressive diarrhoea can sabotage her health very quickly.