Chronic Diarrhoea In Dogs

Updated May 8, 2021

So your dog has had diarrhoea for more than two weeks, and you have ruled out all the more common causes of diarrhoea found here.
A basal cortisol level has even been done to rule out the 4% of these dogs that have Addisons disease.

What do you do now?

The answer is to consider the possibility that your dog has chronic enteropathy, or CE. This is a poorly understood group of related disorders that often respond to dietary, antibiotic or immunosuppressive treatment. Sometimes the solution is more than one of these approaches.

In the past, we have called these overlapping diseases by names you will recognise better:

• Inflammatory Bowel Disease or IBD
• Food Intolerance
• Food Allergy
• Small intestinal Bacterial Overgrowth

Here I will use the more practical and workable definitions of:

• Food Responsive Enteropathy (FRE)
• Antibiotic Responsive Diarrhoea (ARD)
• Steroid Responsive Disease (SRD)

Diagnosis of Chronic Diarrhoea

So how do we work out which one it is? In the absence of any definitive test, a treatment trial is the most common strategy chosen by vets. The only other alternative is intestinal biopsy, but its invasiveness and expense make it worth avoiding if possible. Sometimes however, there’s no alternative, such as with rarer diseases like lymphoma.

Most often, a treatment trial will be done in the following order:

1. Specially formulated diets
2. Antibiotics
3. Immunosuppressives

The final choice of what to do first will depend on factors like the age, breed, severity of signs and laboratory test results.

Food Trials

Around 64% of dogs with CE will respond to a diet trial. These dogs are usually younger, and healthier than the rest. With such good odds and a healthy population, it’s no surprise that a diet trial mostly comes first.

Often it is worth trying several diets. I recently saw a dog who was initially treated with a hydrolysed diet and rice but failed to respond. I put her onto another hydrolysed diet, stopped the rice and her diarrhoea almost instantly resolved.

Responses can be expected to be seen within 2 weeks. You can choose from either commercial diets or one you make yourself. I have written about these diets in depth at this link. A favourable response means you may wish to just keep using the diet for life, or experiment with ingredients until you work out which ones are implicated.

The exception to using regular FRE diets occurs when dogs have very low blood albumin levels such that we suspect (or even better, have proven) lymphangiectasia. This is an intestinal wall disease that responds best to ultra-low fat diets instead.

Antibiotic Trials

A poor or absent response to dietary manipulation might point us towards an antibiotic trial. The drugs used are mostly either metronidazole or tylosin.

Dogs with ARD are generally older large breed dogs, and especially German Shepherd dogs. A favourable response usually means you will need to keep giving the antibiotics for life, although the dose can often be substantially reduced.

Boxers and French Bulldogs are prone to Granulomatous Colitis, a specific condition that responds best to fluoroquinolone antibiotics. These dogs can usually be taken off the drug some time after a cure is achieved.

Immunosuppressive Medications

Dogs that fail to respond to either diet or antibiotics alone can be tried on immunosuppressives. However, some vets will consider the use of such drugs without biopsy as inappropriate. I personally think the decision needs to be made on a case by case basis.

The drug most commonly employed is prednisolone. You can read about its uses and side effects at the link. A second drug, if used, is most commonly cyclosporin.

Other Treatments

All dogs wth CE should either have their serum vitamin B12 checked or receive regular B12 injections. Vitamin B12 levels are affected by intestinal disease, and the deficiency then worsens the problem.

More than once I have seen dogs for whom everything was done right, but who only got better when B12 was given. The response is usually rapid.

There is only low grade evidence for the use of probiotics and none for prebiotics. However, I have had good responses to their use in some cases, and they are well worth trying.

There is much talk of the use of fibre such as psyllium or pumpkin. Apart from dogs on raw diets, I have stopped recommending this due to poor results, but you are welcome to try.

Finally, you should never give up. A 2021 study of 10 dogs who had already failed to respond to both dietary therapy and immunosuppression found that 8 of them responded to further dietary attempts. These diets were mainly focused on ultra-low fat levels, together with novel proteins in most cases. Half were commercially available and half were formulated by a veterinary nutritionist.

My experience with chronic diarrhoea in dogs is that it can always be managed if owners are willing to persist. It can be very frustrating and expensive at its worst. However, for many dog owners, these experiences become just distant memories once the solution is found.

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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here.