Inflammatory Bowel Disease in Dogs
By Krista Williams, BSc, DVM; Ernest Ward, DVM

What is inflammatory bowel disease?dog_intestine_stomach-1-01

Inflammatory bowel disease (IBD) is a syndrome rather than a disease. The syndrome is caused by a specific reaction to chronic irritation of the intestinal tract. Most dogs with IBD have a history of recurrent or chronic vomiting or diarrhea and may have a poor appetite. During periods of vomiting or diarrhea, the dog may lose weight, but is normal otherwise.

What causes this disease?

The cause of IBD is poorly understood. In fact, it appears there are several causes. Whatever the cause, the end result is that the lining of the intestine is invaded by inflammatory cells. An allergic-type response then occurs within the intestinal tract. This inflammation interferes with the ability to digest and absorb nutrients.

In most instances, an exact underlying cause cannot be identified; however, possible causes include:

  • parasitic or bacterial infection (e.g., Salmonella, E. coli, or Giardia)
  • reaction to a specific protein in their diet


What are the clinical signs of IBD?

IBD can involve any part of the digestive gastrointestinal (GI) tract, but most commonly affects the stomach and/or the intestines. If the stomach is involved, your dog will experience chronic vomiting. If the intestines are involved, chronic diarrhea will occur. In some dogs, both parts of the digestive tract are involved so both vomiting and diarrhea occur. If the syndrome lasts for more than a few months, weight loss and poor appetite are common. However, some dogs develop a voracious appetite in response to their inability to digest and absorb what they are eating.

"If the stomach is involved, your dog will experience chronic vomiting. If the intestines are involved, chronic diarrhea will occur."

How is IBD diagnosed?

Initial testing for IBD starts with fecal examinations, blood testing, and imaging of the intestines by either X-ray or ultrasound.

The specific type of IBD is conclusively diagnosed based on tissue biopsies. Obtaining these samples is a surgical procedure requiring general anesthesia. Depending on the suspected location of the IBD, your veterinarian may recommend either an endoscopic procedure or a full abdominal exploratory surgery. If the small intestine or the upper large intestine is suspected to be involved, the procedure will require an exploratory surgery, primarily because these areas are not accessible to an endoscope. In this case, it is common to take samples through all the layers of the wall of the affected organ. If it is mainly the stomach or colon that is affected by the condition, tissue samples can be obtained using an endoscope. When an endoscope is used, a tiny biopsy instrument will be used to take small samples of the lining or mucosa of the affected organ.

The tissue biopsies will be sent to a veterinary pathologist for diagnosis. The pathologist will give a descriptive diagnosis to the syndrome, depending on the main type of inflammatory cells present in the biopsies.

Other tests that may be performed are:

  • fecal tests - these tests look for infectious organisms
  • measurement of the level of vitamin B12 (cobalamin) in the blood - this can indicate whether there is decreased ability to absorb nutrients and a need for supplementation
  • measurement of folate in the blood - this will indicate whether there is an imbalance in the normal bacterial populations in the GI tract. 

Is IBD treatable?dog_food

There is no 'cure' for IBD, but it can be treated. Not all dogs respond to the same medication or food, so a series of drugs and/or foods may be necessary.

Diet. Depending on test results and on which part of the bowel appears to be involved, special diets may be used as a therapeutic trial. These diets include hypoallergenic foods, low residue diets, or high fiber diets. In some cases, it may take eight to twelve weeks for a positive response to be seen. Unfortunately, a true food trial requires that the test diet be fed exclusively for six to twelve weeks. In some cases, your veterinarian will recommend that you feed a true elimination diet, in which a home-prepared diet containing only a single protein and a single carbohydrate are fed. In all food trials, no treats or other foods may be given at all.

Medication. Medication may or may not be given initially, depending on the particular case. Antibiotics, such as metronidazole (brand name Flagyl®), may be prescribed for their anti-inflammatory effect on the GI tract. They may also help restore the balance of the normal bacteria found in the GI tract. Probiotic supplements may also be recommended. These are beneficial bacteria that help restore the normal function of the GI tract. As the quality and effectiveness of probiotics and supplements are not always known, it is always recommended to ask your veterinarian before giving your dog anything of this nature.

Anti-inflammatory drugs such as corticosteroids (prednisone) are sometimes needed to control the clinical signs in many patients, but are used with caution since they have potential for side effects or for obscuring the diagnosis of the disease if biopsies have not already been taken.

Deworming. Broad spectrum deworming is recommended as fecal tests are not always representative of the parasites in the GI tract.

B12. Supplementation with B12 (cobalamin) can be considered as most dogs with inflammatory bowel disease are unable to absorb this important vitamin. This is given by injection under the skin

What is the prognosis?

The prognosis is generally good with a confirmed diagnosis of inflammatory bowel disease. Once the appropriate drugs or diet is determined, many dogs remain on these for life, although it may be possible to decrease the drug dosage over time. Occasionally, a dog will be able to stop drug therapy. Most dogs do well for many years while others require alterations in therapy every few months. Unfortunately, a few dogs will fail to respond to treatment.

Some severe forms of canine inflammatory bowel disease will eventually progress to intestinal cancer. This finding is well documented in humans and, in recent years, it has also been shown to occur in dogs.

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