What is inflammatory bowel disease?
Inflammatory bowel disease (IBD) is a syndrome, despite being called a disease. The syndrome is caused by a specific reaction to chronic irritation of the intestinal tract. Inflammation is the body’s response to an insult, injury, or foreign substance.
With inflammatory bowel disease, specific types of inflammatory cells, depending on the type of IBD, invade the wall of the stomach and/or intestines. As inflammatory cells invade, the lining of the gastrointestinal (GI) tract thickens. This thickening makes it harder for your dog to absorb nutrients and move food along the GI tract.
What causes IBD?
In most instances, an exact underlying cause cannot be identified; however, possible causes include parasitic or bacterial infection or adverse reaction to a specific protein in the diet.
What are the clinical signs of IBD?
IBD can involve any part of the 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, your dog will have chronic diarrhea. In some dogs, both parts of the digestive tract are involved, so they have both vomiting and diarrhea.
If the syndrome lasts for more than a few months, poor appetite and weight loss are common. In some cases, dogs develop a voracious appetite because they are unable to digest or absorb the food they are eating.
How is IBD diagnosed?
The specific type of IBD is conclusively diagnosed based on tissue biopsies. Obtaining these samples is a surgical procedure that requires general anesthesia. Depending on the suspected location of 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 exploratory surgery 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 suspected to be involved, tissue samples can be obtained using an endoscope. Your veterinarian will use a tiny biopsy instrument to take small samples of the lining of the affected organ. The benefit of exploratory surgery is that full-thickness biopsies often provide better samples to make a diagnosis.
"The specific type of IBD is conclusively diagnosed based on tissue biopsies."
The tissue biopsies are sent to a veterinary pathologist for diagnosis. The pathologist will give a descriptive diagnosis of the syndrome, depending on the main type of inflammatory cells present in the biopsies. The chronic irritation that causes IBD stimulates the body to send cells from the immune system to the affected area. IBD is diagnosed when these immune cells are identified at abnormal levels in the tissue.
Determining the cause of the tissue reactions usually requires further testing. Tests or treatments will be performed to rule out internal parasites, cancer, and infections. Blood tests are performed to rule out problems with the kidneys, liver, and pancreas, as well as diseases such as diabetes. In some cases, the exact cause cannot be determined. Other tests that may be performed are:
- Fecal examination to look for infectious organisms
- Measurement of the level of vitamin B12 (cobalamin) in the blood to indicate whether there is a decreased ability to absorb nutrients
- Measurement of folate in the blood to indicate whether there is an imbalance in the normal bacterial populations in the GI tract
How is IBD treated?
The ideal way to treat IBD is to diagnose the underlying disease that is causing the reaction. If an exact cause cannot be found, the disease is called “idiopathic.” Many cases of IBD are considered idiopathic. Other treatments include:
Deworming. Broad-spectrum deworming may be recommended as fecal tests are not always representative of the parasites in the GI tract.
Diet. Depending on test results and which part of the bowel appears to be involved, your veterinarian may recommend an easy-to-digest gastrointestinal diet, an ultra-low-fat diet, a novel protein diet, or a hydrolyzed diet. A novel protein diet contains a single protein source that is new to the dog. A hydrolyzed protein diet contains protein that has been broken down into smaller parts so the body’s immune system doesn’t respond to it. A true food trial requires the test diet to be fed exclusively for 8 to 12 weeks, although an improvement in clinical signs may be seen in less than 2 weeks.
In some cases, your veterinarian will recommend that you feed a true elimination diet, in which you feed your dog a home-prepared diet that contains only a single protein and a single carbohydrate. In the case of such a strict diet trial, follow your veterinarian’s directions closely. The home-prepared diet may not be complete and balanced, so it should only be fed for the recommended amount of time. No treats or other foods may be given in any food trial.
Medication. Medication may or may not be given initially, depending on the particular case. Antibiotics, such as metronidazole (Flagyl®), may be prescribed for their anti-inflammatory effect on the GI tract and re-establishment of a normal GI microbial population. Probiotic and prebiotic supplements may also help restore the balance of the normal bacteria found in the GI tract.
Immunosuppressive medications are sometimes needed to control patients’ clinical signs, and may include corticosteroids like prednisone (Deltasone®, Meticorten®), budesonide (Entocort®, Uceris®), and dexamethasone (Decadron®). These drugs are used with caution because they have the potential for side effects (see below), or for obscuring the diagnosis of the disease, if biopsies have not already been taken.
Other medications, such as chlorambucil (Leukeran®) or azathioprine (Imuran®) are tried if corticosteroids are not successful on their own. Cyclosporin (Atopica®) is also sometimes recommended.
Vitamin B12. Supplementation with Vitamin B12 (cobalamin) can be considered, as most dogs with IBD cannot absorb this important vitamin. Vitamin B12 is usually given by injection under the skin.
Do corticosteroids cause side effects in dogs?
Corticosteroids are notorious for causing a variety of side effects in humans. The typical increased drinking, urination, and appetite are often seen at the beginning, and longer-term use can affect the liver, increase the risk of diabetes, and cause thinning of the skin. To minimize any possible adverse effects, the goal is to use the lowest effective dose and to give it every other day. It will be necessary to begin therapy with a high dose, but once there is a response to the medication, the dose is gradually tapered to the lowest effective dose.
Will I need to give steroids to my dog for the rest of his life?
Long-term therapy is required for most dogs diagnosed with IBD. Generally, a dog is treated for a few months and then the medication is discontinued to see if it is still needed. If vomiting or diarrhea recurs, treatment is resumed. If oral medications are difficult to administer, it may be possible to give periodic injections of a long-acting corticosteroid called methylprednisolone (Depo-Medrol®). The disadvantage of long-acting injections is that once the medication is administered, it cannot be removed from the body if there are any problems.
What is the prognosis?
The prognosis is generally good with a confirmed diagnosis of inflammatory bowel disease. If your dog has a positive response to diet change, they can be maintained on the new diet for the rest of their life, provided the diet is appropriately balanced. If your dog has a positive response to medication, the long-term prognosis is also good. 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.
However, if your dog has no response to diet or corticosteroids, the prognosis is less certain. In these cases, further testing is suggested to see if an underlying disease can be identified.
