What is inflammatory bowel disease?
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. Whatever the cause, the 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. Most dogs with IBD have a history of recurrent or chronic vomiting and/or diarrhea and may have a poor appetite.
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, chronic diarrhea will occur. In some dogs, both parts of the digestive tract are involved and both vomiting and diarrhea occur.
If the syndrome lasts for more than a few months, poor appetite and weight loss are common. However, some dogs develop a voracious appetite in response to their inability to digest and 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 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 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, 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 of the affected organ. The benefit of exploratory surgery is that full-thickness biopsies often provide better samples to make a diagnosis.
"The benefit of exploratory surgery is that full-thickness biopsies often provide better samples to make a diagnosis."
The tissue biopsies will be 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 cells are identified at abnormal levels in the tissue.
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 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?
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. The ideal way to treat this problem 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.
Diet. Depending on test results and which part of the bowel appears to be involved, special diets may be used as a therapeutic trial. These diets contain a single protein source that is new to the dog (what is referred to as a novel protein) or a hydrolyzed protein (where it has been broken down to smaller parts, so the body does not recognize it as a specific protein). A true food trial requires that the prescribed diet be fed exclusively for eight to twelve weeks. In all food trials, no treats or other foods may be given at all. If these food trials are unsuccessful, a high fiber diet may be recommended.
"A true food trial requires that the prescribed diet be fed exclusively for eight to twelve weeks."
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. Probiotic supplements may also be recommended to help restore the balance of the normal bacteria found in the GI tract.
Immunosuppressive medications, such as the corticosteroids prednisone (Deltasone®, Meticorten®), budesonide (Entocort®, Uceris®), and dexamethasone (Decadron®) are sometimes needed to control the clinical signs in many patients. These drugs are used with caution because they have the potential for side effects 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.
Deworming. Broad-spectrum deworming may be recommended as fecal tests are not always representative of the parasites in the GI tract.
Vitamin B12. Supplementation with Vitamin B12 (cobalamin) can be considered as most dogs with IBD are unable to absorb this important vitamin. This is most often 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 long-term use can affect the liver. To minimize any possible adverse effects, the goal is to use the lowest effective dose and to give it on an every-other-day schedule. It will be necessary to begin therapy with a high dose, but once a response to the medication occurs, the dose is gradually tapered to the minimum effective dose.
Does this mean that I will be giving steroids to my dog for the rest of his life?
Long-term therapy may be necessary for most dogs diagnosed with IBD. Generally, a dog is treated for a few months, 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 the long-acting corticosteroid, 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. 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. However, if there is no response to diet or corticosteroids, the prognosis is more guarded. In these cases, further testing is suggested to see if an underlying disease can be identified.