Inflammatory Bowel Disease in Cats

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 cat 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 cat will experience chronic vomiting. This is the most common clinical sign of IBD in cats. If the intestines are involved, your cat will have chronic diarrhea. In some cats, 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, cats develop a voracious appetite because they are unable to absorb the food they are eating, and this sign must be differentiated from hyperthyroidism. Vomiting hairballs more than once a month is not normal, and shows an inability to pass hair through the GI tract; this may be a sign your cat has IBD.

How is IBD diagnosed?

Veterinarians often use ultrasound to help make a diagnosis of IBD. Ultrasound can measure the thickness of the stomach and intestinal linings, and also evaluate the size of the lymph nodes around the intestines. 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 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 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.

"The specific type of IBD is conclusively diagnosed based on tissue biopsies."

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 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 hyperthyroidism and diabetes. In some cases, the exact cause cannot be determined. Other tests that may be performed are:

• Fecal tests to look for infectious organisms
• Measurement of the level of vitamin B12 (cobalamin) 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 is 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, special diets may be used as a therapeutic trial. These diets may contain a single protein source that is new to the cat (what is referred to as a novel protein) or a hydrolyzed protein (which has been broken down into smaller parts, so the body does not recognize it as a specific protein). A true food trial requires that the test diet 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 cat 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. If dietary therapy is not successful or is not possible to perform, and no underlying cause can be found, medications are used to suppress the inflammatory reaction. Corticosteroids such as prednisolone (DeltaCortef®, Prednis-Tab®), budesonide (Entocort®, Uceris®), or dexamethasone (Decadron®) are generally the most effective medications and are used initially. Other medications such as chlorambucil (Leukeran®) are tried if corticosteroids are not successful on their own.

Occasionally, metronidazole (Flagyl®) is used to help calm the inflamed GI tract. Unfortunately, this medication has a bad taste and can cause decreased appetite or vomiting during treatment. In addition, probiotics and prebiotics are sometimes prescribed to help create a more normal GI tract microflora.

Vitamin B12. Supplementation with Vitamin B12 (cobalamin) can be considered, as most cats with IBD cannot absorb this important vitamin. Vitamin B12 is usually given by injection under the skin.

Do corticosteroids cause side effects in cats?

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, but 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 cat for the rest of his life?

Long-term therapy is required for most cats diagnosed with IBD. Generally, a cat 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 cat 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 cat has a positive response to medication, the long-term prognosis is also good. Occasionally, a cat will be able to stop drug therapy. Most cats do well for many years while others require alterations in therapy every few months.

However, if your cat 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. Some forms of inflammatory bowel disease may progress to intestinal cancer. Chronic inflammation has been hypothesized as a cause of GI lymphoma in cats.