What is inflammatory bowel disease?

Inflammatory bowel disease is a condition in which the stomach and/or intestine is chronically infiltrated by inflammatory cells. It is characterized by certain cells invading the wall of the intestine. The cells are those associated with inflammation, which is the body's result to an insult or injury.

Inflammatory cells include lymphocytes and plasmacytes which are directly responsible for the body's immune response. Eosinophils are another cell commonly present in inflammation. Other inflammatory cells called neutrophils are responsible for the actual destruction of foreign invaders such as bacteria or clean up of damaged tissue. Finally, in chronic inflammation, normal tissue may be replaced by fibrous (scar-like) tissue.

The types of cells infiltrating the intestine determine the type of inflammatory bowel disease that is present.

What causes inflammatory bowel disease in dogs?

The cause of inflammatory bowel disease is unknown. Genetics, nutrition, infectious agents, and abnormalities of the immune system may all play a role. Inflammatory bowel disease may not be an actual disease onto itself, but a characteristic response of the body to certain conditions caused by a variety of factors.

What are the symptoms of inflammatory bowel disease?

The most common signs of inflammatory bowel disease in both dogs and cats are diarrhea and vomiting. The signs may vary depending upon the portion of the gastrointestinal involved, i.e., vomiting is more common when the stomach and upper portion of the small intestine are involved and diarrhea is more common when the colon is involved. There is an increase in the frequency of defecation, but less stool produced each time. There is often increased mucous or some blood in the stool. Sometimes stools become loose. Many times the diarrhea and vomiting may be intermittent (comes and goes). If severe, some animals become depressed, will not eat, have a fever, and lose weight.

How is inflammatory bowel disease diagnosed?

To be called inflammatory bowel disease, the condition must be chronic, infiltrates of inflammatory cells must be present, and other causes of these infiltrates (e.g., bacterial infections, parasites) have been excluded.

History: The history of long-standing diarrhea and/or vomiting, weight loss, increased mucous in the stool and possibly blood in the stool would lead a veterinarian to consider IBD as a possible cause.

Physical Exam: The dog may appear thin on physical exam. In some animals, veterinarians may palpate (feel) thickened intestines.

Laboratory Findings: In most cases, the chemistry panel of a dog with inflammatory bowel disease is normal. If the inflammation of the intestines is severe, the neighboring liver and pancreas may also become inflamed. This results in an elevation of liver enzymes and/or amylase which is produced by the pancreas. There may be a decreased amount of protein in the blood, and if the vomiting is significant the electrolytes (especially potassium) may be at abnormal levels.

In most cases, the complete blood count (CBC) is normal. Some animals will demonstrate an increase in the number of eosinophils in the blood.

Radiography (X-rays) and Ultrasound: There is no consistent radiological finding in dogs with inflammatory bowel disease. The intestines may appear thickened and there may be more gas than normal in the intestines, but these signs can occur in many conditions.

Biopsy: The only definitive way to diagnose inflammatory bowel disease is through a biopsy. The biopsy will demonstrate increased numbers of inflammatory cells in the intestinal wall. The types of cells which are present will denote what type of inflammatory bowel disease is present. Biopsies can be obtained through use of an endoscope or exploratory surgery. The stomach and intestines may appear normal to the naked eye, but microscopically the changes can be seen. In other cases, the lesions of the gastrointestinal tract are quite apparent.

Rule Out Other Causes: Other causes of diarrhea and or cellular infiltrates must be ruled out. Therefore, in a complete work-up, a fecal exam would be performed to rule out parasites such as giardia, bacterial cultures would be obtained to rule out e.g., Salmonella, and further blood tests to rule out other concurrent diseases such as hyperthyroidism or liver disease would be conducted.

How is inflammatory bowel disease treated?

The treatment of inflammatory bowel disease usually involves a combination of change in diet and the use of various medications.

Dietary Management: A food trial using hypoallergenic diets is usually one of the first steps in the initial treatment, and is used to verify the diagnosis. The key is to use a protein source and carbohydrate source the animal has never eaten before, such as duck and potato. The pet must eat nothing else, including treats, and the trial should be maintained for two to three months.

If a hypoallergenic diet does not improve the condition, other diets may be tried. When the colon is the major portion of the digestive tract that is involved, diets high in fiber such as Hill's r/d have been beneficial. Oat bran could also be added to the diet to increase the fiber content. When the small intestine is the primary site of involvement, some animals benefit from a highly digestible, low-fiber (low-residue) diet.

Diets low in fat are generally better tolerated in dogs with IBD. Carbohydrates low in gluten may also be helpful; avoid wheat, oats, rye, and barley. Homemade diets are sometimes used, however, they often are not completely balanced and commercial diets are preferred for the long term.

As you can see, multiple diets may have to be tried before one sees improvement in the pet's condition. This takes a lot of patience on the part of the owner.

Fatty Acids: Some studies have suggested that diets enriched in omega-3 fatty acids may help decrease the inflammation in the gastrointestinal tract. Eicosapentanoic acid and docosahexaenoic acid (fatty acids from fish oil) have been beneficial in human patients. More research needs to be done to determine their benefit in dogs and cats with inflammatory bowel disease.

Anti-inflammatory Medications: Various medications are used to reduce the number of inflammatory cells moving into the gastrointestinal tract.

Sulfasalazine, 5-ASA, and Mesalamine Compounds: Sulfasalazine, 5-ASA, mesalamine, and related compounds are the drugs of choice in dogs with primarily large intestine involvement. They can, however, cause a condition called keratoconjunctivitis sicca (KCS or dry eye) so they must be used with caution. KCS results from an abnormally low tear production. Sulfasalazine, by an unknown mechanism, can irreversibly reduce the amount of tears produced. Sulfasalazine and similar compounds contain salicylates (so does aspirin) which can be very toxic to cats. So the use of these drugs in cats must also be closely monitored.

Sulfasalazine or related compounds are generally administered at high doses and the dose is maintained 3-4 weeks after improvement is noted.

Corticosteroids: Corticosteroids (such as Prednisone) are the treatment of choice for cats with inflammatory bowel disease. Corticosteroids are used in dogs when dietary management and sulfasalazine do not adequately improve the condition.

Azathioprine and Cyclophosphamide: These drugs are immunosuppressive agents and are generally used only if other treatments have failed or in combination with corticosteroids to allow a lower dose of the steroid to be used. These drugs can suppress the bone marrow (less blood cells are then produced), so again careful monitoring through regular complete blood counts is recommended.

Metronidazole: Metronidazole can be used alone or in combination with sulfasalazine or corticosteroids. It is an antibiotic and also inhibits the immune system.

Drugs Affecting Motility: Antidiarrheal drugs such as loperamide (Imodium) or diphenoxylate (Lomotil) can have some beneficial effects. Antispasmodic drugs have also been used in some cases.

In the Future: Newer drugs are being used in humans with Crohn's disease and inflammatory bowel disease. The benefits, risks, and dosages of these drugs in dogs has not been determined. Some of these drugs include cyclosporine, sodium cromoglycate, and clonidine.

What is the prognosis for dogs with inflammatory bowel disease?

Inflammatory bowel disease can be controlled, but not cured. Control is dependent upon the proper selection of diet and medications, the correct long-term maintenance dosages, careful monitoring by the veterinarian and owner, and the absence of other concurrent diseases. Even so, persistence of mild signs, or recurrence of more severe signs may occur.