Inflammatory Bowel Disease

Inflammatory Bowel Disease (IBD) occurs when an (often unknown) trigger causes white blood cells to infiltrate into the walls of any part of the gastrointestinal tract (GI tract) such as the stomach, small intestine or large intestine. This infiltration results in a thickening of the walls. This thickening can make it more difficult for cats to digest food and absorb nutrients, and it usually results in gastrointestinal symptoms such as vomiting.

In most cases the exact trigger of the IBD is unknown. It is thought to occur when the body's immune system creates an exaggerated response to something in the gut which it recognises as foreign, for example proteins or bacteria. Genetic abnormalities may play a role in predisposing a cat to IBD, but there isn’t enough evidence to confirm this yet.

There are many different types of IBD. The most common type in cats is called lymphocytic plasmacytic enteritis. This occurs when white blood cells called lymphocytes and plasma cells invade areas of the gut wall, usually the small intestine. The second most common type is called eosinophilic enteritis. This occurs when white blood cells called eosinophils invade the walls of the intestine, again, it usually affects the small intestine.

The most common clinical sign of IBD in cats is vomiting. This is in contrast to dogs where the most common sign of IBD is diarrhoea. Other clinical signs you may notice in your cat include lethargy, weight loss, anorexia (refusal to eat), diarrhoea, abdominal discomfort, increased gut sounds, blood in the vomit and blood in the faeces. In the early stages of the disease it’s possible for a cat with IBD to show signs of an increased appetite due to being unable to absorb enough nutrients. In some cases, IBD can occur alongside inflammation of the liver and pancreas.

Unfortunately, many of the clinical signs of IBD also occur with other diseases. This means IBD is often diagnosed after ruling out other conditions. Your vet may wish to perform blood tests, faecal tests (to check for parasites) and imaging of the GI tract (x-rays or ultrasound or both) as part of a diagnostic work up. Your vet may also recommend a hypoallergenic diet to rule out food allergy.

It is possible that the thickening of the stomach or intestinal walls seen with IBD could be picked up on ultrasound by your vet, this can be an early clue, but other conditions can also cause intestinal wall thickening.

Another clue can be decreased levels of folate and/or vitamin B12 on a blood test due to decreased absorption through the intestinal walls. Folate is normally absorbed in the upper part of the small intestine and B12 is absorbed in the lower part. So depending on whether folate, B12 or both are decreased, this test can give your vet a clue as to which part of the intestine is affected. However, once again, a decreased folate or B12 can be caused by other issues, so it does not confirm a diagnosis of IBD. It is also possible for cats with normal levels of folate and B12 to have IBD.

The only way to get a definitive diagnosis of IBD is via a biopsy of the affected area of the GI tract, which is performed once other conditions have been ruled out. This involves taking a small sample of the stomach, intestines or colon whilst the patient is under general anaesthetic. The sample is then studied under a microscope. It is possible for a sample to be taken via a scope if it’s only the stomach or colon affected, however in most cases samples will need to be taken via a surgical incision into the abdomen.

Cats with IBD can suffer from decreased levels of vitamin B12 and folate, so these should be supplemented where necessary. Supplementation may be required long-term.

An elimination diet can be trialled as a first line treatment for IBD. This involves feeding your cat a source of protein that they’ve never been exposed to before. This may not be suitable if you do not know your cat’s dietary history e.g. if your cat has had multiple owners. Another option is to feed a hydrolysed diet. This is a diet that has been specially treated so that all the proteins are broken down into smaller parts.

Elimination diets should be fed as your cat's only source of food for at least 8-12 weeks. This means that you or anyone else (family members, neighbours) should not feed your cats other food such as treats during this time.

Where an elimination diet does not improve clinical signs, a high fibre diet can be trialled. As with the elimination diet, this should be your cat's only source of food.

Your vet may also recommend trialling a course of antibiotics called metronidazole, either in combination with or after an elimination diet. These should be given for a prolonged period of time (usually 3-4 weeks).

Where other treatments have not worked, immunosuppressive treatments such as steroids may be required. Your cat is usually started on a high dose which is gradually tapered down to the lowest effective dose. If your cat shows improvement, they can then be taken off of immunosuppressive treatment to see if the clinical signs return.

Unfortunately, in a lot of cases clinical signs do recur again and immunosuppressive treatment must be continued long-term at the lowest possible dose.