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Inflammatory Bowel Disease in cats

If your cat has been showing signs of gastrointestinal disease such as diarrhoea and/or vomiting for three weeks or more, there is a significant chance that he is suffering from inflammatory bowel disease (IBD).

IBD is a syndrome where the small or large intestine becomes chronically inflamed and it may be due to any one of a number of causes. In some instances no underlying cause can be identified despite extensive testing, and the condition is then referred to as idiopathic IBD, as the term idiopathic means 'of no known cause'.

Although we don't know the exact cause of idiopathic IBD, there has been a significant amount of research into the problem. It seems likely that it is due to a defect in the cat's immune system so that it reacts abnormally to substances present in the intestines. 

There is probably a genetic predisposition to the condition developing, but then it can be triggered by exposure to a particular substance or infectious agent in the intestines.

Ruling out other causes

Digestive disturbances can be a reflection of problems centred elsewhere within the cat's body, for instance an overactive thyroid gland (hyperthyroidism) that is common in older cats is often associated with diarrhoea. The liver is an organ closely associated with the digestion of food and processing its products, so liver problems also often cause gastrointestinal signs.

Here are a few things that can cause upsets in cats:

  • Diet - any sudden changes to the diet of a cat that is accustomed to a particular food may cause an upset, so new foods should only be introduced very gradually. Adult cats lose the ability to digest the sugars present in milk and, if given significant quantities, may suffer from lactose intolerance where the milk sugars ferment undigested in the large intestine and cause diarrhoea.

  • Pancreatitis - this can be associated with IBD as well as an inflammation of the liver, and can be a very serious and acute condition that causes severe vomiting and even rapid death, or it can be much more chronic, and cause lowgrade vomiting and/or diarrhoea.

  • Infections - there are many different infectious agents that can cause chronic diarrhoea, but less commonly vomiting. Bacteria such as salmonella and campylobacter can cause food poisoning in cats as well as people, with similar signs, although they are usually selflimiting. The importance of single-celled protozoa in cats is being more readily recognized in recent years, including giardia and tritrichomonas foetus, which can cause quite long-term inflammation, particularly of the large bowel.

  • Drugs and toxins commonly cause gastrointestinal problems, particularly vomiting, if ingested. This may occur as a side-effect of a veterinary medicine, and you should always refer back to your vet if any suspected adverse reaction should occur. Cats are sensitive to many drugs that are safe in other species, so only medicines authorized for use in cats should be used for treatment. While cats are generally pretty selective about what they will ingest, great care needs to be taken with potential toxins around the house, such as houseplants. Sometimes they are ingested indirectly when a cat cleans his coat. Lily pollen, which is highly toxic to cats, will stick to the fur if a cat brushes past a plant.

  • Neoplasia (abnormal tissue growth) - it can be difficult to differentiate IBD from lymphoma, which can sometimes cause a diffuse infiltration along the length of the small intestine, rather than forming a discrete mass. Other tumours may cause a blockage of the bowel and lead to vomiting.

Diagnostic testing

Idiopathic IBD is a diagnosis of exclusion - in other words, there is no specific test for it and so the diagnosis can only be reached by ruling out other causes of the signs that the cat is showing, although the response to treatment will also help to confirm it.

A dietary trial with a low allergy, easily digestible food is usually the first step before exhaustive tests are carried out, unless the cat has lost significant amounts of weight and is clearly unwell. 

If a carefully controlled diet does not identify a dietary cause of the condition, a vet will usually run a series of blood tests and possibly urine analysis, and in cases of diarrhoea, may analyse a faecal sample for infectious agents.

The use of ultrasound and endoscopy (looking down into the intestines with a tiny camera) may give additional information, but the ultimate test is an intestinal biopsy, which is usually carried out as a surgical procedure, and is the only specific means of confirming the diagnosis.

Treating IBD

If an underlying cause can be identified then obviously the signs will usually resolve. For example, in the case of a dietary allergy a long-term change to the diet may be all the treatment that is required.

Cases of idiopathic IBD will need to be controlled rather than cured, and there are several approaches that can be used, alone or in combination:

  • While low allergy diets will assist cases that are allergic to a specific foodstuff, cats with idiopathic IBD will often benefit from a highly digestible diet with increased soluble fibre and supplemented with certain essential fatty acids. Pre-prepared veterinary diets are available to meet that need.

  • Prednisolone is a corticosteroid drug that is most commonly used to control this condition. In many cases it is extremely effective, and the dose can be adjusted over time to provide the minimum amount required to control the symptoms. In some instances more potent anti-inflammatory drugs need to be used, but the risk of side-effects is higher.

  • Antibiotics are not generally used to treat this condition, but metronidazole is an antibiotic that is not only active against some of the single-celled organisms that can cause diarrhoea, but also seems to have a direct anti-inflammatory effect within the bowel, so in some cases it may be useful.

  • Many cats that are unable to absorb nutrients from their bowel properly become deficient in vitamin B12, and if given by injection it often aids recovery.

IBD can be a frustrating problem because diagnosis is not always easy and treatment usually involves control rather than cure. But it's not all bad news - most cases are eminently manageable and the long-term outlook for most cats with this condition is good. 

What will your vet need to know?

Getting an accurate history of how the problem has developed is essential to help your vet reach a diagnosis and find an effective treatment. It is particularly important to pass on such information if someone other than the main owner of the cat is taking him to the vet:

  1. When did the problem first start and has it been continual?
  2. Is the problem primarily diarrhoea, vomiting or both?
  3. How is your cat in himself? Is he eating and drinking normally?
  4. Do you think your cat has lost any weight?
  5. If your cat is vomiting, how soon after eating does he vomit and what does the vomit consist of?
  6. How frequently does your cat need to pass a motion?
  7. What is the consistency of the motions? Are they watery or just sloppy? And are you seeing any mucus passed with them?
  8. Is your cat doing a lot of straining to pass motions?
  9. Do you see any signs of blood in your cat's motions? Does it look like fresh blood or is it dark and partly digested?
  10. Has there been any recent change of diet or additions to what the cat is usually fed?
  11. Have you seen your cat eating anything out of the ordinary? For example, are there any house or garden plants that are being chewed?