An In-Depth Look at Inflammatory Bowel Disease in Dogs & Cats

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Many conditions cause cats and dogs to vomit or develop diarrhea. Some are acute in nature and resolve completely with little or no intervention (e.g., a mild case of gastroenteritis secondary to dietary indiscretion). Other acute cases of gastrointestinal upset are more serious (e.g., parvovirus infection) but if the animal receives adequate care and recovers, no long term effects are expected.

In comparison, a pet with chronic vomiting and diarrhea has intermittent or continuous symptoms that do not resolve over two weeks or longer. Chronic gastrointestinal upset can be a sign of serious disease, one of the most common of which is inflammatory bowel disease or IBD.

What is Inflammatory Bowel Disease?

Inflammatory bowel disease is characterized by an over-abundance of inflammatory cells located within parts of the stomach, small intestine, and/or large intestine. Lymphocytes, plasmocytes, neutrophils, eosinophils, and other types of immune cells may be involved. The presence of these inflammatory cells within the gut wall disrupts the ability of the intestinal tract to function normally, resulting in some combination of the following symptoms:

  • Vomiting
  • Diarrhea
  • Excessive flatulence
  • Increased gut sounds
  • An increased or decreased appetite
  • Weight loss

Oftentimes, a pet’s symptoms are mild or intermittent early in the course of the disease but become worse with time. Inflammatory bowel disease can affect pets of any age, but is usually diagnosed in middle aged to older animals.

The precise location of the inflammation determines what symptoms predominate. For example, disease of the stomach typically causes vomiting, while inflammation of the small intestine often results in the occasional production of large amounts of diarrhea with or without vomiting. Large intestinal disease usually results in frequent episodes of small amounts of diarrhea that may contain mucus and blood.

"Treatment for inflammatory bowel disease involves limiting the number of potential triggers a pet’s gastrointestinal tract comes into contact with and possibly suppressing the immune system."

Inflammatory bowel disease can be subclassified based on the predominant type of inflammatory cell involved and the location of the lesion(s) within the gastrointestinal tract. Possibilities include lymphocytic-plasmacytic enteritis, lymphocytic-plasmacytic colitis, eosinophilic gastroenteritis, granulomatous enteritis, etc. Identifying the type and location of the inflammation helps determine a pet’s prognosis and allows doctors to develop a more precise treatment plan.

What Causes Inflammatory Bowel Disease?

Scientists believe that inflammatory bowel disease is caused by a combination of factors including abnormal immune responses, stimulation of the immune system (e.g., food intolerances, gastrointestinal infections, and intestinal parasites), and stress. Genetics also seems to play a role since IBD occurs most frequently in purebred cats and certain breeds of dogs, including basenjis, soft coated wheaten terriers, German shepherd dogs, Yorkshire Terriers, cocker spaniels, shar-peis, rottweilers, weimaraners, border collies, and boxers.

Healthy gastrointestinal tissues are protected from the microorganisms, toxins, and other potentially deleterious substances with which they come in contact by mucus, tight junctions between cells, and other mechanisms. When the gastrointestinal wall becomes inflamed, these protective mechanisms begin to break down. Increased contact with the materials passing through the gastrointestinal tract creates more inflammation, a further decrease in the tissue’s ability to protect itself, and a continuing cycle of increased gut “leakiness” resulting in more inflammation.

Diagnosing Inflammatory Bowel Disease in Pets


Inflammatory bowel disease cannot be definitively diagnosed without examination of gastrointestinal biopsies. Therefore, veterinarians initially try to rule out other more easily diagnosed diseases through a complete history, physical exam, and often blood work, a urinalysis, fecal examination, and abdominal x-rays and/or ultrasound. Some findings (e.g., a thickening of the intestinal wall) are suggestive of inflammatory bowel disease, but a tentative diagnosis must be confirmed via biopsy. In cats, inflammatory bowel disease often occurs in conjunction with liver disease and pancreatitis, so a thorough evaluation of those organs is also in order.

Gastrointestinal tissue samples can either be taken during abdominal surgery or endoscopically. Surgical biopsies are more invasive but allow for a full examination of the abdominal cavity and the collection of full thickness samples. Endoscopy is a simpler procedure but does not allow visualization of the entire gastrointestinal tract or the taking of large tissue samples. Histologic examination of intestinal biopsies is notoriously subjective. Therefore, the pathologist’s report must be evaluated in conjunction with a pet’s history, clinical signs, other diagnostic tests, and response to treatment.

Inflammatory Bowel Disease Treatment

Treatment for inflammatory bowel disease involves limiting the number of potential triggers a pet’s gastrointestinal tract comes into contact with and, if necessary, suppressing the immune system. Common recommendations include:

  • A diet that is either made from novel protein and carbohydrate sources (e.g., Natural Balance Venison and Sweet Potato) or one containing proteins that have been split into tiny pieces (hydrolyzed) and rice to limit adverse immune reactions.
  • Immunosuppressive medications like prednisone, prednisolone, methylprednisolone acetate, cyclosporine, or azathioprine.
  • Antibiotics like metronidazole or sulfasalazine that will decrease bacterial numbers within the intestinal tract and reduce inflammation.
  • Probiotics (beneficial intestinal microorganisms) and prebiotics (non-digestible ingredients that support the growth of probiotic microorganisms).


Most cases of inflammatory bowel disease in dogs and cats can be managed successfully with some combination of dietary modification, nutritional supplements, and immunosuppressive medications. As their condition stabilizes, some pets can be tapered off of some or all of their drugs and be managed with diet alone while others require more aggressive, long-term treatment.

Unfortunately, some pets with IBD do not respond well to treatment and eventually have to be euthanized due to their poor quality of life. There is some evidence that inflammatory bowel disease in cats can sometimes progress to lymphosarcoma, a type of cancer. Dogs with IBD may also be at higher than average risk for gastric dilatation and volvulus, a potentially life-threatening emergency. If a pet’s condition worsens at any time during treatment for IBD, contact a veterinarian immediately.


Merck Veterinary Manual, ninth edition. Editor CM Kahn. Merck & Co., Inc., Whitehouse Station, NJ. 2005.

Inflammatory bowel disease in veterinary medicine. AE Jergens, KW Simpson. Front Biosci (Elite Ed). January 2012; 4(0): 1404-19.

Feline idiopathic inflammatory bowel disease: what we know and what remains to be unraveled. AE Jergens. J Feline Med Surg. 2012 Jul; 14(7): 445-58.

Probiotics and inflammatory bowel disease. D Jonkers, R Stockbrugger. J R Soc Med. 2003 April; 96(4): 167–171.

The above is provided for information purposes only and should not be used for the diagnosis or treatment of any condition. This information does not cover all possible variables, conditions, reactions, or risks relating to any topic, medication, or product and should not be considered complete. Certain products or medications may have risks and you should always consult your local veterinarian concerning the treatment of your pet. Any trademarks are the property of their respective owners.

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