Chronic colitis is defined as persistent signs of colonic inflammation, having greater than 3 weeks duration. The same signs are seen with acute colitis but an owner may see weight loss or anorexia as well. It is much less common than the acute version but can be seen in young to older animals, depending on the cause of the problem.

The causes of chronic colitis can be generally placed into 3 categories. The first one to discuss is Diet-responsive disorders. Having diet-related colitis can be due to the immune system or intolerance due to a non-immunological response. Determining the cause would be to rule out infectious causes, and depending on age, ruling out infiltrative causes as well. If diet-related colitis is suspected, a food trial diet with a novel protein (one which the animal has not eaten before) is recommended. A food trial involves 2-3 months of strict adherence to the new diet. Patience is essential (owners!) with food trials, due to the length of time required for resolution, and discipline of sticking to the diet (no random treats!) for it to be effective. Also, supplementing probiotics or fiber into food may be of help in reducing colonic inflammation.

Infectious disorders are more likely to be seen in younger animals. Whipworms are commonly seen in puppies, uncommonly seen in older dogs. Giardia can be seen in cats and dogs, causing general GI upset, uncommonly colitis can be seen. Tritrichomonas species of protozoa may be seen in younger cats, causing intermittent signs of colitis. Very uncommonly, certain bacteria like Clostridium perfringens may be the source of colonic inflammation. Another rare cause of a specific type of colitis called Histiocytic Ulcerative Colitis is a type of E. coli bacteria. This disease is usually associated with Boxers and French Bulldogs. With these types of disorders, there are specific tests for these organisms, which are treated relatively easily, and animals can be cured.

The final category of disease form for colitis is an infiltrative mucosal disease. This means that the mucosa (inner layer) of the colon has a disease process affecting it, causing inflammation. The roots of this problem may be fungal (histoplasmosis), immune-related (inflammatory bowel disease), or cancer growth in the colon. The most common cause that we see at St. Francis is inflammatory bowel disease in older cats, and less commonly, in older dogs. Diagnosis for these types of cases usually involves more extensive testing and increased costs for the owners. For a definitive diagnosis, colonoscopy and/or sampling colonic tissue for biopsy is usually needed. Fungal causes are very uncommon but can be treated. The prognosis depends on how extensive the disease is throughout the body. Inflammatory bowel disease can be managed but not cured, often involving the use of corticosteroids and a novel protein diet as therapy. Colitis caused by malignant cancer has a poor prognosis and is difficult to treat.

I will reiterate: Most of the time we see a dog or cat with colitis, it is acute, is easily treated, and will resolve quickly. Chronic colitis is unusual and usually involves some diagnostic testing to find the cause of the problem. If you suspect your pet has colitis of any kind, please give us a call with any questions or bring them in for an appointment.

Dr. Jaime Kozelka
St. Francis Hospital for Animals