It is likely a majority of dogs at some time in their lives will need veterinary help due to large bowel disease (colitis).  Fortunately, most of these cases are transient bowel irritations and recovery is rather prompt. In a very small percentage of dogs, chronic, severe colitis is a problem.  In these, accurate diagnosis of the cause and implementation of a treatment can be a challenge.

Probably the vast majority of house cats, due to well-regulated dietary intake, never have colitis problems needing veterinary intervention.  Outdoor cats with free access to hunt prey are more likely to have large bowel flare-ups.  Cats also have unique colon problems, especially with constipation and a problem called megacolon where the colon stretches and looses its intrinsic ability to contract and expel the stool.
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Is colitis more common in puppies (or kittens), adult, or senior pets? Are the causes different at different life stages?

Acute Colitis is a general term for any inflammation or irritation of the large intestine (colon) that suddenly flares up but lasts only a short time.   Chronic Colitis is a long term, difficult-to-treat, large intestine disorder. Acute colitis is fairly common in puppies and kittens less than ten weeks old and can be due to a number of causes such as bacterial imbalance, intolerance to the mother’s milk, or parasites.  Most dogs and cats of any age that eat proper diets and are well regulated regarding food intake seldom experience colon trouble.   Probably the most common cause of adult acute colitis is ingestion of a substance (such as a dead mouse, rotten garbage, food contaminated with pathogenic bacteria) that has a sudden impact on colon physiology. 
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How common is colitis from food allergies?  What approaches do you take to diagnose and correct this problem?

Fortunately, colitis caused by food allergies is rare in dogs and cats but does occur.  It takes lots of searching and testing by the veterinarian, and patience exhibited by the pet owner, for the final diagnosis of food allergy to be ascertained.  Food intolerance, which are different from food allergies, are a bit more common.  Often, these allergies and intolerances affect the small intestine more than the colon, producing watery frequent stools and even systemic effects; however, the large intestine receives whatever the small intestine sends it and an apparent colitis may appear to be present. 

If the small intestine is inflamed and upset (sometimes called small bowel enteritis), the abnormal intra-intestinal contents may be difficult for the colon to manage.  Diagnosis of food allergy is attempted through feeding trials with limited ingredient diets, with the assistance of blood tests to measure immune factors to certain food ingredients, and by ruling out all other potential causes of colitis/enteritis.  A true food allergy can have diverse and intense effects on a dog or cat.
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What parasites are the usual culprits in causing colitis in dogs? What is the best course of diagnosis and treatment?

Most intestinal parasites of dogs and cats affect the small intestine, sparing the colon.  Although not classified as parasites, pathogenic (capable of causing disease) bacteria are commonly associated with colitis.  Treatment depends upon making a correct diagnosis of the individual animal’s problem.
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Is immune-mediated colitis inherited? What are the treatment options?Immune-mediated colitis, often called IBD (irritable bowel disease), is a form of autoimmune disease and results from the body’s abnormal response to its own tissues. It may have inherited predisposing origins.  Much needs to be learned about what triggers the invasion of apparently normal bowel lining by immune cells that try to destroy the target bowel tissues.  Complex biochemical and hematological mechanisms are at play with the result being inflamed, scarred, and damaged bowel lining… and a sick patient.  It is not well understood what genetic factors are at work in these autoimmune colitis patients.

Treatment varies as to the precise diagnosis of the type, extent, and microscopic environment of the individual patient’s affliction.  Hypoallergenic diets are often used, careful medication with cortisone is common, and immune suppressing drugs may be needed.
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What can owners do to prevent constipation in cats?

The best thing is to be aware of any discomfort when passing stool.  If the cat vocalizes, suddenly jumps out of the litter box, defecates in random areas about the house… these are early warning signs that a problem is developing.  A veterinarian should be consulted before long-term colon pathology sets in.  Dietary modification with more or less fiber can be helpful.  Sometimes adding stool softeners every day can assist in easier passage of hard stool.  Enemas may be needed on occasion, too, so that the stretching and thinning of the colon wall won’t result in a flaccid, stretched megacolon condition.
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Can pet owners prevent colitis in their pet dogs and cats?

It is always best to feed only the highest quality pet food!  It may be a bit more expensive than “ordinary” foods but high quality foods are more efficiently digested, have less non-nutritive fiber, provide a better level of nutrition to every cell in the body and impart better resources for competent immune system function.  Then be proactive regarding any difficulty the pet may have defecating.  Alert your veterinarian if episodes of constipation or loose stool occur.  And try to keep the pet on a consistent dietary plan of high quality food fed in amounts that do not promote an overweight body condition.

The colon is responsible for...
  reabsorption of water from the feces
  decreasing the fecal volume
  colonic bacterial activity
  bacterial vitamin generation
  firming the feces
  temporary storage of feces
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Signs:
The most obvious signal of colitis is loose stool, mucus and an increased frequency of passage. The dog often strains to pass small amounts of stool and may appear to be constipated.

Note: Weight loss is not a common finding unless long term (chronic) colitis is present. Rapid weight loss associated with loose stool usually means the small intestine is involved. Red blood, rather than black, tarry blood associated with small intestine bleeding, is indicative of colonic bleeding.

The loose stool commonly seen in colon disorders is due to lack of proper reabsorption of water from the feces. This can be due to:

  A hyperactive colon is contracting too frequently and the feces don't spend enough time in the colon to have the water reabsorbed. Dehydration becomes a serious consideration.

  Impaired reabsorption of the water through the colon wall and then back into the body.  Dehydration becomes a serious consideration.

Diagnosis:
  History - It is very important to observe and describe accurately factors such as the
type and frequency of stool, the dog's environment, diet, stress factors, straining, etc.

  Laboratory analysis - fecal exams for parasites, undigested nutrients, blood.

  Colonoscopy - Direct visual exam by a specialist can be very revealing.

 Biopsy - Often in chronic colitis the biopsy provides the final diagnosis regarding the cause. This requires an anesthetic and surgical procedure, therefore, other modes of diagnosis and treatment are employed first. Barium enema and X-ray imaging can be helpful as a method of diagnosis and better prepares the surgeon if an exploratory abdominal surgery is planned. Surgery for direct visualization of the colon provides direct access to the tissues for hands-on inspection and for obtaining biopsy specimens for histopathology evaluation.

 

Treatment:
The treatment depends of course upon the cause.  Dietary changes may be required so various ingredients can be eliminated or added to keep the colonic environment consistent.  Whipworms must be ruled out even if fecal samples are negative. Antibiotics, proper worming, and adding or removing fiber from the diet are employed with varying success. This is one disorder that requires close cooperation with your vet, good record keeping, and patience.

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