Colitis is the term for inflammation of the colon (the large intestine). The chief feature of colitis is a gooey, frequently splattering diarrhea featuring mucus, fresh blood, or both. The stool may start normal then finish soft or may seem gooey throughout. There is often accompanying cramping, gas and a sense of immediate urgency (the sudden need to run for a bathroom). Vomiting can be a feature of this condition though the characteristic diarrhea is the hallmark. Colitis may be acute (lasting only a few days) or chronic (lasting weeks or months on end). Even in chronic cases, weight loss is usually not a feature of this condition.
The colon is the last segment of the digestive tract. Before reaching the colon, food is extensively processed – chewed up in the mouth, acid-treated in the stomach and enzyme bathed for digestion in the small intestine. Most of the nutrients have already been absorbed by the time unusable leftovers pass into the colon. The colon has three functions: absorbing water, storing stool and further digesting unabsorbed nutrients. The bacterial population in the colon is about 10 times denser than that of the small intestine. These bacteria, often referred to as good or helpful bacteria, take fibers that were undigestible to the host and process them into biochemicals that provide nourishment to the colon cells. The bacteria that live in the colon not only feed the cells of the lining of the colon, they also control the pH of the colon environment so that excreted toxins are trapped in the stool and eliminated by defecation rather than reabsorbed into the body. The bacteria also produce gases and influence the pigments that lead to the ultimate color of stool. The relationship we have with our colon bacteria is mutually beneficial and is an excellent example of symbiosis.
In classifying diarrhea, it is important to determine whether the problem originates from the small intestine, the colon or both. Small intestinal diarrheas tend to be more serious as they involve fundamental problems with absorbing nutrients from food. Diarrheas of the colon are less debilitating but still uncomfortable. The following are characteristics of large intestinal (colon) diarrhea:
Large intestinal diarrheas are generally not associated with weight loss and patients generally have normal energy levels and normal appetites. The exception to this statement is that patients with cancer in their GI tracts typically do exhibit weight loss.
Large intestinal diarrhea is associated with straining to defecate. Often the straining is unproductive, leading to the erroneous conclusion that the patient is constipated.
There is cramping, flatulence and often a sense of urgency. The pet may not be able to get to an appropriate area before the diarrhea erupts.
There is often mucus and fresh blood in the stool.
The stool may also start looking normal and formed but finish as a puddle.
A diagnosis of colitis is generally straight forward given the above classic findings, though how to proceed depends on the signs. Is the problem acute (i.e., suddenly there) or chronic (has been happening for several weeks regularly) or episodic (happens then goes away then happens again)?
Sudden Colitis (Acute Colitis)
A pet that has sudden symptoms of colitis probably has what is commonly referred to as stress colitis (common after boarding, moving, severe weather or other change) or dietary indiscretion-related colitis (usually involves treats or raiding the garbage). These episodes are generally minor, often self-limiting and not consistent. There is a subset of animals that have an underlying enteropathy (abnormal function of the cells of the intestine) sometimes called food or fiber responsive diarrhea, also early cases of inflammatory or infiltrative bowel disease can present in this manner. Another cause of diarrhea is parasites, especially Giardia, protozoa, and whipworms. The pet can be tested for those to be dewormed. In general, a few days of medication and a bland diet often resolves the problem. During recovery, it is common for the pet to have no stool at all for a couple of days because the colon is not storing feces as it normally would so the colon essentially gets emptied out. This is normal and not a sign of constipation. If, however, the pet’s diarrhea is not clearly improved in two to three days, contact the veterinarian to see if further testing is needed.
Chronic Colitis or Recurrent Episodes
If the symptoms of colitis persist for a month or more or if the pet has episodes over and over, then a medical work up is warranted. It is important to make sure simple causes of colitis have been ruled out and a good fecal examination for worms and Coccidia plus testing additional for Giardia are indicated. If these tests are positive, treatment directed at that parasite will be prescribed. Even if these tests are negative, it is reasonable to include a broad-spectrum de-worming because these treatments are safe, effective and inexpensive. Whipworms are difficult to detect and can cause colitis. If chronic, of course, a basic blood panel and urinalysis are in order, as with any chronic disease, to assess the patient’s general health.
If it doesn’t look like one-time treatment of deworming, antibiotics or diarrhea medication is going to solve the problem, then diagnostics continue to the next level. Most reference labs now have the capability to do PCR (DNA) testing on feces samples for more obscure organisms such as Tritrichomonas in cats, Cryptosporidium in dogs and cats, and more.
The last step in colitis diagnostics is imaging. Typically achieved with abdominal ultrasound or colonoscopy with biopsies with the idea of examining colon tissue under the microscope to classify the inflammation. Depending on the type of cells infiltrating the colon lining, the colitis can be classified as lymphocytic/plasmocytic (a form of inflammatory bowel disease), histocytic (which can stem from a type of E. coli infection) or not truly colitis at all and the entire problem may be the condition known as irritable bowel syndrome. All these conditions have different treatments.
Colonoscopy requires a period of fasting (usually a couple of days) and preparation to allow the internist to view the naked tissue of the colon can be viewed and sampled. Referral to a specialty hospital is needed. Colonoscopy is performed under general anesthesia – not every patient can undergo anesthesia and expense may be a concern. These disadvantages must be weighed against the quality and quantity of information that can be obtained through evaluating a tissue sample from the colon.
Management Tips for Colitis
Colitis is best managed when the cause is known and tailored therapy prescribed. When this is not possible, symptomatic management is often attempted. The following are therapeutic medications and strategies that can be helpful in the treatment of colitis.
Elimination Diet Trial and Dietary Fiber
Food-responsive enteropathy is one of the most common forms of chronic enteropathy in dogs and includes those with adverse food reactions (ie: food allergy vs food intolerance) and those with intestinal inflammation that benefits from properties of a different diet. Food-responsive enteropathy is characterized by persistent or intermittent gastrointestinal signs lasting 3 weeks or longer in the absence of other causes such as dietary indiscretion, parasitism, identified intestinal pathogens, or neoplasia) and non-GI diseases.
Dogs with food-responsive enteropathy are more likely to be younger, have less severe clinical signs, and exhibit more large-bowel diarrhea compared to dogs with immunosuppressant-responsive enteropathy.
Since many dogs with chronic idiopathic GI signs respond well to dietary changes, an elimination diet trial is often recommended before endoscopy/colonoscopy for those dogs with mild or moderate signs unless negative prognostic factors (e.g., hypoalbuminemia, hypocobalaminemia, high clinical activity index score) are present.
The goals of nutritional intervention are to provide a complete and balanced diet that avoids known allergens or ingredients that cause adverse food reactions and resolves or minimizes clinical signs
The role of fiber in colitis is confusing as there is an assortment of fiber preparations (soluble fibers, insoluble fibers, and mixtures). In general, colitis is felt to be a fiberresponsive disease but there are so many combinations of fiber types that it is hard to know what the patient may be responding to. Insoluble fibers, like cellulose, bulk up the stool and are stimulating to the colon lining. This may not be what is in order if the colon is already irritated although giving some structure to diarrhea may be a good thing. Soluble fibers, like psyllium, are fermented by the colon bacteria into nutrients for the colon cells, which helps them heal. Prescription high fiber diets often have a mixture of soluble and insoluble fibers that have been scientifically proven to help colitis patients. Alternatively, a low residue diet (one of high digestibility) could be used and soluble fiber added to it. The idea with this strategy is to have maximum intestinal absorption of nutrients in the small intestine so less material enters the colon, but once the material gets there the soluble fibers added help the colon cells to heal.
Fructooligosaccharides (FOS)
Prebiotics are basically food for beneficial colon bacteria. Feeding a diet rich in prebiotics promotes a healthy colon bacterial population, which in turn helps resolve diarrhea.
Fructooligosaccharides are carbohydrates involving fructose (fruit sugar) units attached to glucose (starch sugar) units. Regular dietary carbohydrates are digested by the bacteria of the small intestine, leaving only the undigested fibers and other dregs for the teeming masses of the large intestine. FOSs are not fibers, but they are digested in the large intestine (not the small intestine) in the same way that fibers are, yielding the same biochemicals that fibers do. Why is this good? Tests in healthy animals indicate that this will help remove pathogenic bacteria from the large intestine and promote growing helpful bacteria. Diets that contain FOSs or other prebiotics may be helpful in managing colitis. Several such diets are available.
Probiotics
A probiotic is a protected culture of live helpful bacteria that can colonize the patient’s intestine. The bacteria must be protected from the acid of the stomach to survive to the lower intestine. Once there, the bacteria make a home and make by-products that are nourishing to the intestinal and local immune system cells. There are numerous products on the market for both humans and animals; the problem has been that since these products are not regulated as drugs by the FDA, they are required only to be safe, not necessarily effective. In fact, a recent study found that most such products do not actually contain the live cultures they are advertised to contain. If you want to add a probiotic to a pet’s regimen, we recommend sticking to well-established veterinary companies. That said, probiotics are mainly made to colonize the small intestine, not the large intestine, so their benefit in colitis is still somewhat speculative.
Elimination Diet
Colitis can result from food intolerance (an example would be lactose intolerance from which numerous people suffer). Intolerance can result from dyes, preservatives, contaminants or even natural proteins in the food. Similarly, colitis can result from an actual food allergy. The solution for these intolerances is feeding a “pure” diet, ideally a home-cooked food made with carbohydrates and proteins that are novel or new to the patient. An 8 to 12-week diet course is typically needed and no other chews, treats, flavored toothpaste, flavored chew toys, human food, food to hide pills (lunch meat, cheese, flavored flea/tick/heartworm preventatives, etc.) can be eaten by the animal during the trial. Food allergies cannot be diagnosed by blood test or skin test. Currently, response to elimination diet is the only test for food allergy or intolerance. Most people are not able to cook an appropriate food for their pet. Fortunately, several novel protein diets and hydrolyzed protein diets have been developed. For more details on using an elimination diet trial and if this might be an appropriate diagnostic tool for your pet, please book an appointment with our dermatology focused veterinarian, Dr. Sovik.
Prednisone
is the cornerstone of treatment for inflammatory bowel disease, which must be diagnosed by biopsy. Sometimes a trial course of this medication is suggested for colitis, but it is important to keep in mind that such trials can interfere with future diagnostics and can create some degree of immune suppression. Prednisolone could be disastrous in the event of an E. coli-related histolytic colitis, for example. Many patients with inflammatory bowel disease are never able to fully discontinue prednisolone so be sure to discuss the pros and cons of attempting this therapy without a biopsy.
Histiocytic Ulcerative Colitis: A Specific Form of Colitis
This condition is also called Boxer colitis because the Boxer breed seems predisposed. This form of colitis is ulcerative and involves infiltration of the tender colon lining with cells called histiocytes. These cells are normally present relatively late in the inflammatory process. They digest dead cells and debris created by the inflammatory event. Dogs with this condition typically develop clinical signs early, ie: less than two years of age, and become more debilitated than typical colitis patients. It is currently believed that this condition results from an inappropriate immune response against the common bacteria of the colon, especially E. coli. Dogs with this form of colitis do not respond well to the usual remedies listed above but instead seem to show an excellent response to the antibiotic enrofloxacin. This antibiotic is particularly effective against gram negative bacteria (so classified because of the staining properties of their cell wall).
Histiocytic ulcerative colitis can be confirmed by biopsy, although signs of colitis in a young Boxer are highly suggestive of this condition.
Modified from URL: Colitis-Related Diarrhea in Dogs and Cats Accessed 6 AUG 2024