Colitis is defined simply as inflammation of the colon. Although this is a bit of an over-simplification, the digestive tract of the domestic dog extends from the mouth to the anus, in roughly the following order:
Digestive Tract of the Domestic Dog
Mouth (oral cavity)
Pylorus (junction of the stomach and the small intestine)
Small intestine - 3 main divisions: duodenum, jejunum and ileum
Large intestine - 3 main divisions: cecum, colon (ascending, transverse, descending), rectum
The colon is that part of the large intestine that extends from the cecum to the rectum.
Causes of Colitis
Colitis is commonly caused by one of the various disorders that contribute to inflammatory bowel disease in dogs. These include lymphocytic-plasmacytic enterocolitis, eosinophilic enterocolitis, granulomatous enteritis, neutrophilic enterocolitis and histiocytic ulcerative colitis, among possible others. Infectious causes of colitis are also common – especially from salmonella, campylobacter, giardia, Escherichia coli, histoplasma and/or clostridium. Internal parasites – particularly canine whipworms (Trichuris vulpis) - often contribute to colitis in dogs. Traumatic injuries from foreign bodies, physical trauma or abrasive ingested items, are also causes of canine colitis. Allergic conditions and immunosuppressive disorders are other frequent contributors to inflammation of the colon. Colitis can be associated with irritable bowel syndrome, which is a gut motility disorder most commonly seen in high strung, stressed, nervous dogs. Colitis can also be caused by dietary indiscretion, because as most dog owners know, dogs often eat things that they really shouldn't.
Fungal infections, and a very serious blue-green algae-related disease called Prototheca colitis, are uncommon causes of colitis. They tend to affect dogs with weakened immune systems. Prototheca algae live on both raw and treated sewage and are contaminants of food, soil and water. They can be found in fresh fecal matter, as well.
Prevention of Colitis
One of the best ways to prevent colitis in companion dogs is to keep them away from sources of infectious microorganisms and parasites. Owners should take all necessary steps to keep their dogs from ingesting foreign objects or sharp or abrasive substances that could be irritating or penetrating. Keeping dogs from roaming freely about the neighborhood will greatly reduce the risk of dietary indiscretion. It is always wise to avoid very abrupt changes in diet or in the source of a dog's water supply. Routine de-worming will help to reduce the risk of internal parasite-related colitis.
How Colitis Affects Dogs
Colitis, which simply means inflammation of the colon, is reportedly responsible for up to thirty to fifty percent of the cases of chronic diarrhea in domestic dogs. The colon is the center portion of the large intestine, located between the cecum (the first part) and the rectum (the last part). When the colon become inflamed for whatever reason, substances called inflammatory cytokines begin to accumulate there, disrupting the normal cellular structure and junctions of colonic tissues. This stimulates secretion of mucus and other substances from the large intestinal lining and adversely affects normal gut motility. As a result, the colon's ability to properly absorb water and process feces is compromised, causing profuse diarrhea that often is mixed with mucus and/or frank (fresh) red blood. It is difficult to speculate about what a dog with colitis is feeling. However, based on reports from people suffering from this disorder, it is safe to say that there is a significant amount of discomfort and pain associated with the condition.
Symptoms of Colitis in Dogs
The observable hallmarks of canine colitis include one or more of the following clinical signs:
Profuse watery diarrhea, usually containing fresh red blood and mucus
Passage of frequent, small amounts of liquid to semi-formed fecal matter
Straining to defecate; especially prolonged after defecation (tenesmus; may be mistaken for constipation)
Squatting to defecate
Passage of gas (flatulence)
Lack of appetite (inappetence; anorexia; not common)
Weight loss (also not common)
Basically, dogs with colitis from whatever cause probably are suffering from varying degrees of lower intestinal cramping and nausea. The persistent diarrhea can cause secondary inflammation, redness and irritation of the tissues surrounding the anus.
Dogs at Increased Risk
Some Boxers are predisposed to developing histiocytic ulcerative colitis, which is one of the several diseases that can be part of a syndrome called inflammatory bowel disease, or IBD. Boxers usually develop symptoms of this type of colitis by 2 years of age. German Shepherd Dogs are predisposed to developing lymphocytic-plasmacytic enterocolitis. Irritable bowel syndrome, one of the more common causes of canine colitis, is a gut motility disorder that is frequently associated with stress in nervous, high-strung dogs. Young dogs seem especially predisposed to developing colitis as a result of dietary indiscretion, also called "garbage gut." Free-roaming outdoor dogs obviously have increased opportunities to eat things that they shouldn't, and subsequently to develop colitis as a result of their inappropriate eating habits.
How Colitis is Diagnosed
Because colitis can be caused by so many different things, its diagnosis can be like following a maze to its ultimate conclusion. There will be bumps and dead ends along the way. The veterinary team will have to rule out a number of possible causes of the dog's intestinal troubles before arriving at the final diagnosis. Sometimes, the underlying cause of the condition is never determined.
A veterinarian presented with a dog with symptoms of colitis (straining to defecate and diarrhea combined with fresh blood and mucus) will normally isolate the problem to the colon. Physical examination findings (including abdominal palpation) are usually normal, although some dogs may be underweight and inappetent or painful on palpation of their abdomen, depending upon the cause of their colitis. The results of a urinalysis and routine blood work, including a complete blood count and serum biochemistry profile, are usually unremarkable, unless the dog's colitis is caused by a systemic disease.
Fecal samples may be examined for the presence of fungi and gastrointestinal parasites by procedures called fecal floatation, direct fecal smear, fungal culture and/or bacterial culture. Abdominal radiographs (X-rays) and ultrasound are available and may reveal masses, fecal impaction, thickened large intestinal tissues, enlarged lymph nodes or other abnormalities. However, the results of these procedures in dogs with colitis are also usually fairly normal. Ultrasound tends to be a poor screening tool for colitis, because the obstructive effects of air in the colon can cloud the ultrasound results.
The procedure of choice for diagnosing the underlying cause of canine colitis is a colonoscopy accompanied by the taking of multiple biopsies from different places of tissues lining the colon. This procedure requires either heavy sedation or general anesthesia. The veterinarian will insert a wand-like instrument with a camera at its tip through the anus and rectum up into the colon. The camera lets the veterinarian visualize the lining of the colon and identify any areas that appear abnormal, such as those that are bumpy, bleeding, inflamed, red or otherwise just not looking healthy. She also can take multiple biopsy samples of those areas with the help of the camera. Those samples will be submitted to a diagnostic pathology laboratory for microscopic assessment through a process called histopathology. Biopsy samples obtained through a colonoscopy are greatly preferred in the veterinary community over biopsies of the colon obtained through abdominal exploratory surgery (laparotomy), which is highly invasive and can expose the animal to a greatly increased risk of intraabdominal infection. When a veterinarian opens the abdomen and then opens the large intestine, there is an increased chance of having the bacterial content of the colon spill into the free abdominal cavity, with the attendant risk of developing peritonitis or other forms of abdominal infection.
Some infectious causes of canine colitis have the potential to infect people, especially if the people have weak or compromised immune systems. People owning, working with or treating dogs with colitis should take appropriate precautions to ensure that their environment is kept as clean and as well-sanitized as possible.
Most cases of canine colitis, which is inflammation of the middle portion of the large intestine, can be treated on an out-patient basis. However, if prolonged diarrhea and/or vomiting have caused severe dehydration, the dog may need to be hospitalized so that intravenous fluid and electrolyte replacement therapy can take place.
Treatment of colitis is directed toward resolving the underlying condition or conditions that are causing the colon to become inflamed. Fasting for 24 to 48 hours is a common initial part of treatment. This is typically followed by the slow introduction of a high fiber diet – especially if the dog is suffering from irritable bowel syndrome. High-fiber diets can increase stool bulk, bind fecal water and improve the contractility of the muscles of the colon so as to increase motility and normalize the quality of the stool. Diets with novel proteins, such as duck, fish or venison, are increasingly commercially available and can be beneficial in cases of colitis that are caused by food allergies.
A proper course of broad spectrum antibiotics usually will resolve colitis that is caused by a bacterial infection. Anti-parasitic medications, called anthelmintics, are available to treat intestinal parasites. There currently is no known treatment for the blue-green algae disorder caused by Prototheca. In some cases, anti-inflammatory and/or immunosuppressive drugs may be prescribed to affected dogs; these may include non-steroidal anti-inflammatory drugs or corticosteroids. So-called motility modifiers – medications that are designed to decrease diarrhea and firm up the stool – can be administered for symptomatic relief, although they will not resolve or contribute to a "cure" of the condition.
In severe cases, if portions of the colon have become badly damaged by inflammation and scarring, surgical removal and reconstruction may be necessary. This is called surgical resection and anastamosis. Thankfully, most cases of canine colitis are self-limiting, which means that they resolve on their own with only supportive care and minimal medical treatment.
Dogs with infectious causes of colitis typically have a very good to excellent prognosis with appropriate diagnosis and treatment. Dogs with Prothotheca colitis, which is caused by a blue-green algae infection, have a guarded to grave prognosis, as there presently is no effective treatment for that condition. Dogs with colitis from other causes have a mixed prognosis, depending upon the nature and severity of their condition.