Overview of Canine Colitis
Colitis is an inflammation of the colon, or large intestine. It may be acute, with sudden onset and short duration, or chronic, that is present for at least two to three weeks or exhibiting a pattern of episodic recurrence.
Causes of Colitis in Dogs
There are many potential causes of colitis. These include:
Specific inflammatory disorders of the colon. Lymphocytic-plasmacytic, histiocytic, granulomatous, suppurative, and eosinophilic are terms that describe colitis on the basis of the predominant type of cell present in the inflamed colon.
Infectious agents, such as bacteria, viruses, fungi, or parasites
Dietary intolerance or allergy
Cancer of the colon
Trauma, internal or external
Intussusception, which is a mechanical problem characterized by telescoping of the bowel into itself.
Hemorrhagic Gastroenteritis (HGE), which is an inflammatory disorder of the intestinal tract characterized by hemorrhage and production of a “raspberry jam” appearance to the stool
Pancreatitis (inflammation of the pancreas)
There is no age or gender association with colitis. One exception is histiocytic ulcerative colitis, which most often affects young boxer dogs.
Most often, colitis causes some combination of fresh bright red blood in the stool, mucus in the stool, straining to defecate, and increased frequency of defecation, often many times per day. With acute colitis, the dog usually does not show signs of systemic illness, but dogs with chronic colitis can experience clinically important weight loss.
What To Watch For
An occasional bout of acute colitis is not uncommon in the small animal patient. However, it is important to watch for frequent recurrence or worsening of signs, especially if they include systemic signs of illness. Although occasional vomiting occurs in otherwise healthy dogs, repeated vomiting, poor appetite, weight loss and general lethargy should be reported promptly to your veterinarian.
Veterinary care should include diagnostic tests and subsequent treatment recommendations.
Diagnosis of Colitis in Dogs
Your veterinarian will recommend diagnostic tests in order to recognize colitis and confirm the diagnosis. Tests may include:
A complete medical history and thorough physical examination
Fecal examination to evaluate for the presence of disease-causing bacteria or parasites
A complete blood count (CBC or hemogram) to evaluate for anemia, systemic inflammation, and presence of inflammatory cells (i.e., eosinophils) that may indicate an underlying allergic cause
Serum biochemistry tests to evaluate the general health of your dog and to identify problems in other organ systems
Urinalysis to evaluate kidney function
Abdominal X-rays to look for tumors or enlargement of abdominal organs
Serum trypsin-like immunoreactivity (TLI) in dogs to evaluate for pancreatic disorders
Colonoscopic examination to identify the presence of colitis or colon cancer and biopsy to determine the type of inflammation (eosinophilic, granulomatous, lymphoplasmacytic) or neoplasia (adenocarcinoma, lymphosarcoma). This procedure requires anesthesia, adequate cleansing of the bowel by enemas, and special equipment (a flexible fiberoptic endoscope) that may only be available at veterinary specialty referral centers.
Treatment of Colitis in Dogs
Treatment for colitis is most effective when directed at the underlying cause. Your veterinarian may recommend several symptomatic treatments for an animal with signs of colitis before recommending an extensive diagnostic evaluation.
These treatments include:
Empirical de-worming medication (because whipworms are a common parasitic cause of colitis and they only intermittently shed their eggs in the feces)
Home Care for Dogs with Colitis
Administer as directed any medications prescribed by your veterinarian and follow recommendations for dietary modification. Also, observe your dog’s general condition, watching for worsening of symptoms and bringing any changes to the attention of your veterinarian.
Although some causes of colitis cannot be prevented, try to avoid exposure of your dog to infectious agents or abrupt dietary changes.
Information In-depth on Dogs with Colitis
The history and clinical symptoms of dogs with colitis may vary and other illnesses may cause similar clinical symptoms. Therefore, several different diseases may initially be considered when evaluating a dog with symptoms compatible with colitis.
Common symptoms of colitis include loose stools that contain fresh (bright red) blood or mucus, frequent attempts to defecate, production of small amounts of stool, and straining to defecate.
Many types of inflammatory disorders can cause or be associated with colitis. These disorders collectively are known as “inflammatory bowel disease” because the clinical symptoms of several specific disorders are very similar to one another. Definitive diagnosis of the specific disorder is necessary for proper treatment. The different inflammatory bowel diseases include:
Lymphocytic-plasmacytic colitis is the most common inflammatory bowel disease of dogs. The definitive cause is not known, but it is thought to be caused by an overreaction of the immune system.
Histiocytic ulcerative colitis is characterized by ulcers and inflammation of the colon. It is seen most commonly in young boxer dogs.
Granulomatous colitis is an uncommon, poorly understood and severe disease of the colon that resembles Crohn’s disease in people. The word “granulomatous” refers to the specific types of inflammatory cells that are present in the colon in this disorder.
Eosinophilic colitis is characterized by eosinophils (a type of white blood cell associated with allergic reactions or parasites) in the inflammation. The cause of eosinophilic colitis is unknown, but food allergy or parasitic infection may be involved.
Many infectious agents can cause symptoms of colitis:
Bacteria (Clostridia, Salmonella, E. coli, Campylobacter, and others)
Viruses (corona virus, parvo virus)
Fungal agents (such as the causative agents of histoplasmosis, pythiosis, and protothecosis)
Parasitic worms (whipworms, hookworms)
Parasitic protozoa (Trichomonas, Ameba, Balantidium, Giardia)
Dietary intolerance or allergic reactions also can cause colitis. In this case, colitis often occurs as a reaction to a specific protein, but also can be associated with lactose, high fat content and certain food additives.
Dietary indiscretion may cause acute (abrupt onset and short course) colitis. Examples of dietary indiscretion include eating spoiled food, overeating, ingesting foreign material and sudden dietary changes.
Colonic cancer can cause symptoms similar to those that occur in colitis such as fresh (bright red) blood in the stool, mucus in the stool, straining to defecate, increased frequency of defecation and painful defecation. The most common types of colon cancer in dogs are adenocarcinoma and lymphosarcoma.
Trauma, either internal (foreign bodies) or external (blunt trauma by an automobile) can cause colitis.
Intussusception (telescoping of the bowel into itself) can cause partial or complete blockage and can result in symptoms such as straining to defecate (“tenesmus”)or blood or mucusin the stool.
Hemorrhagic gastroenteritis (“HGE”) is a dramatic, potentially fatal disorder of unknown cause. It occurs primarily in small breeds of dogs. It is characterized by a sudden onset of profuse bloody diarrhea (often “raspberry jam” appearance and consistency) and occasional vomiting.
Pancreatitis (inflammation of the pancreas) can cause blood and mucus in the stools.
Antibiotic-associated colitis can occur after administration of some antibiotics. It usually is self-limiting and ceases after antibiotic treatment is discontinued.
Blood clotting disorders (“coagulopathies”) including clotting problems due to liver failure, some rat poisons, and low platelet count (“thrombocytopenia”) can result in blood in the stool and be mistaken for colitis.
Diagnosis In-depth of Colitis in Dogs
Diagnostic tests are needed to identify colitis and exclude other diseases that may cause similar symptoms. Tests may include:
A complete medical history and thorough physical examination (including a digital rectal examination and thorough abdominal palpation) are the first steps in establishing an accurate diagnosis.
Several fecal studies designed to evaluate for the presence of parasite worm eggs and protozoa (fecal flotation, direct fecal smear, and zinc sulfate tests for Giardia and Balantidium) should be performed in all dogs with suspected colitis. Parasitism is one of the most common causes and contributing factors in dogs with colitis.
A complete blood count (hemogram or CBC) may identify a high white blood cell count in infectious and inflammatory disorders and may disclose anemia due to chronic blood loss in the stool in some forms of colitis.
Serum biochemistry tests usually are normal in dogs with colitis, but such tests help identify abnormalities of other body systems (pancreas, liver) that may cause similar symptoms. These tests also help determine the general health of your dog.
Urinalysis may be performed to evaluate kidney function.
Abdominal X-rays usually are normal but may disclose evidence of abnormalities in other organs (lymph nodes, prostate gland) that may be pressing on the colon and causing symptoms of colitis.
Chest X-rays often are recommended in older dogs and in those suspected to have cancer so as to evaluate for spread (metastasis) of the tumor to the lungs.
Serum trypsin-like immunoreactivity (TLI) is a blood test often recommended in all dogs with chronic colitis if the other tests are not diagnostic. This test will help identify certain pancreatic diseases (pancreatic enzyme deficiency) that can cause loose stools that may be confused with colitis.
Your veterinarian may recommend additional diagnostic tests to ensure optimal medical care if the previous tests were not conclusive. These are selected on a case-by case-basis.
Tests may include:
A barium enema (in which a radiographic contrast dye is placed directly into the colon followed by X-rays of the abdomen) sometimes is recommended to identify masses or changes in the colon that would be difficult to visualize on plain abdominal X-rays. This procedure is cumbersome to perform and often uncomfortable for the dog. Consequently, it is not frequently performed.
Ultrasound examination of the abdomen allows internal organs such as the colon, regional lymph nodes, and prostate gland in males to be visualized and evaluated with minimal discomfort. Abnormal tissues may be sampled with a needle or biopsy instrument with the guidance of ultrasound. Abdominal ultrasound examination often is performed by a veterinary radiologist or a veterinary specialist in internal medicine and may require referral.
Examination of the colon (after withholding food and performing several cleansing enemas) with a flexible fiberoptic endoscope allows direct visualization of the inside surface of the colon so that polyps, tumors, chronic inflammation and occasionally parasites can be identified. During this procedure, several small biopsies of the inner surface of the colon can be taken and submitted for microscopic examination by a veterinary pathologist. Only brief hospitalization is required for colonoscopy but this procedure may require referral to a specialist in veterinary internal medicine. Colonoscopy usually is performed after routine tests have been inconclusive and the dog has not responded to conservative treatment such as anti-parasitic medications and dietary modification.
Treatment In-depth of Colitis in Dogs
Many treatments are available for colitis. If at all possible, a specific cause for colitis should be identified so that proper treatment can be instituted. In otherwise healthy dogs with colitis, outpatient treatments such as anti-parasitic medications or dietary modification may be recommended initially. If this approach is unsuccessful, additional tests (including colonoscopy and biopsy) are recommended to improve the chance of a specific and accurate diagnosis. Complete resolution of clinical symptoms may not be possible, even with an accurate diagnosis and proper treatment.
Treatments for colitis may include one or more of the following:
A 24 to 48 hour fast with gradual introduction of a bland diet followed by gradual re-introduction of the dog’s normal diet may be sufficient treatment for many dogs with acute colitis.
In dogs with chronic colitis, dietary modification using hypoallergenic diets may be tried. Using a home-prepared or commercial diet that contains a “novel” protein source (one which the dog has not previously encountered) sometimes is sufficient to control the colitis and eliminates the need for further medical treatment. No food items except for the “hypoallergenic” diet should be fed to affected dogs during this trial period of treatment. Dogs that respond to this approach are thought to have a food allergy that is manifested as colitis.
Fiber supplementation (either by adding fiber to the dog’s normal diet or choosing a diet that is naturally high in fiber) sometimes is of great benefit to dogs with colitis.
Anti-parasitic (deworming products, anti-protozoal drugs) treatment is indicated in colitis to eliminate the possibility of parasites that are intermittently shed in the stool (whipworms, Giardia). Parasites are a leading causes of colitis, and this approach is routinely done as a first step in the management of colitis.
Antibiotic treatment can play an important role in the management of colitis. Although useful when a bacterial cause of colitis has been identified, antibiotics are sometimes useful even when a bacterial cause of colitis has not been established. Three anti-microbial agents commonly used in this situation are metronidazole, sulfasalazine and tylosin. These drugs have been used successfully as single agents, in combination with one other, or in combination with other drugs.
Anti-inflammatory and immunosuppressive drugs (drugs that suppress the immune system) such as cortisone-like drugs (corticosteroids) and the immunosuppressive agent azathioprine generally are reserved for dogs in which colitis is strongly suspected to be immune-mediated in nature based on microscopic examination of biopsy specimens obtained during colonoscopy. These drugs have potential adverse effects and only should be used under close veterinary guidance with regularly scheduled re-evaluations. These drugs are invaluable and extremely effective when used appropriately.
Motility-modifying drugs (drugs that effect the motor activity of the intestinal tract) most often are used for symptomatic relief rather than for long-term medical management of colitis.
Home Care for Dogs with Colitis
Optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up may include:
Periodic re-evaluation may be necessary until the condition stabilizes. No other follow-up may be required for dogs with an acute bout of colitis except for yearly physical examinations.
In some cases, medication may be necessary for months or years. It often is recommended to wean the dog off drug therapy after a period of time to determine if dietary modification or addition of fiber alone can control the colitis. Even if long-term drug treatment is needed, it is best to determine the lowest possible dosage of medication that effectively controls the dog’s colitis.
Most dogs with colitis have a good prognosis for long-term control, especially those animals in which the underlying cause of colitis has been identified. Most infectious causes of colitis are curable. The prognosis with cancer-related colitis is dependent upon the type of cancer involved and its response to surgical or medical treatment. Patients with inflammatory colitis (lymphoplasmacytic, granulomatous, eosinophilic) seem to have the most variable clinical course. It is important that the owner of a dog with chronic colitis remain in close contact with the attending veterinarian so that appropriate changes in medication or diet can be made in a timely fashion.