Colitis in Dogs
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.
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.
What Causes Colitis in Dogs?
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 of Colitis in Dogs
Diagnostic tests are needed to identify colitis and exclude other diseases that may cause similar symptoms. 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.
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 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 procedures:
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 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 range of healthcare services.
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.