Overview of Canine Inflammatory Bowel Disease (IBD)
Inflammatory bowel disease (IBD) is a group of gastrointestinal (GI) disorders that involve infiltration of the gastrointestinal tract by inflammatory cells (white blood cells) in dogs. IBD can affect both the upper (stomach and small intestine) and lower (colon) gastrointestinal tracts.
IBD is the most common cause of chronic (persistent) vomiting and diarrhea in dogs. The cause of IBD is currently unknown.
The most common form of IBD is usually seen in middle aged to older animals; however, there are some forms of IBD that are seen in young dogs, often less than 5 years old. Breeds that may be at an increased risk for development of IBD include the German shepherd, boxer, shar-pei soft coated wheaton terrier and Rottweiler.
IBD can cause a range of clinical signs from mild gastrointestinal illness to debilitating disease.
What to Watch For
Lack of appetite or increased appetite
Noisy gut sounds
Blood or mucus in the stools
Straining to defecate
Diagnosis of Inflammatory Bowel Disease in Dogs
History and physical exam
Complete blood count (CBC)
Fecal tests for parasites, protozoa and bacteria
Trypsin-like immunoreactivity (test of pancreatic function)
Tests for bacterial overgrowth in the intestine
Treatment of Inflammatory Bowel Disease in Dogs
Corticosteroids for anti-inflammatory effects and to suppress the immune system
Sulfasalazine for anti-inflammatory effects in the colon
Other immunosuppressive (suppress the immune system) drugs
Home Care and Prevention
Give all medications as prescribed by your veterinarian. Careful adherence to dietary recommendations is crucial. Feed only the prescribed diet. Do not feed table scraps or other foods, including natural chew toys (rawhides).
Observe for inappropriate response to treatment or worsening of clinical signs at home. Persistent vomiting and diarrhea, continued weight loss, lack of appetite and lethargy should prompt a call to your veterinarian.
There are no measures that can be taken with respect to preventing the development of IBD. Prevention of relapses after initial treatment may require long-term to life-long therapy.
In-Depth Information on Inflammatory Bowel Disease in Dogs
Although IBD is a common cause of chronic vomiting and diarrhea in dogs and cats, its cause remains unknown. Proposed mechanisms of disease include an abnormal response of the immune system (hyperactivity or hypersensitivity) to either normal bacterial contents of the gut or various components of ingested food, versus an appropriate immune response to a pathogen that causes the disease.
Dietary factors are believed to play a role in the disease process because many animals respond to dietary manipulation. Regardless of the cause, IBD results in vomiting and diarrhea secondary to an accumulation of white blood cells in the lining of the intestinal walls. This infiltration by white cells causes inflammation and inhibits normal digestion and absorption of food. Abnormalities of gastrointestinal motility, or movement of the gut due to muscular activity in the intestinal walls, may also cause some of the clinical signs seen in IBD.
Several different types of IBD exist. These are differentiated based upon the type of white cell that is involved in the infiltrate. The clinical signs that are noticed in your pet depends upon whether the inflammatory process is occurring in the upper or lower gastrointestinal tract. Animals with upper GI involvement tend to experience vomiting, diarrhea with a normal to increased volume of feces, weight loss if signs are chronic and severe, occasional dark, tarry stools, which may represent blood loss into the gut, and occasional gas and borborygmus (loud GI sounds). Animals with lower GI involvement may experience vomiting as well.
The character of the diarrhea is different with lower GI disease. This usually manifests as more frequent defecation of a smaller volume, with straining to defecate, fresh blood and/or mucus in the feces, and a greater urgency associated with defecation. Usually animals with lower GI disease do not show significant weight loss.
Upper and lower GI IBD is common in dogs but cats more commonly suffer from IBD involving the upper GI tract. Many diseases can cause vomiting and diarrhea and must be differentiated from IBD. These include:
Diseases involving other body systems that have gastrointestinal side effects. These might include diseases affecting the kidneys and/or urinary tract, liver, immune system and endocrine system (hormone producing glands).
Bacterial infection of the GI tract. Campylobacter, Salmonella and Clostridium are types of bacteria that can infect the GI tract and cause vomiting and diarrhea.
Parasitism. GI worms or Giardia (a protozoal organism) can also cause vomiting and diarrhea.
Food allergy or intolerance. Animals that have allergies to certain foods may develop vomiting and diarrhea.
Exocrine pancreatic insufficiency. The pancreas plays a vital role in food digestion. If the pancreas is not producing the necessary enzymes that aid in food digestion, this may result in diarrhea, and to a lesser extent, vomiting.
Fungal disease of the GI tract. Histoplasmosis is a fungal infection that can involve the GI tract and cause vomiting and diarrhea. This fungus is limited to the midwestern part of the United States.
Neoplasia (cancer). Cancers affecting the GI tract, most notably lymphosarcoma, can cause the same clinical signs as IBD. Lymhposarcoma is a cancer of the lymphoid tissues, of which there is an abundant supply in the GI tract.
Information In-depth of Diagnosis of IBD in Dogs
A history and physical exam are necessary to guide the diagnostic work-up. Careful history taking should help determine if the clinical signs are primarily consistent with upper or lower GI signs, or both. Physical exam findings of animals with IBD may incluIe thickened intestinal loops and evidence of malnutrition due to intestinal disease.
Complete blood count. The CBC evaluates the red and white blood cells as well as the platelets. Occasionally animals with IBD will have elevated white blood cell counts, but this is a non-specific finding. Animals with the eosinophilic form of IBD may have an elevated eosinophil count. Eosinophils are a specific type of white blood cell. The CBC is helpful to rule out other disease processes that may cause signs similar to IBD.
Biochemical profile. The biochemical profile helps to evaluate liver and kidney function as well as assessing blood sugar, protein and electrolyte levels (sodium and potassium are examples of electrolytes). This is imperative in ruling out diseases of other body systems such as liver and kidney disease. In severe cases of IBD the blood proteins may be low due to protein loss into the GI tract and decreased absorption of protein. Other biochemical parameters are usually within normal limits.
Urinalysis. Evaluation of the urine together with the biochemical profile is necessary to assess kidney function, as well as to rule out protein loss through the kidneys in animals with low blood proteins.
Fecal tests. Fecal analysis is necessary to diagnose bacterial and parasitic infections. A fecal float looks for worm eggs. A fecal culture is necessary to rule out the bacterial causes of infection, and there is a specific fecal test to look for Giardia.
Trypsin-like immunoreactivity (TLI). The TLI assesses production of digestive enzymes by the pancreas and rules out pancreatic insufficiency. This would be more commonly run in dogs, as pancreatic insufficiency is rare in cats. Additionally, pancreatic insufficiency causes signs consistent with upper GI disease, so testing would be limited to animals with the appropriate clinical signs.
Bacterial overgrowth can be assessed in several ways. One method involves getting samples of intestinal juice and culturing it to evaluate the total number of bacteria present. Bacterial overgrowth can also be implied by measuring blood levels of cobalamin (Vitamin B12) and folate. Cobalamin is often consumed by bacteria and folate is a substance produced by bacteria. Therefore, alterations in the levels of these two substances can be suggestive of bacterial overgrowth.
Thoracic radiographs. Chest X-rays are useful to rule out evidence of spread of cancer to the lungs. Since cancer has to be considered in animals presenting with chronic GI illness, chest X-rays are a good idea prior to any invasive diagnostic procedures.
Abdominal ultrasound. Ultrasound exam of the abdomen may help pinpoint the site of the problem. Animals with IBD may have completely normal exams, or they may show evidence of intestinal wall thickening, loss of normal intestinal detail and enlarged abdominal lymph nodes. Ultrasound exam may also be useful in identifying solitary intestinal tumors or abnormalities associated with other abdominal organs such as the liver and kidneys.
Food trial. Switching the animal’s food to a new diet or a hypoallergenic diet may indicate an allergy to a specific food if the signs resolve following cessation of the previous diet.
Intestinal biopsy. Biopsy of the intestine is the only way to obtain a diagnosis of IBD. The microscopic evaluation of tissue from the intestine is required to confirm a suspected diagnosis. However, it is important to rule out other causes of GI disease prior to obtaining a biopsy, as different disease processes can cause a similar appearance on microscopic exam. Intestinal biopsy may be obtained either via endoscopy, which is a scope placed into the GI tract either via the mouth or the rectum, laparoscopy, in which a scope is paced into the abdominal cavity through a small incision made in the body wall, or surgery. The largest biopsies may be obtained via surgery but this is also the most invasive method to obtain a biopsy. Endoscopic biopsies only sample the innermost layer of the intestinal wall.
Treatment In-depth of Inflammatory Bowel Disease (IBD) in Dogs
Dietary therapy consists of introducing a diet that the animal has never eaten. The protein source in the diet is usually thought to cause the greatest response on the part of the immune system, thus a highly digestible protein that the animal has not been previously exposed to is recommended. Available protein sources include rabbit, venison, whitefish, duck and others. To keep the diet as hypoallergenic as possible, additives and preservatives should be avoided. A number of prescription pet foods are available through veterinarians. Home-cooked diets are only recommended if appropriate vitamin and mineral supplementation is provided through the help of a veterinary nutritionist. The alternative to feeding this type of diet is to feed a hydrolyzed protein diet. Hydrolyzed proteins are partially degraded (broken down) such that they are less likely to cause an adverse immune response. Common protein sources such as chicken can be used, but the immune system does not recognize the protein as chicken because it is not in its complete form.
Addition of soluble fiber to the diet is sometimes recommended for cases of lower GI IBD, as it can normalize fecal consistency, improve the motility of the colon and improve general colonic function.
Antibiotics. Metronidazole is a widely used antibiotic for IBD. It has many mechanisms of activity including killing some GI bacteria, which may contribute to clinical signs, killing protozoal organisms, and dampening the immune response. Its effects on the immune system make it a good anti-inflammatory drug to use in management of IBD. Tylosin is another antibiotic that may be useful for treating dogs. The mechanism by which it acts is unclear, but it is effective for some dogs with lower GI signs. Other antibiotics have also been used.
Corticosteroids. Corticosteroids such as prednisone are both anti-inflammatory and immunosuppressive, depending upon the dose at which they are given. They are an important component of treatment for IBD. By inhibiting the immune system, they help control the influx of white cells and the resultant inflammation in the wall of the gastrointestinal tract. Initial doses are generally quite high. Depending on response to therapy, the dose is gradually tapered over weeks to months.
Sulfasalazine. This is an anti-inflammatory drug that works primarily in the colon, and is therefore used for cases of lower GI IBD.
Other immunosuppressive drugs. There are a multitude of other drugs that also suppress the immune system. An example of one of these drugs is azathioprine (Imuran). It works by a different mechanism than corticosteroids do, but also works to inhibit the immune system and decrease the inflammation in the gut wall. Multi-drug therapy with immunosuppressive drugs is sometimes needed in severe cases, or to enable a reduction in the corticosteroid dose. Reducing corticosteroid doses may be indicated if side effects are severe.
Home Care of Dogs with Inflammatory Bowel Disease (IBD)
Optimal treatment for your pet involves a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not rapidly improve.
Administer all prescribed medications as directed. Alert your veterinarian if you are having problems treating your pet.
Strict adherence to a new diet is imperative to successful dietary therapy. The prescribed diet should be the only food that your pet eats. This means that all treats (unless made of the same formulation as the new diet), table scraps and natural chew toys or flavored toys must be eliminated. Even flavored vitamins or flavored heartworm pills should be avoided, as they often contain beef or chicken based protein sources. It is important to notify your veterinarian if your pet is not adjusting to the new diet and is not eating appropriate quantities. Problems with palatability may require changing the diet or even formulating a special home-cooked diet in certain cases. Recovery is dependent on adequate nutrient intake and this must be monitored. Ask your veterinarian to provide you with exact feeding guidelines to insure that your pet is receiving the proper number of daily calories.
Follow-up after the initial 2 to 4 weeks of therapy is very important, as drug dosages may be gradually decreased depending on the pet’s clinical response to therapy. Corticosteroids must be very slowly tapered over a several month period, and should never be abruptly discontinued, as this can make your pet quite ill. Some animals need to be treated with lifelong therapy if relapses occur. Dogs receiving azathioprine or other immunosuppressive drugs should also be monitored with serial complete blood counts every two weeks to monitor for decreased white blood cell or platelet counts which can be side effects of these drugs. Azathioprine should not be used in cats due to the side effects.
Animals that have abnormalities of the biochemical profile should also receive follow-up blood tests to look for improvement in the bloodwork following institution of therapy.
Because of the increased risk of secondary infection when being treated with immunosuppressive drugs, owners must watch for problems. Infections are most commonly seen in the urinary and respiratory tracts, as well as the skin. If you notice straining to urinate or blood in the urine, red, irritated or itchy skin, or coughing and/or nasal discharge, these could all be signs of infection. Contact your veterinarian if any of these symptoms arise.
Certain side effects of high dose corticosteroid therapy are to be expected; animals will drink and urinate more than normal and may have an increased appetite, and dogs may pant. Adverse effects of this therapy may include gastrointestinal upset and even bleeding or ulcer formation. This may manifest as vomiting, diarrhea, dark and tarry stools, or general weakness. Since many of these signs may be similar to the signs caused by IBD, any concerns should be brought to the attention of your veterinarian. You should be particularly alert with respect to changes or worsening of the clinical signs.
Side effects of sulfasalazine therapy may also be seen. These might include lack of appetite, vomiting, and keratoconjunctivitis sicca (KCS), which is decreased tear production. Animals receiving this drug should have periodic measurements of tear production by the veterinarian. If you notice discharge, redness, excessive blinking or rubbing at the eyes, this should be evaluated by the veterinarian.