Diagnosing IBD: Exclude known causes of chronic intestinal disease

Diagnosing IBD: Exclude known causes of chronic intestinal disease

Canine IBD seems to vary in its clinical presentation, natural course, response to treatment and prognosis
Nov 01, 2005

Q. Please review IBD in dogs.

A. Dr. Karin Allenspach and colleagues at the 2005 American College of Veterinary Internal Medicine Forum in Baltimore gave a lecture entitled "Practical Therapy for Difficult Cases of Canine IBD: Beyond Steroids". Some relevant points in this lecture are provided in this article.

Idiopathic inflammatory bowel disease (IBD) is characterized by infiltration of the gastric, small intestinal and/or large intestinal wall with inflammatory cells, such as plasmacytes and lymphocytes, eosinophils or neutrophils. The cause(s) of canine IBD remain(s) largely unknown. It is speculated that abnormal responses of the mucosa-associated lymphoid tissue that are possibly associated with abnormal permeability of the gut barrier and interactions with intestinal microflora are involved in the pathogenesis. Canine IBD seems to vary in its clinical presentation, natural course, response to treatment and prognosis. It likely encompasses a wide variety of different yet unidentified disease entities.

Idiopathic IBD is diagnosed by systematic exclusion of all known causes of chronic intestinal disease in dogs. It is difficult to clearly differentiate food reactions (including food allergy) from IBD. The typical diagnostic work-up includes CBC, serum chemistry profile, urinalysis, fecal parasitological and bacteriological examination, abdominal ultrasonography and serum trypsin-like immunoreactivity (TLI) assay.

The traditional approach to the treatment of canine IBD relies on components that can be used individually or most often combined: dietary modifications, antibiotic treatment, and specific anti-inflammatory and immunosuppressive drugs. Although most specialists agree that dietary therapy is a central component, the routine use of antibiotics in the treatment of dogs tentatively diagnosed with IBD is subject to controversy. In many instances, immunosuppressive doses of corticosteroids are administered for various lengths of time.

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Many dogs with chronic intestinal disease of more than three-weeks duration respond totally or significantly to a one-week food trial with a commercial elimination diet alone (dry formulation). There is currently a wide variety of commercially available diets to recommend for elimination trials. Hydrolyzed diets are a recent alternative to classical diets offering a novel protein source.

The existence of primary small intestinal bacterial overgrowth (SIBO) is subject to controversy. The more generic denomination "idiopathic antibiotic-responsive diarrhea" (ARD) is currently preferred. ARD is most commonly recognized in young German Shepherds with chronic intermittent diarrhea. It is diagnosed based on signalment, history and clinical signs, as well as on response to an empiric course of oral anti-biotics (e.g., oxytetracycline 10-20 mg/kg TID, or metronidazole 10-20 mg BID, or tylosin 20 mg/kg BID to TID). Recently, histiocytic ulcerative colitis, a severe form of IBD affecting Boxers (mainly but not exclusively) has been shown to respond well to enrofloxacin at usual doses.

Treatment protocols for management of canine IBD most often involve the use of immunosuppressive doses of corticosteroids for several weeks followed by slow tapering to reduce the intestinal mucosal inflammation and achieve clinical remission. The usual protocols for prednisone or prednisolone usage recommend dosages of 1-2 mg/kg BID for approximately two to four weeks, followed by a slow tapering period over weeks to months. However, a number of dogs treated with immunosuppressive doses of corti-costeroids will show either no response at all to the drug or will relapse after weeks to months of treatment. About 16 percent to 20 percent of cases with IBD will not respond to corticosteroid therapy. At high dosages, corticosteroids have numerous side effects such as PU/PD, which may become unbearable for the owners, especially in large-breed dogs. In difficult cases that require prolonged corticosteroid therapy and are sensitive to its side effects, the more expensive drug budesonide has been used with good anecdotal success — 3.0 mg/m2 or about 0.5-3.0 mg per dog, depending on body weight, once daily or every other day. Budesonide undergoes a first-pass hepatic extraction of approximately 80 percent to 90 percent, therefore, only a fraction of the absorbed compound reaches the systemic circulation, theoretically decreasing side effects. Budesonide will suppress the hypothalamic-pituitary-adrenal axis in dogs with IBD.