Non-Neoplastic Infiltrative Bowel Diseases

Non-neoplastic (noncancerous) infiltrative bowel diseases are a group of disorders that cause infiltration of the gastrointestinal tract with inflammatory cells. Broadly speaking, there are two major causes: inflammatory bowel disease and fungal or algal infections. The significance of these disorders is that they cause chronic debilitating disease, and they are reliably diagnosed only by gastrointestinal tract biopsy. The cause(s) and therapy of these disorders are widely divergent. Inflammatory bowel disease is the most common cause of intractable vomiting and diarrhea in dogs and cats. Although the exact cause of inflammatory bowel disease is unknown, inflammatory cells probably infiltrate the gut in response to dietary or bacterial challenges. The inflammatory bowel disease disorders may strike anywhere in the gastrointestinal tract, but the small intestine and large intestine are primarily affected. Middle-aged pets are most often diagnosed with this disease. The most common symptoms include vomiting, diarrhea, loss of appetite, and weight loss, but symptoms may vary depending on the severity of inflammation and the extent of gut involvement. A diagnosis of inflammatory bowel disease is one of exclusion (everything else is ruled out, leaving only this diagnosis) and requires ruling out many other diseases that may cause intestinal inflammation. Baseline diagnostic tests that may be recommended by your veterinarian include multiple fecal examinations, routine blood work (to test the kidneys, liver, etc.), urinalysis, radiographic imaging procedures, thyroid testing (in cats), and tests for feline viral diseases (e.g., feline leukemia virus, feline immunodeficiency virus). Surgical or endoscopic biopsy of the intestine is required to confirm the presence of inflammatory cells and to exclude other diseases that mimic inflammatory bowel disease. Therapy for inflammatory bowel disease includes the use of anti-inflammatory drugs to combat gut inflammation and use of a hypoallergenic diet to reduce the workload on the gut. Your pet is likely to require several weeks to months of drug and/or dietary therapy and to require a hypoallergenic diet indefinitely. Most animals with inflammatory bowel disease respond favorably to therapy; however, relapses should be expected. Fungal or algal infections are caused by various organisms that are introduced into the gastrointestinal tract, inciting an inflammatory response to their presence. Histoplasmosis is the most frequently diagnosed fungal infection affecting the gastrointestinal tract of animals (primarily dogs). Infection with the fungus generally causes intractable diarrhea. Other symptoms may include loss of appetite, weight loss, fever, labored breathing, and enlargement of the lymph nodes. Diagnosis requires detecting the organisms (contained within inflammatory cells) in rectal scrapings or in surgical or endoscopic biopsy specimens of the intestines. Current blood tests for histoplasmosis are unreliable. Therapy usually consists of antifungal drugs given over several months. The prognosis varies with the extent of disease activity. Animals with severe symptoms or widespread disease generally fail to respond to therapy. Pythiosis and protothecosis are rare fungal and algal infections that cause infiltrative gastrointestinal disease in animals. Both diseases are most common in dogs, and both preferentially affect the large intestine, causing diarrhea, weight loss, and generalized debilitation. Diagnosis is made only by demonstrating the organisms in affected gastrointestinal tract tissues. Surgical removal of all infected tissue, if possible, is the preferred treatment for pythiosis. There is presently no effective therapy for protothecosis. The above is general veterinary information. Do not begin any course of treatment without consulting your regular veterinarian. All animals should be examined at least once every 12 months.