My dog Apollo has inflammatory bowel disease (IBD), so unfortunately, I have experience with this condition as both an owner and veterinarian.
IBD is a chameleon. Its typical symptoms of vomiting, diarrhea, weight loss, and/or anorexia fit with a whole host of diseases. Couple that to the fact that IBD can only be definitively diagnosed with a biopsy of affected tissues, and I think it’s safe to say that the disease’s incidence is probably even higher than we think.
Both dogs and cats can be affected with IBD. Certain breeds of dogs appear to have a higher than average risk of developing the disease, including basenjis, soft coated wheaten terriers, German shepherd dogs, shar-peis, rottweilers, weimaraners, border collies and boxers. Some combination of altered immunity, antigenic stimulation (e.g., food allergies, bacterial overgrowth, metabolic diseases, food intolerance, parasites, etc.), environmental stress and genetics determines which pets get IBD and when symptoms first develop. IBD is typically diagnosed in middle age, but can develop in younger or older animals as well. Often a pet’s symptoms are mild and/or intermittent to begin with but progress with time.
In Apollo’s case, he developed extremely severe symptoms at about nine months of age. He was not my dog at the time, but I suspect something triggered this acute episode — perhaps a change in diet, a gastrointestinal infection … who knows. His condition remained undiagnosed for awhile, I suspect because of his age. Most vets aren’t thinking IBD in a nine month old, but when he came to me and was failing to respond to symptomatic therapy and I had ruled out GI diseases that are more typical to a dog his age, I dug a little deeper and found some references to boxers developing the disease when they are very young.
As is suggested by its name, the pathophysiology of inflammatory bowel disease centers on abnormal inflammation within the gastrointestinal tract. Normally, the GI system has multiple layers of defense against all that passes through it. When these systems break down or are ineffective to begin with, triggers that are normally kept at bay gain access to the lining of the intestines and stimulate the immune system. The result is inflammation, which serves to recruit more inflammatory cells, further increasing the "leakiness" of the intestinal wall. A vicious, self-perpetuating cycle ensues. IBD is sub-classified by the part of the GI tract affected as well as the predominant type of inflammatory cell involved. The most common form goes by the name plasmocytic lymphocytic enteritis.
Treatment takes a two-pronged approach: eliminating triggers to inflammation within the GI tract, and suppressing the immune system. Hypoallergenic diets are key. Apollo remains symptom-free without drug intervention as long as he eats only a diet made from hydrolyzed protein (i.e., proteins broken down into pieces so tiny that they evade detection by the immune system) and a single carbohydrate source. Antibiotics may be used to help control bacterial numbers in the gut, and some antibiotics like metronidazole also have an immunosuppressive effect. Corticosteroids are the most common way to reduce the immune system’s over-exuberant response, but other medications like azathioprine (dogs) or chlorambucil (cats) can be used when corticosteroids are not fully effective or cause unacceptable side effects.
Some cases of IBD respond beautifully to treatment, but unfortunately, others do not. I recently euthanized an otherwise healthy cat and dog that had both been treated appropriately and aggressively for this disease. Fingers crossed that Apollo continues to do as well as he has so far.