inflammatory bowel disease in cats and dogs
Inflammatory bowel disease (IBD) can be a frustrating disease for cat and dog owners and their veterinarians. It occurs when inflammatory cells accumulate in the lining of the gastrointestinal tract due to an overactive immune response. When cells buildup in the lining of the bowels, the walls become thickened and the way the bowels function is disrupted. Both the absorptive capabilities and the motility of the bowels are affected, leading to chronic gastrointestinal troubles like vomiting or diarrhea.
The exact cause of IBD is currently unknown, though we do believe there are many contributing factors. One theory suggests that normal intestinal bacteria or food allergies trigger the disease.
Signs and symptoms of IBD
Clinical signs of IBD can wax and wane. Diarrhea and vomiting are the most common complaint, but because these signs can come and go, owners often wait to pursue diagnosis thinking that their pet’s illness has resolved. Over time, though, pets with IBD can develop other subtle (or not so subtle) signs such as appetite change, lethargy, and weight loss. Stool may become bloody and pets may strain to defecate.
Diagnosing IBD in pets
Trying to diagnose IBD starts out as a diagnosis of exclusion. Because so many things can cause diarrhea and vomiting, your veterinarian will want to be thorough about diagnostic testing to rule out other more sinister causes. A fecal sample will be checked for parasites, and your pet will probably be dewormed just to be on the safe side.
In addition, your veterinarian will want to perform basic blood work to ensure that metabolic abnormalities are not the reason behind your pet’s signs. Electrolyte levels will be checked and your vet will pay special attention to your pet’s protein levels, too. Severely affected bowels can allow protein to be lost through the stool, and if protein levels drop too low, ascites can result.
From there, digestive panels can be run to assess serum folate and cobalamin levels. Altered levels can signify where in the bowel inflammation is occurring and whether there is concurrent bacterial overgrowth in the small intestine. Exocrine pancreatic insufficiency and pancreatitis can also be ruled out with a blood test.
Finally, an ultrasound may be performed to visualize the bowels. Masses in the gastrointestinal tract and intestinal foreign bodies can sometimes cause clinical signs that mimic IBD. Typically, pets with IBD will have thickened bowel loops, but unfortunately this is not a finding that is specific to IBD. For example, pets with lymphoma will have thickened bowel loops and display clinical signs similar to pets with IBD, notably vomiting and diarrhea.
To make a very long story short, the only way to definitively diagnose IBD, even if a long list of other conditions has already been ruled out, is through a tissue biopsy. Tissue samples can be obtained via endoscopy or surgically. While endoscopic biopsies are certainly less invasive, the sample they produce is not full thickness and may not be diagnostic.
Treating IBD typically centers on suppressing the overactive immune system. Corticosteroids like prednisone are a common treatment, and sometimes even heavier hitters like cyclosporine and azothioprine are called upon. Controlling underlying intestinal bacterial overgrowth is important, and the use of prebiotics and probiotics is recommended.
If your pet has IBD, it’s worth changing her food. Hypoallergenic diets use hydrolyzed proteins that are too small to stimulate the immune system. Novel protein diets are also sometimes recommended, as your pet will not have had the chance to build up an allergy to a brand new protein source. Currently, there are many exotic choices, from bison to kangaroo! If your pet’s symptoms are mild, it is possible that a diet change alone will resolve the clinical signs.
The process of diagnosing IBD is fraught with frustration. All of these tests take time and, of course, cost money (which won’t be a problem if you have pet insurance). And all the while, your pet continues to have clinical signs and may feel poorly, which is hard for both owners and veterinarians to watch.
In some cases, your veterinarian may give you the option of trying medications just to gauge your pet’s response. This is always an option, with one caveat. In cases of lymphoma, the use of prednisone can make your pet less responsive to chemotherapy. So, if you would pursue chemotherapy in the face of lymphoma, you should get a definitive diagnosis of IBD before starting treatment.