Cats are plagued by a variety of chronic gastrointestinal (GI) disorders ranging from inflammatory bowel disease (IBD) to cancer (lymphoma). Unfortunately, many of these disorders have very similar presenting symptoms such as lack of appetite, weight loss, vomiting, and diarrhea. A trial and error approach with dietary changes, antibiotic and anti-inflammatory medications is helpful in relieving symptoms in some patients. However, there remain a large number of cats that fail to respond to this approach. In these cats, stomach and intestinal biopsies are often necessary to determine the underlying cause and optimize treatment. Even with biopsy samples, it can be difficult to distinguish between IBD and lymphoma in some cats. Since treatment and outcome is different for IBD and lymphoma, it would be valuable to have a simple test that could distinguish between the two diseases without performing invasive biopsies. This study will evaluate whether a blood test, based on determining the pattern of blood proteins, can differentiate cats with IBD from those with lymphoma.