Inflammatory bowel disease (IBD) is not a specific disease. Rather, it is a specific reaction of the gastrointestinal tract to chronic irritation. It is most commonly diagnosed in the middle-aged to older cats. Clinical signs include vomiting and/or diarrhea and weight loss. Diagnosis is usually made by obtaining biopsy samples via endoscopy. Biopsy samples are required to rule out the more serious lymphoma which clinically appears very similar. Below are excellent sources for additional information.
Inflammatory Bowel Disease (VetMedCenter)
Lymphocytic-Plasmacytic Enteritis (VetMedCenter)
Inflammatory Bowel Disease (Marvistavet)
Vomiting (Washington State University)
Diarrhea (Washington State University)