Gastrointestinal disorders include some of the most common reasons why cats are presented for veterinary care. Diseases both within and outside of the gastrointestinal tract (GIT) affect the function of the GIT and can result in similar clinical signs. The term inflammatory bowel disease (IBD) does not indicate one specific, unique disease, but rather encompasses a variety of conditions that cause chronic inflammation within the gastrointestinal tract.

Etiology and pathogenesis

Inflammatory bowel disease is by definition an idiopathic disorder. Most likely, IBD encompasses a group of diseases which have similar clinical signs. IBD is classified by the region of the gastrointestinal tract (GIT) affected and by the predominant inflammatory cell type. Lymphocytic-plasmacytic inflammation is most commonly found, followed by eosinophilic inflammation. IBD is believed to be immune-mediated in origin. The normal intestinal mucosa is supposed to serve as a barrier and control exposure of antigens to the GI lymphoid tissue (GALT). The function of GALT is to generate appropriate, protective immune responses against pathogens while remaining tolerant of harmless antigens such as commensal bacteria and food. IBD develops when there is a break-down in this process and inappropriate immune responses occur.

The clinical signs for cats with IBD reflect the portion of the GIT that is involved. Gastric involvement may accompany small intestinal disease in IBD but does not occur as a sole site of disease. Patients with small intestinal disease often present for inappetance, weight loss, vomiting, and diarrhea. Because cats are so good at conserving water, it may be difficult for owners to notice small bowel diarrhea. Small bowel diarrhea is characterized by large volumes with only a minimal increase in frequency of defecation. In contrast, large bowel diarrhea is characterized by frequent defecations of small amounts. Large bowel diarrhea often contains mucous and frank blood. Some patients will have involvement of both the small and large intestine with clinical signs referable to both components of the GIT. Typically in those cats, large bowel diarrhea will predominant in terms of fecal quality but the cat will also lose weight and vomit. Regardless of whether it is small or large intestine involvement, there are not any clinical signs which are pathognomonic for inflammatory bowel disease.

No gender predispositions have been documented for inflammatory bowel disease in cats. It is typically diagnosed in middle-aged cats but can be seen in any age. Siamese cats may be predisposed to develop lymphocytic-plasmacytic enteritis.

Physical examination findings are more likely to be abnormal in cats with small intestinal involvement. Affected cats may be thin or have an appreciable loss of muscle mass. Thickened, "ropey" bowel loops are often appreciated during abdominal palpation. This finding is both non-specific and subjective.