Feline idiopathic inflammatory bowel disease: what we know and what remains to be unraveled

Abstract

Practical relevance: Feline idiopathic inflammatory bowel disease (IBD) denotes one form of chronic enteropathy that is immunologically mediated and characterized by persistent or recurrent gastrointestinal (GI) signs and histologic inflammation. Signs of vomiting, diarrhea and weight loss generally predominate, and mucosal inflammation may occur in any portion of the GI tract (especially the small intestine). Affected cats may also have concurrent inflammation in other organs, such as the pancreas and liver, which may impact clinical disease severity.

Clinical challenges: The exact etiologies of this heterogeneous group of disorders have yet to be determined, though results from basic science and clinical studies suggest that interplay between genetic factors and enteric bacteria is crucial for disease development. The diagnosis is one of exclusion and requires intestinal mucosal biopsy to characterize the type and severity of the inflammatory infiltrate, and to differentiate IBD from other disorders, including alimentary lymphoma. Controversy exists concerning the relative diagnostic accuracy of endoscopic versus full-thickness specimens for the diagnosis of IBD and its differentiation from alimentary lymphoma.

Audience: This article is intended to provide veterinary practitioners with a comprehensive clinical update on idiopathic IBD in cats. It reviews the current evidence-based data, the diagnostic approach, the evolving histologic criteria, and treatment options and outcome for feline patients with this syndrome.

Figure 1

Chronic intestinal inflammation in feline IBD involves a complex interplay between the mucosal immune system and the enteric microbiota in a genetically susceptible host. Potential genetic factors affecting barrier function or innate and adaptive immunity may predispose susceptible cats to gastrointestinal (GI) signs, aberrant host responses and microbial imbalances (dysbiosis). Environmental factors (dietary constituents, exposure to enteropathogens, NSAID or antibiotic administration, etc) likely govern inflammation onset or reactivation (disease flares)

Figure 2

Increased granularity (a,b), mucosal friability (c) and erosions (d,e,f) are associated with GI signs and histopathologic lesions in affected cats

Figure 3

(a) Histopathologic inflammation in cases of feline IBD is predominantly lymphoplasmacytic in character, as seen in this endoscopic duodenal specimen. (b) Exfoliative cytology performed in the same cat shows a cluster of small lymphocytes embedded within a raft of normal small intestinal (epithelial) cells. This cytologic appearance is consistent with lymphocytic enteritis

Figure 4

The ileum is a common site for GI inflammation in cats. Whenever possible, ileal biopsies should be procured by either direct mucosal assessment (ie, ileoscopy) or by passing the endoscope forceps blindly through the ileocolic sphincter