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33 JANUARY/FEBRUARY 2018 ● TVPJOURNAL.COM CONTINUING EDUCATION DIFFERENTIAL DIAGNOSIS A clinical diagnosis of IBD is based on 7,33 : 1. Presence of persistent (>3 weeks) GI signs 2. Inability to identify enteropathogens or other causes of GI disease 3. Histopathologic evidence of intestinal inflammation A diagnosis of IBD is primarily one of exclusion and requires elimination of IBD mimics through complete clinical examination, laboratory testing, and specialized instrumentation. Differentiation of severe IBD from well-differentiated (small cell) lymphoma may be especially problematic in cats. 35,36 After the exclusion of infectious and parasitic agents, nongastrointestinal disorders, exocrine pancreatic insufficiency, and intestinal structural abnormalities requiring surgery ( BOX 1 ), the most common diagnoses of chronic enteropathy include food-responsive enteropathy (FRE), antibiotic- responsive diarrhea (ARD), and idiopathic IBD. DIAGNOSTICS Fecal Examination Fecal examination by direct wet mount or flotation techniques can rule out parasitic causes for mucosal inflammation ( BOX 1 ). Giardia and Cryptosporidium infections are best detected using indirect fluorescent antibody tests. Cats with chronic large bowel diarrhea should be screened for Tritrichomonas foetus infection by polymerase chain reaction. 37 Hematology Routine hematology may reveal nonregenerative anemia reflective of chronic inflammation or enteric blood loss. Neutrophilia with or without a left shift is associated with erosive/ulcerative intestinal lesions. Eosinophilia is seen with some forms of IBD such as eosinophilic enteritis. 1,4,38,39 Serum Biochemistry and Specialized Serologies Results from biochemical analysis rarely provide definitive evidence for IBD, but they do facilitate the recognition of abnormalities in other organs that may cause GI signs. BOX 1. Diagnostic Differentials for IBD in Dogs and Cats GASTROINTESTINAL Parasites Giardia species Toxocara species Trichuis species Isospora species Tritrichomonas species (cats) Physaloptera species Ollulanus tricuspis (cats) Heterobilharzia americana Pathogenic bacteria Escherchia coli Campylobacter species Salmonella species Mycobacteria species Fungi and algae Histoplasma species Prototheca species Pythium insidiosum Neoplasia Lymphoma Mast cell tumor Adenocarcinoma Leiomyosarcoma Gastrinoma Anatomic and functional disorders Hypertrophic pyloric gastropathy Gastric emptying disorders Other Food allergy Dietary indiscretion Transient gastroenteritis Persistent foreign body EXTRA-GASTROINTESTINAL Viruses Feline leukemia virus Feline immunodeficiency virus Organ dysfunction Hepatic disease Renal disease Pancreatitis Exocrine pancreatic insufficiency Hyperthyroidism Hypoadrenocorticism Other Neoplasia Persistent toxin exposure