Inflammatory bowel disease: Diagnostic and treatment approaches (Proceedings)
Inflammatory bowel disease is a somewhat loosely defined term that describes chronic gastrointestinal (GI) tract signs in dogs and cats, especially weight loss, vomiting and diarrhea. The term inflammatory bowel disease is often used to define a picture of intestinal mucosal inflammation from a variety of cell types, most commonly lymphoplasmacytic, without apparent cause. Because some animals with intestinal inflammation will respond to changes in diet, or to administration of antibiotics, some clinicians term the clinical syndrome chronic enteropathy and subdivide the syndrome into food responsive, antibiotic responsive, and steroid responsive disease. This presentation will primarily address the diagnostic and treatment considerations of inflammatory bowel disease /chronic enteropathy in dogs and cats.
Inflammatory bowel disease should be considered a differential diagnosis for any dog or cat with a chronic history of weight loss, vomiting or diarrhea. Appetites in affected animals can range from good to poor. In severe cases, there can be enough enteric protein loss to cause peripheral edema, or thoracic or abdominal effusions. Clinical signs can be cyclic with spontaneous waxing and waning, particularly early in the clinical course.Diagnostic approach
Most patients will have had a laboratory data base (CBC, biochemical profile, urinalysis) at some point in the clinical evaluation. There are no pathognomic clinical pathology features. Affected animals can have anemia of inflammatory disease, inflammatory or stress leukograms; thrombocytosis is a relatively common hematologic abnormality and is attributed to chronic inflammation. Biochemical profile abnormalities can include increases in liver enzyme activity, which are typically mild to moderate, hypoalbuminemia/ panhypoproteinemia, or hyperglobulinemia. There are no urinalysis abnormalities that specifically suggest gastrointestinal disease, but a urinalysis can exclude the urinary tract as a source of protein loss in hypoalbuminemic patients. Comprehensive fecal examinations are important to exclude gastrointestinal parasites as the cause of clinical signs. Fecal floats, direct smears and wet mounts allow for a thorough assessment of stool samples for intestinal parasitism. Before embarking on an expensive diagnostic or treatment protocol, it may well be worth empiric treatment with fenbendazole or other broad-spectrum anthelmintic.
Other readily available diagnostic tests that can be important in the evaluation of the inflammatory bowel disease candidate are serum trypsin-like immunoreactivity (TLI), folate and cobalamin concentrations. Exclusion of exocrine pancreatic insufficiency is an important early step in the evaluation of animals (both dogs and cats) with signs compatible with chronic small bowel disease, thus a TLI should be performed early in the diagnostic process. High serum folate and low cobalamin concentrations can indicate the presence of bacterial overgrowth, which can complicate inflammatory bowel disease, or cause intestinal inflammation. If bacterial overgrowth is suspected, a search for an underlying cause such as, for example, exocrine pancreatic insufficiency, partial intestinal tract obstructions, or motility disorders is warranted.
The author is an advocate of abdominal imaging in candidates for inflammatory bowel disease. Abdominal imaging can help rule out partially obstructive diseases, which in some patients can have overlap in clinical features with those of inflammatory bowel disease, can help raise or lower the index of suspicion for gastrointestinal neoplasia. Imaging approaches that are useful include abdominal radiography (with contrast as needed) or abdominal ultrasonography, which is often the author's preferred imaging approach. Abdominal ultrasonography can be very helpful in assessment of intra-abdominal lymph nodes, which if large, can be aspirated under ultrasound guidance for cytologic examination. This is an advantage as intestinal lymphoma is a competing differential for inflammatory bowel disease, and the diagnosis of intestinal lymphoma can be established by cytological examination precluding the need for more aggressive biopsy approaches. In some parts of the country infectious diseases, such as Pythium or Histoplasma, can cause disease similar to inflammatory bowel disease and these agents can be found on cytological samples as well. Abdominal ultrasound can also help exclude focal disease as a cause of clinical signs, an important consideration as many patients that are suspects for inflammatory bowel disease are eligible for endoscopic biopsies, and endoscopic examinations may be of limited use in patients with focal disease. Abdominal ultrasonography also helps evaluate other organs, which can provide important staging information for patients with gastrointestinal neoplasms, for which clinical signs may be similar to those of inflammatory bowel disease.