Canine Chronic Enteropathy

Dogs with chronic intestinal disease typically present for investigation of clinical signs such as diarrhea, weight loss or vomiting. Clinical signs attributed to gastrointestinal disease that has lasted 3 weeks, or more is consistent with a chronic enteropathy. After the exclusion of infectious / parasitic agents, non-gastrointestinal disorders, exocrine pancreatic insufficiency, and intestinal structural abnormalities requiring surgery, the most common group of intestinal diseases associated with chronic enteropathies are idiopathic inflammatory bowel disease, diet responsive enteropathy, antibiotic responsive enteropathy and lymphangiectasia.

Diagnostic Approach

The approach to this group of patients is usually determined by the severity of clinical signs (frequent severe diarrhea, excessive weight loss, decreased activity or appetite) and the presence of hypoalbuminemia, intestinal thickening, or mesenteric lymphadenopathy. Patients with these abnormalities require an intestinal biopsy to define the cause (e.g. IBD, lymphangiectasia, lymphoma,) and to optimize therapy. Controlled studies have shown that hypoalbuminemia is associated with a poor outcome in dogs with chronic enteropathy (Craven 2004, Allenspach 2007). Serum concentrations of cobalamin and folate can be measured to determine if supplementation is required and low serum cobalamin concentration (<200ng/L) has also been associated with a negative prognosis (Allenspach 2007). Evaluation of hemostatic function is recommended to determine if hypo- or hyper- coagulability have arisen as a consequence of enteric protein loss.

The clinical severity of intestinal disease can be quantified by determining the clinical disease activity index (attitude activity, appetite, vomiting, stool consistency, stool frequency, weight loss) (Jergens 2003). Measurement of serum C- reactive protein (has been shown to correlate with clinical disease activity (CIBDAI) and implies that severe clinical disease is accompanied by a systemic inflammatory response (Jergens 2003). Measurement of clinical disease activity or CRP can also serve as a baseline for determining the response to treatment however, these diagnostics tests are not yet in wide use.

The measurement of serum cobalamin and folate can be performed in stable patients (i.e. good attitude, appetite, mild weight loss, normal serum proteins and no intestinal thickening or lymphadenopathy) to evaluate disease severity, aid localization of intestinal disease, and to determine if supplementation is required. Moreover, the option of empirical treatment trials with diet, followed by antibiotics if there is no response to diet is available to these stable patients. Failure to respond to empirical therapy, low serum cobalamin, hypoproteinemia, or worsening of disease, is an indication for intestinal biopsy.

Intestinal biopsies can be acquired endoscopically or surgically. In patients without an indication for surgery e.g. intestinal masses, anatomic or structural disease, perforation, diagnostic endoscopy to visually inspect the esophageal, gastric and intestinal mucosa and to procure endoscopic biopsies is preferred. Surgical biopsy is usually performed where intestinal disease is suspected to involve the submucosa or muscularis and where the results of endoscopic biopsies do not adequately explain the clinical picture.

Unfortunately, the interpretation of gastrointestinal histopathology varies considerably among pathologists (Willard et al 2003). To try to correct this problem a working group established by the WSAVA has formulated a scheme to standardize the evaluation of intestinal histopathology (Day et al 2008). The ability of this scheme to increase agreement between pathologists, and the clinical relevance of the criteria it evaluates remain to be determined, but it is a step in the right direction. The most common histopathological diagnoses in dogs with chronic enteropathy are inflammatory bowel disease, lymphangiectasia and lymphoma and predisposed breeds include Basenji, Lundehund and Chinese Sharpei.

The presence of moderate to large numbers of eosinophils in intestinal biopsies, which is often accompanied by circulating eosinophilia, suggests possible parasitic infestation or dietary intolerance. Moderate to high numbers of macrophages and neutrophils raise the possibility of an infectious process, and culture and special stains are indicated.

Treatment

The therapeutic approach to chronic enteropathies is influenced by suspicion of a breed-related problem; severity of disease as characterized by clinical signs, albumin and cobalamin concentrations, and endoscopic appearance; type of cellular infiltrate; the presence of bacteria or fungi; and presence of architectural changes, such as atrophy, ulceration, lymphangiectasia/crypt cysts. Therapeutic intervention is directed at correcting nutritional deficiencies (e.g. cobalamin) and counteracting inflammation and dysbioisis. The clinical severity of disease, nature and severity of histopathological lesions, and the presence or absence of hypoalbuminemia guides treatment.

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