Gastrointestinal disorders are frequently either unrecognized or misdiagnosed. The appropriate recognition of a specific condition
and subsequent therapy may resolve the disorder. The purpose of this presentation is to provide important practice tips for
diagnosing and managing various gastrointestinal disorders associated with diarrhea.
Chronic diarrhea is a common complaint, and the potential etiologies are extensive. Parasites, dietary intolerances, metabolic
disease, pancreatic disease, bacterial causes, and inflammatory bowel disease are but a few etiologies of chronic diarrhea.
Inflammatory bowel disease (IBD) is a common condition diagnosed in dogs and cats; however, it is not a specific disease but
rather a term that describes animals having gastrointestinal (GI) signs with histologic evidence of inflammation within the
intestine. IBD does not, however, describe the etiology, nor does the extent of inflammatory cells parallel the severity of
clinical signs. Before beginning extensive diagnostic tests or obtaining an intestinal biopsy specimen from a patient with
chronic diarrhea, there are a few diagnostic tests or trial therapies to consider (Figure 1). Obviously the course of action is predicated, in part, on a good clinical evaluation and based on the severity of the clinical
Figure 1. A basic approach in the work-up and clinical management of a chronic diarrhea case.
Every patient with chronic GI signs should have a thorough history, physical examination, complete blood count, serum chemistry
profile, urinalysis, and fecal examination performed. In many cases, this initial evaluation will determine if the etiology
of the diarrhea is primary GI disease or secondary to other systemic or metabolic disease, or if the diarrhea is predominantly
of small bowel or large bowel origin. For example, Addison's disease, liver disease, and renal disease can all be associated
with secondary GI involvement. If the initial work-up fails to provide a clue as to the etiology, then begin a specific GI
evaluation. The fecal examination should include standard fecal flotation, wet-mount preparation, and stained cytology. A
Diff-Quik-stained cytologic slide may reveal such things as neutrophils, eosinophils, fungal organisms, or clostridial spores
and may provide clues about the etiology (Figures 2A-2D). This is also the time to classify the patient based on the severity of disease: minimal signs and debilitation or those cases
having severe disease obviously requiring an in-depth GI work-up.
Figures 2A-2D. Fecal cytology showing: (A) a Diff-Quik-stained thin fecal smear, (B) normal feces with amorphous debris and
mixed bacterial flora, (C) abundant clostridial spores, and (D) many neutrophils.
For the animal with relatively mild diarrhea without weight loss or debilitation, I prefer to use trial therapy as part of
the clinical evaluation. Trial therapy involves antiparasitic therapy, dietary food trials, and antibiotic therapy. If these
trial therapies fail to resolve the diarrhea, further GI evaluation is indicated. Additional diagnostic testing may include
imaging studies (ultrasonography is preferred, as barium studies are rarely helpful), serology (trypsin-like immunoreactivity,
folate, cobalamin), and endoscopy or surgery for intestinal biopsies.