Dogs that come to a veterinary clinic because of diarrhea may be suffering from an extensive array of underlying problems. However, the initial assessment of the animal will be the same. The veterinarian will take a thorough history from the dog’s owner, including information about the dog’s living environment, vaccination status, diet and the circumstances surrounding the onset of diarrhea. She will also perform a complete physical examination, which will include a rectal examination. Fresh fecal samples will be taken and evaluated by fecal floatation and fecal smear, to look for evidence of eggs or larva of internal parasites or bacterial infection. These tests probably will be repeated several times on different fecal samples. Many dogs with acute diarrhea have their symptoms resolve spontaneously and don’t require any further diagnostic tests or procedures.
When more advanced diagnostics are appropriate, the veterinarian will usually recommend taking blood samples (for a complete blood count and serum chemistry panel) and urine samples (for a urinalysis) and submitting them to a pathology laboratory for analysis. These routine tests are relatively non-invasive and inexpensive and can provide a great deal of diagnostic information. In cases of chronic diarrhea, blood tests for pancreatitis, exocrine pancreatic insufficiency (EPI), hypoadrenocorticism (Addison’s Disease) and thyroxine, colbalmin and folate insufficiencies are available. Blood work can also evaluate hormone and serum bile acid levels, which can disclose liver, kidney or endocrine abnormalities. Special fecal and blood tests, called ELISA, PCR and FA, can be used to check for parvovirus, Giardia, Clostridium perfringens, Clostridium difficile, Campylobacter, Cryptosporidium, Salmonella and Cryptococcus infections, among others. Fresh fecal samples can be cultured to look for infective organisms, including E. coli, Salmonella, Clostridium, and others.
Abdominal radiographs (X-rays) can help the veterinarian identify intestinal obstructions, gastric torsion or lodged foreign bodies. Ultrasonography and contrast abdominal radiographs are also available as advanced diagnostic tools. Dogs with severe chronic diarrhea may need to have surgical biopsies of several areas of their intestines taken, to get at the root of the problem. These tissue samples can be taken by the traditional surgical technique, which involves opening the abdominal wall and then removing samples of the intestine, or by using an endoscope, which is a wand-like instrument with a camera and a claw-like clutch on its end. Endoscopy is increasingly available at veterinary clinics and is a less invasive way of obtaining biopsy samples.
In cases of mild diarrhea, or if the owner’s financial constraints are paramount, the veterinarian may recommend empirical treatment as a form of diagnosis. This involves administering de-worming medications (anthelmintics), antibiotics or anti-inflammatory medications and/or starting dietary ingredient elimination trials.