Diarrhea is one of the most common clinical signs of intestinal disease in companion animals and sometimes one of the most
frustrating conditions for veterinarians to diagnose and successfully manage. It is best, and easiest, if the clinician has
a logical, systematic approach to work up dogs and cats with diarrhea and be able to arrive at an accurate diagnosis. One
should be able to wade through the myriad of available tests and be able to recognize the benefits and limitations of each.
Clues obtained during the history and physical exam will in most cases help to order your rule-out list. Clinicians cannot
overlook this basic, simple step. Signalment is important as breed predilections for diarrheal disease can help order your
rule-out list. For example a four-month-old febrile, unvaccinated Pitt Bull with small intestinal diarrhea will probably have
a different rule-out list compared to a four-year-old Yorkshire terrier with small intestinal diarrhea.
With the economic climate and pressure today clinicians are often rushed during appointments. Despite the importance of a
detailed history, important pieces of important information are often overlooked. A comprehensive history is essential to
the diagnosis. The dietary history should include the diet being fed, measured meal size, meal time/s, recent and past diet
changes, supplements and medications, and the possibility of dietary indiscretion. Dietary indiscretion can be a recent purposeful
diet change, non-purposeful diet change, diet additive, new treats or table scraps, free-roaming behavior, possible foreign
body ingestion, possible garbage ingestion, and exposure to toxins.
It is also important to describe and characterize the duration, frequency (continuous or intermittent), and appearance of
the diarrhea. Is there mucus, hematochezia, melena, tenesmus or fecal incontinence? Has the fecal volume increased? Is the
animal's appetite the same, increased or decreased? Has the animal lost weight and if so how much? Ask the owner if there
are any inciting factors that trigger the diarrhea. Examples would include: other animals in the house, stress, travel, new
household members, visitors, thunderstorms, loss of a pet or household member or a move. Does vomiting accompany the diarrhea?
Does anything else accompany the diarrhea? The above answers to characterize the diarrhea will direct the diagnostic and treatment
plan. To save time but ensure a thorough history is obtained develop your own gastrointestinal questionnaire. The client can
answer while waiting or during the physical examination.
Based on your thorough history you should be able to determine if the diarrhea is small bowel, large bowel or mixed bowel
Small bowel diarrhea is characterized by weight loss, a mildly increased frequency of defecation and a large amount of feces
produced per defecation. Patients with large bowel diarrhea do not lose weight but have an increased defecation frequency
but less feces produced per defecation. Excess mucus, hematochezia and tenesmus are often seen. Accordingly, mixed bowel diarrhea
has elements of small and large bowel diarrhea. This initial analysis is very important to guide the diagnostic and treatment
The physical exam should begin as the patient walks into the examination room. The physical examination should detect fever,
dehydration, weakness, lethargy, cachexia, pallor, tachycardia or bradycardia, effusion or edema. Particular attention should
be paid to intestinal loop palpation to discern thickening, masses, distension or pain. A thorough rectal examination may
reveal thickening of the rectum, sublumbar lymphadenopathy or masses.