Diagnostic approach to chronic diarrhea in dogs and cats (Proceedings)


Diagnostic approach to chronic diarrhea in dogs and cats (Proceedings)

Aug 01, 2010

Chronic diarrhea is a common problem in dogs and cats. Diagnosis can be difficult and challenging for veterinarians due to the large number of possible causes of chronic diarrhea. Following a logical and thorough diagnostic plan is essential to efficiently arrive at an accurate diagnosis. This seminar will review the author's approach to the diagnosis of chronic diarrhea.

Table 1 Chronic Diarrhea History Form
Clues obtained during the history and physical examination may suggest a diagnosis or help to rank the differential diagnosis. A thorough description of the diarrhea should be obtained (Table 1: diarrhea history form). The dietary history should include the diet being fed, meal size, meals / day, past diet changes and effects on clinical signs, supplements, and the existence of dietary indiscretion. Dietary indiscretion includes a recent and sudden diet change, feeding of table scraps, free roaming behavior allowing ingestion of garbage, ingestion of foreign objects, exposure to toxins (including house plants), excessive ingestion of hair, or feeding a low-quality poorly digestible diet. The duration of the problem should be identified and the diarrhea should be categorized as continuous or intermittent. If intermittent, how long are the episodes and how frequently do they occur? Are there any inciting factors the owner can relate to the origin of the diarrhea or that make the clinical signs worse? Examples include any stress, travel thunderstorms, new pet, loss of a pet, new family member, household move, etc. Does vomiting accompany diarrhea? How many times a day does vomiting occur, how many days / week, what is its association with eating, and what does the vomitus look like? What is the animal's deworming history? What previous treatments have been used, including dosage, frequency / day, and duration, and what response has been seen?

Table 2: Localization of Chronic Diarrhea
Specific information should be obtained describing and characterizing the diarrhea. What is the frequency / day, is there melena or hematochezia, mucus, tenesmus, or accidents in the house? What is the volume of stool / defecation, compared to what is normal for the dog or cat? Is the animal's appetite normal, reduced, or increased? Has weight loss occurred, and how much? Finally, the consistency of the stool should be graded from 1 (watery diarrhea) to 5 (formed stool). The above characteristics should be based on the animals average clinical signs during the period prior to your examination. Based on a thorough history, the initial step in evaluation of dogs and cats with chronic diarrhea is to determine if diarrhea is of small bowel, large bowel, or mixed bowel origin (Table 2). Small bowel diarrhea is characterized by weight loss, a mildly increased frequency of defecation, and a large quantity of stool produced per defecation. Blood, if present, is partially digested (melena). On the other hand, large bowel diarrhea is characterized by the absence of weight loss, and a moderate to greatly increased frequency of defecation, with a reduced to scant volume produced per defecation. Tenesmus, excess fecal mucus, and frank blood (hematochezia) is often present. Mixed bowel diarrhea has some characteristics of both. This initial distinction between small and large bowel is extremely important because the diagnostic plans and differential diagnoses are different.

Physical examination is often normal in dogs and cats with chronic diarrhea with the exception of weight loss. Mildly thickened bowel wall may be palpated. If a severe episode of clinical signs is present, signs of dehydration may be detected (delayed capillary refill time, enophthalmos, decreased skin turgor, tachycardia, pale mucous membranes, and cold extremities). Careful attention should be devoted to abdominal palpation to detect abnormalities such as dilated (gas, fluid, or ingesta) loops of bowel or extremely thickened bowel wall, abdominal masses, intraluminal foreign bodies, or ascites. These abnormalities are detected in <5% of cases seen at the author's hospital. Digital rectal examination may elicit pain and reveal an intraluminal mass, rough corrugated mucosa, sublumbar lymphadenopathy, narrowed lumen, foreign material, blood on the glove, or a perineal hernia.