Today's Veterinary Practice

MAY-JUN 2013

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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Peer revieweD GI INTERVENTION Approach to Diagnosis and Therapy of the Patient with Acute Diarrhea P. Jane Armstrong, DVM, MS, MBA, Diplomate ACVIM D iarrhea can be defined as increased fecal fluidity, usually accompanied by increased defecation frequency and volume of feces. Most cases of diarrhea are mild and self-limiting, requiring minimal diagnostics and therapy. Life-threatening cases can occur, however, that require greater diagnostic efforts and intensive care. ACUTE VERSUS CHRONIC Diarrhea is considered:1 • Acute if it lasts for less than 14 days • Chronic if it persists for longer than 14 days. Historical and clinical findings and appearance of the feces are used to differentiate whether the diarrhea is of small bowel or large bowel origin (Table 1). This differentiation is most important in cases of chronic diarrhea, when selection of diagnostic tests is influenced by the presumed location of enteric pathology. Additionally, many pets with acute diarrhea display signs of enterocolitis (mixed small and large bowel signs). PREVALENCE & INCIDENCE While diarrhea is a very common presenting problem in companion animal practice, it is either more common in dogs than cats, or dogs with diarrhea are more likely to be examined by a veterinarian. A report of diagnoses from over 2 million dogs and almost 430,000 cats in 2011 indicated that "gastroenteritis (GI upset)" and "colitis" both ranked in the top 19 diagnoses for dogs, but were not among the most common diagnoses in cats.2 Incidence of diarrhea and vomiting was investigated prospectively in a Norwegian study of 585 large-breed dogs followed from birth to 2 years of age.3 • Most dogs had only one episode of diarrhea and/or vomiting during the study period; those suffering from several episodes demonstrated relatively long periods between episodes. 20 Today's Veterinary Practice May/June 2013 • There was a positive association between occurrence of diarrhea and vomiting in the same dog, but episodes of diarrhea and vomiting did not usually occur at the same time. • Diarrhea and vomiting had a much higher frequency in young puppies despite complete vaccination and deworming protocols. • Risk for diarrhea decreased from 16% in 7-to-12-weekold puppies to 5.4% in 12-to-18-month-old dogs. An early study showed that frequency of both vomiting and diarrhea were highest in puppies and declined with increasing age4; this is supported by Banfield data demonstrating that "gastroenteritis (GI upset)" was common in dogs up to 3 years but much less common in dogs above that age.2 OWNER IDENTIFICATION Diarrhea is generally recognized by owners, as long as the feces are observed. Most owners realize that diarrhea is usually self-limiting and may be more prone to "wait and see" when pets develop gastrointestinal (GI) signs, compared to clinical signs that are not as familiar. In a study of 772 pet dogs in England, 70% of the reports of diarrhea involved only 1 or 2 episodes, and 78% lasted 2 days or less. Veterinary attention was sought for only 10% of dogs with diarrhea (and 5% of vomiting dogs).5 All dogs with diarrhea persisting for 7 days or longer were presented to a veterinarian. PATHOPHYSIOLOGY Four major pathophysiologic mechanisms can cause diarrhea. Osmotic forces and changes in mucosal permeability are the most important mechanisms in dogs and cats. In most small animal diseases, multiple mechanisms contribute to diarrhea, and it can be difficult to determine the predominant mechanism. 1. Osmotic diarrhea: The number of osmotically active particles in feces determines water content, and pres-

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