Acute Vomiting & Diarrhea: Diagnostic & Treatment Plan

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Diagnostic Work

In addition to history and physical examination results, the minimum database for a patient with acute vomiting and/or diarrhea includes diagnostic imaging, a fresh fecal sample for analysis, and blood for packed cell volume (PCV) and total protein (TP). Values gleaned from rapid measurement of electrolytes (ie, K+, Na+, Cl-) can be helpful, as can other in-practice tests (eg, blood glucose, blood urea nitrogen [BUN]). Fecal analysis should go beyond simple flotation for parasites and include a gross examination for color, consistency, foreign material, mucus, and the presence or absence of blood (eg, melena, hematochezia). Other diagnostic testing should include:

  • Wet mount (saline smear): Reveals protozoa or other parasites
  • Stained fecal cytology (dry mount): Detects blood cells and (rarely) fungal organisms or neoplastic cells. Stained smears can identify bacteria and yeast, which are visible but nondiagnostic.
  • Flotation by centrifugation: Detects parasite ova and oocysts
  • Fecal culture: Rarely diagnostic except for detection of Tritrichomonas blagburni (foetus) in cats
  • ELISA (enzyme-linked immunosorbent assay): Detects antigens associated with parvovirus, giardiasis, and cryptosporidiosis
  • PCR GI panels: Detects multiple organisms. These recently became available at some laboratories; however, interpretation can be difficult because both false-positive and false-negative results are possible.

Additional laboratory work (eg, CBC, serum chemistry panel, urinalysis, specific GI testing [eg, pancreatic function, cobalamin, folate]) can be performed based on severity or responsiveness.


Imaging (eg, survey radiographs, contrast studies, abdominal ultrasonography) should be used during a more comprehensive evaluation. Two views of the abdomen (ie, right lateral, ventrodorsal) should be obtained routinely, but consider the opposite lateral when assessing for obstruction or masses. Barium can be administered orally or rectally for contrast studies of the entire GI tract or specific areas (eg, esophagus, colon). A skilled ultrasonographer can perform imaging of the stomach, intestines, and associated organs (eg, pancreas, liver, kidneys, adrenal glands). Endoscopy, CT, MRI, and other imaging techniques may be available; however, these require anesthesia and are thus generally reserved for more serious or chronic cases.


Treatment should be directed toward the underlying cause. Symptomatic therapy may include fluids and electrolytes, nutritional support, and various medications. Administer a balanced crystalloid solution if dehydration is present or suspected.

Previous recommendations to “rest” the GI tract by withholding food and water are considered outdated except during active vomiting. Highly digestible, low-residue, energy-dense veterinary therapeutic diets are available to help restore GI health (eg, Purina Veterinary Diets EN Gastroenteric; Iams Veterinary Formula Intestinal Plus Low-Residue; Hill’s Prescription Diet i/d Gastrointestinal Health; Royal Canin Veterinary Diet Gastrointestinal). Fat restriction is recommended for dogs that have confirmed or suspected acute pancreatitis.

Many medications are available for the management of vomiting and diarrhea. Maropitant is often effective and is approved for control of vomiting in dogs and cats. Antacids are frequently prescribed for vomiting and/or diarrhea, but they are not antiemetics and are indicated only if gastric ulceration is suspected. In general, routine use of antibiotics should be avoided in acute cases unless there is a clear bacterial etiology or risk of septicemia. Some studies indicate faster recovery from acute diarrhea with probiotic use.1,2

Editor’s note: Dr. Craig Datz is employed by Royal Canin, in addition to his affiliation with University of Missouri.

References Show

Clinical benefits of probiotic canine-derived Bifidobacterium animalis strain AHC7 in dogs with acute idiopathic diarrhea. Kelley RL, Minikhiem D, Kiely B, et al. Vet Ther 10(3):121-130, 2009.
Effects of a probiotic intervention in acute canine gastroenteritis—A controlled clinical trial. Herstad HK, Nesheim BB, L'Abée-Lund T, et al. J Small Anim Pract 51(1):34-38, 2010.
Small Animal Clinical Nutrition, 5th ed. Hand MS, Thatcher CD, Remillard RL, et al—Topeka: Mark Morris Institute, 2010.

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