Nutritional management quiz

Nutritional management of patients with vomiting and diarrhea

SEATTLE, WA – One of the most important things to remember when dealing with a patient with vomiting or diarrhea is that neither of these are diseases, but rather signs of disease. Diet selection will be ultimately determined by the cause of the signs as well as individual patient response, explained Ann Wortinger BIS, LVT, VTS (ECC, SAIM, Nutrition), speaking at the American College of Veterinary Internal Medicine Forum. As there are no physical test findings, lab test results, or historical facts that are predictive of which feeding method will be most successful, individual response and follow-up with the veterinary staff is necessary for optimal success.     

Causes of vomiting

Vomiting can be induced by motion sickness, ingestion of emetogenic substances, gastrointestinal tract obstruction, abdominal infection, or inflammation or extra-gastrointestinal diseases that stimulate the chemoreceptor trigger zone.  The most important clinical sign of chronic gastric disease is vomiting.

Causes of diarrhea

Dietary indiscretion or intolerance, intestinal parasites, and infectious diseases such as Salmonella or E. coli most typically cause acute diarrhea.  Chronic diarrhea is most commonly caused by intestinal disease, though other systemic diseases may affect intestinal function and can induce secondary hypersecretion or intestinal malabsorption. Ms. Wortinger said that the most common cause of chronic vomiting and diarrhea in dogs and cats is the constellation of diseases found under the heading of inflammatory bowel disease.

Acute diarrhea can often be treated symptomatically and will resolve within 2-3 days with minimal treatment.  Chronic diarrhea is rarely self-limiting, with treatment based on definitive diagnosis.

To withhold food or not

Ms. Wortinger explained that for years the standard treatment for acute vomiting or diarrhea has been to withhold food for 12-48 hours.  The belief has been that removing food would allow the upset GI tract to clear itself of luminal contents that may be causing the problem, help prevent mucosal cell abrasion by the GI contents, deprive the opportunistic luminal bacteria of nutrients preventing proliferation, prevent absorption of dietary antigens that may be present due to maldigestion, and permit restabilization of the brush border enzyme function. The problem with this approach, she said, is that in almost all cases of enteritis, there is a decreased motility with delayed gastric emptying and reduced segmental contractions. Therefore, fasting would not immediately provide any physical rest for clearing the GI tract.  

Evidence suggests that the prokinetic effect of feeding may decrease the vomiting response in some patients.  In fact, oral fasting alone can induce an intestinal insult, with mucosal atrophy occurring within 12 hours of a fasting state.

Treatment options

The primary goal for the management of vomiting or diarrhea is to maintain delivery of nutrition to the GI tract, and to prevent nutrient deficiency and malnutrition.  The most common first step is introducing a highly digestible, low fat diet.  Ms. Wortinger said that often a “bland” diet is recommended, though there is little evidence to support this, and the term ‘bland’ is poorly defined and vague.  Instead, she added, diet selection should be based on the specific disease being treated, the area of the GI tract affected, and the ability of the diet to promote tissue healing and maintain remission of clinical signs.

Our long-term goal in managing vomiting and diarrhea, she stressed, is to help repair the damaged GI tract lining, restore normal GI bacterial populations, promote normal GI motility and function, support the immune system, and decrease GI tract inflammation. 

Adverse food reactions and food responsive diarrhea

Some clinicians believe that food allergies in dogs and cats are more likely to occur with diets consumed during periods of acute gastritis.  If an adverse food reaction is suspected, the current recommendation is to feed a highly digestible, single source novel protein diet and to monitor patient response. A minimum trial of 3-4 weeks is recommended, though some clinicians will go for 3-4 months before making any diet changes.

Gluten, specifically wheat gluten, has received a lot of press lately with the advent of new, ‘grain-free’ and ‘gluten-free’ diets for pets.  Gluten is a plant protein that provides an excellent source of amino acids.  On average, gluten contains 80-82% protein, with low dietary fibre and a digestibility of approximately 99%.  Irish setters are the only breed of dog for which gluten sensitivity has been documented.  For these dogs, a gluten-free diet would be recommended. Rice and corn do not contain gluten, whereas wheat, rye, barley, and oats do. 


Proteins in the diet are essential for secretion of hormones and enzymes required for digestion. This includes the release of the pancreatic enzymes as well as the hormones insulin, gastrin, and cholecystokinin.  A protein source that is of high quality, easily digested and assimilated, and contains all of the essential amino acids in the correct proportions, would be recommended. The quality of a protein is measured by digestibility, as determined by feeding trials and by the biologic value of the protein.  For example, eggs are the highest source of protein, with a biologic value of 100.  Minimum total diet digestibility of levels of 85-88% dry matter are recommended with a protein digestibility of > 92%.


As fats are the most calorically dense nutrient, patients who are malnourished may benefit. However, the absorption of fats through the intestinal lymphatic system may be impaired and may contribute to a postprandial increase of fluid into the intestinal tract. The recommended fat content of diets is approximately 11-15% dry matter, or feeding a reduced amount of the diet.

The presence of the omega-3 class of fatty acids has been found to be helpful in management of inflammatory responses in the body, including those occurring in the GI tract. 

Carbohydrates and fibres

Similar to proteins, carbohydrates should be easily digested and assimilated by the intestinal tract.  The carbohydrate with the highest digestibility is cooked and blended white rice.  Fibres are useful in the management of GI disease, as well as maintenance of GI health.  The type of fibre used, as well as the level found in the diet, is important.  Those fibres that result in production of the short-chain fatty acid (SCFA) butyrate are preferred. The addition of highly fermentable fibres that produce high levels of SCFAs can cause diarrhea and flatulence and may interfere with the digestion and absorption of other nutrients.


There are many commercially available therapeutic diets that offer options for management of intestinal diseases including low fat, novel protein, and modified fibre diets.  As diet selection will be based on the cause of the signs and individual patient response, and there is no “best” diet for all patients, ongoing care and follow-up by well-trained veterinary staff is critically important.CVT