Vomiting and Diarrhea

Vomiting and diarrhea are two of the most common problems encountered in dogs and cats and they can often occur together. Vomiting and/or diarrhea are not a specific disease, but are symptoms of an underlying issue or disease, which can range from mild to life-threatening.


Vomiting is the forceful, active expulsion of stomach contents such as food, water, bile or foreign material like grass or hair. Blood can also be vomited as bright red blood or digested blood that looks like coffee grounds. Knowing what's in your pet's vomit can provide valuable information to help diagnose the underlying disease.

The seriousness of vomiting depends on the frequency, duration and underlying cause.  Many acute (sudden) conditions improve on their own without medical intervention within 24 hours. Vomiting needs immediate medical attention if it continues beyond this time frame, is frequent, contains blood or is associated with a declining patient status.

Possible causes of vomiting include:

  • Dietary indiscretion (eating garbage, table scraps, spoiled food, toxins, insects or irritants)
  • Intestinal parasites
  • Viral or bacterial infections
  • Inflammatory conditions of the stomach or adjacent organ (pancreatitis) and foreign body obstructions
  • Food allergies
  • Diseases in other organs (liver, kidney, pancreas, adrenal)
  • Cancer


Diarrhea is the passage of unformed or loose stools that usually results in an increased volume of stool, an increased frequency of defecation or both. The small and large intestine can each be responsible for diarrhea and the characteristics of the stool will be different depending on which one is responsible.

  • Small intestinal diarrhea is often seen as a mild increase in frequency of defecation, but a large volume of watery stool.  Because of the increased water loss and risk of dehydration and electrolyte disturbance, small intestinal diarrhea can be a more serious condition.
  • Large intestinal diarrhea is often seen as a marked increase in frequency of defecation, small volumes of stools, more prominent straining involved with the act of defecation (sometimes with no significant feces produced), and often includes the presence of mucus and or bright red blood. Because fluid and electrolyte loss is minimal, these patients often seem to “feel ok”.

Possible causes of acute (sudden) diarrhea include:

  • Ingestion offensive or irritating materials (like what a pet may find in the garbage)
  • Sudden change in diet
  • Stress, especially brought on by travel, boarding or other changes in the environment
  • Intestinal worms
  • Infectious agents including viruses, bacteria, and protozoal agents
  • Obstruction of the intestinal tract with a foreign body

Possible causes of chronic (long-standing) diarrhea include:

  • Food allergies
  • Inflammatory intestinal disease
  • Structural changes of the intestine resulting in the inability to absorb food and water
  • Diseases of other organs (liver, pancreas, adrenal)

Finding the Cause

If the condition is both mild and acute, the condition may be temporary and may not require a search for the cause. Pets showing severe or long-standing symptoms will need tests to determine the cause and the most appropriate therapy. These tests may include:

  • Fecal examination for parasites and bacteria
  • Blood and urine tests
  • Radiography (X-rays), sometimes with barium or other contrast dye
  • Ultrasonography
  • Endoscopy with collection of tissue for biopsy
  • Exploratory abdominal surgery


Specific treatment for the underlying disease problems will depend on the diagnosis.

In cases in which the signs are acute and mild and the patient is healthy, we may elect a conservative approach. This course of treatment should only be chosen if the animal is stable and healthy and should only be continued for 24-48 hours without seeing a resolution of the signs. If signs persist past that period of time or if the patient status declines, immediate veterinary attention is needed.

Dietary management is critical. Most cases of vomiting and diarrhea will benefit from “resting” the gastrointestinal tract.  During the first 12-24 hours, withhold all solid food. If the patient is having diarrhea only, provide free access to fresh water and encourage drinking. If vomiting is the primary concern, limit the intake of water to help prevent further episodes of vomiting. This can be done by allowing the patient to drink a very small amount and then removing the water source. Repeat this multiple times during the day (every 1-2 hours). Instead you could place ice cubes in a pan and allow the patient to drink the water as the ice melts.

After this period of fasting from solid foods, feed your pet small portions of a bland, easily digestible food and continue the bland diet for 5-7 days. Feeding small portions frequently throughout the day is preferable to larger meals. Specific diets like Prescription Diet® I/D are available, or you can opt for a homemade diet. Examples of homemade diets include low fat cottage cheese and boiled white rice, lean boiled chicken breast and boiled rice or lean, boiled ground beef and boiled white rice.  Once the symptoms have resolved, mix your pet’s regular diet in with the bland diet for a few days to help the transition back to the regular diet.

We can also perscribe specific medications and treatments based on a specific diagnosis such as:

  • Antibiotics
  • Anti-parasite drugs
  • Antacids
  • Intestinal protectants
  • Motility enhancers
  • Anti-inflammatory medications
  • Immune modulators
  • Probiotics
  • Digestive enzyme supplements

In all cases of vomiting and/or diarrhea, seek veterinary attention if the condition lasts longer than 48 hours of conservative care or is associated with any decline in the health status of your pet. Many cases of vomiting and diarrhea can have serious, life threatening underlying causes and need a complete medical diagnostic work-up and possible hospitalization.

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