Gastroenteritis in Dogs

By Malcolm Weir, DVM, MSc, MPH; Tammy Hunter, DVM; Ernest Ward, DVM

Gastroenteritis is inflammation of the gastrointestinal tract (stomach and the intestines). It can be caused by infection with bacteria, viruses, parasites, medications, or even new foods. The condition often causes abdominal pain, diarrhea, vomiting, and other clinical signs.

What are the clinical signs of gastroenteritis?

Most dogs with gastroenteritis will have intermittent episodes of vomiting and diarrhea. The vomit may contain foamy, yellowish bile, especially after emptying the stomach. Many owners observe dry heaving or gagging after their dog eats or drinks. Characteristically, large volumes of diarrhea will be produced several times a day. The diarrhea may have the consistency of soft-serve ice cream.

Many dogs will be tender when picked up around the abdomen or resist handling the stomach and hindquarters. Most dogs affected with gastroenteritis will appear less active (lethargic) and have a decreased appetite. A low-grade fever is also common. Dehydration can occur quickly if the vomiting and diarrhea persist for more than 24 hours.

How is gastroenteritis diagnosed?

Gastroenteritis is a diagnosis of exclusion. This means that your veterinarian will eliminate or rule out other more serious causes of the clinical signs before making a general diagnosis, such as gastroenteritis. A good medical history is the first step toward determining what is causing your dog's vomiting, diarrhea, lethargy, and other associated clinical signs. Some critical information in your dog's medical history includes:

  • Your dog's current diet, how much you feed, and how often you feed your dog
  • Everything your dog ate or drank within the past 48 hours
  • Any new foods, treats, or rewards
  • Any recent exposure to pesticides, medications, cleaning agents, or any other new materials
  • Any recent exposure to a new animal or person
  • Any previous episodes of vomiting and diarrhea (including their cause and treatment)
  • Any illness within the past month
  • Any medications, vitamins, or supplements given within the past month

Your veterinary health team may have you complete a questionnaire before your visit. See the “Diarrhea Questionnaire and Checklist for Dogs” handout for an example.

After obtaining the medical history, your veterinarian will perform a thorough physical examination. Your veterinarian will look for evidence of dehydration, abdominal pain, tenderness, bloating or gas, swellings, or any other physical abnormality. Your dog's temperature and other vital signs (heart and respiratory rates) will be recorded.

At this stage, diagnostic testing will be recommended and may include:

  • Complete blood cell count (CBC) - indicates the presence of dehydration and infection
  • Serum chemistries and electrolytes - detect organ system abnormalities and electrolyte imbalances due to vomiting and diarrhea
  • Urinalysis - detects urinary tract infections, kidney disease, dehydration, urine glucose for diabetes, etc. 
  • Abdominal radiographs (X-rays) - to search for stomach or intestinal obstruction or other abnormal findings
  • Abdominal ultrasound - to look for intestinal obstructions or other abnormalities

Your dog's specific diagnostic workup will be determined by the severity and duration of clinical signs, medical history, and physical examination. Once the diagnostic tests are complete and other causes of the clinical signs have been eliminated, treatment will be prescribed.

What are some of the causes of gastroenteritis?

There are many causes of the symptoms of vomiting and diarrhea in dogs. Some of the more common conditions that your veterinarian will attempt to eliminate during the diagnostic workup include:

  • Infections (e.g., bacterial, viral, fungal, or parasitic)
  • Foreign bodies (especially string or thread) or other objects
  • Intussusception (the telescoping of the intestine into itself, causing an intestinal blockage) • Tumors/cancer • Poisoning/toxins (e.g., plants, cleaning agents)
  • Endocrine disease (e.g., diabetes, hyperthyroidism)
  • Pancreatic, liver, or kidney disease

This is only a partial list of more serious conditions that can cause vomiting and diarrhea in dogs. Your veterinarian may discuss other possibilities based on your dog's specific condition.

How is gastroenteritis treated?

The principal treatment of gastroenteritis is rehydration and restoring blood electrolyte balance (sodium, potassium, and chloride). Depending on the degree of dehydration, this fluid replacement will be given orally, subcutaneously (beneath the skin), or by intravenous (IV) treatment. Medical treatment may also include:

  • Antibiotics (e.g., metronidazole, ampicillin) if the clinical signs are severe or if diagnostic tests suggest a bacterial infection. 
  • Antidiarrheal drugs may be used to alter intestinal motility (activity) after intestinal obstruction or other mechanical and anatomical issues have been ruled out. Motility-modifying agents are generally not recommended if your dog is experiencing severe colitis.
  • Anti-emetic (anti-vomiting) medications, such as maropitant (Cerenia®) or metoclopramide (Reglan®)
  • Gastrointestinal protectants used to prevent stomach ulcers, such as famotidine (Pepcid®) or ranitidine (Zantac®)

Food is often withheld during the initial stages of treatment for 12-24 hours and then slowly reintroduced. Small, frequent feedings of a highly digestible, low-fat, low-fiber diet are generally prescribed. Your veterinarian will advise you on the best diet to feed your dog for a speedy recovery.

What is the prognosis for gastroenteritis?

Most cases of acute gastroenteritis improve rapidly after rehydration. Call your veterinarian if the vomiting and diarrhea do not improve significantly within 48 hours of treatment. Gastroenteritis is a common condition seen in veterinary practice. Early recognition and treatment are the cornerstones to returning your dog to a normal healthy state as quickly as possible.

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