Gastroenteritis in Dogs

Liz Bales, VMD
By Liz Bales, VMD on Oct. 21, 2021
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What Is Gastroenteritis in Dogs?

Gastroenteritis in dogs is defined as an inflammation of a dog’s stomach (gastro-) and small intestine (-enteritis). In simple terms, gastroenteritis is an upset stomach. Pet parents might use the term “dog stomach bug” to describe this kind of illness, but the possible causes go beyond a viral infection.

If your dog has bloody diarrhea or vomit, go to the emergency vet immediately, as these are signs of acute hemorrhagic diarrhea syndrome (AHDS).

Acute Hemorrhagic Diarrhea Syndrome (AHDS) / Hemorrhagic Gastroenteritis (HGE)

Acute hemorrhagic diarrhea syndrome, also known as hemorrhagic gastroenteritis (HGE), is a specific and critical form of enteritis. It is a medical emergency and one of the most serious causes of diarrhea in dogs.

AHDS can be fatal—your dog can become septic (caused by a dangerous infection in the bloodstream), lose too much protein, or experience complications.

Dogs affected with this disease have been shown to have inflammation of only the intestines, not the stomach. If you suspect your dog has AHDS, take them to the vet immediately.

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Symptoms of Gastroenteritis in Dogs

Take your dog to the emergency vet if you see the signs of AHDS:

  • Sudden onset of bloody diarrhea with no known cause, such as a change in diet

  • Vomiting, with or without blood

  • Lethargy  (moving slowly, sluggish)

Call your vet if your dog is showing any signs of gastroenteritis:

  • Sudden vomiting

  • Sudden diarrhea

  • Lethargy

Dogs suffering from gastroenteritis exhibit a sudden onset of vomiting and/or diarrhea and may lose a large volume of body fluids and electrolytes. This can cause dehydration. Monitor your dog’s hydration and activity level.

If your dog is dehydrated and/or lethargic, go to the emergency vet. This indicates a more serious situation that needs immediate treatment.

You can check for dehydration by gently lifting the skin on the back of your dog’s neck. If it stays raised and doesn’t go back to place quickly, your dog is probably dehydrated.

Another tip to test your dog for dehydration: press on your dog’s gums, which should turn from white back to pink within 2 seconds. If the pink takes any longer to come back, your dog is probably dehydrated.

Other signs of dehydration include:

  • Panting

  • Dry nose and eyes

  • Dry, pasty gums and thick saliva

  • Loss of appetite

  • Loss of skin elasticity (when you pull your dog’s skin and it is slow to snap back)

Causes of Gastroenteritis and AHDS in Dogs

Gastroenteritis in dogs can be caused by many underlying issues. Your vet can run diagnostic tests to help you figure out why your dog is sick. Some possible causes include:

The exact cause of AHDS remains unknown. Some vets theorize that the condition begins with a bacterial infection in the intestine caused by Clostridium perfringens type A.

This infection creates dangerous toxins that erode the protective lining of the intestine, allowing fluids and blood to leak out.

How Vets Diagnose Gastroenteritis in Dogs

This diagnosis is made when a dog has a sudden case of vomiting or diarrhea, has been sluggish and lethargic, and hasn’t had an appetite. Describing your dog’s symptoms can help your veterinarian make the diagnosis. Your vet will also check your dog for dehydration and signs of abdominal pain.

To rule out other possible causes of vomiting and diarrhea, such as parvovirus, parasites, a gastrointestinal obstruction, cancer, kidney disease, and other more serious conditions, your veterinarian may need a fecal analysis, bloodwork, X-ray, or ultrasound.

Diagnosis for AHDS in Dogs

Your vet will also consider AHDS as a possible cause if your dog has bloody, watery diarrhea; dehydration; and an elevated packed cell volume (the number of red blood cells currently circulating).

There is no specific test to diagnose AHDS in dogs. If no other cause is found for your dog’s symptoms, a diagnosis of AHDS may be made as a "diagnosis of exclusion.”

An Addisonian crisis, which is when a dog with Addison’s disease has acute gastrointestinal symptoms that are often bloody, can look exactly like AHDS. This is fatal if untreated.

Since an Addisonian crisis and AHDS are both so serious, it is critical to take your dog to the vet immediately if they are dehydrated or have bloody diarrhea.

Treatment for Gastroenteritis in Dogs

The goal of treatment is to stop the vomiting/diarrhea and maintain hydration.

Depending on your dog’s condition and the underlying cause, your veterinarian may administer anti-vomiting medication, antibiotics, and antacid medications specifically formulated for dogs.

If your dog is vomiting, the medications will be administered through injection. Your dog may also require hospitalization for IV (intravenous) fluids and electrolytes.

Treatment for AHDS in Dogs

AHDS is very serious and cannot be treated at home. If your dog has bloody diarrhea or vomit, go to the emergency vet immediately.

Dogs with AHDS are losing a life-threatening amount of fluid, protein, and electrolytes, and they must be hospitalized for aggressive IV therapy, electrolyte supplementation, and medication.

With AHDS, the survival rate is 90–95% if appropriate, aggressive therapy is started quickly. Most dogs recover in two or three days.

Recovery and Management of Gastroenteritis in Dogs

After your dog comes home from the vet, you can continue care. If the vet finds that your dog’s gastroenteritis is caused by something that’s contagious, isolate your dog from your other pets. Do not allow your dog to eat or drink until there has been no vomiting for six to eight hours.

Then you may give your dog small amounts of clear liquids (water, Gatorade, Pedialyte, or other electrolyte solution) every two hours.

If your dog does not vomit the fluid after 12 hours, give frequent, small meals of boiled hamburger and rice or boiled chicken and rice, about ¼ cup or less per feeding. Your vet might also send you home with samples of a low-fat, easily digestible prescription diet such as these

Recovery From AHDS in Dogs

Part of your dog’s recovery plan from AHDS should be a bland diet that’s high in carbohydrates and low in protein and fat. Your vet may offer you special canned food, or you can cook for your dog.

Cooked rice or pasta; potatoes with some cottage cheese; lean, boiled ground beef; or skinless chicken are good choices for a couple of weeks as your dog's gut heals and their appetite returns. Ask your veterinarian about options for cooking for your dog to ensure that you provide the right nutrients in the right amounts.

Gastroenteritis in Dogs FAQs

How can I treat my dog’s gastroenteritis at home?

If your dog is vomiting or has diarrhea, you should always call your veterinarian. They can ask you specific questions to help assess how serious the situation is.

If your dog is lethargic or showing blood in their vomit or diarrhea, take them to the vet immediately. Dogs with AHDS need to be hospitalized for care and cannot be managed safely at home.

After a vet evaluates your dog’s symptoms, they might determine that your dog can be safely managed at home, and they will give you a treatment plan for home care. This may include giving your dog small amounts of clear liquids (water, Gatorade, Pedialyte, or other electrolyte solution) every 2 hours, but only after vomiting has stopped for 6 to 8 hours.

If your dog does not vomit the fluid after 12 hours, give frequent, small meals of boiled hamburger and rice or boiled chicken and rice, about ¼ cup or less per feeding. Do not give your dog over-the-counter or prescription medication unless you speak to your veterinarian.

Can gastroenteritis kill dogs?

Yes. Gastroenteritis can often become acute hemorrhagic diarrhea syndrome (AHDS) when left untreated. This is the most acute form of gastroenteritis in dogs and can lead to life-threatening dehydration if not treated quickly.

Is gastroenteritis contagious from dogs to humans?

Some of the causes of gastroenteritis are zoonotic, meaning they are contagious from dogs to humans. Bacterial infections like E. coli, salmonella, and listeria would fall into this category.

Some of the causes are specific to dogs and harmless to humans, such as canine parvovirus and distemper. 

Liz Bales, VMD


Liz Bales, VMD


Dr. Liz Bales is a graduate of Middlebury College and The University of Pennsylvania School Of Veterinary Medicine. She focuses on unique...

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