Gastroenteritis in Dogs: Symptoms, Treatment and Recovery

Gastroenteritis is the medical term for inflammation of the stomach and intestines. It's one of the most common reasons dogs are presented to emergency veterinary clinics, and it can range from a mild, self-limiting condition to a severe, life-threatening emergency.

"Gastroenteritis is essentially the umbrella diagnosis for when both the stomach and intestines are inflamed simultaneously. The clinical signs are predictable — vomiting and diarrhoea together — but the underlying causes are remarkably varied, which is why a thorough workup is often necessary." — Dr. Sarah Chen, DVM

The condition can be acute (sudden onset, lasting days) or chronic (recurring over weeks or months). Acute gastroenteritis is far more common and is usually triggered by dietary indiscretion — the veterinary euphemism for your dog eating something they shouldn't have.

While most dogs recover fully from gastroenteritis with appropriate treatment, a particularly dangerous form called haemorrhagic gastroenteritis (HGE), now more accurately termed acute haemorrhagic diarrhoea syndrome (AHDS), can cause severe bloody diarrhoea, rapid dehydration, and shock. Understanding the spectrum of this disease helps owners respond appropriately.

Gastroenteritis in dogs can be triggered by a wide range of factors:

Dietary Causes (Most Common)

• Dietary indiscretion — eating rubbish, compost, dead animals, fatty table scraps, or non-food items
• Sudden food changes — switching brands or protein sources without gradual transition
• Toxic foods — chocolate, grapes, xylitol, onions, and other foods toxic to pets
• Food intolerance or allergy — reactions to specific proteins or ingredients

Infectious Causes

• Viral — parvovirus (especially in unvaccinated puppies), coronavirus, distemper
• Bacterial — Salmonella, Campylobacter, Clostridium perfringens, E. coli
• Parasitic — Giardia, roundworms, hookworms, whipworms, coccidia

Other Causes

• Foreign body ingestion — toys, socks, bones, or other objects causing obstruction or irritation
• Medications — NSAIDs, antibiotics, and certain supplements can irritate the GI tract
• Pancreatitis — inflammation of the pancreas, often triggered by fatty foods
• Stress — boarding, travel, new environments, or household changes
• Underlying diseases — kidney disease, liver disease, Addison's disease, or inflammatory bowel disease

In many cases, the exact cause is never definitively identified, particularly when the dog recovers quickly with supportive care. However, recurrent episodes warrant a more thorough diagnostic investigation.

The hallmark symptoms of gastroenteritis are vomiting and diarrhoea occurring together, though one may be more prominent than the other. Here's what to watch for:

Primary Symptoms

• Vomiting — may contain food, bile (yellow-green fluid), foam, or occasionally blood
• Diarrhoea — ranging from soft stools to profuse, watery diarrhoea. May contain mucus or blood
• Loss of appetite — partial or complete refusal to eat
• Abdominal pain — may manifest as restlessness, a hunched posture, reluctance to be touched on the belly, or whimpering

Secondary Symptoms (Indicating Severity)

• Lethargy — reduced energy, reluctance to move or play
• Dehydration — dry, tacky gums, skin tenting, sunken eyes
• Fever — temperature above 39.2°C (102.5°F)
• Weight loss — noticeable in chronic cases

Emergency Signs (HGE/AHDS)

Haemorrhagic gastroenteritis presents with a distinctive pattern that requires immediate emergency care:

• Sudden onset of profuse, bright red, jam-like bloody diarrhoea
• Rapid dehydration — the dog may become weak or collapse within hours
• The dog may or may not be vomiting
• Small breeds (Miniature Schnauzers, Toy Poodles, Yorkshire Terriers) are overrepresented

If you see these signs, don't wait — read our guide on bloody stool in dogs and head to an emergency vet immediately.

When you bring your dog to the vet with suspected gastroenteritis, the diagnostic approach will depend on the severity of symptoms, the dog's age, vaccination status, and history.

Diagnostic Tests

• Physical examination — assessing hydration, abdominal pain, body temperature
• Blood work — complete blood count and biochemistry to check for infection, organ function, and electrolyte imbalances
• Faecal analysis — testing for parasites, bacteria, and viral antigens (especially parvovirus in unvaccinated dogs)
• Abdominal X-rays or ultrasound — to rule out foreign bodies, obstruction, or pancreatitis
• Packed cell volume (PCV) — in suspected HGE, a dramatically elevated PCV (above 60%) is characteristic

Treatment

Treatment is largely supportive and tailored to severity:

• Fluid therapy — the cornerstone of treatment. Mild cases may need subcutaneous fluids; severe cases require intravenous (IV) fluids to correct dehydration and electrolyte imbalances
• Anti-emetics — medications like maropitant (Cerenia) or metoclopramide to control vomiting
• Gastroprotectants — omeprazole or sucralfate to protect the stomach lining
• Antibiotics — only if bacterial infection is confirmed or strongly suspected. Routine antibiotic use for uncomplicated gastroenteritis is discouraged
• Pain management — if abdominal pain is present
• Dietary management — a prescription gastrointestinal diet or bland diet once vomiting is controlled

For HGE/AHDS, hospitalisation with aggressive IV fluid therapy is usually required for 24-72 hours. The prognosis is generally good with prompt treatment, but delay can lead to hypovolaemic shock and, in rare cases, disseminated intravascular coagulation (DIC).

Most dogs with uncomplicated acute gastroenteritis recover within 2-5 days with appropriate treatment. Here's what to expect during recovery:

Recovery Timeline

• Days 1-2: Vomiting typically resolves first. Diarrhoea may continue for another day or two
• Days 2-4: Appetite gradually returns. Stools begin to firm up
• Days 4-7: Most dogs are back to normal. Continue the bland diet transition for the full period

During Recovery

• Feed small, frequent meals of a bland or prescription GI diet
• Transition back to regular food gradually over 5-7 days
• Limit exercise to gentle, short walks
• Monitor stool consistency and appetite daily
• Ensure plenty of fresh water is available

Prevention Strategies

• Supervise outdoor time — prevent scavenging, rubbish raiding, and eating unknown substances
• Secure rubbish bins — a common source of dietary indiscretion
• Change food gradually — always transition over 7-10 days
• Avoid fatty table scraps — especially during holidays and barbecues when pancreatitis risk spikes
• Keep up with vaccinations — especially parvovirus
• Regular parasite prevention — year-round deworming and flea/tick control
• Regular vet check-ups — learn about how often your dog needs vet visits

If your dog experiences repeated bouts of gastroenteritis, your vet may recommend further investigation for chronic conditions like inflammatory bowel disease (IBD), food allergies, or exocrine pancreatic insufficiency.