Everything You Need to Know About Diarrhea in Dogs

The Dog’s Digestive System

The dog’s digestive tract is the main organ responsible for digesting and absorbing nutrients from ingested food ingredients. Food travels from the mouth where it’s mechanically broken down into smaller pieces, then moves to the stomach and intestines for chemical and enzymatic digestion and absorption. The undigested and unabsorbed materials eventually pass out the other end via the rectum.

The last segment of the intestinal tract, called the large intestine, is responsible for reabsorbing water from the digested food and bulking up the undigested part to make it into solid feces. This part of the intestine also houses beneficial bacteria that ferments some undigested and unabsorbed food ingredients like fiber and transforms them into absorbable substances that the body can use.

The presence of beneficial bacteria on the large intestine also plays a role in maintaining proper intestinal health in dogs. The fermentation that these bacteria perform produces lactic acid that can kill pathogenic bacteria and prevent intestinal infection.

What happens when a dog has diarrhea?

There are different mechanisms as to how diarrhea occurs, depending on the segment of the intestinal tract affected. Since the large intestine is the main segment responsible for the reabsorption of water, most diarrhea cases in dogs stem from problems in the large intestine.

When the lining of the large intestine becomes inflamed, such as in cases of bacterial or viral infection, it compromises its ability to reabsorb water, making the dog’s stool soft and watery. Inflammatory processes along the lining of the large intestine also cause breaks along the protective barrier, causing water to leak from the cells of the intestine towards the lumen, leading to diarrhea.

Inflammation also causes an increase in the rate of peristalsis (movement) of the intestinal segment, speeding up the transit of the ingested food. This leads to poor nutrient absorption and water retention, both resulting in diarrhea in dogs.

If the inflammation occurs mostly in the small intestine, nutrient absorption will be compromised, resulting in soft stool that is often fatty or frothy in appearance and consistency.

7 Common Causes Diarrhea in Dogs

1. Dietary Indiscretion

Garbage Guts! Dietary indiscretion refers to your dog eating things he shouldn’t. Some dogs will go through the trash, others find something rotting and tasty when out walking, skillfully sweeping it into their mouths while you, on the end of the leash, are unaware! The ingested waste can cause diarrhea in a variety of ways:

• Toxins - These range from mild to serious toxins and therefore cause a range of different symptoms, but diarrhea is most common.

• Mechanical effect of indigestible food - Indigestible food, (like leaves, acorns, fruit pits, or other foreign material) can act like sandpaper on the lining of the bowels, causing irritation. In some cases, this can cause blood in the stool (See our article on bloody diarrhea). Importantly but less commonly, indigestible material can become lodged, obstructing the intestines. A partial obstruction can cause diarrhea but is a very serious condition that may need to be treated surgically.

• Ingestion of harmful bacteria (E.coli, Salmonella, etc.) - These are true cases of “food poisoning” and could be transmitted to humans. It should be noted that it’s preferable to wear your own PPE if you need to clean up your pet’s diarrhea.

2. Dietary Intolerance/Food Allergy

True food allergies are uncommon. Most are intolerances that can be caused by any part of the diet. Some pet foods are rich in additives, flavorings, and preservatives and some foods can have inconsistent manufacturing processes. These make certain foods more likely to cause a reaction.

3. Sudden Change of Diet

A new diet should be introduced gradually. A sudden switch can cause diarrhea by upsetting the gut microbiome.

4. Parasites

Many parasites can cause diarrhea. Examples include giardia, coccidia, and whipworms. Most vets recommend regular deworming and a yearly fecal exam as part of an annual checkup. These intestinal parasites are usually passed from dog-to-dog and some pets can reinfect themselves even after treatment.

5. Viral Infections

Usually passed from dog-to-dog, these include serious infections such as Parvovirus and Distemper virus that can occur in unvaccinated puppies. More endemic and less serious viruses such as canine coronavirus (not COVID) and rotavirus also cause milder versions of diarrhea in dogs.

6. Prescribed Medications

Prescription drugs such as anti-inflammatories or antibiotics can cause diarrhea. A vet must be consulted before deciding to continue or discard the medication.

7. Other Causes of Diarrhea in Dogs

Less commonly, diarrhea may be caused by certain types of endocrine disease, liver disease, and certain types of intestinal tumors. These are likely to produce ongoing signs, so diarrhea that doesn’t resolve should be investigated further by your vet.

My dog is having diarrhea. What do I do?

The treatment approach in addressing and managing diarrhea in dogs will ultimately depend on the severity of the condition and the underlying cause of the problem. It’s best to contact your vet so a proper diagnosis and treatment protocol can be made.

Mild cases of diarrhea are often self-limiting and will correct themselves after a couple of days.Diarrhea brought about by food intolerance can be corrected by changing the diet to something that your dog isn’t reactive to historically. Another alternative is transitioning the dog to a highly digestible diet for a week or so until diarrhea is resolved. A highly digestible diet will help ensure proper nutrient absorption and control intestinal peristalsis. This, in turn, will help control the dog’s diarrhea.Adding fiber supplements to the dog’s diet helps in several ways.

The non-fermentable component of most dietary fiber supplements helps bulk up the feces and regulate the transit of the ingesta along the intestinal tract, which helps improve the stool’s consistency. The fermentable component provides proper nourishment to the beneficial bacteria of the large intestine, helping improve the ability of the large intestine to solidify the feces and reabsorb water which improves the fecal consistency.

Probiotic supplementation helps control diarrhea in dogs by introducing beneficial bacteria into the dog’s large intestine. These beneficial bacteria will help improve the intestine’s ability to reabsorb water and fight off pathogenic microorganisms that often cause diarrhea in dogs.

Certain anti-diarrheal medications may be prescribed by your vet. However, there are health conditions where the use of antidiarrheal medications is not recommended. Therefore, you should never give your dog any anti-diarrheal medications without consulting your vet first.The use of loperamide (Imodium) is NOT recommended in cases of bacterial enterotoxicity in dogs. In such cases, the enterotoxin produced by the pathogenic bacteria infecting the gastrointestinal tract worsens the condition and needs to be eliminated. Loperamide will delay the elimination of these enterotoxins which makes the condition more severe.

Diarrhea caused by intestinal parasites can be treated with deworming medications. Severe intestinal worm infestation will often require more than 2 doses of deworming medicine at 2-3-week intervals for complete eradication of the parasite. Proper identification of the parasite is important so that the correct medication can be prescribed.

Severe cases of diarrhea, such as in cases of viral infections, will need immediate veterinary care. Viral intestinal infections, such as parvoviral enteritis (Parvo), don’t have a specific treatment or cure. Management will rely on supporting the body to fight off the virus on its own while controlling the symptoms that go with the disease. Cases like these require intensive care in a hospital setting and can be fatal if not treated or addressed properly.

What about giving my dog over-the-counter medication for diarrhea?

Do not give any over-the-counter (OTC) medications to your dog without talking to your vet first. Not only can OTC medications be dangerous for pets, but they can also hide an underlying problem.

Home Remedies for Doggy Diarrhea

If your vet suspects that your dog’s diarrhea isn’t any more serious than a case of dietary indiscretion or isolated food intolerance then they may suggest remedies available at home, particularly if you’re unable to attend an appointment or visit the clinic that day.

1. Offer Bland Food

After the fast, reintroduce bland food in small quantities. Homemade examples of bland food are boiled white rice mixed with equal amounts of white meat such as chicken or fish. The meat should be baked, steamed, or microwaved, with no added fat. Offer each meal in small quantities - think 1 tablespoon for small dogs/cats and 2 tablespoons for larger dogs. This can be offered every 3-4 hours.

Proprietary brands of hypoallergenic food for digestive upsets exist for this purpose and are superior to homemade food due to a precise and tailored mix of nutrients. Some of these foods also include a pre/probiotic. The author always keeps a few cans of this in the pantry in case diarrhea strikes!

Feed the bland diet for at least 48 hours after a normal stool has formed. This may take several days so it’s ideal to purchase one of these formulated diets to ensure that your dog receives appropriate vitamins and minerals. Properly formulated diets become very important if your dog has diarrhea for a longer period of time.

For more feeding instructions and recipes, follow this link!

2. Probiotics

Probiotics have been proven to speed diarrhea recovery times. The studies looking at this used a proprietary blend of probiotics for dogs or cats. However, if you can’t get your hands on that right away you can try some natural yogurt. A teaspoon is plenty for cats and small dogs, a dessert spoon for larger dogs.

3. Electrolyte Solutions

Electrolyte solutions are not essential for mild bouts of diarrhea and they aren’t easy to make at home. Generally, if the diarrhea is severe enough to cause electrolyte imbalances then it’s time to see the vet. However, adding a very small amount of salt-free meat broth to your dog’s water may encourage him to drink.

If the diarrhea persists for more than 24 hours, or more serious signs develop at any stage (such as vomiting, lethargy, or weakness) then veterinary care should be sought immediately.

What to Do if Your Puppy Has Diarrhea

It’s important to speak to a vet as soon as possible if your puppy has diarrhea. Your vet will likely run a test on a fresh stool sample to screen for parasites. Worms such as Roundworm and Whipworm, or Protozoa such as Giardia and Coccidia are very common causes of diarrhea in puppies.

Your vet will request further information about the health of your puppy, specifically whether she is vaccinated for diseases such as Distemper and Parvovirus. Though these are less common, both cause diarrhea and have a high mortality rate. The diarrhea is usually profuse and the puppy will appear very unwell.

Other things to consider include a recent change in diet, environment, or addition of training treats. These are much more common causes of diarrhea in dogs. The symptoms are mild and usually your pup will appear well and happy if these are the cause.

Your vet will be able to determine whether your pup needs further diagnostics or if some simple remedies can be tried at home.

Home Remedies for Puppy Diarrhea

Home remedy options need to be modified for puppies. Generally, young puppies are fed 3-4 times per day. Reintroducing bland food is a good idea: 1 tablespoon of chicken/rice mixture can be offered approximately every 2-3 hours.

Puppies recover quickly but can also deteriorate quickly. Keep a close eye on their energy levels and appetite. Never hesitate to contact your vet again if you have concerns about your pup’s recovery.

Tips for Cleaning Up When Your Dog Has Diarrhea:

• Wear gloves and use a good disinfectant to clean the area.
• Try to wash your puppy’s bottom if it has become soiled. Using an antibacterial soap such as Dial is okay if you don’t have an antibacterial dog shampoo.
• If you can, collect a sample of stool. It’s likely your vet will want to test it for common parasites.
• Keep your puppy in a confined, easy-to-clean area in case diarrhea strikes again, but ensure you let them outside regularly.
• Be cautious if you have other dogs or children. Occasionally diarrhea will be caused by an infection that can be passed on to others. Practice strict hygiene and keep them separated if possible.

My dog’s diarrhea isn’t getting better. When should I take him to the vet?

If your dog is experiencing any of these symptoms, it's time to schedule a vet appointment:

• The diarrhea is bloody or very dark/black
• Your dog is becoming lethargic or weak
• Your dog won’t eat food for more than 24-48 hours or doesn’t want to drink water
• Your dog is dehydrated (check for dry sticky gums)
• An object may have been swallowed that could block the stomach or intestines
• Your pup has stomach pain or a swollen abdomen
• There has been no response to home care for 3-4 days (for young puppies and older dogs you should seek help earlier)
• Your dog has multiple episodes of vomiting and/or diarrhea

How will the vet treat my dog’s diarrhea?

If your dog is very sick or dehydrated, he may need to stay in the hospital.

• Your dog may be given IV fluids to correct dehydration and replace lost electrolytes (sodium, potassium, chloride).
• Blood work may be done to check red and white blood cell counts, as well as evaluate internal organ function (liver, kidneys, pancreas).
• Other diagnostics might be recommended to determine the cause of your dog’s diarrhea. These include x-rays or ultrasound of the abdomen, fecal exam, and tests for diseases like pancreatitis or parvovirus.

Treatments for the diarrhea and any underlying issues will likely continue once your dog is discharged to go home:

• A bland diet that requires minimal digestion will likely be prescribed.
• Your dog may go home with prescriptions for anti-nausea medication, antacids, pain relief, and probiotics to replace normal gut bacteria.

Read more:

Parvovirus in Puppies: A Treatment and Prevention Q&A

Should you be worried if your dog’s stool changes color?

Deworming Your Dog - Q&A

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