Most Common Causes of Dog Diarrhea Most Common Causes of Dog Diarrhea


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Most Common Causes of Dog Diarrhea

Diarrhea is never pleasant for anyone. And diarrhea in a dog is flat-out horrible. When your canine companion has “to go” every five minutes, or frequent and watery bowel movements start collecting on your floor and couch, no one is happy.

Diarrhea can also be accompanied by pain, cramping and irritation. If your dog has an occasional bout of diarrhea, it’s unlikely to be cause for concern. But if it continues or worsens, please take your dog to your veterinarian. Diarrhea not only leads to dehydration, a condition that can quickly become serious on its own,  but the diarrhea may also be an indication of a more serious condition or illness.

The most likely cause of diarrhea in your dog is going to depend greatly on the dog’s age, breed, eating habits and recent history.

  • If the dog just consumed a turkey dinner from the owner’s plate and the diarrhea comes and leaves suddenly, dietary indiscretion, or eating too much of things they shouldn’t, is a very common and likely cause.
  • If the dog is a young puppy and he and his siblings are all having smelly diarrhea with blood and vomiting, they should be evaluated immediately for parvovirus, a disease that is serious, contagious, and deadly.


Acute Diarrhea

Acute diarrhea, or diarrhea that starts suddenly, is most often due to dietary indiscretion or dietary change. Dogs commonly present with diarrhea after overeating or ingesting trash, road kill or other spoiled foods. Eating plants, sticks, rocks, bones, fabric or other animal’s feces are also frequent complaints. Dogs may also experience intolerance or allergies to certain foods, including additives, milk products, corn, wheat gluten, etc.

Acute diarrhea typically lasts a short while and often resolves on its own or with supportive care. Acute diarrhea caused by parasites, infectious diseases or other factors may require additional diagnostics and treatments. If the dog has no history of diet change or eating something he shouldn’t, a trip to the vet should be in order if the diarrhea:

  • Worsens
  • Lasts more than 24-48 hours
  • Contains blood

Chronic Diarrhea

Chronic diarrhea is diarrhea that lasts longer than two to three weeks. The diarrhea can be constant or occur persistently and episodically. Parasites, dietary intolerance or allergies, infectious diseases, and neoplasia (cancer) can all cause chronic diarrhea.

The easiest way to help your veterinarian determine what is causing your pet’s diarrhea and provide appropriate diagnostics and treatment is to provide a description of your animal’s bathroom behavior. This description can help localize the problem or find the abnormal area or areas of the body that are causing diarrhea.

Diarrhea can be due to abnormality in a dog’s small intestines, large intestines or organs outside of the digestive/intestinal tracts.

  • Small intestines are the tube-like structures the food enters after it leaves the stomach. They’re responsible for most of the body’s digestion and absorption of nutrients.
  • Large intestines, critical for water re-absorption and hydration, immediately follow the small intestines. They escort the food the remainder of the way to the anus, where any remains leave the body.


Small Intestinal Diarrhea

Dogs suffering small intestinal diarrhea often pass larger amounts of stool and may have an increase in the number of bowel movements per day. These animals also commonly vomit and lose weight. Excess gas is another common compliant, and some owners will report hearing rumblings in their dog’s belly.

If there is bleeding into the small intestines, that blood will be digested and may turn the stool dark black. Food intolerance, pancreatic insufficiency (more prevalent in large breed dogs, especially German shepherds), and inflammatory bowel disease commonly present as small intestinal diarrhea.

Large Intestinal Diarrhea

Large intestinal diarrhea will typically result in dogs having to go to the bathroom with great frequency, more than five times per day. Small amounts of stool are produced with each bowel movement, and straining is frequently observed as the dog attempts to pass the feces.

Mucus is frequently seen on stool caused by large intestinal diarrhea. Any bleeding into the large intestine will appear bright red in the feces. Parasites such as whipworms or giardia, and stress colitis typically present as large intestinal diarrhea.

The most common causes of diarrhea vary, depending on whether the diarrhea is originating from a problem with the small or large intestines. Different diagnostics and different treatments will be offered, depending on the clinical signs described. Make sure to let you veterinarian known the answers to the following questions:

  • How frequently is your pet is going to the bathroom? (<5 or >5 times a day)
  • How much stool is being passed with each bowel movement? (smaller or larger than normal)
  • What color is the feces? (dark black, obvious red blood, slimy with mucous)
  • Have you noticed any weight loss?
  • Is your pet also vomiting or showing other signs of illness?
  • How long has your pet had diarrhea?


Many diseases can present with either small or large intestinal diarrhea, or both. Others can present as acute diarrhea, chronic diarrhea, or acute diarrhea that becomes chronic. Simple cases of diarrhea may resolve without treatment, but many others may become serious and even life threatening for your pet. Head to the veterinarian immediately if your dog:

  • May have eaten something toxic or poisonous
  • Ingested a foreign body (stones, toys)
  • Is a young puppy (vaccinated or not)
  • Has digested blood (dark black) or obvious blood in his feces
  • Has continuous or worsening diarrhea after 24-48 hours

Vomiting, lethargy, straining to defecate, decreased appetite, and weight loss are also signs of a more serious condition that may initially present as diarrhea.


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