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Why Does My Dog Have Diarrhea?

Whether it is acute or chronic, here’s what you need to know about diarrhea in dogs and when to worry.


Gastroenteritis is an inflammation of the gastrointestinal system and is the most common cause of acute diarrhea in dogs. The most common cause of gastroenteritis is ‘dietary indiscretion’. Indiscretion is defined as a ‘behavior that displays a lack of judgment’ – and this often sums up your puppy’s behavior when he chows down on a dead rodent or smelly sock! Gastroenteritis is actually quite rare due to what we relate to as ‘food poisoning’, simply in that, it is often not bacterial in nature.

One of the best ways to treat a gastrointestinal (GI) upset from dietary indiscretion, if the diarrhea is not profuse and the dog is otherwise bright, well and eating, is to rest the GI system for 24 hours and then introduce a bland food (eg  boiled chicken and white rice) little and often until the upset has resolved.

Drug reactions (eg.  Antibiotics, antiinflammatories, others) can cause diarrhea in dogs on occasion.

Gastrointestinal inflammation from viruses (parvo, , rotovirus, coronovirus) or bacteria (Salmonella, Campylobacter, Clostridium, E.Coli) are surprisingly rare causes of diarrhea in dogs.  Parvo virus is preventable by vaccines, so it is important to have your dog properly vaccinated.

Hemorrhagic gastroenteritis (HGE) is a potentially serious cause of diarrhea as the condition can lead to fairly severe dehydration. It can be accompanied by bloody diarrhea, often described as looking like ‘raspberry jam’ (sorry to put you off your lunch!)

GI parasitism (worms) is a relatively uncommon cause of diarrhea in an otherwise healthy dog. Dogs should be wormed regularly however to prevent GI parasites.

Systemic (ie. affecting the whole body) and metabolic diseases such as liver or kidney disease, electrolyte imbalance, pancreatitis, sepsis, peritonitis, pyometra, diabetic ketoacidosis, hypoadrenocorticism, intussusception or neurologic disease can all cause diarrhea in dogs. Usually, there are other accompanying signs such as vomiting anorexia, lethargy or weight loss.

Another cause of diarrhea, especially in younger curious dogs is a GI foreign obstruction where something that has been ingested becomes lodged somewhere in the GI system. An intestinal foreign body usually, but not always, causes quite frequent vomiting as well, and these objects may need to be removed surgically. Dogs that eat pieces of string-like material are at risk of what is called a ‘linear foreign body’. In this situation, the string is unable to pass through the GI tract and the intestines can become bunched, as they try to pass the linear material. In the worst-case scenario foreign bodies can pierce the intestinal wall, and if you suspect your dog has eaten something they shouldn’t have then take them to the vet immediately.


Any cause of chronic diarrhea (ie. diarrhea that lasts more than just a few days) is definitely best assessed by a Veterinarian especially if accompanied by weight loss, appetite changes or other symptoms.

There can be numerous possible causes pertaining to virtually any body organ system, but some of the more common are neoplasia (cancer), GI parasitism, liver or kidney disease, inflammatory bowel disease, food intolerance, diabetes, hypoadrenocorticism, chronic pancreatitis, bacterial or viral infection, partial obstruction of the intestines (either from a cancer, intussusception or foreign body eg. sock), gastric ulcer, constant diet change, drug reaction, Addison’s disease or food intolerance/allergy.

When to worry:

  • Your dog is older (greater than 7 years) – older dogs are sometimes less able to cope with the potential dehydration diarrhea can lead to, and older dogs are more prone to serious illnesses than young healthy dogs.
  • There are other symptoms such as weight loss, poor appetite, profuse vomiting or lethargy.

When to be slightly less concerned:

  • When your dog is otherwise healthy, bright, happy and with good appetite.

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