Diarrhoea 101 | Diarrhoea In Dogs

by Nancy Boland

Diarrhoea is the passage of loose, unformed stools. In most cases there is a large volume of stool and an increased number of bowel movements. The two most common causes of diarrhoea in dogs are dietary indiscretion and intestinal parasites. Many canine infectious diseases are also associated with acute diarrhoea.

Food takes about eight hours to pass through the small intestines. During that time, the bulk of the food and 80 percent of the water is absorbed. The colon concentrates the remainder. At the end, a well-formed stool is evacuated. A “normal” means no mucus, blood, or undigested food.

With rapid transit through the bowel, food arrives at the rectum in a liquid state, resulting in a loose, unformed bowel movement. This type of rapid transit accounts for the majority of temporary diarrhoea in dogs. Dietary indiscretion is a common cause of this rapid transit.


Dogs are natural scavengers and tend to eat many indigestible substances, including garbage and decayed food, dead animals, grass, wild and ornamental plants, and pieces of plastic, wood, paper, and other foreign materials.

Another reason for diarrhoea could be food intolerance. Foods that some dogs seem unable to tolerate can include beef, pork, chicken, horsemeat, fish, eggs, spices, corn, wheat, soy, gravies, salts, spices, fats, and some commercial dog foods, especially those with lots of artificial ingredients. Note that food intolerance is not the same as food allergy, which causes dermatitis and possibly vomiting, but rarely diarrhoea.

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Underlying issues

Intestinal parasites are a common cause of acute and chronic diarrhoea in puppies and adults. The greatest problems are caused by roundworms, hookworms, and threadworms.

Diarrhoea is a common side effect of many drugs and medications, particularly the NSAIDs, which include aspirin. Some heart medications, some de-wormers, and most antibiotics also can cause diarrhoea, so it’s worth really checking the side-effects and being aware of any your dog may be suffering from.


Dogs can experience diarrhoea when they’re excited or upset-for example, when they’re going to the vets or visit an environment that is stressful to them. In fact, any sudden change in a dog’s diet or living circumstances may cause emotional diarrhoea; moving house for example.

The most important step in treating acute diarrhoea is to rest the GI tract by withholding all food for 24 hours. Encourage your dog to drink as much water as he wants. With persistent diarrhoea, consider giving a supplemental solution such as Pro-Kolin + which is a probiotic providing an immediate response to digestive upsets

Acute diarrhoea usually responds within 24 hours to intestinal rest. Start the dog out on an easily digestible diet that’s low in fat. Examples are and boiled chicken with the skin removed. Cooked white rice, cooked porridge oats, and soft-boiled eggs are other easily digestible foods. Feed three or four small meals a day for the first two days. Then slowly inrtdroduce his regular food back into his diet.

Obtain immediate veterinary care if:

  • The diarrhoea continues for more than 24 hours
  • The stool contains blood or is black and tarry
  • The diarrhoea is accompanied by vomiting
  • The dog appears weak or depressed or has a fever


Chronic Diarrhoea

The first step is to find and treat the underlying cause. Diarrhoea resulting from a change in diet can be corrected by switching back to the old diet and then making step-by-step changes to pinpoint the cause.

Diarrhoea caused by overeating Chronic, intermittent diarrhoea that persists for more than three weeks requires veterinary attention and is investigated in several steps. The first being antibiotics to ensure no gastro infections. The second is by stool samples to investigate any underlying causes. If those two options are cleared, then the only other way to diagnose what is truly going on is to look inside the stomach via ultrasound.

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