One of the more common problems we see in pets is diarrhea. There are numerous possible causes, but often your pet can initially be treated safely at home.

The Signs:

Diarrhea is the passing of loose or liquid stool, generally more frequently than normal. Diarrhea is categorized as small intestinal or large intestinal. Small intestinal diseases result in a larger amount of stool passed with a mild increase in frequency, about 3 to 5 bowel movements per day. The pet doesn't strain or have difficulty passing stool. Animals with small intestinal disease may also vomit and lose weight. Excess gas production is sometimes seen and you may hear the rumbling of gas in the belly. If there is blood in the stool it is black in color. Disease of the large intestine causes the pet to pass small amounts of loose stool very often, usually more than 5 times daily. The pet strains to pass stool. If there is blood in the stool, it is red in color. The stool may be slimy with mucus. The pet does not usually vomit or lose weight with large bowel diarrhea.

The Causes:

Common causes are a sudden change in your pet’s normal diet, or dietary indiscretion, i.e. your pet consumes something s/he shouldn't resulting in diarrhea. Foreign bodies including bones, sticks and other objects can pass through the stomach and get stuck in the intestine causing both diarrhea and vomiting. These same foreign materials may pass through the intestinal tract without getting stuck but may damage the lining of the intestinal tract causing diarrhea.  Food allergies in dogs and cats can cause diarrhea, vomiting and/or itchy skin. Toxins can cause diarrhea usually with vomiting.

Diarrhea can be caused by diseases of the small intestine, large intestine, or by diseases of organs other than the intestinal tract. Your ability to answer questions about your pet's diet, habits, environment and specific details about the diarrhea can help the veterinarian narrow the list of possible causes, and to plan for specific tests to determine the cause of diarrhea.

Small intestinal and large intestinal diarrheas have different causes, require different tests to diagnose and are treated differently.  Worms and giardia can cause small intestinal diarrhea, mostly in young animals. A sudden onset of small intestinal diarrhea in young and/or poorly vaccinated pets may be caused by viruses including canine distemper, canine parvovirus, canine coronavirus, feline panleukopenia virus or feline coronavirus. Small intestinal diarrhea can be caused by bacteria such as salmonella, clostridia, or campylobacter; although, these same bacteria can be found in the stool of normal dogs and cats.

Whipworms, polyps, inflammatory bowel disease, colonic ulcers, or colonic cancer can cause diarrhea of large intestinal origin. Stress can cause large bowel diarrhea in excitable dogs.  The diagnosis of large intestinal diarrhea is also made by blood tests and examination of the stool. A rectal exam may provide some information about the cause of large bowel problems including rectal polyps and rectal cancer.  Endoscopy to examine the large intestine may be recommended. Because the rectum is often very irritated, colon exams are usually performed under general anesthesia. The treatment of large bowel diarrhea may be based on a specific diagnosis. Non-specific treatment of large bowel diarrhea often includes diet and an anti-inflammatory drug. Inflammatory bowel disease (IBD) occurs commonly in both dogs and cats. In IBD the walls of the intestine contain abnormal numbers of inflammatory cells. The cause of IBD is not known but is suspected to be an allergic reaction to components of food, bacteria, or parasites. IBD can be congenital in some breeds of dogs, for example Basenji dogs may develop a severe inflammatory bowel disease. Tumors of the intestine are another cause of diarrhea usually occurring in older pets.


ASSESS SEVERITY - If the pet is active, not dehydrated, and has been previously healthy, acute diarrhea can often be managed at home. Diarrhea that continues for more than a few days or is accompanied by depression or other signs is an indication to contact your veterinarian. When should you take your dog to the veterinarian? If your dog seems to:

  • Act very sick
  • Be lethargic
  • Show bloating or abdominal pain
  • Be feverish (rectal temperatures above 103.5 degrees F)
  • Be dehydrated (one way to try to decide if a dog is dehydrated is to feel his or her gums... if they feel dry or tacky, there may be dehydration present)
  • Have persistent vomiting
  • Be passing large amounts of blood in the stool

FASTING TIME & PEPTO BISMOL - Acute small intestinal diarrhea can be managed by withholding food, but not water for 24 to 48 hours. Additionally, we recommend giving your pet Pepto Bismol (liquid or tablet). The dosage is determined by weight: 1 to 10 pounds = 1/8 teaspoon; 10 to 30 pounds = ¼ teaspoon; 30 to 60 pounds = ½ teaspoon; 60+ pounds = 1 teaspoon. Give the appropriate dosage every ½ hour for 6 doses. One teaspoon of liquid is equal to 1 tablet. If diarrhea stops, offer small amounts of bland food such as plain white cooked rice, or boiled unsalted chicken and rice 3 to 6 times daily for a few days, with a gradual increase in the amount fed and a gradual transition to the pet's normal diet.

FOOD ALLERGENS - For dogs and cats with problems of chronic diarrhea related to food allergy, a diet change may be recommended by your veterinarian. Preferably switch to a hypoallergenic food or homemade allergy diet. At the very least, change to a premium quality food.


Lakeside Veterinary clinic assumes no liability for injury to you or your pet incurred by following these descriptions or procedures.