All Pets Veterinary Clinic


Because diarrhea is an obvious sign of a petís health status, it is one of the most common
reasons animals are presented to the veterinary clinic. Diarrhea can range from mild to
severe and from acute to chronic. Animals with diarrhea can act totally normal or be
seriously ill. These variations are because diarrhea can result from many different
situations, diseases, and conditions. This article will explore some of the more common
causes of diarrhea in veterinary patients. Additionally, diagnostic tests and treatments
will be reviewed.

Dietary indiscretion is perhaps, the most common cause of acute diarrhea in dogs and
cats. While some animals are not sensitive to the addition of different food items to
their diet, others will have dramatic episodes of diarrhea after eating something that
they donít normally eat. Human food items and non-food items both can be a source of

Sudden food change. Changing from one brand of food to another brand of food
without an appropriate transition period can also cause diarrhea in animals. Again,
for animals that have sensitive GI tracts, even the addition of a different brand of
treat can trigger diarrhea. To avoid diarrhea from food change, it is recommended to
slowly mix increasing amounts of the new food with the old food over one week.

Parasites are also a very common cause of diarrhea in animals. Most of the common
parasites that can cause diarrhea are obtained through fecal-oral contamination. (i.e.
the pet eats something contaminated with infected feces.) Roundworms, hookworms, whipworms,
coccidia, and giardia are the most common parasites that can cause diarrhea.

Toxic/Poison Ingestion. Many chemicals, pesticides, household products, etc. can
cause GI irritation if ingested. Some toxins can cause other signs besides diarrhea.

Pancreatitis is inflammation of the pancreas. It will often cause diarrhea in
conjunction with other signs. The most common cause of pancreatitis is dietary indiscretion
or the ingestion of greasy foods.

Liver disease is lesser common cause of diarrhea but some of the diseases that
affect the liver can result in diarrhea.

Drugs such as aspirin or other NSAIDs, steroids, antibiotics, etc. can cause
diarrhea in some instances. Over dosage or long term administration of some of these
medications can increase the risk of diarrhea.

Food allergies can have a variety of signs including diarrhea, vomiting, abdominal
cramping, picky eating, and skin problems. Animals with food allergies are most commonly
allergic to beef, chicken, turkey, corn, wheat, egg, and soy. These items are in most pet
foods so changing from one to the next often does not remedy the diarrhea. Food allergies
can be difficult to diagnose because there is not a specific, reliable food allergy test.

Infections. Bacterial, viral, or fungal infections can cause diarrhea. The most
common viral causes of diarrhea in dogs are parvo and corona. In cats, the most common viral
infections are feline leukemia (FeLV) and feline infectious viremia (FIV). Many bacteria
can cause diarrhea as well. Some diarrhea causing bacteria can come from an outside source,
such as Salmonella, Clostridium, or Campylobacter, whereas some bacterial infections are a
result of bacterial overgrowth, or an increase in the numbers of normal bacteria in the gut.

Inflammatory bowel disease (IBD) is actually a collection of conditions that can
cause diarrhea and/or vomiting. There are many causes including food allergies.

Intestinal Cancer. Several types of cancer can affect the GI tract. The most
common is lymphosarcoma. Some evidence exists to suggest that chronic, untreated
inflammation/irritation can result in cancer.

Addisonís disease or hypoadrenocorticism is a decrease in the function of the
adrenal gland. Diarrhea is usually not the only sign associated with Addisonís.
Typically animals can experience periods of weakness, vomiting, episodes of collapse,
or other problems in addition to episodes of diarrhea.

Because of the wide variety of causes of diarrhea, a series of tests is often needed to
determine the exact cause. In simple cases of acute onset diarrhea only basic diagnostic
tests, such as a fecal float, may be run. However, testing becomes much more important when
diarrhea fails to respond to symptomatic treatment and/or when diarrhea reoccurs. More
advanced tests may include: the giardia Snap Test, blood tests, fecal cultures, and
biopsy/histopathology. Additionally, treatment trials such as a food trial or deworming
trial, may be conducted.

In many cases of simple, acute onset diarrhea, treatment is often symptomatic. In other
words, treatment is aimed at stopping the diarrhea not necessarily treating the cause.
These treatments may include medications such as Reglan, Centrine, or chlorpromazine and
a food change to a bland, easily digestible diet. Additionally, if the animal has become
dehydrated, fluids may be needed. If these symptomatic treatments fail, more specific
treatmentsótreatments tailored to the cause, may be started. Again, a specific diagnosis
is critical to being able to treat chronic or repeat episodes of diarrhea.

The information provided is for educational purposes only and is not
intended to take the place of your regular veterinarian. Please do not hesitate
to contact your regular veterinarian if you have questions regarding your pet.

Karen Blakeley, DVM, MPH
24 June 2006