Diarrhea

Because diarrhea is an obvious sign of a pet's 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 don't normally eat. Human food items and non-food items both can be a source of diarrhea. 

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 a 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 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.

Addison's disease or hypoadrenocorticism is a decrease in the function of the adrenal gland. Diarrhea is usually not the only sign associated with Addison's. 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 are 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 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 treatments 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.