Diarrhea in Dogs and Cats


All pets have the occasional episode of diarrhea at some point in their lives. This is an unpleasant fact for both the pet and the pet owner. The important thing to remember is that diarrhea is a symptom, not a disease. It is essential to investigate what is actually causing the diarrhea in order to effectively treat your pet.

In most circumstances, there is little to worry about. The majority of animals with acute diarrhea do not require investigation as their diarrhea is most likely to be dietary induced and will be self-limiting. Though many cases of diarrhea will resolve within a week, some will cause nutrient loss, dehydration, electrolyte disturbances, and lead to severe illness if left untreated. If you are at all concerned about your pet’s health, always consult a veterinarian.

What causes diarrhea?

The intestines absorb nutrients and water from digested food as it moves along the gastrointestinal tract. Diarrhea usually occurs when the absorption of nutrients from the digested food material is impaired or interrupted. Digesta then accumulates in the intestines, leading to excessive water moving into the intestines. The end result is loose watery feces.

Most bouts of diarrhea are invariably associated with a problem in the diet. For dogs, who are indiscriminate eaters, dietary indiscretion (eating garbage, spoiled or rotten food, scavenging) is at the top of the list of probable causes of diarrhea. Other dietary problems include a sudden diet change, overeating, or consuming too much human food.

Besides those episodes that are dietary induced, there are many other causes of diarrhea:

Primary causes of diarrhea:

•    Viral infections (e.g. Parvovirus in dogs, Coronavirus in cats)
•    Bacterial infections (e.g. Salmonella, Campylobacter, E. coli, etc.)
•    Giardia
•    Worms (especially hookworms and whipworms)
•    Pancreatitis (inflammation of the pancreas)
•    Exocrine pancreatic insufficiency
•    Inflammatory bowel disease (IBD)
•    Antibiotic responsive diarrhea (ARD)
•    Cancer
•    Poisoning
•    Stress
•    Drugs (e.g. antibiotics)

Secondary causes of diarrhea:

•    Liver disease
•    Renal disease
•    Hyperthyroidism in cats
•    Addison’s disease (hypoadrenocorticism)

Never hesitate to take your pet to the veterinarian if you suspect it is ill. Mild cases of diarrhea can be the first signal of a serious underlying disease.

What should I watch for if my pet has diarrhea?

Diarrhea is the increase in the bulk and fluidity of feces. Most pet owners can easily recognize a case of diarrhea. In order to diagnose the source of the diarrhea, your veterinarian will require further information. Owners should note:

•    Fecal volume (is it normal or increased?)
•    Frequency of defecation (how many times per day does your pet defecate?)
•    Appearance of feces (e.g. liquid, greasy, bloody, black, etc.)
•    Presence of blood, mucus, or worms in feces
•    Straining to defecate
•    Flatulence
•    Vomiting
•    Loss of appetite
•    Weight loss
•    Length of illness

How does the veterinarian investigate cases of diarrhea?

The veterinarian relies heavily on the history given by the pet owner. The owner should provide details of the vaccination and worming status, any previous history of gastrointestinal upsets, dietary management, the character of the diarrhea, and any scavenging behavior, vomiting, weight loss, etc.

The vet will perform a thorough physical exam. Based on the clinical history and physical exam, vets can usually diagnose simple cases of dietary induced diarrhea. Further investigation can be carried out by examination of a fecal sample, blood tests, urinalysis, X-rays, ultrasound, and endoscopy.

How should mild cases of diarrhea be treated?

Mild cases of diarrhea, especially those induced by dietary changes, are often self-resolving. If your pet is still bright and active, interested in eating and drinking, and not showing any other signs of illness such as vomiting or depression, it may not need a trip to the veterinarian. Food should be withheld for 12-24 hours in order to allow the gastrointestinal tract time to recover.

Pets should still be offered small amounts of water at regular intervals as diarrhea can quickly lead to dehydration. Following the fast, pets should be started on a bland, easily digested diet. Good foods to offer are boiled chicken or fish mixed with rice, potatoes or pasta. Initially, offer many small meals (instead of one large meal) before resuming a normal feeding schedule. Do not administer any over the counter diarrhea medications unless directed by a veterinarian.

Some pets may require further treatment that can only be provided by a veterinarian: fluid therapy, antibiotics, intestinal protectants, etc. Never hesitate to call the vet if your animal’s health seems to be declining, or if you simply want advice on what to do next.

What are some signs that indicate my pet needs veterinary treatment?

Pet owners should never hesitate to call a veterinarian, even if it’s only for advice. While some pets can be safely managed at home, some situations will merit immediate veterinary attention. If any of the following refers to your pet, it may be an indicator that your pet has more than just a mild case of diarrhea and requires veterinary treatment.

•    Your animal has missed a vaccination or never been vaccinated
•    Your pet is very young (i.e. puppies and kittens), older, or has concurrent disease
•    There is blood in the diarrhea
•    Vomiting occurs as well as diarrhea
•    Animal becomes depressed or listless
•    Poisoning is suspected
•    There is noticeable weight loss
•    Diarrhea lasts more than a day or two
•    Other signs of illness are present

Prompt action in taking your pet to the veterinarian may not only result in a swifter recovery, it may also save your pet’s life.

How can I prevent my pet from getting diarrhea?

Preventing an animal from having an episode of diarrhea is impossible. Even perfectly healthy pets have the occasional bout of diarrhea. There are, however, steps that pet owners can take to reduce the frequency of episodes:

•    Keep up to date with vaccinations
•    Worm your pet every 3 months (especially if your pet hunts or scavenges)
•    Prevent access to garbage, spoiled food, etc.
•    Minimize stress
•    Do not make sudden diet changes. If you wish to start a new diet, gradually transition your pet by adding small amounts of the new diet in with the old diet till your pet has become accustomed to the new diet.

(photo: foxypar4)