Why Does My Dog Have Diarrhoea?

Why Does My Dog, Cat Or Ferret Have Diarrhoea?

Diarrhoea accidents in your pet often warrant a rush to the veterinarian. This article tells you how I go about discovering the cause of diarrhoea in you pet and some of the ways I treat it. Not every cause of diarrhoea or medication is covered, but the most important ones are. I limit this article to problems in dogs, cats and ferrets - but it could also apply to any of the exotic and wild animals I treat.

I am always delighted when a client actually brings me a sample of the mess that their pet made. In more than half the cases, the diagnosis can be made from a faecal specimen and history alone. Try to bring in a fresh specimen - no need for more than a few tablespoons full.

Because my patients can't talk, the history that you give me is extremely important. The first question I will ask you is whether this is a sudden acute problem or if it is chronic and has been going on quite a while. The next thing I will ask is if you fed something unusual to the pet or if torn remnants of some household object are strewn about the house.

Sudden diarrhoea is most serious in very young, very old and very small pets. They can quickly become severely dehydrated. Dehydration in small pets and frail elderly animals can be fatal because their surface area is large in proportion to their body weight. As dehydration progresses, these pets have trouble maintaining their body temperature and may lapse into coma. I hospitalize all pets in this group immediately and concentrate on maintaining hydration and body temperature. Intestinal inflammation in young pets with diarrhoea causes the intestines to thrash about vigorously. Intestines sometimes tie themselves in knots (volvulus) or fold in upon themselves (intussusception). Both these conditions can be life threatening.

High Intestinal Problem vs. Low Intestinal Problem

Cases of diarrhoea fall into two groups in approximately equal numbers. In the first group, the problem is in the small intestine and in the second group in the large intestine, cecum or rectum. High diarrhoeas are the most dangerous. When the problem is high in the small intestine the pet voids large amounts of stool, but the frequency of bowel movements is not increased. If there is blood in this stool it is chocolate-coloured, not bright red and there is no straining when these pets eliminate. The stool is never mucoid. These pets may also have a tummy ache. The second group have a problem in their large intestine. These pets have frequent, uncomfortable eliminations. When they go, the amount of stool is small and often covered with mucus. Frequently the stool is coated with flecks of bright red or rust-coloured blood. These pets often sit straining to defecate without success. Vomiting may accompany high small intestinal problems but never low colonic ones.

A Primary or Secondary Problem

I then have to decide whether the problem is intestinal; or the result of a problem in some other organ. I do a physical examination and perhaps laboratory blood analysis to see if the dog has signs of other illnesses. Generally, there are very few abnormal blood work results when the problem is in the intestine itself. In primary intestinal disease, abnormal physical exam findings are limited to an inflamed, thickened, painful intestine. With primary intestinal problems I can often detect enlarged lymph nodes that collect lymph from the intestines.

Diarrhoea also occurs due to secondary to non-enteric or non-intestinal diseases of the organs of the body. When I am fortunate, blood work panels and a careful physical examination identify these diseases. Kidney failure causing uraemia is a common cause of diarrhoea in dogs, cats and ferrets. So is liver disease or hepatitis. Addison's disease or an under active adrenal gland as well as an over-active thyroid or hyperthyroidism also cause diarrhoea in dogs and cats. An acute inflammation of the pancreas or pancreatitis will also cause diarrhoea in dogs and cats.

Non-Specific Treatment

Diarrhoeas in dogs and cats caused by eating the wrong things or transient stress often improve if you withhold food for 24 hours and give the pet either kaopectate 0.5-1.0 ml/pound every four hours or loperamide (0.2mg/ml Imodium) at 1ml per four pounds two or three times a day. If the diarrhoea persists longer than 48 hours you should see your local veterinarian. If you visit your veterinarian, bring along a cup full of stool. I often find the cause of the problem by passing the stool through a sieve. Be sure they drink plenty of water so they do not become dehydrated.

Classification of the Process

This is the fun part about being a veterinarian - poking through poop. Next I try to decide a bit more about the problem by examining the stool. I often pass the material through a strainer to hunt for objects such as leaves, sticks, glass, or aluminium foil that are the source of the problem. Then I prepare slides of the material to examine under my microscope. Some of these cases show a normal digestive process where food is being digested and absorbed. In others, fat globules are present and protein particles are sharp - evidence of poor digestion. These cases are either maldigestion or malabsorption. They can be due to a hyper-motile intestine or the lack of normal liver and pancreatic enzymes. Some stools are abnormally light due to a lack of these enzymes. Many times, I find things like bug parts that allow me to diagnose the problem without further tests. Other times parasites are visible under the microscope.

Diarrhoea Caused By Husbandry

Pet Food Quality

Buying that marked down generic brand of dog or cat food instead of your regular name brand is a very common cause of diarrhoea. Quality has a particular cost; and when you go below this cost the ingredients of pet foods suffer. 'High Protein' means very little. Feathers, hooves and beaks are all protein. But they are not digestible protein.

Overeating

Some dogs and many cats over-eat when they are fed once a day. This can result in diarrhoea, colic and vomission. I suggest feeding dogs and cats with this problem three times a day, or leaving the food where they can munch when they please.

Foods That Don't Agree with Pets

Some pets are intolerant to certain ingredients in pet foods. This can be beef, liver or chicken, preservatives, dyes and the like. Very few pets are actually allergic to pet food ingredients.

Stress

Some pets - toy dogs and ferrets in particular - vent stress through their intestines. This can take the form of vomission, refusal to eat, diarrhoea or blood in the stool. After this occurs several times, owners usually draw the connection between events that upset the pet and bouts of diarrhoea.

Dietary Indiscretions

The most common cause of diarrhoea in dogs and ferrets (not so in cats) is dietary indiscretions - the eating of garbage, grass, plant leaves, etc. It is amazing the things pets will eat. Many of these pets are actually separation anxiety cases where a panicky pet eats everything in sight.  Placing these pets on a large dose of petrolatum-based cat laxative helps slide this material out with the stool. These pets need to be monitored carefully for seventy-two hours to be sure the intestine does not block. I sometimes feed them craft glitter and wait for it to come out the other end. At the first sign of abdominal distress, depression, general weakness, fever or blood in vomitus or stool, they should be rushed to a veterinarian for further testing.

Diarrhoea Caused By Medications and Chemicals

Antibiotics and Sulphonamides

Many antibiotics and sulphas disrupt the normal helpful bacterial flora in the intestine as well as killing pathogenic (dangerous) bacteria. When the normal bacterial flora of the intestine is destroyed, diarrhoea may result. This problem can occur with injected antibiotics as well as oral medicines. Giving the pet yoghurt or bacterial gel pastes, and decreasing the antibiotic dose and changing to a different antibiotic all help.

Other Drugs from the Pharmacy

Many medications that we dispense to your pet can cause diarrhoea. Thyroid medication, NSAI drugs such as Rimadyl and aspirin, worming medications, and topical insecticides are only a few of the medications that can cause diarrhoea.

Parasites of the Intestine

Nematode Parasites

I have never found nematode parasites in ferrets. Hookworms, roundworms, whipworms and strongyloides are some of the nematode parasites that cause diarrhoea in dogs and cats. These organisms are the most common causes of diarrhoea in puppies and kittens. They are a threat to children who are accidentally exposed to animal stool. The eggs of these parasites are usually seen in microscopic examination of the stool.

Protozoan Parasites

Protozoan parasites are single-celled microscopic parasites of the intestine. Diarrhoea is their primary sign. This group includes coccidia and giardia. We treat them with bland diets, sulphonamides and metronidazole. Giardia can cause similar problems in pet owners - particularly children.

Viral Infection

Parvovirus of Dogs

Parvovirus infection of dogs causes severe foul-smelling diarrhoea. Mature dogs recover after a period of diarrhoea but the disease is often fatal in young unvaccinated pups. Parvovirus attacks the lining of the small intestine causing bloody diarrhoea and vomiting. Dogs are severely depressed, dehydrated and in much pain. These pets die from fluid loss so most of my efforts aim at replacing these fluids. Parvo-infected dogs cannot keep oral fluids and medicines down, so I give our fluids and medications by injection.

Bacterial Infections

Spoiled Food - Food Poisoning

Spoiled food is often contaminated with toxins and bacteria that cause pets to have diarrhoea and vomit. Food poisoning usually resolves itself after the contaminated material is purged from the body. It is unwise to give these pets medications that prevent diarrhoea and vomiting because this traps harmful bacteria and toxins within the body. Two common bacteria involved in these cases are Staphylococcus and Escherichia coli (E. coli). Dehydration is the most serious side effect of diarrhoea and vomiting. Infant animals can quickly go into shock from dehydration. Products such as Gatorade or Pedialyte are excellent for preventing this. If the pet cannot hold any liquids down the fluids must be given intravenously or subcutaneously.

Salmonella and Campylobacter in Dogs and Cats

Feeding poorly cooked meat products and chicken pass these bacteria to pets and humans. As with food poisonings, keeping the pet well hydrated is extremely important. In catteries, adult cats carrying salmonella often pass it to their kittens with sometimes fatal results. I have found it very difficult to get Salmonella out of a group of cats once it has become established. Batryl (enrofloxacin) is an excellent drug to use in adult pets with diarrhoea but it cannot be used in growing animals.

Problems of Unknown Cause (Idiopathic)

Hemorrhagic Gastroenteritis of Dogs

Toy breeds of dogs are susceptible to bloody diarrhoea; the cause of which remains unknown. No doubt many of these cases fall into other groups I have mentioned but were not diagnosed. Many of these cases are due to stress. Some emotional dogs exhibit stress through their intestines. In other dogs, the problem is probably undiagnosed Addison's disease in which the body is deficient in cortisone. All these cases respond well to food deprivation for 24-48 hours and then gradually increasing amounts of bland diet feed. I give most of these cases the oral corticosteroids, prednisolone or prednisone and place many of them on the sulphonamide or Tylocin. These problems tend to reoccur in the pet from time to time.

Lymphangiectasia of Dogs

Cometimes called plasmacytic enteritis, this condition is diagnosed by a pathologist's examination of snippets of the wall of the small intestine which are removed at surgery. Lymphangiectasia is an improperly formed intestinal lymphatic system, which results in protein being lost from the body (protein-loosing enteropathy). We think that in some cases the pets were born with this disease and in others they acquired it later in life. Most affected pets respond to a combination of bland diet and anti-inflammatory doses of corticosteroid drugs such as dexamethasone or prednisolone, but the disease is never cured. Diets you prepared should contain minimal fat with ample amounts of high-quality protein.

In 2004, an organism call Bartonella was implicated in chronic gastrointestinal infections in cats and dogs. Until recently, Bartonella was primarily associated with Cat Scratch Fever. The diagnosis of Bartonella infection is made using a laboratory test called the Western Blot. When cats or dogs are positive for this organism it can be successfully treated using azithromycin, doxycycline or rifampin.

By Dr. Ronald Hines DVM PhD
Consult With Dr. Hines

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