Dog Diarrhea Causes and Remedies

The messy truth about dog diarrhea: diagnosing the cause of a dog's diarrhea and firming things up can be complicated!

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All dog owners know the feeling of coming home after a work day and smelling that smell. Uh-oh. Your dog has diarrhea. It’s a pretty common affliction of our canine friends. Now comes the inevitable question: “Should we go to the veterinarian?”

The truth is, much like people, sometimes dogs just get diarrhea. Much as we do not see the doctor for every bout of diarrhea, similarly, dogs do not always need medical attention for a short-lived enteritis (inflammation of the intestines). Often, diarrhea can be managed with at-home therapy and convalescent care.

Why Do Dogs Get Diarrhea?

The causes for acute diarrhea in the absence of other signs are varied and include dietary indiscretion (for example: getting into the garbage), gastrointestinal bacteria including Campylobacter, and GI parasites such as hookworms, roundworms, whipworms, and protozoal infections. In most cases of acute, self-limiting diarrhea, a cause is never identified.

If your dog seems otherwise normal, and he is currently on monthly parasite preventative medication, then symptomatic treatment at home is appropriate. Usually most diarrhea will run its course within two to four days, although in some cases, it can last longer. If there are any other signs of illness like vomiting, loss of appetite, depression, or pain, a veterinary trip is in order.

At-home treatment for acute diarrhea can include the following: a bland diet such as boiled hamburger or chicken with broth and rice for a few days, a probiotic such as Fortiflora (available only through veterinarians) or an over-the-counter probiotic and frequent walks. Avoid using human remedies such as loperamide, also called Immodium. This medication has an opioid in it, and it is easy to overdose a dog unintentionally.

If your dog continues to do well other than diarrhea, three to four days of at-home treatment is appropriate.

puppy sitting in doorway

If Your Dog’s Diarrhea Doesn’t Go Away:

If diarrhea doesn’t resolve with treatment, or your dog develops other signs, it is time to seek a veterinarian’s opinion. Diarrhea is considered chronic when it persists for more than three weeks despite treatment.

Diarrhea may seem like a simple problem, but it can actually be very complicated. Your veterinarian will proceed in a stepwise fashion (outlined below) to find the cause:

Thorough Questioning

Your veterinarian will ask a series of questions about your dog’s overall health, diet, vaccine history, and preventive care strategy. He will then ask more in-depth questions about the diarrhea itself. This will help determine what kind of diarrhea is occurring.

Diarrhea can be characterized as small bowel, large bowel, or mixed. In the case of small bowel diarrhea, you may see a normal to increased frequency, small volumes of loose, watery stool that can be tarry or black (representing digested blood). Often, your dog can “hold it” until going outside.

In the case of large bowel diarrhea, there will be an urgency to go. Your dog may not make it outside unless you are paying close attention. There is often mucus covering the stool, and there may be bright red blood as well. Your dog will usually strain for quite some time during or after having a bowel movement.

In some cases, the diarrhea can be mixed small and large, and this can be more difficult to sort out. Your veterinarian will likely ask many questions during this part of the visit.

Head-to-Toe Physical Examination

Next comes a thorough physical examination. Initially, your pet should be weighed. Weight loss is always a concerning sign. The exam will include checking the eyes, mouth, ears, palpating the lymph nodes, listening to the heart and lungs, deep palpation of the abdomen, and a rectal exam.

The rectal exam is the most important part! This will help the veterinarian see what the diarrhea looks like, as well as feel for any problems in the rectal area and descending colon. A temperature should also be checked. If a fever is present, this can help focus your veterinarian’s attention to certain areas such as viruses and bacteria.

Once this is completed, your veterinarian should have a good sense of what type of diarrhea your pet is having, possible causes, diagnostics, and treatment options.

Small Bowel Diarrhea

Generally, veterinarians will start out with conservative diagnostics and treatment for this type of diarrhea. The causes for small bowel diarrhea can be incredibly varied and run the gamut from fairly benign and treatable (parasites) to more serious (Addison’s disease).

Initially, a fecal examination may be the only test conducted. This requires a small sample of stool from your dog. The veterinarian will check this to rule out parasites such as hookworms, roundworms, whipworms, protozoal organisms, and bacterial overgrowth.

Even if your dog is up-to-date on monthly prevention, it is still possible to find breakthrough parasitic infection. This is why a fecal is done. If parasites are found, your veterinarian will treat with an anti-parasiticide like fenbendazole, pyrantel, and/or Albon. He will also discuss environmental control, as these parasites can persist in the soil for long periods of time.

If nothing is found on the fecal, your veterinarian will likely still prescribe a course of the dewormer fenbendazole in case of a false negative fecal. Other treatments at this stage should include a novel protein diet, as your pet may have a dietary sensitivity or allergy. This means switching your dog to a protein and carbohydrate source to which he has no previous exposure. Examples include bison, venison, duck, and kangaroo usually paired with potato, rice, or pea.

dog diarrhea treatment

At this stage, many veterinarians also prescribe metronidazole (also known as Flagyl). Metronidazole is an antibiotic, but it is also thought to have immunomodulating properties that help calm an inflamed GI tract. Many dogs will have an “antibiotic-responsive” diarrhea that will clear up with this treatment.

With this initial approach, your dog should be back to normal within three to 10 days. If within a week, you are not seeing improvement in your dog’s signs, then your veterinarian will move on to further diagnostics and treatments.

A complete blood count and chemistry analysis should also be run (see “Physical Exams for Senior Dogs“). This will give a global picture of your dog’s health. Significant dehydration, a decrease in protein levels, or changes in your dog’s condition (loss of appetite and/or weight loss) can indicate a more systemic health problem.

If metronidazole is not helping, then Tylosin may be used. Tylosin is another immunomodulating antibiotic that can help with GI inflammation. It may also have a probiotic effect in the gut by increasing the numbers of enterococci bacteria in the small intestine. It is very unpalatable to dogs and cats, and your veterinarian will have this medication compounded, in most cases (or have you place it in their food).

Again, your veterinarian will monitor for around a week. If symptoms do not improve, more advanced testing will be recommended.

A gastrointestinal panel (blood test) must be submitted to an outside laboratory. The veterinarian will likely recommend fasting your dog beforehand. This evaluates levels of vitamins found in the body – particularly cobalamin (vitamin B12) and folate (vitamin B9). Dogs with gastrointestinal disease often display impaired absorption of these critical vitamins. This diagnostic also evaluates trypsin-like immunoreactivity. These tests can indicate whether there is a bacterial overgrowth or a condition called exocrine pancreatic insufficiency.

In the case of bacterial overgrowth, antibiotic therapy may be needed.

Exocrine pancreatic insufficiency is a common disorder of German Shepherd Dogs, as well as other breeds. With this disease, the pancreas does not secrete appropriate digestive enzymes. Treatment is supplementing the diet with enzymes to help break down food and assist your pet in absorbing nutrients.

Another test that may be done concurrently is a resting cortisol test. Cortisol is a steroid made by the adrenal glands. In Addison’s disease (also called hypoadrenocorticism), the body does not produce enough cortisol or water-regulating hormones (called mineralocorticoids).

Addison’s can be difficult to diagnose, as symptoms can present in many ways including weight loss, shivering, decreased appetite, lethargy, chronic diarrhea, intermittent vomiting, and electrolyte imbalances.

Treatment for Addison’s involves replacing the cortisol and mineralocorticoids that the adrenal glands are not making. There is also a form of Addison’s called atypical. This occurs when only cortisol production is reduced. Replacing this lack with oral steroids can manage this condition.

If all of these tests are normal, and no obvious cause is found for the ongoing diarrhea, your veterinarian may offer referral to a veterinary internal medicine specialist (DACVIM). At that time, more extensive testing such as abdominal ultrasound, exploratory surgery, and biopsy may be recommended. These will rule out invasive fungal infection such as histoplasmosis and pythiosis, inflammatory bowel disease, and cancer.

Large Bowel Diarrhea

Large bowel diarrhea presents a diagnostic dilemma. Frequently, the causes are difficult to fully diagnose. In many cases, a response to treatment rather than extensive testing is used to make a presumptive diagnosis.

Like small bowel diarrhea, large bowel diarrhea can be caused by parasites, particularly whipworms. An initial diagnostic test will be a fecal examination. Keep in mind, however, that whipworm eggs are very heavy and are not always found on a fecal examination.

If your veterinarian does not find parasites, as with small bowel diarrhea, he will likely still recommend a course of fenbendazole, an effective anti-parasiticide that kills whipworms. They persist for long periods of time in the soil, so managing the environment is critical to preventing re-infection. Further, not all preventives cover against whipworm infection. Check with your veterinarian regarding your monthly treatment to ensure that your dog is protected against whipworms.

An antibiotic trial may be the next step. Clostridial colitis is a possible cause of large bowel diarrhea. It is poorly understood, as some dogs can have Clostridium bacteria but not be ill, while others can become very sick. Diagnosis is very tricky and recommendations change continually. Generally, clostridial infections respond very well to amoxicillin or Tylosin, so your veterinarian may try a course of antibiotics to both diagnose and treat the diarrhea.

A fiber trial – a dietary trial with a fiber-enriched food – may also help diagnose and resolve the problem. In some cases, the addition of a fiber-enriched food may be all that your dog needs to get back to normal. Your veterinarian can help select a fiber diet appropriate for your dog.

Many dogs are allergic to certain components in food (the immune system responds and causes the diarrhea), while other dogs are just “sensitive to” to specific dietary items (immune system is not involved). Again, diagnosis might be tricky. As a result, your veterinarian will likely prescribe a dietary trial. In this case, your dog will be placed on a hypoallergenic diet. There are several on the market that are made from hydrolyzed protein. This is when the protein is broken down into such small units that the immune system does not recognize the initial protein. This type of diet must be rigorously followed if it is to be successful. Treats, flavored heartworm medications, and table food will render the trial useless.

a senior boxer dog

At this point, more blood tests will likely be called for. If your dog has evidence of bloodwork changes and weight loss, concerns for more serious systemic illnesses such as fungal disease and cancer come to the forefront. At that time, you should consider that referral to a veterinary internal medicine specialist (DACVIM) is likely best for your dog.

A Note About Boxers

About 30 years ago, Boxers were noted to have a severe, progressive disease of the colon (histiocytic ulcerative colitis) that caused very bloody, mucoid, large bowel diarrhea and resultant weight loss.

It was recently found that this is highly responsive to a common antibiotic called enrofloxacin (also known as Baytril). If empirical treatment is attempted, it must be continued for several weeks to ensure that all the bacteria are killed; if the bacterial population is not completely eliminated, the most resistant bacteria can come back with a vengeance.

If enrofloxacin doesn’t work, a biopsy of tissue from the colon is the best way to diagnose or rule out other possibly treatable diseases such as fungal infections.

Dog Diarrhea: Not A Simple Matter

As you can see, diarrhea can be a complicated problem to solve. Keeping a thorough history on your dog, documenting his diet and parasite prevention strategy in particular, as well as monitoring bowel movements closely, can help your veterinarian tremendously.

When diarrhea becomes chronic, it can take weeks to months to sort out the underlying cause and find an effective treatment. Be patient and work closely with your veterinarian. Follow recommendations and do not try random remedies recommended by random sources! With time, patience, and a good veterinarian, a solution can generally be found.

Catherine Ashe graduated the University of Tennessee College of Veterinary Medicine in 2008. After a small-animal intensive emergency internship, she practiced ER medicine for nine years. She now works as a relief veterinarian in Asheville, North Carolina, and loves the GP side of medicine. In her spare time, she spends time with her family, reads voraciously, and enjoys the mountain lifestyle.

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