One of the most common medical problems I see in small animals is diarrhea. It is much more common in dogs than in cats so most of this article will address diarrhea in dogs. It can occur at any age of dog at any time of the year and can range in severity from “I couldn’t pick up my dog’s poop on our walk”, to “I didn’t think my dog would make it through the night.”
There are so many reasons for diarrhea, that it is often treated without specifically defining its cause. If possible we try to classify the diarrhea into sub-categories. How long has it been occurring (acute vs. chronic)? What is the frequency (normal or increased)? Is there urgency? Answers to these questions can help narrow down likely causes. We also like to know if the diarrhea is a primary (diarrhea results from an abnormality within the gastrointestinal (GI) tract) or a secondary (diarrhea is caused by a medical disorder involving an organ system other than the GI tract).
The most common test done to find the cause of diarrhea is a fecal microscopic examination. This is done to identify intestinal parasites and to look for abnormal bacteria and blood. More specific tests can be done to look for specific bacteria or parasites that are not typically seen on microscopic examination. Blood tests can be run to determine if there is illness outside the GI tract that might be causing diarrhea. Sometimes with difficult cases, samples, or biopsies, of the intestines may be needed to find the cause of diarrhea.
Animals may experience diarrhea from eating something they’re not used to, such as table scraps, trash or dead animals found in the yard. Even switching dog foods can cause a stool change. Young animals are more susceptible to intestinal parasites. Older animals may be more likely to develop diarrhea as a result of other medical problems they’re developing.
Depending on the reason for the diarrhea, different therapies may be recommended. If parasites are found, antibiotics or dewormers may be prescribed. Sometimes fasting for a short period and a bland diet is all that is needed. We recommend year-round monthly heartworm medication because it also protects dogs from intestinal worms, which may be transmissible to people. If a human is infected with an intestinal worm normally found in dogs, serious complications can arise such as blindness or even death. Because of the various causes and potential for serious disease causing diarrhea, it is advisable to contact your veterinarian when diarrhea is encountered.