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).