Diarrhea is categorized based on the location of the problem causing the diarrhea. Diarrhea is considered large bowel when the problem causing the diarrhea occurs in the colon or large intestine. Symptoms of large bowel diarrhea are feces with mucous (sometimes the feces will look like jelly) and red blood. Your dog may strain to defecate, and the amount of feces produced may or may not be larger than normal. Some causes of large bowel diarrhea are gastrointestinal parasites (giardiasis or roundworm for example), inflammatory bowel disease, tumors, large bowel bacterial overload, dietary changes or indiscretions, medications and stress. Diarrhea is considered small bowel when the problem is located in the small intestines. Symptoms of small bowel diarrhea include increased feces volume and changes in feces color. In general, there will be no mucous in the feces, and your dog will not usually strain to defecate. Some causes of small bowel diarrhea are small bowel bacterial overload, inflammatory bowel disease, other malabsorption diseases, exocrine pancreatic insufficiency, food allergies, tumors and gastrointestinal parasites.

If your dog has diarrhea that contains a lot of blood or mucous, if his stomach seems bloated, if his gums are pale or a strange color, or if he seems upset, lethargic, weak, or in pain he needs to go to the veterinarian immediately. Repeated diarrhea in puppies, senior dogs, and dogs with any pre-existing health condition also requires veterinary assistance.