Every dog gets diarrhea from time to time, but in most cases it will disappear pretty quickly. But while most cases of diarrhea in dogs are not serious, there are a few occasions when diarrhea means more than just cleaning up the mess. Two things immediately come to mind: when your dog has diarrhea that lasts more than a couple of days, and second, if your dog has bloody diarrhea. In this article we're going to address the second issue.
The first thing to note is that diarrhea really isn't a "condition" or disease all in itself. When a dog has loose stools that is a symptom that something else is wrong. For example, it could mean that your dog is passing his stools more rapidly than he should. If the diarrhea is bloody, then that tells us (obviously) that the dog has internal bleeding somewhere.
Here's our first clue. Bloody diarrhea in dogs can come in two colors:
If the diarrhea is black, that means the blood has been in the stool longer, because the black blood isn't "fresh", so to speak. This indicates bleeding further up in the gastrointestinal tract. it might even be in the stomach, or it could be in the small intestine. This could happen if the dog had ulcerations in the stomach, for example.
If the blood is red, then there is bleeding in the large intestine closer to the exit or even bleeding in the rectum.
If you have a puppy, bloody diarrhea especially red, bloody diarrhea is a serious concern. This is because bloody diarrhea is a sign of a parvo virus infection, a serious medical emergency in dogs that is often fatal for puppies. If your puppy has bloody diarrhea get her to a vet right away.
Actually any case of bloody diarrhea in dogs should mean a trip to the vet. Besides parvo virus, the list of possible causes is very long. It may be that the dog has eaten something that led to ulceration somewhere. Or it could mean cancer if its chronic, although dogs don't get colon cancer as often as we do. Dogs are much more likely to get other types of cancer. However when dogs do get cancer of the GI tract, it tends to be aggressive.
The bottom line: Get your pet to the vet at any sign of bloody diarrhea in dogs.