Why does my dog have bloody diarrhea?

Original Question: My dog has diarrhea with blood that was first discovered this morning. - Jem

May 15, 2019

Hi Jem,

So I’m going to start off with what the causes of diarrhea with blood. A simple colitis is the most common, so that’s an inflammation of the lower intestinal tract that is not up by the stomach but lower down. So that will typically be blood flex rather than a stool that is completely bloody and there’s very often also some mucous present in that stool and simple colitis also often causes straining. So it might be that your dog is straining and seems to want to go to the toilet, but actually very little is being produced and that’s another normal sign of colitis as well. There are other causes of bloody diarrhea in dogs and some of those include a hemorrhagic gastroenteritis. That is a condition that more often than not comes on very suddenly. It’s thought to be due to maybe a clostridial infection which is a certain type of bacteria although that’s not always the case leaving a stool or diarrhea that is just incredibly bloody. So it almost looks like complete blood sometimes and that can cause dogs to become unwell very quickly. They get very dehydrated and they definitely need treatment at the hospital with a vet clinic for that. You can also get infections such as parvovirus, which is a very serious infection and one of the main diseases that we vaccinate our dogs against. We can get bloody diarrhea due to parasites so different types of parasites within the gut, so worms and that sort of thing. You can have an intestinal foreign body, so a dog who’s eaten something and it’s working its way down causing irritation and ulceration of the lower intestines or even getting obstructed. Now by the time it gets down to the lower intestines and when we would expect to be seeing blood, often it will pass because it’s already gotten through the most narrow areas. If something is getting stuck higher up in the intestine, so in the small intestines or even in the stomach, if that’s causing bleeding, then what will happen is we’ll see kind of a dark tarry stool because the blood that’s being produced and leaking into the intestines is getting digested and that causes a dark black tarry stool. Other causes of bloody diarrhea can be tumors of the colon and they can be bleeding and tumors can also be interrupting the normal absorption and digestion of the food within the intestines. And then another thing that can sometimes cause what we think is maybe a bit of blood on the stool is actually a ruptured anal gland abscess. So the anal glands are two sacks that normally express on either side of the anus. If they become infected and enlarged than they can burst out through the skin, which can cause quite a bloody, pussy discharge and if that’s coating the stool, then you might think that your dog has got bloody diarrhea when in fact they’ve got an anal gland abscess. So those are kind of the most common causes of diarrhea with blood in dogs.

What’s the treatment then? Well, if we’re dealing with a simple colitis the most common thing if a dog is otherwise well, if they’re eating, if they’re drinking, if there’s no vomiting, if they’re bright and active is a really bland diet and monitoring are likely to be sufficient.

If your dog is unwell, if there’s lots of blood within the stool and not a small amount then it’s definitely best to get your dog checked out by your vet.