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Causes of Blood in Dog Stool

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Causes of blood in dog stool: noticing blood in a dog's stool may be scary to many dog owners possibly because blood in feces is often associated with cancer, but in dogs bloody stools are more likely to have other causes. Blood in the stool in dogs may present in two different ways. You may notice the passage of bright red blood with the stools (hematochezia) or the passage of black, tarry stools (melena). In the first case, bright, red blood is indicative of bleeding in the dog's lower digestive tract, whereas, in the second case, it's indicative of bleeding in the dog's upper digestive tract. Causes of bloody stools in dogs may vary, following are some causes of hematochezia and melena in dogs.

Causes of Bright Red Blood in Dog Stools

As mentioned, hematochezia in dogs is the term that depicts the presence of red, fresh blood in the dog's stool. The blood often appears as streaks of blood that are found on the surface of the dog's stool or the blood may be mixed within loose stool. Sometimes, the dog's stool is normal, but at the end of the bowel movement, the dog leaks a few droplets of blood. The blood in this case derives from the dog's lower intestinal tract involving either the anal, rectal, or descending colon. Following are some medical conditions in dogs known for causing hematochezia.

Presence of Rectal Polyps

Dogs do not get hemorrhoids as humans do, but they're more likely to get rectal polyps in some cases and this may cause rectal bleeding in dogs. Dogs with rectal polyps usually have formed stools with blood on the surface. This occurs because as the stool passes, it causes the polyp to bleed. Polyps are highly vascularized and prone to easily bleed and sometimes may be felt by the vet when conducting a rectal examination.

Inflammatory Disorders

Dogs who pass soft stools with blood are more likely to have some inflammatory disorder of the lower intestinal tract. Colitis, the inflammation of the colon is one of the most common causes of bloody stools with mucus in dogs. The most common symptoms of colitis are soft stools that end up more liquid towards the end, accompanied by blood and mucus. Hemorrhagic gastroenteritis, the inflammation of the stomach and small intestine, is a condition known for causing rapid onset of bloody diarrhea. Affected dogs require prompt treatment.This condition most commonly affects small toy breeds and other accompanying symptoms may include vomiting, lethargy and foul smelling diarrhea of currant-jelly consistency.

[adinserter block="4"]Parasites

In some cases, parasites are a common cause of a dog pooping blood. According to the Handbook of Small Animal Gastroenterology, hookworms and whipworms, are a possible culprit for hematochezia in dogs. It's always a good idea for dog owners to bring in a fecal sample to the vet if a dog has blood in his feces so to rule out parasites. Protozoans such as coccidia can also be a potential cause.

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A puppy who has diarrhea, vomiting, lethargy and bloody stools warrants an expedited vet visit to rule out parvo, a potentially life threatening condition often seen in puppies. According to Drs. Foster and Smith, parvo virus is often differentiated from hemorrhagic gastroenteritis by checking if there is a fever. An elevated temperature is quite common in parvo, while in hemorrhagic gastroenteritis it is not. Increased packed-cell volume is also a common finding in dogs with hemorrhagic gastroenteritis.

Causes of Dark, Tarry Blood in Stools

When a dog bleeds from the upper digestive tract, the blood is digested causing the presence of dark, tarry stools. Bleeding may derive from the esophagus, stomach or upper small intestine. Sometimes, the blood may come from the pharynx or lungs and in this case the blood is coughed up and then swallowed. Dog owners often refer to the stools as appearing jet black. It usually takes a large amount of blood to make the stools look dark and tarry. With heavy bleeding, affected dogs may develop pale gums, lethargy and anemia. However, not all dark stools in dogs is indicative of presence of blood. Following are some medical conditions known for causing black, tarry stools in dogs.


When an ulcer takes place, there may be associated bleeding that will turn the stools dark. As mentioned, the bleeding must be quite heavy for dogs to develop melena. According to a study, where 43 dogs suffering from stomach or duodenal ulcers, only 40 percent of them showed melena. Ulcers can be caused by non-steroidal antinflammatoriy drugs, so when giving medications such as Rimadyl or aspirin, it's important to watch for symptoms such as vomiting with or without blood , abdominal pain and possibly, tarry stools. Consult with your vet at once if you notice any of these. Ulceration can in some cases be indicative of tumors.


[adinserter block="5"]Conditions that affect the dog's blood ability to clot can cause presence of digested blood in the dog's stools. Affected dogs may present other signs of coagulation problems such as presence of bruising or pin-point bleeding under the skin. There are several conditions that cause blood clotting disorders in dogs. Other than blood clotting issues caused by medical conditions, exposure to rat poison may cause bleeding and melena in dogs.

As seen, there are many potential causes for blood in the stool in dogs and these are just a few. While cancer isn't at the top of the list, there are several serious medical conditions that require a prompt vet visit. Other causes for blood in dog feces may include intestinal blockages in dogs, surgery complications, trauma and cancerous masses. Dog owners should also consider that in some cases, the ingestion of Pepto bismol can cause dark stools, but this is due to the way the medication is formulated and not because of bleeding. If your dog shows signs of hematochezia or melena, see your veterinarian.

Dog's Upset Stomach About Did you know?

There's a secret of the trade to verify if a dog's dark stool is actually melena. Simply place the stool on an absorbent paper towel and note whether a a reddish tint diffuses from it. If it does, most likely you are dealing with melena, suggests Michael D. Willard, a board-certified veterinarian specializing in veterinary medicine.

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