Dog Blood in Stool

Seeing blood in a dog's stool can be alarming for dog parents. Learn more about the possible reasons that may result in blood in dog stool.

Dog Blood in Stool Dog blood in stool can be medically categorized as either hematochezia or melena.

In the case of hematochezia, the blood in the dog stools is bright red and is usually mixed in with the stools. The red color indicates that the blood comes from the lower intestines, most likely from the colon and the rectum.

In melena, however, the blood causes the stools to turn black and tarry, indicating that the source of bleeding is in the stomach or upper small intestine, and the blood has been partially digested.

There are numerous possible causes of dog bloody stools - some are more serious than others. Below are some common causes of hematochezia and melena.

Possible Causes of Hematochezia

  • Injuries or Trauma to the Anus

    A common cause of hematochezia is some kind of injury or trauma to the anus or the anal area (e.g. getting bitten in the hindquarters during a dog fight). It may also be due to a ruptured anal sac abscess.

    Dogs with tails that set low and carried close to the body (e.g. German Shepherds) are prone to a condition called perianal fistulas which are infected lesions caused possibly by inflammation of the sweat and sebaceous glands in and around the anus.

    In all these cases, the blood in stools does not come from the inside of the dog's body.

    When you see bright red blood in your dog stool, therefore, first check the anal area to find out where the blood is coming from.

    If it is from an injury in the anal area, try to stop the bleeding and disinfect the area. Get to the vet for further treatment.

  • Intestinal Parasites

    Another common cause of bright red bloody stools in dogs is intestinal worms such as whipworms and roundworms, and intestinal parasites such as Coccidia and giardia.

  • Bacterial and Viral Infections

    Bacterial infections such as Salmonella, E. Coli, and viral infections such as parvovirus and corona virus can also cause dog blood in stool.

  • Inflammatory Bowel Diseases

    Inflammatory bowel diseases (e.g. colitis) can cause dog blood in stools. Look for other accompanying symptoms such as abdominal distention, diarrhea, and vomiting.

  • Dietary Intolerance or Indiscretion

    Eating too much, eating spoilt foods or food intolerance and food allergies can sometimes cause bloody stools in dogs. Usually the dog will also vomit, have stomach cramps, and diarrhea.

  • Hemorrhagic Gastroenteritis (HGE)

    HGE is a disease in dogs whose cause is unknown. It usually causes a very sudden onset of diarrhea with fresh blood in it. Look for other symptoms such as vomiting, not eating, and listlessness. Sometimes black, tarry stools (melena) can also be seen.

  • Colorectal Polyps or Cancer

    Hematochezia may indicate more serious conditions such as polyps in the colon or rectum, or colon cancer.

Possible Causes of Melena

  • Stomach Ulcers

    Dog Blood in Stool Stomach ulcers in dogs can produce black, tarry stools.

    Ulcers in dogs may be caused by medications such as NSAIDs, corticosteroid, aspirin, etc. Ulcers may also occur following acute gastric dilatation and volvulus, heat stroke, stress, and a type of mast cell cancer in the skin.

  • Metabolic Diseases

    Certain metabolic diseases, such as kidney and liver failure, pancreatitis and Addison's disease can cause bleeding into the intestinal tract, resulting in melena.

  • Ingestion of Blood

    This type of dog blood in stool may also result from ingestion of blood. For example, your dog may have licked a bloody wound or he may have had a mouth injury causing him to swallow blood. The partially digested blood turns the stools to black and tarry.

  • After Surgery

    Melena can occur 12 to 72 hours after surgery performed on the upper gastrointestinal tract.

  • Abnormalities in Blood Clotting

    Blood clotting disorders result in internal bleeding, causing dog blood in stool. Check for evidence of bleeding from other body sites. For example, purple tinted skin suggests that there is bleeding under the skin.

When to See a Vet

As you can see, there are many possible causes of dog blood in stool. The most important thing to do if your dog produces bloody stools is, be sure to collect a fecal sample and take it to your vet for analysis. Note that the sample needs to be no longer than 12 hours old to ensure testing accuracy.

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See a Vet Immediately if...

... your dog shows the following symptoms besides having bloody stools:

  • Pale gums
  • Weakness and lethargy
  • Restlessness
  • Vomiting
  • Diarrhea
  • Dehydration