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Ask a Vet: What Causes Blood in a Dog's Stool?

Causes of Blood in a Dog's Stool

Blood in a dog's stool can be a scary sight for many dog owners who witness it for the first time. Of course it is not normal and warrants the attention of a veterinarian so to determine the underlying cause. There can be several causes of blood in a dog's stool, and as a starting point, it is helpful distinguishing on whether you are dealing with a case of hematochezia or melena. Veterinarian Dr. Ivana Vukasinovic discusses several causes of blood in a dog's stool.

What causes blood in a dog's stool?

What causes blood in a dog's stool?

What Causes Blood in a Dog's Stool?

Blood is always an alarming sight, and seeing blood in a dog’s stool is usually a symptom of some potentially serious problem, and you, as an owner of a dog should be concerned.

There are many reasons that could cause blood in a dog's stool and some of these reasons include internal parasites, cancer, inflammation of the bowels ( inflammation of the colon – colitis), upset stomach due to bad food, viral infections such as parvovirus, bacterial infection, foreign body, allergies or even autoimmune disorders.

No matter the reason, the real cause should always be determined. Blood in dog’s stool should never be ignored, but some cases are more worrying than others. Usually, the blood in stool is just a simple problem, caused by abundant amounts of food or food that is too rich for the dog. These kinds of problems usually clear up after or day or two.

Causes of Red Blood in a Dog's Stool (Hematochezia)

When we speak about blood and feces there are two types of bloody stool: hematochezia and melena.

Hematochezia is the term from Greek: hemato – blood and chezia – to defecate. This finding is associated usually with lower gastrointestinal bleeding. Hematochezia is the passage of the fresh, red blood through the anus, in or with feces or even without it.

Bright, red blood is the primary symptom of this condition while feces may be loose or fully formed from color ranging from normal looking to discolored depending on the primary cause. Defecation may be more frequent, or the dog can show no symptoms at all, which also depends on the cause of the bleeding.

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The causes of hematochezia are usually located in the lower digestive tract, and this includes irritation from a foreign object such as toys, bone shards, plastic, etc, ulcers, cancer, colitis, polyps infections, allergies or even inflammatory bowel disease.

Blood may be mixed in with the feces, lie on top of it or appear like a few droplets. If blood appears more than once or consistently every time a dog defecates, a veterinarian should be consulted.

For diagnosing a cause of this condition, the veterinarian will perform lab work and different kinds of imaging combined with anamnesis and verbal history. Many additional tests may be required like endoscopy or radiographs.

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Causes of Dark, Tarry Stools in Dogs (Melena)

Melena is the term used to describe tarry or inky stools. While red blood in the stool can mean acute occurrence without any actual problem, dark and tarry stools mean that the blood has been digested.

Melena usually occurs when the bleeding happens in the upper portion of the digestive system. One of the most common causes of melena is cancer, but it is also seen after ingesting blood from the respiratory system (like from nosebleed), or some other bleeding. Melena does not necessarily mean that there is a problem in the gastrointestinal tract.

As said, melena is dark feces resembling tar or coffee grounds and can be followed by many different symptoms depending on the main cause of bleeding. Other symptoms include decreased appetite, polyuria, weight loss, pale mucous membranes, throwing up and diarrhea.

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Usual reasons for melena include infection, cancer, NSAIDs usage, and some other medications, foreign objects, toxic materials, and heavy metals intoxication, blood ingestion and bleeding disorders as well as some of the metabolic diseases (like ‎Addison's Disease). Melena does not primarily indicate a gastrointestinal problem, but it is a serious symptom that must be checked out.

Diagnosis includes a thorough history and complete physical examination with different laboratory testing usually including CBC, fecal examination and urinalysis. Additional imaging and testing may be necessary.

How Blood in Dog's Stool is Treated

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When we are talking about the bleeding located in the gastrointestinal system, melena develops if the bleeding is located in the small intestines or the stomach, higher up in the system in order for the blood to be digested, while hematochezia occurs when there is a bleeding into the colon or rectum and the blood is not digested or discolored.

Before contacting your veterinarian you need to examine your dog’s feces for determining if the blood is fresh or digested.

Also, it is helpful to know how often your dog poops, because straining or increased toileting may be a valuable clue. Is blood in stool a sudden problem, or recurring one? Did you change the diet recently? Also, anxious dogs can react to stress with changes in the digestive system. Is your dog on some medication, or did he have any other non-related symptoms?

With a sudden offset of blood in stool symptoms, it is advised to change the diet to something bland and simple and to watch for deterioration of the condition or some other symptoms that can appear. If the reason behind the condition is simple, blood in stool will stop after 24 hours or less, but usually, it is suggested to keep an eye on your dog. If the symptom is still present or recurring, professional help is advised.

About the Author 

Dr. Ivana Vukasinovic is a veterinarian in Belgrade, capital city of Serbia. She received her B.S from University of Belgrade in 2012, and her master’s degree from Veterinary University, Belgrade


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