Seeing blood in your pet’s stool can be quite alarming, and it’s worth a call to your veterinarian. There is an almost endless list of things that can cause bloody stool, but the first thing your veterinarian will want to do is determine the source of the blood.

There are two types of bloody stool. Hematochezia is the term for bright red (or fresh) blood that coats the stool. This is the more common complaint of the two. The second type of bloody stool that we see is called melena and shows itself as dark, tarry stool. Let’s talk a little more specifically about each.


Hematochezia is bright red blood in or around an otherwise normal stool, and it is caused by either external or internal factors:

External: Rectal masses, anal gland masses, anal gland abscesses, anal fistulas, and rectal tears can all cause bleeding that shows up in the stool.

Internal: Colitis, stress, constipation, intestinal parasites, polyps, and blood clotting disorders can cause red blood in the stool.

Often times, straining to defecate accompanies hematochezia. In these cases, straining doesn’t necessarily mean constipation. In fact, most dogs that strain during defecation actually have diarrhea, which may often contain blood.

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Melena is caused by bleeding higher up in the gastrointestinal tract. Bleeding can occur anywhere above the first part of the small intestine, including the oral cavity, respiratory tract (nasal passages and lungs), stomach or esophagus

The dark, tarry stools are a result of digested blood. The causes of melena are many – from gastric ulcers, kidney failure, blood clotting disorders and pancreatitis to a simple mouth wound leading to ingested blood. Because melena is not usually associated with clinical signs like diarrhea or straining, it may be more difficult for pet owners to notice.

Treating both hematochezia and melena depends on the underlying cause. Your veterinarian will want to know your pet’s history, including any appetite changes, incidents of diarrhea or vomiting, or any other recent unusual symptom. From there, he or she will perform a thorough exam and likely will do other tests like fecal analysis or blood work to find an underlying cause. Further treatment will then be discussed based on the results of the exam and diagnostic tests. Protecting your dog or cat from an early age with veterinary pet insurance from Petplan can help you manage the costs of the diagnostics involved as well as any treatment that may be necessary.

If you see any type of blood in your pet’s stool, you should call your veterinarian. While most cases of hematochezia are easily resolved, many cases of melena are caused by serious illnesses that may carry a poor prognosis.

Apr 3, 2012
Pet Health

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