Seeing blood in your dog's stool can be a quite frightening event, perhaps mainly because we most usually associate it with cancer, but luckily in dogs the causes may be a lot less dramatic. However, as a responsible pet owner, it is always savvy to have the potential causes investigated to rule out the more serious triggers.

Blood in stool is medically known as hematochezia or melena. In hematochezia the blood is bright red meaning the it is fresh and most likely deriving from the lower intestines, typically the colon and the rectum. It is often mixed in the dog's stools. In melena, the blood in the stools causes feces to appear as black and tarry suggesting the blood is digested and coming from the upper intestinal tract. Usually, but not always, melena is more worrisome than an occasional case of hematochezia.

The causes of blood in stools can be various and they can range from minor issues such as a diet changes to severe cases such as cancer of Parvo. Below are some common causes that may be investigated by your veterinarian.

Common causes of Hematochezia

Parvo

This is a serious disease often found in puppies. Black and tan breeds such as Rottweilers, German Shephards and Dobermans are more prone. Typically, a puppy with Parvo will exhibit vomiting, diarrhea, lethargy, loss of appetite and blood in stools. Because this disease can be deadly, puppies suspected of having Parvo should be seen by a vet promptly.

Parasites

Usually, this is the most common cause of blood in the stool. The most common parasites that cause blood in the stool are hookworms, whipworms, and roundworms. Protozoans such as coccidia may also cause bloody stools. With appropriate identification of the offending parasites, a veterinarian will prescribe specific dewormers to help get rid of these annoying beings.

Dietary indiscretions

Over eating or dietary indiscretion may irritate a dog's intestines, causing vomiting, diarrhea and bloody stools. Dogs must be switched to new foods gradually. If a diet change is done too sudden vomiting and diarrhea may take place. Other causes may be eating spoiled foods or food intolerance and allergies.

HGE

Hemorrhagic gastro-enteritis involves copious blood in stools along with vomiting and diarrhea. Often the cause cannot be found, but your dog may need intravenous fluids and proper medications to let this condition subside.

Rectal injuries

Dogs that ingest sticks or bones or anything that is sharp may eventually scrape a bit the lower intestinal lining or the rectum as they make their way out through the feces. Often such sharp items may be seen in the feces protruding out. In such cases the blood is bright red and will eventually stop. Avoid giving cooked bones and sticks to play with. Also check the rectal area for any rectal injuries especially involving the anal glands.

Common causes of melena

Use of NSAIDS

If your dog is on aspirin or some type of Non Steroidal Anti-Inflammatory drug it may develop ulcers from its use. Dogs with bleeding ulcers will typically have black, tarry stools meaning digested blood coming from the stomach. Inform your vet promptly and if your dog is on such medication, keep a watchful eye on the stools.

Pepto-Bismol

If you have recently given Pepto Bismol, consider that it may turn stools black. It also says so on the bottle. Stop giving it if possible and the stools should turn back to normal.

Ingestion of blood

A dog's stool may appear black and tarry also from ingesting blood. For instance, your dog may have licked a bloody wound or he may have had a mouth injury causing him to swallow blood.

Blood clotting disorders

There are several canine conditions that may cause blood clotting disorders and bleeding. Affected dogs may also exhibit other symptoms other than black tarry stools such as purple tinted skin suggesting bleeding under the skin. Rat poison may also cause blood clotting disorders and bleeding and it may manifest as dark tarry stools. If you think this may be a possibilty have your dog seen ASAP.

Post surgery complication

If your dog has undergone some type of surgery recently and has black stools call your vet immediately. There may be internal bleeding somewhere. Possible complication as such may show up to 72 hours post surgery.

Tumors/Cancers

Any time your dog presents dark, blackish stools, have your dog seen. You want to rule out the possibility of tumors such as polyps or cancer.

While these are just some causes, there may be several more such as bloat or intestinal obstructions. Also, some of the causes above may both cause melena or hematochezia. Whichever the cause, should your dog show bloody stools make sure you collect a fecal sample so your vet can start by ruling out parasites and protozoans. The stool sample needs to be no longer than 12 hours old to grant testing accuracy.

Always have a dog seen immediately if it has pale gums, becomes lethargic, has vomiting and diarrhea or is not acting its normal self. Blood in stools may turn out to be nothing, but it is always best to have the cause investigated in order to be safe rather than sorry.

Disclaimer: The above article is not be used as a diagnostic tool or as a substitute for veterinary advice. Always consult with a vet should your dog exhibit bloody stools.