What Are the Causes of Bloody Diarrhea in Dogs?

By Jane Meggitt

It's bad enough that your dog is experiencing diarrhea. If you see blood in his loose feces, you're bound to worry. Bloody diarrhea in canines results from a number of causes, so take your dog to the veterinarian as soon as possible after seeing blood in the stool.

Rectal Disorders

Tumors growing in a dog's rectum can cause bloody feces and diarrhea. Other symptoms of rectal tumors include straining to defecate and pain while passing feces. If your dog is diagnosed with a rectal tumor, your vet will remove the tumor via surgery. However, if the tumor has spread, the prognosis for the dog isn't good. Another rectal growth, the polyp, has similar symptoms. You might see a polyp sticking out from your dog's anus. Although most polyps are benign, malignancy is a possibility. For benign polyps, surgery is generally curative, although new polyps might develop in the future. If your dog consumed a foreign object, that can also cause bloody diarrhea. Most other causes of bloody diarrhea result in hemorrhaghic gastroenteritis.

Hemorrhagic Gastroenteritis

Dogs suffering from hemorrhagic gastroenteritis experience sudden explosive episodes of bloody diarrhea, often with no prior apparent illness. Affected dogs can go downhill and die rapidly, so rush your pet to an emergency veterinary hospital. Diagnosis is determined via a complete blood count, fecal testing, urinalysis and an X-ray to make sure the bloody diarrhea isn't caused by a foreign object in the gut. The vet will likely give your dog intravenous fluid therapy and antibiotics. Your dog might require hospitalization for several days until his condition stabilizes.

Hemorrhagic Gastroenteritis Causes

Hemorrhagic gastroenteritis can result from food poisoning, infection, parasites or endotoxic shock. Sometimes, the cause appears relatively benign -- in certain dogs, a sudden change of diet can trigger this extreme reaction. While parvovirus can cause hemorrhagic gastroenteritis, that's unlikely for a dog current on his vaccinations. Since intestinal worms can cause hemorrhagic gastroenteritis, keep your dog on a veterinarian-approved worming regimen. In otherwise healthy dogs, the culprit behind hemorrhagic gastroenteritis might be salmonella or E. coli.

Affected Dogs

Because hemorrhagic gastroenteritis often results from conditions outside of an owner's control, any dog is vulnerable. However, hemorrhagic gastroenteritis occurs more often in small breed dogs, especially those living in urban areas. Miniature poodles, Yorkshire terriers, miniature schnauzers, Cavalier King Charles spaniels, Pekingese and dachshunds are the most affected breeds, but they are also among the small dogs most often kept by city dwellers.