Blood in Dog Stool - Should You Be Concerned?

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Seeing blood is always worrying, whatever the circumstances. Blood in your dog’s poo is no exception. Sometimes you might see very bright red, fresh blood, but bleeding higher inside the intestines causes a darker, blacker appearance, which might go unnoticed as bleeding. There are lots of different reasons why you might see a bloody stool, and these range from fairly benign to potentially life-threatening, so it’s good to know what to do if you do see it. Let’s look at the possible common causes and then when to take action.

Common causes of blood in dog poo

  • Colitis. This is an inflamed large bowel and is pretty common in dogs. Because of the inflammation and the fact your dog strains to go to the toilet, fresh blood and mucus are frequently seen. Colitis is often caused by a dietary indiscretion like raiding the bin, but can have some more serious causes too.
  • Haemorrhagic diarrhoea or gastroenteritis. This can rapidly become very serious. It is caused by things like viral diseases, e.g. parvovirus, so it’s essential to keep your dog’s vaccines up to date.
  • Bowel injury. Swallowing sharp objects like bones or gravel can injure the lining of the intestines and cause bleeding.
  • Chronic enteropathies, such as food- or antibiotic-responsive enteropathy.
  • Parasites. Try to keep your dog’s parasite control up to date as recommended by your vet.
  • Cancer or intestinal polyps.
  • Food allergies or intolerances.
  • Poisons. Some poisons, such as rodent bait, cause bleeding throughout the body, including in the intestines.

These are some of the most common causes of blood in your dog’s poo, but when can you relax and when should you see your vet?

When to be concerned

The sight of blood in the stool is not necessarily a ‘dash straight to the vet emergency’, even though it may be shocking. For example, most cases of colitis get better on their own in a day or two. However, there are times that you should be concerned and get help as soon as you can.

  • Severe diarrhoea. With or without blood, severe, watery diarrhoea can very quickly result in dehydration and loss of important minerals, especially if there is vomiting too. If there is blood loss, your dog can also become anaemic very quickly. Be sure to tell your vet if your dog isn't vaccinated because infectious diseases are a big risk to other patients in the hospital setting.
  • Is your dog unwell or bright? You know your dog better than anyone. If they seem bright, happy and alert, and they’re eating and playing normally, then you can probably wait a day or two and see if things improve on their own. If, however, your dog seems lethargic, cries in pain or stops eating, then you should get to your vet.
  • How long has it been? Even if your dog seems bright and well, if the blood continues for more than 48 hours, it’s best to get it investigated.
  • Was there an event that started it? It may seem obvious, but always try to think back the last few days before you first see the blood. Has your dog had a bone as a treat, or stolen some food from the bin? Have you used poisons in the garden that they may have found? Ask your neighbours the same thing. Have you changed your dog’s food suddenly?

If you do decide you need to go to the vet, it’s really useful if you can take a sample of the poo with you. Your vet will want to test it for parasites, blood, infections, etc. Even photographs can be useful if you’re caught off guard and can’t get a sample.

It may be that just a few days of treatment and some highly digestible recovery food is all that’s needed. However, your vet may need to do blood tests and even imaging, such as x-rays or ultrasound, if there is a risk of foreign bodies or injury. In the case of things like IBD and possible tumours, then biopsies or surgery may be necessary.

If ever you’re concerned, ask your vet. We would always prefer to be safe than sorry.

Reviewed by Dr. Hein Meyer, DVM, PhD, Dipl-ECVIM-CA