Bloody Diarrhea In Dogs: The Whiff of Hell

Bloody Diarrhea In Dogs
Wyatt Robinson
Written by Wyatt Robinson

It’s bad enough when your dog has diarrhea, but if you find blood in it things get a whole lot more complicated fast. And that’s because bloody diarrhea in dogs can indicate a serious condition, which can actually prove to be fatal. As such, we advise you to take your dog to the vet immediately if your see traces of blood in his stool.

However, in this article we’ll review the main symptoms and causes of this condition, as well as give you an insight about what questions the vet will ask you to establish a diagnosis, what the actual diagnosis tests are and what you can expect treatment-wise.

Related symptoms

Apart from your dog’s bloody diarrhea, you can also notice some other symptoms:

  • Sluggishness.
  • Inactivity.
  • Lack of appetite.
  • Weight loss.
  • Dehydration.
  • Fluid loss.
  • Electrolyte imbalance.
  • Hemoconcentration.
  • Hypovolemic shock.

If your dog isn’t feeling well, of course he won’t feel as energetic and playful as usual. Moreover, if his condition is caused by a pathogen or by a more serious affection as ulcer or cancer, he will definitely need to rest more, which is why you’ll see an increase in his hours of sleep. He will also be more inactive and sluggish than normal when he’s awake too; after all, he’s suffering and he’s probably in pain as well.

Since he could be affected by a pathogen, his body will try to expel the negative influence by starving itself and that, combined with a lethargic disposition, will cause your dog to eat less. If, on the other hand, your dog has a more serious illness like cancer, the toxins in his body will actually make him nauseous at the sight or smell of food.

Dog lost weight

This lack of appetite can lead to a dramatic weight loss, which is not a good sign at all. You want your dog strong, in order for his body to be able to fight whatever is making him feel so bad. Besides, if your dog is not eating properly, then he probably isn’t drinking the necessary amount of water either.

Fluid loss is even worse than weight loss, because it can lead to dehydration and electrolyte imbalance. If your dog is dehydrated, then his body can’t get the amount of energy it needs to function at optimum levels. That will make him weaker, and he will have less force to fight his condition. In fact he may end up in a vicious circle, where a pathogen or other illness is making him feel bad in order to expel the vicious catalyst, while his lethargy is actually aiding it.

Moreover, if your dog isn’t eating nor drinking, that means he will lose important electrolytes, which come from the foods and liquids he’s supposed to ingest. These electrolytes are actually salt, potassium, calcium, and chloride, and not eating limits their intake. Plus, the fluid in your dog’s body contains cells, proteins, glucose, and electrolytes. That’s why fluid loss determines an electrolyte imbalance.

So why are electrolytes so important? Well, when they dissolve in your dog’s blood, they can either take a positive or a negative charge. That means they are responsible with creating the vital energy your dog needs to sustain his life. The crucial role of electric charges is keeping animals and humans alive, including the operation of our brains, nerves, muscles, and the creation of new tissue.

The last two symptoms (hemoconcentration and hypovolemic shock) are the most worrying, because they point to a life-threatening stage of your dog’s condition.

Hemoconcentration is diagnosed through blood tests, and it shows an increase in your dog’s red blood cells and solid matter in their blood. That leads to a decrease in the volume of plasma in relation to red blood cells and it’s caused by loss of fluid to the tissues. So, if you’re dog is dehydrated because of his diarrhea, losing not only fluids but also blood, he can get to the stage where hemoconcentration can be observed.

Dog on blood test

If your dog reaches hypovolemic shock, it’s because the lack of blood and fluids in his body make it impossible for the heart to continue pumping blood. That in turn can lead to multiple organ failure and at this point your dog’s life really is in danger. However, if things have escalated very quickly and you haven’t had the time to take him to the vet by now, which means he isn’t under medical supervision, you can notice the onset of hypovolemic shock by these signs:

  • Anxiety or agitation.
  • Confusion.
  • Decreased or no urine output.
  • General weakness
  • Paleness around his mouth, nose and on the linings of his ears.
  • Rapid breathing.
  • Unconsciousness.

In fact, if your dog has reached the stage of hypovolemic shock and you suspect massive internal bleeding, the symptoms by which you can guide your conclusions – apart from bloody diarrhea – are:

  • Abdominal pain.
  • Black, tarry stool (melena).
  • Blood in the urine.
  • Vaginal bleeding.
  • Vomiting blood.
  • Chest pain.
  • Abdominal swelling.

At this point the medical emergency is crystal clear, and you need to call an ambulance for your dog as soon as possible.

Keep your dog warm

In the meantime, you can follow the advice listed below, as not to worsen your dog’s condition:

  • Lay your dog flat.
  • Keep him warm.
  • DO NOT move him.
  • DO NOT give him fluids through the mouth because he may choke.


Your dog’s bloody diarrhea can have a number of causes, but the truth is that this condition – also called hemorrhagic gastroenteritis – makes the list of medical mysteries. Vets admit that they can’t point to a single, certain cause in about 80% of the cases.

However, there are some things we do know about this illness.

First of all, this is an intestinal condition, which can prove life-threatening to your dog. It manifests itself mainly by the instantaneous beginning of a watery and bloody diarrhea that can also be accompanied by vomiting and by a number of other symptoms listed above.

Causes of blood in dogs stool

If there is a serious inflammation of the intestines, then chunks of the intestinal lining can detach itself and can be noticed in the actual stool. The whole thing leads to extreme dehydration, hemoconcentration and electrolyte imbalance, and can become pretty serious as it really endangers your dog’s life. At this point, the hemorrhagic gastroenteritis has to be treated really fast or otherwise it will get your dog in the hypovolemic shock stage.

Another thing we know about this condition is that smaller dogs and puppies are predisposed towards it. In fact, the direct correlation between a dog’s size and the possibility of hemorrhagic gastroenteritis’s onset occurs because smaller dogs can become dehydrated faster. Since their bodies are more tiny, they don’t have the necessary blood, fluids and fat reserves to keep them alive for longer. Apart from this, dogs blessed with sensitive gastro-intestinal tracts have a higher probability or recurrence.

However, if this condition is treated effectively it will not negatively impact your dog’s future life.

The actual causes for bloody diarrhea are:

  • Stress.
  • Sudden dietary changes.
  • Hyperactivity.
  • An upset stomach from eating bad food.
  • Inflammation of the colon (colitis).
  • Internal parasites (such as roundworms).
  • A viral infection (like parvovirus).
  • A bacterial infection.
  • An intestinal foreign body.
  • Cancer.
  • Allergies.
  • Autoimmune disorders (such as inflammatory bowel disease).

Let’s take these causes individually and try to understand them better.

Stress and hyperactivity cause an irritation to your dog’s bowels. In fact, gastritis induced by stress is not uncommon at all. This illness can determine the onset of various erosions on your dog’s intestines or on their stomach. That’s what explains the apparition of blood in his stool. As such, if you know that your dog has been experiencing high levels of psychological stress, be sure to mention it to your vet.

Stress and hyperactivity

Moreover, you can also look at the blood’s color. If it’s bright red, that suggests a problem with your dog’s stomach or small intestine. If the color is a brownish sort of red, that entails your dog’s problem is located in the large intestine or in the rectum.

Apart from this, sudden dietary changes are also a cause of irritation to the stomach or intestines, as well as dietary toxins which can likewise affect your dog’s immune system. Consequently, you should be very careful about your dog’s diet and know that not all human foods are good for dogs. It may also happen that your dog has accidentally eaten something from your dinner table which he shouldn’t have, like:

  • Apple seeds.
  • Avocado.
  • Baby food.
  • Cooked bones.
  • Candies.
  • Chewing gum.
  • Chocolate.
  • Fish.
  • Grapes.
  • Macadamia nuts.
  • Milk.
  • Mushrooms.
  • Onions.
  • Peaches.
  • Plums.
  • Tomatoes.
  • Yeast.

Many of the above listed foods can cause toxins in your dog’s gastrointestinal tract, bloating and diarrhea. In fact, cooked bones are the most dangerous of them all because many dog owners don’t know they shouldn’t feed dogs that. This ignorance can be easily explained by all the images promoted in the media or in cartoons where a dog is happier when he gets a bone of his own to chew, eat or bury. Either way, an upset stomach from eating bad food is a very important cause that leads to your dog’s bloody diarrhea.


Another cause of hemorrhagic diarrhea can be colitis, which is an inflammation or irritation of the colon or large intestine and can be either acute or chronic. An acute colitis has a sudden onset, while a chronic one is recurring and lasts longer. You may suspect that your dog has colitis if he sometimes strains to defecate, while at other times he does it more than usual and presents blood in his diarrhea.

Moreover, the blood in your dog’s liquid poop may be caused by infectious agents called pathogens. The most common pathogens which trigger the onset on hemorrhagic diarrhea in dogs are:

  • Bacteria (e.g., Campylobacter, Salmonella, Escherichia coli, Clostridia).
  • Virus (e.g., Parvovirus, Canine distemper).
  • Parasites (e.g., Roundworms, Hookworms, Tapeworms, Whipworms, Coccidia).

The bacteria listed above can infect your dog’s intestines and that’s how this type of diarrhea occurs. The Campylobacter is most commonly found in bad poultry meat; Salmonella comes from bad beef, poultry, milk, and eggs;  Escherichia coli (E. coli) is found in infected raw milk or in traces of contaminated stool your dog may have come in contact with, like the gas-causing Clostridia. E. coli and Salmonella can also be passed from animal to human or vice versa. Salmonella infections are likewise associated with reproductive disorders, which makes them more dangerous.

The virus named Parvovirus is responsible for a very contagious viral illness for dogs. If your dog has blood in his diarrhea, it’s more likely that he’s been affected by the intestinal form of this Parvovirus. Your dog can contract this virus either by coming into contact with an already sick dog, either by coming in contact with some infected feces. While most of the cases consist of young puppies, with an age ranging from 6 weeks to 6 months, the spreading of this virus has been drastically reduced lately because so many young dogs are vaccinated on time.

Puppy with Parvovirus

Canine distemper is an illness seen in dogs as well as other wild animals, like raccoons, wolves, foxes, and skunks. The virus causing it can be contracted by your dog either by direct contact, either by way of air. It behaves by firstly going for your dog’s lymph nodes and tonsils. After it reproduces there for about a week, the virus moves forward to your dog’s other systems: respiratory, uro-genital, nervous and gastrointestinal.

The parasites listed above can be contracted in the same way: by direct contact or by coming into contact with contaminated feces. Your dog shouldn’t be allowed to sniff or come near other dog’s feces, and you should also be very careful in handling his poop because people can get these parasites from their dogs too.

An intestinal foreign body can also be a very likely cause of your dog’s blood traces in his diarrhea. We’re talking about a physical obstruction of his gastro-intestinal tract, because maybe he swallowed a little toy or something he shouldn’t have eaten. That can very well scratch or rupture his stomachs or intestines, causing blood to appear in his stool.

Food allergies can be a very likely cause of bloody diarrhea for your dog. As we’ve previously listed the perilous foods your dog can eat, it’s also important to notice that some of them trigger a chronic form of illness known as Eosinophilic gastroenteritis.

Basically, we’re talking about an irritation of the gastrointestinal tract caused by allergens. The most likely allergens for your dog that can lead to this condition come from raw milk or other raw dairy products. Nevertheless, a connection has been observed between this type of gastroenteritis and eggs, pork, beef, and gluten-flour products.

Inflammatory Bowel Disease is the name given to a group of gastrointestinal diseases which swell the intestines and give chronic symptoms related to the gastrointestinal system. Doctors don’t know exactly what causes IBD, but it’s generally accepted that it comes as an uncommon reaction of your dog’s immune system to some bacteria that normally live in his intestines and that are actually good for your dog.

Either way, IBD is responsible for many dogs suffering, especially those who are middle-aged or older. If you own a Basenji, Lundehund, French bulldog or Irish setter, you should know that these breeds are prone to IBD.

Cancer of the colon or of the rectum may be another cause linked to your dog’s hemorrhagic diarrhea. The reason is that the said tumors can become irritated and rupture. Either way an environment full of feces like the intestines isn’t a very hygienic one, which may cause your dog’s tumor to act up and give him another unpleasant symptom to handle.


The vet will use a number of invasive and non-invasive procedures so that he can first be able to correctly see what causes your dog’s condition and to further see the extent to which this condition has evolved.

Dog food allergies checking at vet

You may also be asked to answer some clarifying questions, so be ready with your dog’s medical history and vaccination record. The questions you should prepare yourself for are:

  1. When did you first see signs of blood in his stool?
  2. What color is the stool?
  3. How frequently does he defecate?
  4. Does he only have diarrhea?
  5. Does your dog sometimes strain to defecate?
  6. What color is your dog’s poop?
  7. Did your dog eat something he shouldn’t have?
  8. Do you normally feed your dog cooked bones?
  9. Did your dog ingest a foreign object, like a small toy?
  10. Is your dog agitated or stressed?
  11. Does your dog have other symptoms, like vomiting?
  12. Is your dog more lethargic than usual?
  13. Does your dog eat and drink less than usual?
  14. Does your dog have any other medical conditions, like a tumor, an ulcer or IBD?
  15. Has your dog recently been in contact with other wildlife?
  16. Has your dog recently been in contact with feces?
  17. Is your dog vaccinated?

The tests that a vet can perform to further assess your dog’s condition are:

  • Physical observations.
  • Routine blood/ biochemical tests.
  • Fecal Study.
  • Radiography/ Endoscopy.

The physical observations consist of:

  • A skin test for evaluating the level of dehydration.
  • An abdominal palpation to see if your dog feels any abdominal pain and if there’s something stuck in his intestines
  • An examination of mucus membranes to assess if there’s a blood loss and how serious that is.
  • A check of his cardiovascular function and his pulse is very important, as it can indicate how dehydrated he is or how much blood your dog has lost.
  • Visual observation of the vomit and/or stool to check for blood, color and consistency.

The blood test is typically a packed cell volume, also called a hematocrit test, which checks the proportion of your dog’s total blood volume that is composed of red blood cells. This test aims to find out the hemoconcentration we’ve previously talked about and how much red blood cells are in your dog’s body. The hematocrit test wants to further confirm if you’re dealing with a hemorrhagic gastroenteritis.

The biochemical test will check your dog’s internal organs, like the liver and the kidneys, as well as his total blood proteins and blood sugar. This test is looking to see if it can find an electrolyte imbalance in your dog’s body, which can aggravate his condition.

The fecal study consists of a stool sample which is checked for virus, bacteria or parasites that may explain the presence of blood in his stool.

If these tests don’t give any indication as what the source of your dog’s condition may be, a further radioscopy or endoscopy may be necessary, so the doctor can see more clearly if there is some mass or obstruction in your dog’s intestines. In fact, ulcers and tumors can be better observed using these techniques.


Now that the hard part is over, the easy part may begin, which is the treatment. Happily enough, most dogs respond very well to treatment and their recovery time is pretty quick.

Dog on treatment

Depending on the causes mentioned above, the treatment consists of:

  • Fluid therapy for dehydration.
  • Electrolyte therapy for electrolyte imbalance.
  • Antibiotics for infections.
  • Corticosteroids for hypovolemic shock.
  • Anti-inflammatory drugs for swollen intestines.
  • Anti-parasitic drugs for parasites.
  • Surgery for physical obstructions, ulcers and tumors.

That being said, in the future you should always take care of your dog’s diet to prevent other intestinal infections and disorders from happening. Reduce dietary irritants, like protein, and make sure to follow your doctor’s advice when it comes to allergenic foods. Moreover, your vet can make a sound diet plan for your dog’s nutritional needs taking into account the illnesses he’s had and the ones he’s prone to.

About the author
Wyatt Robinson
Wyatt Robinson

Wyatt Robinson had a great 25-years career as a veterinarian in United Kingdom. He used to be a member of British Veterinary Association and worked in 3 pet hospitals in London and Manchester. He is shining when he sees his pets healthy and full of energy and it is his duty to help other dog owners to keep their best friends full of life.