Bloody diarrhea in dogs is a temporary or chronic ailment that usually indicates an underlying health issue. There are many potential causes of bloody diarrhea, including infections, cancer, ulcers, and stress. A veterinarian will diagnose bloody diarrhea by examining the dog and running tests to determine the underlying cause. Treatment depends on the reason for bloody diarrhea and may involve medication or surgery. Here's what you need to know about bloody diarrhea in dogs, including when it's time to contact a vet.

What Is Bloody Diarrhea?

Bloody diarrhea is a mixture of loose, watery stool and blood. Sometimes, mucus is seen in the stool as well. The presence of blood in the stool means that the dog is bleeding somewhere in the gastrointestinal tract. This blood can enter the stool at any point in the digestive process, beginning in the mouth and ending at the anus. The color and appearance of the stool can offer clues as to where the bleeding originated.

Hematochezia

Hematochezia is the medical term for red blood in the stool. It typically looks streaky and red if the stool is formed, but may be a bright red or reddish-brown liquid if the dog also has diarrhea. Red blood in stool usually means the bleeding is happening in the lower gastrointestinal tract, most likely the colon or anus.

Melena

The term melena describes black, tarry stool. Digestion causes the blood to appear black and points to bleeding in a location in the upper GI tract, such as the stomach. Stools are often pitch-black and have a gooey consistency. Some dogs with melena will also vomit blood (hematemesis), which may resemble coffee grounds.

Other symptoms may accompany your dog's bloody diarrhea depending on the condition causing diarrhea. Potential signs include:

• Vomiting
• Lethargy
• Loss of appetite
  
• Pale gums
• Straining to defecate (tenesmus)
  

Causes of Bloody Diarrhea

Bloody diarrhea is typically caused by lesions in the stomach (gastritis) and/or inflammation in the small intestines (enteritis). This inflammation may result from an underlying health problem, such as a disease, infection, or gastrointestinal injury. Any inflammatory condition affecting the bowels can cause bloody diarrhea. Some of the more common causes of bloody diarrhea in dogs include:

Stress

Stress can cause a dog's bowels to leak excess fluid and blood from inflammation. This is often called stress colitis and may be accompanied by ulcers.

Intestinal Parasites

Worms and protozoa, such as hookworms and Giardia, can cause bloody diarrhea. Parasites often feed off the host's blood or food and irritate the intestinal wall.

Bacterial and Viral Infections

Infections like Salmonella, E. coli, and parvovirus, can cause bloody diarrhea. Some infections are contagious and spread by other dogs while others come from eating spoiled food or dead animals. A condition called acute hemorrhagic diarrhea syndrome is often associated with bacteria.

Trauma

If a dog becomes injured or has surgery in the digestive tract, this can lead to bloody diarrhea. In addition, bloody diarrhea may also occur when a dog eats an undigestible object and it becomes stuck in the digestive tract.

Toxins

Ingestion of poisons or toxic human food may create inflammation and bleeding, leading to bloody diarrhea.

Anal Gland Problems

Anal glands are located at the sides of the anus, and if they become infected, impacted, or inflamed, blood may be present in the stool. Anytime a dog strains to defecate it could burst small blood vessels around the rectal area.

Organ Disease

When vital organs are impaired, it may lead to bloody diarrhea. The pancreas plays a vital role in digestion, and bloody diarrhea may result if it becomes inflamed (pancreatitis) or doesn't work correctly. Severe liver disease and kidney disease may also cause problems that lead to bloody diarrhea.

Cancer

Many kinds of cancer can affect the digestive tract and cause bloody diarrhea. Tumors in the GI tract may rupture and bleed. Cancer elsewhere in the body can cause inflammation that leads to bloody diarrhea.

Blood Clotting Disorders

Dogs with blood clotting disorders, such as Von Willebrand disease, are prone to bleeding in various parts of the body. If this bleeding occurs in the GI tract, it may lead to blood in the stool.

Medications

Some prescription medications can cause ulcers and erosion to occur in the gastrointestinal tract, including NSAIDs like carprofen. Give these medications with food to prevent irritation, but stop the meds and call the vet if diarrhea develops (bloody or not).

What to Do If Your Dog Has Bloody Diarrhea

Contact your veterinarian if you notice blood in your dog's stool. While a small amount of blood in otherwise normal stool may be of no concern, it's always best to make sure. And if there's diarrhea along with the blood, your dog will need some relief as soon as possible.

A vet will diagnose bloody diarrhea by examining your dog and analyzing their stool. Depending on the signs present and the exam findings, your vet may recommend additional tests, including blood work, urinalysis, X-rays, ultrasounds, and tissue biopsies.

Treatment & Prevention

The treatment plan for your dog's bloody diarrhea will vary widely depending on the cause and severity:

• Your vet may prescribe medications to ease the diarrhea and/or treat the underlying cause, such as probiotics, prescription diets, and anti-diarrheal drugs.
• Surgical intervention may be required if a tumor or foreign object obstruction is causing the bloody stool.
• Fluids and blood transfusions are sometimes necessary for dehydrated or anemic dogs.
• You may need to change your dog's diet to reduce inflammation or alter fiber intake.

You can't always prevent illnesses from happening, but there are ways to reduce the risk:

• Make food transitions slowly when switching to a new diet
• Keep foreign objects and toxins out of reach
• Monitor stress levels
• Use intestinal parasite prevention
• Visit the vet for regular check-ups
  

Generally, bloody diarrhea is highly treatable, but the prognosis varies based on the cause of the illness. Once your dog's underlying health issue has been treated effectively, you must allow their inflamed intestines to rest and heal. Be sure to follow up with your vet as recommended and report any changes right away.