Black, Tarry Feces Due to Presence of Blood in Dogs

Melena in Dogs

The term melena is used to describe a black, tarry appearing feces, which occurs due to the presence of digested blood in the intestines, or to internal bleeding that has passed into the intestine.

Melena is typically seen due to bleeding in the upper portion of the gastrointestinal tract. It has also been seen in dogs after they have ingested a sufficient amount of blood from the oral cavity or respiratory tract. It is not a disease in itself but a symptom of some other underlying disease. The dark color of the blood is due to the oxidation of iron in the hemoglobin (the oxygen carrying pigment of red blood cells) as it passes through the small intestine and colon.

Symptoms and Types

The symptoms relate to the underlying cause and location of bleeding.

  • In patients with gastrointestinal bleeding:
    • Vomit containing blood
    • Lack of appetite
    • Weight loss
    • Weakness
    • Pale mucous membranes
    • Anemia
  • In patients with bleeding in respiratory tract:
    • Nose bleed
    • Sneezing
    • Coughing up blood
    • Pale mucous membranes
    • Anemia
    • Weakness
    • Difficult breathing
  • In patients with abnormal blood clotting disorders
    • Nose bleed
    • Blood in urine
    • Blood in eye (hyphema)
    • Anemia
    • Pale mucous membranes
    • Weakness


  • Ulcers in the gastrointestinal system
  • Tumors of the esophagus or stomach
  • Infections
  • Foreign body in the gastrointestinal system
  • Disorders involving inflammation of the intestinal system
  • Kidney failure
  • Drug toxicity (e.g., anticoagulant drugs)
  • Diet containing raw food
  • Pneumonia
  • Trauma
  • Disorders involving abnormal clotting of blood


You will need to give a thorough history of your dog's health, onset of symptoms, and possible incidents that might have led to this condition. The history you provide may give your veterinarian clues as to where the blood is originating from. After taking a complete history, your pet’s veterinarian will conduct a complete physical examination. Standard laboratory tests include a complete blood count (CBC), biochemistry profile, and urinalysis. The results of these tests will depend upon the underlying cause of the problem.

Blood testing may reveal anemia with smaller (microcytic) and paler than normal (hypochromic) red blood cells. In cases with chronic blood loss the anemia is usually nonregenerative, meaning the bone marrow does not respond in a normal way to the body's increased demand for red blood cells. In acute cases the anemia is mostly regenerative, as the bone marrow responds normally to the body's increased demands by supplying new red blood cells.

Other abnormalities may include a decreased number of platelets (the cells responsible for blood clotting), an increased number of a type of white blood cells called neutrophils (neutrophilia), and a decrease in the number of both red blood cells and white blood cells. A biochemistry profile may reveal changes related to a diseased state other than intestinal causes of melena, including those of the kidney and liver. The urinalysis may reveal blood in the urine, which is commonly seen in patients with blood clotting defects.

Abdominal x-rays will be taken to look for any masses, foreign bodies that may have been swallowed, and abnormalities in the size and shape of the kidneys and/or liver. Thoracic (chest) x-rays will help in identifying lesions of the lungs and esophagus, also a relatively common underlying cause for melena.

Ultrasounds are also used for internal imaging, and will often return more detailed images of the abdominal cavity and gastrointestinal tract. Ultrasound may reveal masses, liver disease, inflammation of the pancreas, or kidney disease. Another diagnostic tool that your veterinarian is likely to use is an endoscope, a flexible tube that is threaded down into the stomach through the esophagus for direct visualization of masses and/or ulcers in the esophagus, stomach, and/or intestines. Endoscopy also helps in taking biopsy samples for tissue analysis and removing the foreign body, if there is one present.

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