Intestinal Cancer (Adenocarcinoma) in Dogs

3 min read

Adenocarcinoma of the Stomach, Intestine, or Rectum in Dogs

Adenocarcinoma is a malignant tumor originating in the glandular and epithelial tissue (the lining of the internal organs). This type of malignant tumor growth can take place in many parts of the body, including the gastrointestinal system of dogs. It may invade any part of the gastrointestinal system, including the stomach, the small and large intestine, and rectum. It commonly affects older dogs, usually more than six years of age. No particular breed is known to be predisposed and it is more common in male dogs than females. This type of cancer usually has a poor prognosis.

Symptoms and Types

Symptoms are most commonly related to the gastrointestinal system and include:

  • Vomiting
  • Weight loss
  • Poor appetite
  • Abdominal pain
  • Hematemesis (vomiting of blood)
  • Melena (black colored feces due to hemorrhage in gastrointestinal system)
  • Bright red blood in feces
  • Tenesmus (urgent but ineffective defecation)


  • The exact cause is still unknown
  • Genetic cause is suspected in Belgian shepherds


You will need to provide a thorough history of your dog’s health leading up to the onset of symptoms. Your veterinarian will perform a complete physical examination on your dog, with blood tests, fecal tests and a biochemistry profile. The blood tests usually show mild to severe anemia, which is mainly due to gradual blood loss through the feces. Feces samples will also be observed under microscope to examine for the presence of hidden blood that is not visible grossly. Contrast radiography (using an injected contrast chemical agent to view the internal organs) may reveal the presence, location, and size of the neoplasm. Ultrasound is also a valuable tool in the diagnosis of adenocarcinoma of the gastrointestinal tract. Using ultrasound, your veterinarian may take a sample from the intestines or stomach, using a needle, to look for the presence of neoplastic cells in the sample fluid. An endoscope, a tubular diagnostic viewing tool that is inserted into the body, may also be used to collect a sample biopsy. If none of the above-mentioned procedures works well in confirming a diagnosis, your veterinarian may decide to perform surgery, which will ultimately establish the diagnosis.

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