Gastrointestinal (GI) Neoplasia in Dogs

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Overview of Canine Gastrointestinal Cancer

Gastrointestinal neoplasia is cancer located anywhere throughout the gastrointestinal (GI) tract, including the oral cavity (mouth), esophagus, stomach, small intestines, large intestines and rectum. GI cancer can be primary, which means it originates in the GI tract, or metastatic, which is spread from another site.

No specific causes of primary cancer have been identified, although it has been associated with several disorders. Chronic inflammation or irritation has been thought to be a contributing factor in some cases. Spirocerca lupi, a parasite of the esophagus, may cause associated cancer.

Cancer usually occurs in middle-aged to older dogs. Depending on the tumor type and location, different breeds, ages, and species can be affected. The Belgian shepherd and Scottish terrier have a higher incidence of gastric carcinoma than other breeds. Collies are also more likely to develop malignant intestinal cancer.

What to Watch For

With gastrointestinal cancer, clinical signs are largely dependent on the location of the cancer, size of the mass, and to a degree, the specific type of cancer. General signs to watch for by location include:

  • Oral. Watch for halitosis (bad breath), bleeding from the mouth, difficulty eating and drooling.
  • Esophageal. Watch for regurgitation, excessive salivation and weight loss.
  • Gastric (stomach). Watch for vomiting (with or without blood), weight loss, inappetence and black tarry feces.
  • Small intestinal. Watch for diarrhea, vomiting, weight loss, anorexia, black, tarry feces and gas.
  • Colonic (large intestinal). Watch for diarrhea (with mucus or blood) and straining to defecate.
  • Rectal. Watch for straining and blood in stool.
  • Diagnosis of Gastrointestinal Neoplasia in Dogs

    Your veterinarian may recommend the following diagnostic tests:

  • Baseline tests to include a complete blood count (CBC), biochemical profile and urinalysis
  • Fecal examination
  • Abdominal radiographs (x-rays)
  • Thoracic (chest) radiographs
  • Abdominal ultrasound
  • Upper gastrointestinal contrast radiography (dye study)
  • Endoscopy of the upper and/or lower bowel and biopsy
  • Abdominal exploratory and biopsy
  • Treatment of Gastrointestinal Neoplasia in Dogs

  • Hospitalization and support as needed, such as fluid therapy or blood transfusions
  • Surgical resection (removal), which is the treatment of choice
  • Surgical debulking (removing as much as possible) to help improve clinical signs
  • Chemotherapy
  • Radiation therapy
  • Dietary manipulation
  • Home Care

    Administer medication and diet as directed by your veterinarian. Return for follow-up as directed by your veterinarian. If your pet has a recurrence of signs, contact your veterinarian at once.

    Prognosis varies depending on the location, size, type and ability to remove the tumor surgically.

    There is no known specific prevention of gastrointestinal cancer. Treat all underlying inflammatory disorders in their early stages if possible.

    In-depth Information on Gastrointestinal Neoplasia in Dogs

    Gastrointestinal (GI) neoplasia (cancer) occurs infrequently in dogs as compared to neoplasia involving other systems. Over two-thirds of GI neoplasms in dogs are malignant – they are aggressive, and often spread locally or to other areas. The most common types of gastrointestinal tumors include adenocarcinoma, lymphoma, leiomyosarcoma, leiomyoma, squamous cell carcinoma, fibrosarcoma, plasmacytoma, and mast cell tumors. In general, older animals are affected most commonly.

    The cause of GI neoplasia is rarely evident, and signs can be extremely variable from patient to patient as signs usually reflect the size, location, and type of tumor. Some patients may be relatively asymptomatic, while others may be in immediate need of intensive support and hospitalization, to include intravenous fluid therapy and blood transfusions. There are many diseases/disorders that cause similar clinical signs to patients with gastrointestinal neoplasia.

    Esophageal Neoplasia

    Esophageal cancer is the least common site for tumors in the GI tract. The most common tumors associated with the esophagus include squamous cell carcinoma, fibrosarcoma, and sarcoma (associated with the parasite Spirocerca lupi).

    Megaesophagus, which is a distended and/or poorly functional esophagus, and as the clinical signs seen with this condition (regurgitation, excessive salivation, and difficulty eating/swallowing) often mimic esophageal neoplasia, it needs to be considered and differentiated.

    There are many diseases associated with megaesophagus:

  • Intrathoracic masses/growths may put pressure on the esophagus from the outside, creating a blockage
  • Vascular ring anomaly is an entrapment of the esophagus within several structures, causing a partial megaesophagus
  • Neuromuscular diseases (nerve and muscle) including myasthenia gravis, polymyositis, systemic lupus erythematosus, polyradiculoneuritis, botulism, tetanus and dysautonomia
  • Central nervous system diseases including infectious, inflammatory, neoplastic (cancerous) and traumatic disorders
  • Miscellaneous disorders including endocrine diseases (hypothyroidism, hypoadrenocorticism), certain toxicities (lead, thallium, acetycholinesterase), and thymomas, which are tumors arising from an organ in the chest
  • Esophagitis is the inflammation of the esophagus and needs to be differentiated
  • Esophageal foreign body is an object within the esophagus and have symptoms similar to esophageal neoplasia
  • Esophageal stricture is an abnormal narrowing of the esophagus and should be ruled out
  • Esophageal diverticula are pouch-like dilatations of the esophageal wall and should be ruled out
  • Esophageal fistula is an abnormal communication between the esophagus and another structure
  • Hiatal hernia is an abnormality of the diaphragm allowing part of the stomach to be displaced into the chest cavity and needs to be ruled out
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