Gastrointestinal (GI) Neoplasia in Dogs

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:

Diagnosis of Gastrointestinal Neoplasia in Dogs

Your veterinarian may recommend the following diagnostic tests:

Treatment of Gastrointestinal Neoplasia in Dogs

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:

Gastric and Small Intestinal Neoplasia

Adenocarcinoma is the most common gastric and small intestinal tumor of dogs. In general, the most common tumors seen in the stomach and small intestines of dogs are adenocarcinoma, lymphosarcoma, leiomyosarcoma, leiomyomas, fibrosarcoma, squamous cell carcinoma, plasmacytoma, and mast cell tumors.

Many diseases/disorders cause similar clinical signs to patients with gastric and small intestinal neoplasia such as vomiting (with or without blood), diarrhea, melena (dark, tarry feces), inappetence and weight loss, and should be considered and differentiated.

Large Intestinal and Rectal Neoplasia

Adenocarcinoma is the most common tumor of the colon in dogs. The most common tumors of the colon/rectum in general are adenocarcinoma, lymphosarcoma and plasmacytoma. There are many diseases/disorders that cause similar clinical signs to patients with large intestinal and rectal neoplasia including tenesmus (straining to defecate) and hematochezia (blood in the stool), and should be considered and differentiated.

Colonic/rectal disorders include:

Perineal/perianal (around the anus) disorders include:

Miscellaneous Disorders

In-depth Information on Diagnosis

A diagnosis of gastrointestinal neoplasia in dogs can be made more easily in some cases than in others. A full diagnostic work up is recommended. A definitive diagnosis can only be made with the evaluation of tissue; therefore, a biopsy is necessary for a bottom line diagnosis of GI neoplasia and specific tumor type.

Your veterinarian may recommend additional tests to insure optimal medical care. These are selected on a case-by-case basis.

In-depth Information on Therapy

Treatment of gastrointestinal neoplasia in dogs largely depends on surgical excision. If complete excision of the primary tumor is impossible, or metastasis has occurred, other therapy can be attempted. These treatments may reduce severity of symptoms or provide relief for your pet.