Signs & Symptoms of Colon Cancer in Dogs

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Your vet can identify types of colon cancer by taking small samples with a needle.
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Changes in weight, appetite and energy levels are all potential signs of colon cancer in your dog. Diarrhea, constipation and vomiting also indicate that something is wrong with your pet's digestive system. The thought of colon cancer is certainly a frightening prospect, but keep in mind there are many noncancerous causes of these symptoms. Always consider these warning signs seriously and take your dog to the vet for a medical evaluation.


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Types of Colon Tumors

There are several types of tumors that can appear in your dog's digestive tract. While many cases of intestinal cancer in canines are malignant, it is also possible for the tumors to be benign and have little risk of spreading. Adenocarcinoma and lymphoma are malignant tumors that make up nearly half of reported cases of colon cancer, according to the National Canine Cancer Foundation. Dogs can develop smaller benign growths, polyps or adenomas, in the membrane at the end of the colon near the rectum. Even benign cancers can pose a deadly risk to your pet if their size or number obstructs normal digestive function.


Prevalence and Risk Factors

Intestinal tumors affect less than 10 percent of dogs, so chances are you won't have to worry about colon cancer in your pup. This type of cancer is most common in adult male dogs, although it can affect dogs of any gender or age. Collies and German shepherds are thought to have a genetic predisposition to adenocarcinoma and other colon cancers compared to the average, according to University of Pennsylvania's Ryan Hospital in Philadelphia.


Warning Signs

Colon cancer is difficult to diagnose at home, because the early symptoms are similar to a range of gastrointestinal disorders. Affected dogs tend to suffer from diminished appetite, which results in weight loss and lethargy from lower blood sugar levels. Vomiting, frequent diarrhea and other severe digestive symptoms emerge as the cancer grows or spreads. Changes in stool composition or color should raise a warning flag immediately, as cancer can cause internal blood loss and other life-threatening issues in your pet. Contact your veterinarian immediately if you notice any of these symptoms.


Clinical Diagnosis

If your vet believes colon cancer may be the root of your pet's health issues, he will conduct a physical exam and laboratory tests to reach a definitive diagnosis. Manual palpation or probing of the stomach is a common first step, followed by a rectal examination. Your vet may take blood samples to look for changes in internal chemistry, which can help him find the location and type of cancer. High levels of calcium in the blood is a sign of lymphoma, while lesions of the colon may reduce the amount of protein present. Your vet may conduct radiography or an ultrasound to take images of your dog's colon and small intestine.


Treatment and Prognosis

Lymphoma and other malignant colon cancers have the potential to spread to your dog's lymph system, lungs and other internal organs. In cases where the cancer has spread, chemotherapy may be the only viable choice for treatment. Surgery can remove isolated growths in the intestines, although the size and aggressiveness of the tumors impact the success rate. Dogs who survive surgical treatment for some colon cancers, such as leiomyosarcoma and colorectal lesions, have a good shot at recovery. Unfortunately, pups with metastatic tumors usually succumb to the cancer within a few months. Even if curing the disease is not a viable option, there are medications that temporarily can ease your pet's discomfort and help restore his digestive function.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.