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Colon cancer

Diagnosis of colon cancer

A colon cancer diagnosis typically happens when the doctor notices signs during an annual exam or screening appointment, or when patients notice an unusual symptom.

If you have symptoms of colon cancer, your doctor may use one or more of these standard tests:

  • Stool tests, which analyze your stool to check for blood or other signs of cancer in your digestive system.
  • Blood tests, which examine your blood for elevated liver enzymes and the presence of tumor markers. False-positive and false-negative blood tests are possible, so blood testing alone isn’t typically used to diagnose colon cancer. Your doctor may use it to rule out other conditions or monitor the progression of cancer that’s already been diagnosed.
  • Colonoscopy, a procedure to examine the colon with a colonoscope, a thin tube with a camera at the end. A colonoscopy allows your doctor to visually inspect the inner lining of your colon to check for polyps or possible cancerous growths. During a colonoscopy, your doctor may also take a tissue sample (biopsy) for later analysis, or remove polyps using instruments inserted through the colonoscope.
  • Proctoscopy, a similar procedure to a colonoscopy, in which your doctor will look at the tissue lining the rectum to check for cancerous growths.
  • Imaging tests, including ultrasound, MRI, x-ray, angiography, CT/CAT scans, and PET scans. Imaging tests are also commonly used to see whether cancer is spreading or if treatment is working. The type of scan you receive will depend on why your doctor is using the test.


Treatment for colon cancer includes both systemic treatments such as chemotherapy, which act throughout the body, and localized therapies such as surgery, which target cancer cells where they are growing directly.

The type of treatment you receive for colon cancer will vary depending on cancer stage and how big it has grown. No matter what the stage of colon cancer, surgery is the most common treatment. The extent of surgery will depend upon the stage.

Many early-stage cancers can be removed during a colonoscopy, a minimally invasive procedure that uses a long flexible tube inserted through the rectum and into the colon.

Partial or complete removal of the colon (called a colectomy) is also a common surgical treatment for colon cancer. During this procedure, the surgeon will make an incision through the abdomen and remove the colon, or use a laparoscope and several tiny incisions to remove the colon less invasively. In some cases, the lymph nodes surrounding the colon will also be removed to make sure that any cancer cells which have spread beyond the colon are removed.

If the colon cancer has caused a blockage, your doctor may perform a stent placement procedure to relieve the obstruction until a more complete surgery can occur.

Your doctor may also recommend these treatment options:

  • Radiation
  • Chemotherapy
  • Targeted therapy


Before a colonoscopy or colon surgery of any kind, you will need to prepare by emptying your colon. This typically means eating a specific diet determined by your doctor, drinking a lot of water, taking laxatives, and potentially using enemas to make sure your colon is clean and empty before surgery.


Current treatments for colon cancer are more effective than ever, and thanks to regular screenings, colon cancer is becoming an increasingly survivable cancer. For those diagnosed when colon cancer is in an early stage, the 5-year survival rate is above 90 percent.

Treatments for colon cancer are also becoming more advanced and successful. Today, more than 1 million Americans are colon cancer survivors.

After you’ve been treated for colon cancer, you may need to undergo more frequent screenings for a while to ensure that you have not developed any complications from surgery and that cancer does not return. Your doctor will advise you about what type of follow-up screenings are needed.

After colon cancer, some people need a colostomy (or ileostomy). This is when the colon is diverted through a hole in the abdomen or “stoma.” Stool is then collected in a bag called an ostomy bag. Most colostomy procedures are temporary, but in rare cases, they may be permanent. Getting used to this change can take some time and adjustment, but your doctor can help support you in learning how to manage it.

Dignity Health provides comprehensive and individualized colon cancer treatment as part of our oncology services.

The information contained in this article is meant for educational purposes only and should not replace advice from your healthcare provider.