Colon cancer also known as colorectal cancer, is a type of cancer that occurs in the large intestine (colon) or rectum (area just inside the anus).

It’s the third most common cancer in both men and women, according to the National Cancer Institute (NCI).

Knowing the symptoms of colon cancer, and getting screened for it, can help you receive early treatment and improve your chances of survival.

Signs and Symptoms of Colon Cancer

Colon cancer may cause one or more of the following symptoms:

• Pain and tenderness in the lower abdomen
• Bloody stool
• Unexplained weight loss
• Rectal bleeding
• Diarrhea, constipation, or other changes in bowel habits that last for more than a few days
• Weakness and fatigue
• Vomiting
• Frequent gas, bloating, cramps, or other digestive issues
• A feeling of needing to have a bowel movement that doesn’t go away

Colon Cancer Diagnosis

To find out if you have colon cancer, your doctor will begin by getting your medical and family history to see if you have any symptoms or risk factors for the disease.

Your doctor will also perform a physical exam, most likely including a digital rectal exam, in which a gloved, lubricated finger is inserted into the rectum to feel for anything unusual.

Your doctor may also run tests on your stool to detect occult blood (blood that isn’t visible to the naked eye), and to test your blood for anemia and iron deficiency.

If these preliminary examinations suggest colon cancer, your doctor may refer you to a gastroenterologist who can perform a colonoscopy.

In this procedure, a colonoscope — a type of endoscope with a light and small camera attached to it — will be inserted first into your rectum and then into the rest of your colon.

If your doctor finds a small polyp — an abnormal growth that can become cancerous — it can be removed by passing a wire loop through the colonoscope and cutting off the polyp with an electric current.

If instead your doctor finds a large polyp or what appears to be a tumor, it may be best to perform a biopsy,  in which a tissue sample is taken (again through the colonoscope) to inspect under a microscope for signs of cancer.

CT scan of the colon, or a double-contrast barium enema (a series of  X-rays  taken after the colon has been coated with a barium solution using a tube inserted through the rectum), may also help reveal polyps and tumors.

If these tests reveal cancer, your doctor may perform additional imaging tests — including ultrasounds , larger CT scans, and  MRI scans  — to see how far your cancer has spread.

Colon Cancer Stages

Colon cancer is “staged” depending on how far it has spread.

The higher the stage, the more advanced the cancer is and the further it has spread.

Colon cancer in Stage 0 is confined to the innermost layer (the lining) of the intestine.

In Stage I colon cancer, the disease has spread to the space between the lining and the muscle layer of the colon, which contains nerves and blood and lymph vessels.

In Stage II colon cancer, the cancer has spread to the muscle layer and outer layer of the colon, but has not yet spread beyond the colon.

In Stage III colon cancer, the cancer has spread beyond the colon and to the nearby lymph nodes.

In the final stage of colon cancer, Stage IV, the disease has made its way to other organs, such as the liver or lungs.