All About the Colon

Where is the colon and what does it do?

The large intestine is another name for the colon and the rectum—the two portions of your gastrointestinal tract responsible for the final stages of the body’s processing of food.

The food you eat travels through the esophagus to the stomach to the small bowel. It moves on into the large intestine, traveling through the colon and then, finally, the rectum.

By the time your food reaches the large intestine, all vitamins and most nutrients have been removed to support your body’s activity. What remains is mostly liquid which the colon absorbs.

The colon passes on the material that is still left after all the processing as waste that remains in the rectum for storage and eventual evacuation.
 

Colon Cancer

What’s the difference between colon cancer and colorectal cancer?

Cancer that begins in the colon is called colon cancer, and cancer that begins in the rectum is called rectal cancer.

Although cancer can develop in either the colon or the rectum or both, cancers in the large intestine are very similar in biology. Appearance and treatments are largely the same. Cancer in the colon is more common than cancer in the rectum.

Having a Colonoscopy

What happens when I have a colonoscopy?

In a colonoscopy procedure, a doctor inserts a flexible, slender steerable tube called a colonoscope into your rectum and slowly moves it up through the colon. The tube carries a light and a camera to allow the doctor to see the interior of your colon in great detail. The tube has a channel through which tools can be advanced to remove any polyps that may be found. The standard sedation that accompanies colonoscopy, sometimes called twilight sleep, makes the procedure itself something you usually will not feel or remember at all.

Chemotherapy and Colon Cancer

Is chemotherapy used to treat colon cancer?

Chemotherapy is typically not used for the earliest stages of colon cancer. In some high-risk early cancers (stage II), chemotherapy may be used after discussion with the medical oncologists. It is routinely used for Stage III and Stage IV cancers. Advanced disease can now be managed for many years with chemotherapy that still allows a full and productive life.

Learn more about how chemotherapy.

How is a particular chemotherapy treatment selected?

When selecting chemotherapy, doctors consider the stage of disease, a patient’s general state of health and other health problems. Choice of different chemotherapy regimens is based on evidence-based guidelines that are determined by results of clinical trials. At Stanford, doctors will use a tissue sample from the tumor of metastatic colon cancers to analyze its genome—the particular set of biochemical directions that order a tumor’s growth. Some tumors will have a genetic profile with particular molecular pathways that can be targeted with chemotherapy. Doctors are continuously learning new ways to combine chemotherapies with and without targeted therapies and new chemotherapies are emerging.

Learn more about treatment for colon cancer.

What kind of side effects can I expect from chemotherapy for colon cancer?

The side effects depend on the particular chemotherapy drug selected. These side effects may include fatigue, nausea and vomiting or loss of appetite. But, these symptoms are managed with medications that are more effective than those used in the past. Stanford doctors work with their patients with colon cancer to provide supportive care to reduce side effects.

Learn more about managing the side effects of cancer treatment.

Genetics and Colon Cancer

Is there a known genetic risk for colon cancer?

Hereditary risk for colon cancer is found in 10% to 20% of families where a member is diagnosed with colon cancer. One-third of those cases are related to very specific gene mutations. 

At Stanford, patients and their families will be seen at the Cancer Genetics Clinic for a detailed discussion of relevant family medical history. Not everyone who inherits such a genetic cancer risk will develop cancer.

Learn more about colon cancer genetic risk.