What is colonoscopy? Colonoscopy is a diagnostic test in which a physician uses an endoscope, a long, flexible fiber-optic tube, to visually examine the entire length of your colon and rectum. Usually, a colonoscopy procedure is performed to detect the presence of polyps or any other cancerous or precancerous tissue.
While there are other tests to screen for colorectal cancer, colonoscopy is considered the most effective because it allows your doctor access to the entire four-to-six-foot length of your colon for the most thorough examination possible. In addition, in the colonoscopy procedure, the doctor has the opportunity to take tissue samples for analysis and to remove any polyps that may be growing — an action called polypectomy — and thus eliminate the danger of cancer developing from them.
What is colorectal cancer?
Cancers are diseases caused by the out-of-control growth of cells in the body's tissues that invade and destroy the normal cells around them. They are named for the organs or systems of the body in which they first develop, and more than 100 types of cancer have been defined. As the name suggests, colorectal cancer originates in either the colon or rectum.
After food is eaten and begins to travel through your intestinal tract, it is broken down in the stomach, the small intestine (where most of the food's nutrients are absorbed) and the large intestine, a broad, four-to-six-foot long muscular tube that continues to absorb water and nutrients and that passes along waste to the rectum and anus for elimination from the body. Your colon is divided into four parts — progressively, the ascending colon, the transverse colon, the descending colon and the sigmoid colon. The rectum is the final six to eight inches of the large intestine, connecting the sigmoid colon to the anus, through which waste is excreted.
Why is colonoscopy important?
Colorectal cancer is the third most diagnosed cancer in the United States, and is the third leading cause (after lung cancer) of cancer-related deaths. In the course of a year, more than 150,000 people are diagnosed with colorectal cancer, and more than a third of them die of it.
Most colorectal cancer develops from polyps that grow in the colon. While not all polyps become cancerous, enough turn out to be cancerous, or precancerous, that detecting and removing them is an important action for preventing cancer and measuring your risk of it.
In addition to colorectal cancer, colonoscopy may be used to obtain information related to other conditions, such as gastroenteritis and colitis.
What are polyps?
Polyps are growths that develop on the inner walls of the colon and rectum. Your chance of experiencing them increases as you age; they're fairly common in people 50 or older.
Three important facts are that:
Some polyps will never become cancerous.
None are cancerous as they first develop.
Enough of them can become cancerous over a period of several years that doctors take them very seriously. Most colon cancers develop from polyps, so detecting them is an extremely important step in preventing colorectal cancer or detecting it early when it is treatable.
Polyps can develop anywhere throughout the length of your colon or rectum. They can be large or small, and mushroom-shaped or flat.
Two common types of polyps are:
Hyperplastic polyps, usually quite small and rarely a risk factor for colorectal cancer.
Adenomas, which have the potential to become cancerous. Your surgeon usually will remove these during colonoscopy or sigmoidoscopy procedures — two forms of endoscopic examination utilizing flexible fiber-optic tubes — to both eliminate the risk factor they represent and to have them analyzed by a pathologist for their cancerous or benign nature.
While family history and age are major factors in a propensity for polyp development, contributing factors are believed to be high fat diets, cigarette smoking, high alcohol consumption, lack of exercise and lack of dietary fiber.
In addition, individuals with a personal or family history of ulcerative colitis or other inflammatory bowel diseases may be at risk of developing polyps regardless of age.
What is endoscopy?
Endoscopy is the technique of using endoscopes — long flexible fiber-optic tubes that can be inserted through openings in your body — to visually examine internal areas. Traditional endoscopy involved instruments with which the physician directly observed the area being studied through an eyepiece, much like a flexible telescope. Today, endoscopes are as likely to utilize tiny video cameras connected to a computer that can record an image of the procedure, and to be guided by the image projected onto a video monitor.
The first uses of endoscopy involved inserting the scopes through natural openings such as the mouth, to examine the esophagus and stomach, and the anus, to examine the rectum and colon. Today, additionally, endoscopes are used in many minimally invasive surgical procedures for which the surgeon can create very small incisions, decreasing trauma on the body and shortening recovery time.
The use of colonoscopes to examine the rectum and colon continues to be an important endoscopic procedure. Whereas sigmoidoscopy inspects the rectum and the sigmoid colon — the first two feet or so of the colon (where 50 percent of polyps develop) — colonoscopy enables your physician to view the full four-to-six-foot length of your colon.
In addition to its channel for visualization, a colonoscope contains channels through which your physician can operate tiny instruments to remove polyps or to take tissue samples for analysis by a pathologist.
How is a colonoscopy procedure performed?
While the idea of a colonoscopy procedure may seem intimidating, it is performed under a mild sedative, and while you will be aware of the test, it is not especially uncomfortable. Many people find the preparation for the procedure, which involves fasting and cleaning the bowel of all solid matter through the use of laxatives, more bothersome than the test itself. For more information, see "Preparation Instructions" or (Click Here).
Before the procedure, you will first receive a mild sedative and perhaps a pain reliever. For the examination itself, you will lie on you left side with your knees drawn up. Your doctor will insert the colonoscope through your anus and gently maneuver it along your colon, using an image on the monitor as his guide (you may be able to watch it yourself, if you are so inclined). Air may be inserted through the endoscope to facilitate the visualization. Your physician may utilize suction through another channel to remove secretions. The video image can be operated to retain photographic images, if anything significant is observed.
The colonoscope will be guided all the way to the end of the colon, where it joins the small intestine. In actuality, your doctor will be doing the most careful examination during withdrawal of the colonoscope, since his or her visibility is better during withdrawal than insertion. If a suspicious lesion is detected, it can be removed with tiny forceps inserted through the additional channel. If a polyp is observed, it can be removed with a snare or electrocautery. Samples taken will be sent to a pathologist for biopsy. If necessary, surgery will be scheduled.
The procedure itself usually takes less than an hour. You will be asked to be at the endoscopy suite an hour to 2 hours before the procedure, and you will be held in the Recovery Room for at least an hour while the sedative wears off. For your safety, you will be required to have someone to drive you home; full recovery from the sedative can take a day.
What are the side effects, the risks and the follow-up to colonoscopy?
You may experience gas, or a bloated feeling, for a time after the procedure. If a biopsy sample was taken, you may observe a small amount of blood in your stool during bowel movements soon after the procedure. This is normal. If it continues, however, contact your physician.
As with any medical procedure, there are risks involved with colonoscopy, but they are very small. One risk is of bowel perforation, requiring surgery to repair it; it's estimated this may occur in two out of 1,000 procedures. Significant bleeding from a polyp-removal or biopsy site may occur in one out of 1,000 procedures. Infection is very rare, as instruments are thoroughly sterilized between procedures.
Follow-up will depend on your physician's findings from the examination. These could range from a need for surgery if a significant lesion was found, to a need for subsequent colonoscopies every few years if noncancerous polyps were found, to a clean bill of health, a recommendation for reexamination in five to seven years, or as directed by a surgeon.
For additional information about colorectal cancer
You can find additional information about colorectal cancer at web sites sponsored by government agencies, societies and healthcare institutions. It should perhaps be noted that the World Wide Web is open to many sources posting questionable information and promises, and you are encouraged to seek information from established, reputable organizations.
Likely sources include:
The National Cancer Institute www.cancer.gov
800-422-6237
TTY for hearing-impaired 1-800-332-8615
