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Sigmoidoscopy is the visual examination of the inside of the rectum and sigmoid colon using a lighted, flexible fiberoptic endoscope. During a sigmoidoscopy, the last half of the colon, called the sigmoid colon, is examined.
A risk factor is anything that increases a person's chance of getting a disease such as cancer. Different cancers have different risk factors. For example, unprotected exposure to strong sunlight is a risk factor for skin cancer and smoking is a risk factor for cancers of the lungs, larynx, mouth, throat, esophagus, kidneys, bladder and several other organs. Researchers have identified several risk factors that increase a person's chance of developing colorectal cancer.
A family history of colorectal cancer: If you have relatives who have had colorectal cancer you have a higher risk for developing this disease. In about 5 to 10% of patients with colorectal cancer there is a known inherited genetic abnormality that causes the cancer. One abnormality is called familial adenomatous polyposis (FAP) and a second is called hereditary nonpolyposis colorectal cancer (HNPCC). These abnormalities are described below. No other clearly identified genetic abnormalities have been described.
Colorectal cancer is more often seen in families that do not have one of these syndromes. Accurate identification of people with these syndromes is important because their doctors will recommend specific measures to prevent cancer or find it as early as possible, when treatment is most successful. Some doctors recommend that all people with colorectal cancer have an evaluation of their family history of the disease. People with a family history suggesting a colorectal cancer syndrome should consider getting screened at an early age. The American Cancer Society and several other medical organizations recommend screening test schedules for people with increased colorectal cancer risk that differ from those generally recommended for people at average risk. For more information, speak with your doctor and/or refer to the table in the "Can Colorectal Cancer Be Found Early?" section of this document.
Familial colorectal cancer syndromes: The following conditions make it more likely that a family member could develop cancer. Familial adenomatous polyposis is a hereditary condition that greatly increases a person's risk of developing colorectal cancer. People with this syndrome typically develop hundreds of polyps in the colon and rectum. Cancer nearly always develops in one or more of these polyps between the ages of 30 and 50 if preventive surgery is not done. Familial adenomatous polyposis is sometimes associated with Gardener’s syndrome, a condition that has benign (not cancerous) tumors of the skin, soft connective tissue, and bones.
Hereditary nonpolyposis colon cancer is the other clearly defined genetic syndrome. This also develops in people at a relatively young age. Although these people also have polyps, they only have a few, not hundreds. Women with this condition also have an increased risk of developing cancer of the endometrium (lining of the upper part of the uterus). Doctors have found that there are certain characteristics of families that have this syndrome. These are that: 1) at least 3 relatives have colorectal cancer, 2) two successive generations are involved, 3) one of these had their cancer when they were younger than 50, and 4) at least two of the people are first-degree relatives. If this is true of your family, then you might want to seek genetic counseling.
Recent research has found an inherited tendency to develop colorectal cancer among some Jews of Eastern European descent. Like people with FAP, Gardner's syndrome, and HNPCC, their increased risk is due to an inherited mutation (change in DNA). This DNA change occurs much more commonly than the 3 other colorectal cancer syndromes, and is present in about 6% of American Jews. Additional research is needed to determine the extent to which this change increases risk. So far, there appears to be a relatively small increase in risk, much less than that caused by FAP, Gardner's syndrome, or HNPCC.
A personal history of colorectal cancer: If you have had colorectal cancer, even though it has been completely removed, you are more likely to develop new cancers in other areas of the colon and rectum.
A personal history of intestinal polyps: Some types of polyps (hyperplastic polyps and inflammatory polyps) do not increase the risk of colorectal cancer. Other types, such as adenomatous polyps, do increase the risk of colorectal cancer, especially if they are large or there are many of them.
A personal history of chronic inflammatory bowel disease: Chronic inflammatory bowel disease (ulcerative colitis or Crohn's colitis) is a condition in which the colon is inflamed over a long period of time and may have ulcers in its lining. If you have chronic inflammatory bowel disease, your risk of developing colon cancer is increased. You should start being screened at a young age and it should be repeated frequently. Often the first sign that cancer may be developing is called dysplasia. Dysplasia means the cells lining your colon or rectum look as if they will turn into cancer.
Aging: Your chances of developing colorectal cancer increase markedly after age 50. About 90% of people found to have colorectal cancer are older than 50.
A diet mostly from animal sources: A diet that consists mostly of foods that are high in fat, especially from animal sources, can increase your risk of colorectal cancer. Instead, the American Cancer Society recommends choosing most of your foods from plant sources and limiting your intake of high-fat foods such as those from animal sources. The ACS also recommends eating at least five servings of fruits and vegetables every day and several servings of other foods from plant sources such as breads, cereals, grain products, rice, pasta, or beans. Many fruits and vegetables contain substances that interfere with the process of cancer formation.
Physical inactivity: If you are not at least moderately physically active, you have an increased risk of developing colorectal cancer.
Obesity: If you are very overweight your risk of developing colorectal cancer is increased. This is particularly true if your excess fat is in your waist area more than in your thighs or hips. Researchers suggest that the excess fat changes metabolism in a way that increases growth of cells in the colon and rectum, and that fat cells in the waist area have the largest impact on metabolism.
Smoking: Recent studies indicate that smokers are 30% to 40% more likely than nonsmokers to die of colorectal cancer. Smoking may be responsible for causing about 12% of fatal colorectal cancers. Almost everyone knows that smoking causes cancers in sites in the body that come in direct contact with the smoke, such as the mouth, larynx, and lungs. However, some of the cancer-causing substances are swallowed and can cause digestive system cancers, such as esophageal and colorectal cancer. Some of these substances are also absorbed into the bloodstream and can increase the risk of developing cancers of the kidneys, bladder, cervix, and other organs.
While we do not know the exact cause of most colorectal cancers, there are certain known risk factors, and there is a great deal of ongoing research into the question.
Aging, family history, poor diet, and physical inactivity are some of the risk factors.
About 5%-10% of colorectal cancers are caused by inherited gene mutations (changes in DNA). Recently, scientists have discovered many of these DNA changes, learned how they change growth control of cells and how the changes can be detected in people before colorectal cancers develop.
Changes in a gene called APC are responsible for familial adenomatous polyposis (FAP) and Gardner's syndrome. People with these conditions have a change in this gene, which is normally responsible for retarding the growth of cells. Because this "brake" on cell growth is turned off, hundreds of polyps develop in the colon. Over time, cancer will nearly always develop in one or more of these polyps because of new gene mutations in the cells of the polyps. These new gene mutations occur in all of us. They rarely lead to cancer because the cells die instead of continuing to grow as they do when the APC "brake" is turned off.
A defective DNA repair mechanism is responsible for hereditary nonpolyposis colon cancer (HNPCC). Cells must make a new copy of their DNA each time they divide. Occasional errors are made in copying the DNA code. Fortunately, cells have DNA repair enzymes that act like proofreaders or "spell checkers". Mutations in certain DNA repair enzyme genes allow DNA errors to go uncorrected. These errors will sometimes affect growth-regulating genes, which can lead to the development of cancer.
Tests are available that can detect gene mutations associated with FAP and HNPCC. If you have a family history of colorectal cancer you should ask your doctor about genetic counseling and genetic testing. The ACS recommends discussing the benefits and drawbacks of genetic testing with a qualified physician or genetic counselor before any genetic testing is done. Genetic counseling with a qualified person should always precede the testing.
Even though the exact cause of most colorectal cancer is not known, it is possible to prevent many colon cancers. Following screening guidelines can lower the number of cases of the disease by detecting and removing polyps that could become cancerous, and can also lower the death rate from colorectal cancer by finding disease early when it is highly curable.
Following the American Cancer Society screening guidelines listed under "Can Colorectal Cancer Be Found Early?" can thus greatly reduce the risk of getting or dying from colorectal cancer. Prevention and early detection are possible because most colon cancers develop from adenomatous polyps. Polyps are precancerous growths in the colon and rectum. Removing them can lower a person's risk by preventing some colorectal cancers before they are fully formed.
People can lower their risk of developing colorectal cancer by managing the risk factors that they can control, such as diet and physical activity. It is important to eat plenty of fruits, vegetables, and whole grain foods and to limit intake of high-fat foods. Physical activity is another area that people can control. Even small amounts of exercise on a regular basis can be helpful. The American Cancer Society recommends at least 30 minutes of physical activity on most days. Also, achieve and maintain a healthy weight. For more information about diet and physical activity, refer to our document "American Cancer Society Guidelines for Nutrition and Cancer Prevention."
Some studies suggest that taking a daily multivitamin containing folic acid or folate can lower colorectal cancer risk. Other studies suggest that increasing calcium intake via supplements or low-fat dairy products may lower risk. Studies of vitamin A, C, D, and E supplements have yielded conflicting results, and additional research is needed.
Approximately 20 epidemiologic studies have found that people who regularly use aspirin and other non-steroidal antiinflammatory drugs (NSAIDs [Advil, Aleve]) have 40% to 50% lower risk of colorectal cancer and adenomatous polyps. However, no randomized trials have yet proven that aspirin-like drugs cause this reduction. Furthermore, researchers have not yet defined the dose of NSAIDs or who should receive them. For these reasons, NSAIDs are not routinely recommended for lowering colorectal cancer risk in the general population. However, the value of these drugs for people at increased colorectal cancer risk is being actively studied. Celecoxib, (Celebrex), has recently been approved by the FDA for reducing polyp formation in people with familial adenomatous polyposis. The advantage of this drug and another drug called rofecoxib (Vioxx) is they do not cause bleeding from the stomach, which is a common side effect of other NSAIDs.
Hormone replacement therapy (HRT) in post-menopausal women may slightly reduce their risk of colorectal cancer. HRT lowers the risk of developing osteoporosis in post-menopausal women but may increase breast and uterine cancer risk. The overall health effect of HRT is a positive one for most women but the decision to take estrogen should be based on discussion of benefits and risks with a physician.
There are other risk factors, such as a strong family history of colorectal cancer, which people cannot control. Even when people have a history of colorectal cancer in their family, they may be able to prevent the disease. They should ask their doctors for information and advice about prevention and early detection. For example, people with a family history of colorectal cancer may benefit from starting screening at a younger age and having screening tests done more often than people without this risk factor.
Genetic tests can help determine which members of certain families have inherited a high risk for developing colorectal cancer. Most doctors recommend that people with familial adenomatous polyposis (FAP) start colonoscopy during their teens and have their colon removed during their twenties to prevent cancer from developing.
The risk for people with hereditary nonpolyposis colon cancer (HNPCC) is not as great as for those with FAP. Doctors recommend that people with HNPCC start colonoscopy during their twenties to remove any polyps and find any cancers at the earliest possible stage. But, preventive removal of the colon is not usually suggested for HNPCC.
Ashkenazi Jews with the I1307K APC mutation have a slightly increased colorectal cancer risk, but do not develop these cancers at a very young age. For these reasons, most doctors recommend carefully following the usual recommendations for colorectal cancer screening, but earlier or more frequent testing is usually not suggested.
Since some colorectal cancers can't be prevented, finding them early is the best way to improve the chance of a cure and reduce the number of deaths caused by this disease.
from the American Cancer Society, Cancer Resource Center
- The day prior to the exam, have:
- A regular breakfast.
- A light lunch
- Clear liquid supper (clear soup, plain gelatin, non-pulpy unsweetened juice, sugar-free sodas, black coffee, no cream)
- Please have nothing to eat or drink the morning of the exam
- Approximately 1 hour before the exam, use 2 Fleet’s enemas (use one and then repeat in 5 to 10 minutes).
- If not clear, you may fill the bottles with warm soapy water and repeat the procedure.
- If still not clear, inform the nurse. Following these procedures will result in fewer cancellations.
- If you have any questions, please call our offices.