Colorectal cancer is a term used to refer to cancer that develops in the colon or the rectum. These cancers are sometimes referred to separately as colon cancer or rectal cancer, depending on where they start. Colon cancer and rectal cancer have many features in common, which is why they are discussed together in this document.

The normal digestive system

The colon and rectum are parts of the digestive system, which is also called the gastrointestinal (GI) system. The first part of digestive system processes food for energy, while the last part (the colon and rectum) removes solid waste (fecal matter or stool) from the body.

In order to understand colorectal cancer, it helps to have some basic knowledge about the normal structure and function of the digestive system (see picture below).

After food is chewed and swallowed, it travels through the esophagus to the stomach. There it is partly broken down and then sent to the small intestine, also known as the small bowel. The word "small" refers to the diameter of the small intestine, which is narrower than that of the large bowel (colon and rectum). Actually the small intestine is the longest segment of the digestive system -- about 20 feet. The small intestine continues breaking down the food and absorbs most of the nutrients.

The small bowel joins the colon in the right lower abdomen. The colon (also called the large bowel or large intestine) is a muscular tube about 5 feet long. The colon absorbs water and salt from the food matter and serves as a storage place for waste matter.

The colon has 4 sections:

• The first section is called the ascending colon. It starts with a small pouch (the cecum) where the small bowel attaches to the colon and extends upward on the right side of the abdomen. The cecum is also where the appendix attaches to the colon.
• The second section is called the transverse colon since it goes across the body from the right to the left side in the upper abdomen.
• The third section, the descending colon, continues downward on the left side.
• The fourth and last section is known as the sigmoid colon because of its "S" or "sigmoid" shape.

The waste matter that is left after going through the colon is known as feces or stool. It goes into the rectum, the final 6 inches of the digestive system. From there it passes out of the body through the anus.

The wall of the colon and rectum is made up of several layers of tissue. Colorectal cancer starts in the innermost layer and can grow through some or all of the other layers. Knowing a little about these layers is important, because the stage (extent of spread) of a colorectal cancer depends to a great degree on how deeply it invades into these layers. The stage of a cancer helps determine treatment options and prognosis (outlook).

Abnormal growths in the colon or rectum

In most people, colorectal cancers develop slowly over a period of several years. Before a cancer develops, a growth of tissue or tumor usually begins as a non-cancerous polyp on the inner lining of the colon or rectum. A tumor is abnormal tissue and can be benign (not cancer) or malignant (cancer). A polyp is a benign, non-cancerous tumor. Some polyps can change into cancer, but not all do. The chance of changing into a cancer depends upon the kind of polyp:

• Adenomatous polyps (adenomas) are polyps that have the potential to change into cancer. Because of this, adenomas are called a pre-cancerous condition.
• Hyperplastic polyps and inflammatory polyps, in general, are not pre-cancerous. But some doctors think that some hyperplastic polyps can become pre-cancerous or might be a sign of having a greater risk of developing adenomas and cancer, particularly when these polyps grow in the ascending colon.

Another kind of pre-cancerous condition is called dysplasia. Dysplasia is an area in the lining of the colon or rectum where the cells look abnormal (but not like true cancer cells) when viewed under a microscope. These cells have the potential to change into cancer over time. This is usually seen in people who have had diseases such as ulcerative colitis or Crohns disease for many years. Both ulcerative colitis and Crohns disease cause chronic inflammation of the colon.

Start and spread of colorectal cancer

If cancer forms within a polyp, it can eventually begin to grow into the wall of the colon or rectum. When cancer cells are in the wall, they can then grow into blood vessels or lymph vessels. Lymph vessels are thin, tiny channels that carry away waste and fluid. They first drain into nearby lymph nodes, which are bean-shaped structures that help fight infections. Once cancer cells spread into blood or lymph vessels, they can travel to distant parts of the body, such as the liver. This process of spread is called metastasis.

Types of cancer in the colon and rectum

Adenocarcinomas: More than 95% of colorectal cancers are a type of cancer known as adenocarcinomas. These are cancers that start in cells that form glands that make mucus to lubricate the inside of the colon and rectum. When doctors speak of colorectal cancer, this is almost always what they are referring to.

Other, less common types of tumors may also develop in the colon and rectum. These include:

Carcinoid tumors: These tumors develop from specialized hormone-producing cells of the intestine. They are discussed in the separate American Cancer Society document, Gastrointestinal Carcinoid Tumors.

Gastrointestinal stromal tumors (GISTs): These tumors develop from specialized cells in the wall of the colon called the "interstitial cells of Cajal." Some are benign (non-cancerous); others are malignant (cancerous). Although these tumors can be found anywhere in the digestive tract, they are unusual in the colon. They are discussed in the separate American Cancer Society document, Gastrointestinal Stromal Tumors.

Lymphomas: These are cancers of immune system cells that typically develop in lymph nodes, but they may also start in the colon and rectum or other organs. Information on lymphomas of the digestive system is included in the separate American Cancer Society document, Non-Hodgkin Lymphoma.

The remainder of this document focuses only on colorectal adenocarcinomas.

Importance of colorectal cancer screening

Excluding skin cancers, colorectal cancer is the third most common cancer diagnosed in both men and women in the United States. The American Cancer Society estimates that about 108,070 new cases of colon cancer (53,760 in men and 54,310 in women) and 40,740 new cases of rectal cancer (23,490 in men and 17,250 in women) will be diagnosed in 2008.

Overall, the lifetime risk for developing colorectal cancer is about 1 in 19 (5.4%). This risk is slightly higher in men than in women. A number of other factors (described in the section, "Risk factors for colorectal cancer") may also affect a person's risk.

Colorectal cancer is the third leading cause of cancer-related deaths in the United States when men and women are considered seperately, and the second leading cause when both sexes are combined. It is expected to cause about 49,960 deaths (24,260 men and 25,700 women) during 2008.

The death rate (the number of deaths per 100,000 people per year) from colorectal cancer has been dropping for more than 20 years. There are a number of likely reasons for this. One is that polyps are being found by screening and removed before they can develop into cancers. Screening is also allowing more colorectal cancers to be found earlier, when the disease is easier to cure. In addition, treatment for colorectal cancer has improved over the last several years. As a result, there are now more than 1 million survivors of colorectal cancer in the United States.

One of the most powerful weapons in preventing colorectal cancer is regular colorectal cancer screening or testing. Regular colorectal cancer screening can, in many cases, prevent colorectal cancer altogether. This is because most colorectal cancers start as polyps, which are non-cancerous growths in the lining of the colon or rectum. From the time the first abnormal cells start to grow, it usually takes about 10 to 15 years for them to develop into colorectal cancer. Testing often finds these polyps, and allows them to be removed before they have the chance to turn into cancer. Screening can also result in finding colorectal cancer early, when it is highly curable.

There are several tests used to screen for colorectal cancer in those with an average risk of colorectal cancer. Ask your doctor which tests are available where you live and which option is best for you. People who have no identified risk factors (other than age) should begin regular screening at age 50. Those who have a family history or other risk factors for colorectal polyps or cancer (see below) should talk with their doctor about starting screening at a younger age and/or getting screened at more frequent intervals.

Risk factors for colorectal cancer

A risk factor is anything that affects your chance of getting a disease such as cancer. Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer, and smoking is a risk factor for cancers of the larynx, mouth, throat, esophagus, kidneys, bladder, colon, and several other organs.

But risk factors don't tell us everything. Having a risk factor, or even several risk factors, does not mean that you will get the disease. And some people who get the disease may not have any known risk factors. Even if a person with colorectal cancer has a risk factor, it is often very hard to know how much that risk factor may have contributed to the cancer.

Researchers have found several risk factors that may increase a person's chance of developing colorectal polyps or colorectal cancer.

Risk factors you cannot change

Age

While younger adults can develop colorectal cancer, the chances of developing colorectal cancer increase markedly after age 50. More than 90% of people diagnosed with colorectal cancer are older than 50.

Personal history of colorectal polyps or colorectal cancer

If you have a history of adenomatous polyps (adenomas), you are at increased risk of developing colorectal cancer. This is especially true if the polyps are large or if there are many of them.

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. The chances of this happening are greater if you had your first colorectal cancer when you were younger than age 60.

Personal history of inflammatory bowel disease

Inflammatory bowel disease (IBD), which includes ulcerative colitis and Crohn's disease, is a condition in which the colon is inflamed over a long period of time. If you have IBD, your risk of developing colorectal cancer is increased, and you need to be screened for colorectal cancer on a more frequent basis. Often the first sign that cancer may be developing is called dysplasia. Dysplasia is a term that refers to abnormal cells that have the potential to progress to cancer.

Inflammatory bowel disease is different from irritable bowel syndrome (IBS), which does not carry an increased risk for colorectal cancer.

Family history of colorectal cancer

Most colorectal cancers occur in people without a family history of colorectal cancer. Still, up to 20% of people who develop colorectal cancer have other family members who have been affected by this disease.

Those with a history of colorectal cancer or adenomatous polyps in one or more first-degree relatives (parents, siblings, children) are at increased risk. The risk is about doubled in those with a single affected first-degree relative, and is even higher in those with a stronger family history, such as:

• a history of colorectal cancer or adenomatous polyps in any first-degree relative (parent, sibling, or child) younger than age 60
• a history of colorectal cancer or adenomatous polyps in 2 or more first-degree relatives at any age

The reasons for the increased risk are not clear in all cases. Cancers can "run in the family" because of inherited genes, shared environmental factors, or some combination of these.

People diagnosed with adenomatous polyps or colorectal cancer should inform other family members. Those with a family history of colorectal cancer need to talk with their doctor about the possible need to begin screening before age 50.

Inherited syndromes

About 5% of people who develop colorectal cancer have an inherited genetic susceptibility to the disease. The 2 most common inherited syndromes linked with colorectal cancers are familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC).

Familial adenomatous polyposis (FAP): FAP is caused by changes (mutations) in the APC gene that a person inherits from his or her parents. About 1% of all colorectal cancers are due to FAP.

People with this disease typically develop hundreds or thousands of polyps in their colon and rectum, usually in their teens or early adulthood. Cancer usually develops in 1 or more of these polyps as early as age 20. By age 40, almost all people with this disorder will have developed cancer if preventive surgery (removing the colon) is not done.

FAP is sometimes associated with Gardner syndrome, a condition that involves benign (non-cancerous) tumors of the skin, soft connective tissue, and bones.

Hereditary non-polyposis colon cancer (HNPCC): HNPCC, also known as Lynch syndrome, is another clearly defined genetic syndrome. It accounts for about 3% to 4% of all colorectal cancers. HNPCC can be caused by inherited changes in a number of different genes that normally help repair DNA damage.

This syndrome also develops when people are relatively young. People with HNPCC have polyps, but they only have a few, not hundreds as in FAP. The lifetime risk of colorectal cancer in people with this condition may be as high as 70% to 80%.

Women with this condition also have a very high risk of developing cancer of the endometrium (lining of the uterus). Other cancers linked with HNPCC include cancer of the ovary, stomach, small bowel, pancreas, kidney, ureters (tubes that carry urine from the kidneys to the bladder), and bile duct.

For more information on HNPCC, see the sections "Do we know what causes colorectal cancer?" and "Can colorectal cancer be prevented?" in our larger Colorectal Cancer document.

Peutz-Jeghers syndrome: People with this rare inherited condition tend to have freckles around the mouth (and sometimes on the hands and feet) and large polyps in their digestive tracts. They are at greatly increased risk for colorectal cancer, as well as several other cancers, which usually appear at a younger than normal age.

Identifying families with these inherited syndromes is important because it allows doctors to recommend specific steps, such as screening and other preventive measures, at an early age.

Because several types of cancer can be linked with these syndromes, people should check their family medical history for polyps or any type of cancer. Those who develop polyps or cancer should inform other family members. People with a family history of colorectal polyps or cancer should consider genetic counseling to review their family medical tree and determine whether genetic testing may be right for them. If needed, this can help them to decide about getting screened and treated at an early age.

Racial and ethnic background

African Americans have the highest colorectal cancer incidence and mortality rates of all racial groups in the United States. The reason for this is not yet understood.

Jews of Eastern European descent (Ashkenazi Jews) have one of the highest colorectal cancer risks of any ethnic group in the world. Several gene mutations leading to an increased risk of colorectal cancer have been found in this group. The most common of these DNA changes, called the I1307K APC mutation, is present in about 6% of American Jews.

Lifestyle-related factors

Several lifestyle-related factors have been linked to colorectal cancer. In fact, the links between diet, weight, and exercise and colorectal cancer risk are some of the strongest for any type of cancer.

Certain types of diets

A diet that is high in red meats (beef, pork, lamb) and processed meats (hot dogs, bologna, luncheon meat) can increase colorectal cancer risk. Methods of cooking meats at very high temperatures (frying, broiling, or grilling) create chemicals that might increase cancer risk, although it's not clear how much this might contribute to an increase in colorectal cancer risk. Diets high in vegetables and fruits have been linked with decreased risk of colorectal cancer. Whether other dietary components (fiber, certain types of fats, etc.) affect colorectal cancer risk is not clear.

Physical inactivity

If you are not physically active, you have a greater chance of developing colorectal cancer. Increasing activity may help reduce your risk.

Obesity

If you are very overweight, your risk of developing and dying from colorectal cancer is increased. While obesity raises the risk of colon cancer in both men and women, the link seems to be stronger in men.

Smoking

Long-term smokers are more likely than non-smokers to develop and die from colorectal cancer. While smoking is a well-known cause of lung cancer, some of the cancer-causing substances are swallowed and can cause digestive system cancers, such as colorectal cancer.

Heavy alcohol use

Colorectal cancer has been linked to the heavy use of alcohol. At least some of this may be due to the fact that heavy alcohol users tend to have low levels of folic acid in the body. Still, it would be wise to limit alcohol use to no more than 2 drinks a day for men and 1 drink a day for women.

Type 2 diabetes

People with type 2 (usually non-insulin dependent) diabetes have an increased risk of developing colorectal cancer. Both type 2 diabetes and colorectal cancer share some of the same risk factors (such as excess weight). But even after taking these into account, people with type 2 diabetes still have an increased risk. They also tend to have a less favorable prognosis (outlook) after diagnosis.

Factors with uncertain, controversial, or unproven effects on colorectal cancer

Night shift work

Results of one study suggested working a night shift at least 3 nights a month for at least 15 years may increase the risk of colorectal cancer in women. The study authors suggested this might be due to changes in levels of melatonin (a hormone that responds to changes in light) in the body. More research is needed to confirm or refute this finding.

Previous treatment for certain cancers

Some studies have found that men who survive testicular cancer seem to have a higher rate of colorectal cancer and some other cancers. This might be due to the treatments they have received.

Some early studies suggested that men who received radiation therapy to treat prostate cancer might have a higher risk of rectal cancer, as the rectum receives some radiation during treatment. However, other studies have not found such a link.

The American Cancer Society and several other medical organizations recommend earlier screening for people with increased colorectal cancer risk. These recommendations differ from those for people at average risk. For more information, speak with your doctor and refer to the tables below.

Finding colorectal cancer early

While colorectal cancer is often found after symptoms appear, most people with early colon or rectal cancer have no symptoms of the disease. Symptoms usually appear only with more advanced disease. This is why getting the recommended screening tests (as described in the next section) before any symptoms develop is so important.

If your doctor finds something suspicious during a screening exam, or if you have any of the symptoms of colorectal cancer described below, you will likely need to undergo a diagnostic workup to determine if cancer is present.

Signs and symptoms of colorectal cancer

If you have any of the following you should check with your doctor for prompt diagnosis and treatment:

• a change in bowel habits, such as diarrhea, constipation, or narrowing of the stool, that lasts for more than a few days 
• a feeling that you need to have a bowel movement that is not relieved by doing so 
• rectal bleeding, dark stools, or blood in the stool (often, though, the stool will look normal) 
• cramping or abdominal (stomach area) pain 
• weakness and fatigue

Most of these symptoms are more likely to be caused by conditions other than colorectal cancer, such as infection, hemorrhoids, or inflammatory bowel disease. Still, if you have any of these problems, it's important to see your doctor right away so the cause can be found and treated, if needed.

Colorectal cancer screening tests

Screening is the process of looking for cancer in people who have no symptoms of the disease. There are several different tests that can be used to screen for colorectal cancers. These tests can be divided into 2 broad groups:

• tests that can find both colorectal polyps and cancer: These tests look at the structure of the colon itself to find any abnormal areas. This is done either with a scope inserted into the rectum or with special imaging (x-ray) tests. Polyps found before they turn cancerous can be removed, so these tests may prevent colorectal cancer. Because of this, these tests are preferred if they are available and you are willing to have them.

• tests that mainly find cancer: These involve testing the stool (feces) for signs that cancer may be present. These tests are less invasive and easier to have done, but they are less likely to detect polyps.

These tests as well as others can also be used when people have symptoms of colorectal cancer and other digestive diseases.

Tests that can find both colorectal polyps and cancer

Flexible sigmoidoscopy

During this test, the doctor looks at part of the colon and rectum with a sigmoidoscope -- a flexible, lighted tube about the thickness of a finger with a small video camera on the end. It is inserted through the rectum and into the lower part of the colon. Images from the scope are viewed on a display monitor.

Using the sigmoidoscope, your doctor can view the inside of the rectum and part of the colon to detect (and possibly remove) any abnormality. Because the sigmoidoscope is only 60 centimeters (about 2 feet) long, the doctor is able to see the entire rectum but less than half of the colon with this procedure.

Before the test: You will need to have a bowel preparation to clean out your lower colon. The colon and rectum must be empty and clean so your doctor can view the lining of the sigmoid colon and rectum. Your doctor will give you specific instructions to follow. You may be asked to follow a special diet (such as drinking only clear liquids) for a day before the exam. You may also be asked to use enemas or to drink a strong laxative solution to clean out your colon before the exam.

During the test: A sigmoidoscopy usually takes 10 to 20 minutes. Most people do not need to be sedated for this test, but this may be an option you can discuss with your doctor. While sedation may make the test less uncomfortable, it requires having someone with you to take you home after the test. You will likely be placed on a table on your left side with your knees positioned near your chest.

Your doctor should do a digital rectal exam (DRE) before inserting the sigmoidoscope. The sigmoidoscope is lubricated so it is easy to insert into the rectum. The scope may feel cool going in. The sigmoidoscope may stretch the wall of the colon, which may cause muscle spasms or lower abdominal pain. Air will be placed into the sigmoid colon through the sigmoidoscope so the doctor can see the colon better. During the procedure, you might feel pressure and slight cramping in your lower abdomen. To ease discomfort and the urge to have a bowel movement, it helps to breathe deeply and slowly through your mouth. You will feel better after the test once the air leaves your colon.

If a small polyp is found during the test your doctor may remove it with a small instrument passed through the scope. The polyp will be sent to a lab to be looked at by a pathologist. If a pre-cancerous polyp (an adenoma) or colorectal cancer is found during the test, you will need to have a colonoscopy at a later date to look for polyps or cancer in the rest of the colon.

Possible complications and side effects: This test may be uncomfortable because of the air put into the colon, but it should not be painful. Be sure to let your doctor know if you feel pain during the procedure. You may see a small amount of blood in your first bowel movement after the test. Significant bleeding and puncture of the colon are possible complications, but they are very uncommon.

Colonoscopy

For this test, the doctor looks at the entire length of the colon and rectum with a colonoscope, which is basically a longer version of a sigmoidoscope. It is inserted through the rectum into the colon. The colonoscope has a video camera on the end that is connected to a display monitor so the doctor can see and closely examine the inside of the colon. Special instruments can be passed through the colonoscope to remove any suspicious looking areas such as polyps, if needed.

Colonoscopy may be done in a hospital outpatient department, in a clinic, or in a doctor's office.

Before the test: The colon and rectum must be empty and clean so your doctor can view their inner linings during the test. You will need to take laxatives (liquids, pills, or both) the day before the test and possibly an enema that morning. Your doctor will give you specific instructions. It is important to read these carefully a few days ahead of time, since you may need to shop for special supplies and get laxatives from a pharmacy. If you are not sure about any of the instructions, call the doctor's office and go over them step by step with the nurse. Many people consider the bowel preparation to be the most unpleasant part of the test, as it usually requires you to be in the bathroom quite a bit.

You may be given other instructions as well. For example, your doctor may instruct that you drink only clear liquids (water, apple or cranberry juice, and any gelatin except red or purple) for a day or 2 before the exam. Plain tea or coffee with sugar is usually okay, but no milk or creamer is allowed. Clear broth, ginger ale, and most soft drinks or sports drinks are usually allowed unless they have red or purple food colorings, which can discolor the colon.

You will likely also be told not to eat or drink anything after midnight the night before your test. If you normally take prescription medicines in the mornings, talk with your doctor or nurse about how to manage them for the day.

You may need to arrange for someone to drive you home from the test because the sedative used during the test can affect your ability to drive. Depending on the medicines that are used, some doctors require that someone drive you home.

During the test: The test itself usually takes about 30 minutes, although it may take longer if a polyp is found and removed. Before the colonoscopy begins, you will be given a sedating medicine through your vein to make you feel comfortable and sleepy during the procedure. You will probably be awake, but you may not be aware of what is going on and may not remember the procedure afterward. Most people will be fully awake by the time they get home from the test.

During the procedure, you will be placed on your side with your knees flexed and a drape will cover you. Your blood pressure, heart rate, and breathing rate will be monitored during and after the test.

Your doctor should do a digital rectal exam (DRE) before inserting the colonoscope. The colonoscope is lubricated so it can be easily inserted into the rectum. Once in the rectum, the colonoscope is passed through the transverse colon and into the ascending colon. You may feel an urge to have a bowel movement when the colonoscope is inserted or pushed further up the colon. To ease any discomfort it may help to breathe deeply and slowly through your mouth. The colonoscope will deliver air into the colon so that it is easier to see the lining of the colon and use the instruments to perform the test. Suction will be used to remove any blood or liquid stools.

If a small polyp is found, the doctor may remove it. Some small polyps may eventually become cancerous. For this reason, they are usually removed. This is done by passing a wire loop through the colonoscope to cut the polyp from the wall of the colon with an electrical current. The polyp can then be sent to a lab to be checked under a microscope to see if it has any areas that have changed into cancer.

If your doctor sees a large polyp or tumor or anything else abnormal, a biopsy may be done. For this procedure, a small piece of tissue is taken out through the colonoscope. The tissue is looked at under a microscope to determine if it is a cancer, a benign (non-cancerous) growth, or a result of inflammation.

Possible side effects and complications: The bowel preparation before the test can be unpleasant. The test itself may be uncomfortable, but the sedative usually prevents this, and most people feel normal once the effects of the sedative wear off. Some people may have gas pains or cramping for a while after the test.

In some cases, people may have low blood pressure or changes in heart rhythms due to the sedation during the test, although these are rarely serious.

If a polyp is removed or a biopsy is done during the colonoscopy, you may notice some blood in your stool for a day or 2 after the test. Significant bleeding is slightly more likely with colonoscopy than with sigmoidoscopy, but it is still uncommon. In rare cases, continued bleeding might require treatment.

Although colonoscopy is a safe procedure, on rare occasions the colonoscope can puncture the wall of the colon or rectum. This is called a perforation. It can be a serious complication and at times requires surgical repair. Talk to your doctor about the risk of this complication.

Double contrast barium enema (DCBE)

This procedure is also called an air-contrast barium enema or a barium enema with air contrast. It is basically a type of x-ray test. Barium sulfate, which is a chalky liquid, and air are used to outline the inner part of the colon and rectum to look for abnormal areas on x-rays. If suspicious areas are seen on this test, a colonoscopy will be needed to explore them further.

Before the test: As with colonoscopy, it is very important that the colon and rectum are empty and clean so your doctor can view them during the test. Your doctor will give you specific instructions on preparing for the test. Be sure to follow them. For example, you may be asked to clean your bowel the night before with laxatives and/or take an enema the morning of the exam. You will likely be asked to follow a clear liquid diet for a day or 2 before the procedure. You may also be told to avoid eating or drinking dairy products the day before the test, and to not eat or drink anything after midnight on the night before the procedure. Many people consider the bowel preparation to be the most unpleasant part of the test, as it usually requires you to be in the bathroom quite a bit.

During the test: The procedure takes about 30 to 45 minutes to perform, and it does not require sedation. For this test, you lie on a table on your side in an x-ray room. A small, flexible tube is inserted into the rectum, and barium sulfate is used to partially fill and open up the colon. When the colon is about half-full of barium, you are turned on the x-ray table so the barium spreads throughout the colon. Then air is pumped into the colon through the same tube to make it expand. This may cause some discomfort, and you may feel the urge to have a bowel movement.

X-ray pictures of the lining of your colon are then taken, allowing the doctor to identify any polyps or cancers. You may be asked to change positions so that different views of the colon and rectum can be seen on the x-rays.

If polyps or other suspicious areas are seen on this test, a colonoscopy will likely be needed to remove them or to explore them fully.

Possible side effects and complications: You may have bloating or cramping after the test, and will likely feel the need to empty your bowels almost immediately after the test is done. The barium can cause constipation for a few days, and your stool may appear grey or white until the barium leaves the body. There is a very small risk that inflating the colon with air could injure or puncture the colon, but this risk is thought to be much less than with colonoscopy.

CT colonography (virtual colonoscopy)

This test is an advanced type of computed tomography (CT or CAT) scan of the colon and rectum. A CT scan is an x-ray test that produces detailed cross-sectional images of your body. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you while you lie on a table. A computer then combines these pictures into images of slices of the part of your body being studied. CT colonography involves the use of special computer programs to create both two dimensional x-ray pictures and a three-dimensional "fly-through" view of the inside of the colon and rectum, which allows the doctor to look for polyps or cancer.

This test may be especially useful for some people who can't have or don't want to have more invasive tests such as colonoscopy. It can be done fairly quickly and does not require sedation. But while this test is not invasive like colonoscopy, it still requires the same type of bowel preparation. If polyps or other suspicious areas are seen on this test, a colonoscopy will likely be needed to remove them or to explore them fully.

Before the test: It is important that the colon and rectum are emptied before this test to provide the best images. Because of this, the preparation for this test is similar to that for a double contrast barium enema or colonoscopy. You will likely be told to follow a clear liquid diet for a day or 2 before the test. You will also be given instructions for taking strong laxatives and/or enemas the night before or morning of the exam. This will likely require you to be in the bathroom quite a bit.

During the test: This test is done in a special room with a CT scanner, and takes about 10 minutes. You may be asked to drink a contrast solution before the test to help "tag" any remaining stool in the colon or rectum, which helps the doctor when looking at the test images. You will be asked to lie in a thin table that is part of the CT scanner, and will have a small, flexible tube inserted into your rectum. Air is pumped through the tube into the colon to expand it to provide better images. The table then slides into the CT scanner, and you will be asked to hold your breath while the scan takes place. You will likely have 2 scans: one while you are lying on your back and one while you are on your stomach. Each scan typically takes only about 10 to 15 seconds.

Possible side effects and complications: There are usually very few side effects after CT colonography. You may feel bloated or have cramps due to the air in the colon, but this should go away once the air passes from the body. There is a very small risk that inflating the colon with air could injure or puncture the colon, but this risk is thought to be much less than with colonoscopy.

Tests that mainly find colorectal cancer

These tests examine the stool to look for signs of cancer. Most people find these tests to be easier because they are not invasive and can often be done at home. But they are not as good at detecting polyps as the tests described above, and a positive result on one of these screening tests will likely require a more invasive test such as colonoscopy.

Fecal occult blood test

The fecal occult blood test (FOBT) is used to find occult (hidden) blood in feces. The idea behind this test is that blood vessels at the surface of larger colorectal polyps or cancers are often fragile and easily damaged by the passage of feces. The damaged vessels usually release a small amount of blood into the feces, but only rarely is there enough bleeding to be noticeable in the stool.

The FOBT detects blood in the stool through a chemical reaction. This test cannot tell whether the blood is from the colon or from other portions of the digestive tract (such as the stomach). Therefore, if this test is positive, a colonoscopy is needed to see if there is a cancer, polyp, or other cause of bleeding such as ulcers, hemorrhoids, diverticulosis (tiny pouches that form at weak spots in the colon wall), or inflammatory bowel disease (colitis).

This is a take-home kit that is used in the privacy of your own home. An FOBT done during a digital rectal exam in the doctor's office is not sufficient for screening. In order to be beneficial the test must be repeated every year.

People having this test will receive a kit with instructions from their doctor's office or clinic. The kit will explain how to take a stool or feces sample at home (usually specimens from 3 consecutive bowel movements that are smeared onto small squares of paper). The kit should then be returned to the doctor's office or medical lab (usually within 2 weeks) for testing. See below for more details.

Before the test: Some foods or drugs can affect the test, so your doctor may suggest that you try to avoid the following before this test:

• non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil), naproxen (Aleve), or aspirin (more than 1 adult aspirin per day), for 7 days before testing (they can cause bleeding, which can lead to a false-positive result). Acetaminophen (Tylenol) can be taken as needed.

• vitamin C in excess of 250 mg daily from either supplements or citrus fruits and juices for 3 days before testing (this can affect the chemicals in the test and make it show negative)

• red meats (beef, lamb, or liver) for 3 days before testing (components of blood in the meat may cause the test to show positive)

Some people who are given the test never do it or don't give it to their doctor because they worry that something they ate may interfere with the test. For this reason, many doctors tell their patients it isn't essential to follow any restrictions in their diet. The most important thing is to get the test done. People should try to avoid taking aspirin or related drugs for minor aches. But if you take these medicines daily for heart problems or other conditions, don't stop them for this test without approval from your doctor.

Collecting the samples: Have all of your supplies ready and in one place. Supplies will include a test kit, test cards, either a brush or wooden applicator, and a mailing envelope. The kit will give you detailed instructions on how to collect the specimen. The instructions below can be used as a guide, but your kit instructions might be a little different. Always follow the instructions on your kit.

• You will need to collect a sample from your bowel movement. You can place a sheet of plastic wrap across the toilet bowl to catch the stool or you can use a dry container to collect the stool. Do not let the stool specimen mix with urine. After you obtain a sample, you can flush the remaining stool down the toilet.

• Use a wooden applicator or a brush to smear a thin film of the stool sample onto one of the slots in the test card or slide.

• Next, collect a specimen from a different area of the same stool and smear a thin film of the sample onto the other slot in the test card or slide.

• Close the slots and put your name and the date on the test kit. Store the kit overnight in a paper envelope to allow it time to dry.

• Repeat the test on your next 2 bowel movements if instructed. Most tests require collecting more than one sample from different bowel movements. This improves the accuracy of the test because many cancers bleed intermittently and blood may not be present in all stool samples.

• Place the test kit in the mailing pouch provided and return it to your doctor or lab as soon as possible (but within 14 days of taking the first sample).

If this test finds blood, a colonoscopy will be needed to look for the source. It is not sufficient to simply repeat the FOBT or follow up with other types of tests.

Fecal immunochemical test

The fecal immunochemical test (FIT), also called an immunochemical fecal occult blood test (iFOBT), is a newer kind of test that also detects occult (hidden) blood in the stool. This test reacts to part of the hemoglobin molecule, which is found on red blood cells.

The FIT is done essentially the same way as the FOBT, but some people may find it easier to use because there are no drug or dietary restrictions (vitamins or foods do not affect the FIT) and sample collection may take less effort. This test is also less likely to react to bleeding from the upper digestive tract, such as the stomach.

As with the FOBT, the FIT may not detect a tumor that is not bleeding, so multiple stool samples should be tested. And if the results are positive for hidden blood, a colonoscopy is required to investigate further. In order to be beneficial the test must be repeated every year.

Collecting the samples: Have all of your supplies ready and in one place. Supplies will include a test kit, test cards, long brushes, waste bags, and a mailing envelope. The kit will give you detailed instructions on how to collect the specimen. The instructions below can be used as a guide, but your kit instructions might be a little different. Always follow the instructions on your kit.

• Flush the toilet before your bowel movement. After you go, place used toilet paper in the waste bag from the kit, not in the toilet.

• Brush the surface of the stool with one of the brushes, then dip the brush in the toilet water. Dab the end of the brush onto one of the slots in the test card or slide.

• Close the slot and put your name and the date on the test kit.

• Repeat the test on your next bowel movement if instructed. Most tests require collecting more than one sample from different bowel movements. This improves the accuracy of the test because many cancers bleed intermittently and blood may not be present in all stool samples.

• Place the test kit in the mailing envelope provided and return it to your doctor or lab as soon as possible (but within 14 days of taking the first sample).

Stool DNA tests

Instead of looking for blood in the stool, these tests look for certain abnormal sections of DNA (genetic material) from cancer or polyp cells. Colorectal cancer cells often contain DNA mutations (changes) in certain genes such as APC, K-ras, and p53. Cells from colorectal cancers or polyps with these mutations are often shed into the stool, where tests may be able to detect them.

This is a newer test, and the best length of time to go between tests is not yet clear. This test is also much more expensive than other forms of stool testing.

This test is not invasive and doesn't require any special preparation. But as with other stool tests, if the results are positive, a colonoscopy is required to investigate further.

People having this test will receive a kit with detailed instructions from their doctor's office or clinic on how to collect the specimen. Always follow the instructions on your kit.

This test requires an entire stool sample. It is obtained using a special container, which is placed in a bracket that stretches across the seat of the toilet. You have your bowel movement while sitting on the toilet, making sure it goes into the container. You then place the container and an ice pack in a shipping box and close and label the box. The specimen must be shipped to the lab within 24 hours of having the bowel movement.

What are some of the pros and cons of these screening tests?

American Cancer Society recommendations for colorectal cancer early detection

People at average risk

The American Cancer Society believes that preventing colorectal cancer (and not just finding it early) should be a major reason for getting tested. Finding and removing polyps keeps some people from getting colorectal cancer. Tests that have the best chance of finding both polyps and cancer are preferred if these tests are available to you and you are willing to have them.

Beginning at age 50, both men and women at average risk for developing colorectal cancer should use one of the screening tests below:

Tests that find polyps and cancer

• flexible sigmoidoscopy every 5 years* 
• colonoscopy every 10 years 
• double contrast barium enema every 5 years* 
• CT colonography (virtual colonoscopy) every 5 years*

• fecal occult blood test (FOBT) every year*,**
• fecal immunochemical test (FIT) every year*,**
• stool DNA test (sDNA), interval uncertain*

*Colonoscopy should be done if test results are positive.
**For FOBT or FIT used as a screening test, the take-home multiple sample method should be used. A FOBT or FIT done during a digital rectal exam in the doctor's office is not adequate for screening.

In a digital rectal examination (DRE), a doctor examines your rectum with a lubricated, gloved finger. Although a DRE is often included as part of a routine physical exam, it is not recommended as a stand-alone test for colorectal cancer. This simple test, which is not usually painful, can detect masses in the anal canal or lower rectum. By itself, however, it is not a very sensitive test for detecting colorectal cancer due to its limited reach.

Doctors often find a small amount of stool when doing a DRE. However, simply checking stool obtained in this fashion for evidence of bleeding with a FOBT or FIT is not an acceptable method of screening for colorectal cancer. Research has shown that this type of stool examination will miss more than 90% of colon abnormalities, including most cancers.

People at increased or high risk

If you are at an increased risk or higher than average risk of colorectal cancer, you should begin colorectal cancer screening earlier and/or be screened more often. The following conditions place you at higher than average risk:

• a personal history of colorectal cancer or adenomatous polyps 
• a personal history of inflammatory bowel disease (ulcerative colitis or Crohns disease) 
• a strong family history of colorectal cancer or polyps (see "Risk factors for colorectal cancer" above) 
• a known family history of hereditary colorectal cancer syndromes such as familial adenomatous polyposis (FAP) or hereditary non-polyposis colon cancer (HNPCC)

The table below suggests screening guidelines for those with increased or high risk of colorectal cancer based on specific risk factors. Some people may have more than one risk factor. Refer to the table below and discuss these recommendations with your doctor. Based on your individual situation and any risk factors you may have, your doctor can suggest the best screening option for you, as well as any changes in the schedule based on your individual risk.

American Cancer Society Guidelines on Screening and Surveillance for the Early Detection of Colorectal Adenomas and Cancer in People at Increased Risk or at High Risk

Risk Category	Age to Begin	Recommended Test(s)	Comment
INCREASED RISK -- Patients With a History of Polyps on Prior Colonoscopy
People with small rectal hyperplastic polyps	Same as those with average risk	Colonoscopy, or other screening options at regular intervals as for those at average risk	Those with hyperplastic polyposis syndrome are at increased risk for adenomatous polyps and cancer and should have more intensive follow-up.
People with 1 or 2 small (less than 1 cm) tubular adenomas with low-grade dysplasia	5 to 10 years after the polyps are removed	Colonoscopy	Time between tests should be based on other factors such as prior colonoscopy findings, family history, and patient and doctor preferences.
People with 3 to 10 adenomas, or a large (1 cm +) adenoma, or any adenomas with high-grade dysplasia or villous features	3 years after the polyps are removed	Colonoscopy	Adenomas must have been completely removed. If colonoscopy is normal or shows only 1 or 2 small tubular adenomas with low-grade dysplasia, future colonoscopies can be done every 5 years.
People with more than 10 adenomas on a single exam	Within 3 years after the polyps are removed	Colonoscopy	Doctor should consider possibility of genetic syndrome (such as FAP or HNPCC).
People with sessile adenomas that are removed in pieces	2 to 6 months after adenoma removal	Colonoscopy	If entire adenoma has been removed, further testing should be based on doctor’s judgment
INCREASED RISK – Patients With Colorectal Cancer
People diagnosed with colon or rectal cancer	At time of colorectal surgery, or can be 3 to 6 months later if person doesn't have cancer spread that can't be removed	Colonoscopy to view entire colon and remove all polyps	If the tumor presses on the colon/rectum and prevents colonoscopy, CT colonoscopy (with IV contrast) or DCBE may be done to look at the rest of the colon.
People who have had colon or rectal cancer removed by surgery	Within 1 year after cancer resection (or 1 year after colonoscopy to make sure the rest of the colon/rectum was clear)	Colonoscopy	If normal, repeat exam in 3 years. If normal then, repeat exam every 5 years. Time between tests may be shorter if polyps are found or there is reason to suspect HNPCC. After low anterior resection for rectal cancer, exams of the rectum may be done every 3 to 6 months for the first 2 to 3 years to look for signs of recurrence.
INCREASED RISK – Patients With a Family History
Colorectal cancer or adenomatous polyps in any first-degree relative before age 60, or in 2 or more first-degree relatives at any age (if not a hereditary syndrome).	Age 40, or 10 years before the youngest case in the immediate family, whichever is earlier	Colonoscopy	Every 5 years.
Colorectal cancer or adenomatous polyps in any first-degree relative aged 60 or higher, or in at least 2 second-degree relatives at any age	Age 40	Same options as for those at average risk.	Same intervals as for those at average risk.
HIGH RISK
Familial adenomatous polyposis (FAP) diagnosed by genetic testing, or suspected FAP without genetic testing	Age 10 to 12	Yearly flexible sigmoidoscopy to look for signs of FAP; counseling to consider genetic testing if it hasn't been done	If genetic test is positive, removal of colon (colectomy) should be considered.
Hereditary non-polyposis colon cancer (HNPCC), or at increased risk of HNPCC based on family history without genetic testing	Age 20 to 25 years, or 10 years before the youngest case in the immediate family	Colonoscopy every 1 to 2 years; counseling to consider genetic testing if it hasn't been done	Genetic testing should be offered to first-degree relatives of people found to have HNPCC mutations by genetic tests. It should also be offered if 1 of the first 3 of the modified Bethesda criteria is met.1
Inflammatory bowel disease -Chronic ulcerative colitis -Crohn's disease	Cancer risk begins to be significant 8 years after the onset of pancolitis (involvement of entire large intestine), or 12-15 years after the onset of left-sided colitis	Colonoscopy every 1 to 2 years with biopsies for dysplasia	These people are best referred to a center with experience in the surveillance and management of inflammatory bowel disease.

¹The Bethesda criteria can be found in the "Can colorectal cancer be prevented?" section of our larger Colorectal Cancer document.

Colorectal cancer screening: State and federal coverage laws

The benefits of early detection colorectal cancer screening

Non-cancerous colorectal polyps can be found through screening and removed before they become cancerous. If colorectal cancer does occur, early detection and treatment dramatically increase chances of survival.

The relative 5-year survival rate for colorectal cancer, when diagnosed at an early stage before it has spread is about 90%. But only about 39% of colorectal cancers are found at that early stage. Once the cancer has spread to nearby organs or lymph nodes, the 5-year relative survival rate goes down, and if cancer has spread to distant organs (like the liver or lung) the rate is about 10%.

(A standard 5-year survival rate refers to the percentage of patients who live at least 5 years after their cancer is diagnosed; it includes people with colorectal cancer who may die of other causes, such as heart disease. Five-year relative survival rates are adjusted for patients dying of other diseases, so they reflect the chances of not dying specifically from colorectal cancer.)

Not only does colorectal cancer screening save lives, but it also is cost effective. Studies have shown that the cost-effectiveness of colorectal screening is consistent with many other kinds of preventive services and is lower than some common interventions. It is much less expensive to remove a polyp during screening than to try to treat advanced colorectal cancer. With sharp cost increases possible as new treatments become standards of care, the cost-effectiveness of screening is likely to become even more attractive.

What is needed to increase the use of colorectal cancer screening?

Several effective colorectal cancer screening tests are available but not enough people have them. Some factors affecting their use could include lack of public and health professional awareness of screening tools, financial barriers, and inadequate health insurance coverage and/or benefits.

The American Cancer Society believes that all people should benefit from cancer screenings, without regard to health insurance coverage. Limitations on covered benefits should not block your ability to benefit from early detection of cancer. To that end, the Society supports policies that give all people access to and coverage of early detection screening for cancer. Such policies should be age and risk appropriate and based on current scientific evidence as outlined in the American Cancer Society's early detection guidelines.

State activity

A number of states, as well as the District of Columbia, have passed laws requiring insurance coverage for the full range of colorectal cancer screening tests. A few other states require that insurance for testing be offered or available through Medicare Supplemental policies.

States where screening laws ensure coverage for the full range of tests:

• Alaska 
• Arkansas 
• California 
• Connecticut 
• Delaware 
• Georgia 
• Illinois 
• Indiana 
• Louisiana 
• Maryland 
• Missouri 
• Nebraska 
• Nevada 
• New Jersey 
• New Mexico 
• North Carolina 
• Oregon 
• Rhode Island 
• Texas 
• Virginia 
• Washington 
• Washington, D.C. 
• West Virginia

States where screening laws require insurers to cover some but not all tests, or where insurers have voluntarily agreed to cover the full range of tests:

• New York 
• Vermont 
• Wyoming

Laws on coverage may vary by state.

In all other states, either there are no laws requiring insurance coverage, or there are laws that require insurers to offer (not necessarily provide) coverage.

Medicare coverage

As of 2005, Medicare covers an initial preventive physical exam for all new Medicare beneficiaries that must occur within 6 months of enrolling in Medicare. The "Welcome to Medicare" physical includes referrals for preventive services already covered under Medicare, including colon cancer screening tests.

What colorectal cancer screening tests does Medicare cover?

• fecal occult blood test (FOBT) or fecal immunochemical test (FIT) yearly for all Medicare beneficiaries 50 years and older

• flexible sigmoidoscopy:

• colonoscopy:

• double contrast barium enema (DCBE) as an alternative if a doctor determines that its screening value is equal to or better than flexible sigmoidoscopy or colonoscopy:

What would a Medicare beneficiary expect to pay for a colorectal cancer screening test?

• FOBT/FIT: People age 50 years or older with Medicare pay no coinsurance and no Part B deductible.

• flexible sigmoidoscopy: Beneficiary pays coinsurance or copayment. No Part B deductible unless the test results in the biopsy or removal of a growth. If the test is done in an outpatient hospital department or ambulatory surgical center, the beneficiary pays 25% of the Medicare approved amount.

• colonoscopy: Beneficiary pays coinsurance or copayment. No Part B deductible unless the test results in the biopsy or removal of a growth. If the test is done in an outpatient hospital department or ambulatory surgical center, the beneficiary pays 25% of the Medicare approved amount.

• DCBE: Beneficiary pays coinsurance or copayment. No Part B deductible unless the test results in the biopsy or removal of a growth. If the test is done in an outpatient hospital department or ambulatory surgical center, the beneficiary pays 25% of the Medicare approved amount.

Medicaid

States are authorized to cover colorectal screening under their Medicaid programs. Unlike Medicare, however, there is no federal assurance that all state Medicaid programs must cover colorectal cancer screening in people without symptoms. Medicaid coverage for colorectal cancer screening varies by state. Some states cover fecal occult blood testing (FOBT), others cover colorectal cancer screening if a doctor determines the test to be medically necessary, and in some states, coverage varies depending in which Medicaid managed care plan a person is enrolled.

Additional resources

More information from your American Cancer Society

The following related information may also be helpful to you. These materials may be viewed on our Web site or ordered from our toll-free number, 1-800-ACS-2345.

Colorectal Cancer - Overview (also available in Spanish)

Colorectal Cancer (also available in Spanish)

The following books are available from the American Cancer Society. Call us at 1-800-ACS-2345 to ask about costs or to place your order.

The American Cancer Society's Complete Guide to Colorectal Cancer

QuickFACTS Colon Cancer

National organizations and Web sites*

In addition to the American Cancer Society, other sources of patient information and support include:

American College of Gastroenterology Web site: http://www.acg.gi.org

American Gastroenterological Association Telephone: 1-301-654-2055 Web site: http://www.gastro.org

American Society of Colon and Rectal Surgeons Web site: http://www.fascrs.org

Colon Cancer Alliance Toll-free number: 1-877-422-2030 Web site: http://www.ccalliance.org

National Cancer Institute Toll-free number: 1-800-422-6237 (1-800-4-CANCER); TYY: 1-800-332-8615 Web site: http://www.cancer.gov

National Colorectal Cancer Research Alliance Web site: http://www.eif.nccra.org

*Inclusion on this list does not imply endorsement by the American Cancer Society.

No matter who you are, we can help. Contact us anytime, day or night, for information and support. Call us at 1-800-ACS-2345 or visit www.cancer.org.

References

American Cancer Society. Cancer Facts & Figures 2008. Atlanta, Ga: American Cancer Society; 2008.

American Cancer Society. Cancer Prevention & Early Detection Facts & Figures 2007. Atlanta, Ga: American Cancer Society; 2007.

American Cancer Society. Detailed Guide: Colon and Rectum Cancer. 2008. Available at: http://www.cancer.org/docroot/CRI/CRI_2_3x.asp?dt=10.

Byers T, Levin B, Rothenberger D, Dodd GD, Smith RA. American Cancer Society guidelines for screening and surveillance for early detection of colorectal polyps and cancer: Update 1997. CA Cancer J Clin. 1997;47:154-160.

Centers for Medicare and Medicaid Services. Colon Cancer Screening. 2008. Available at: http://www.cms.hhs.gov/ColorectalCancerScreening. Accessed January 31, 2008.

Frazier AL, Colditz GA, Fuchs CS, and Kuntz KM. Cost-effectiveness of screening for colorectal cancer in the general population. JAMA. 2000;284:1954-1961.

Hendriks YM, deJong AE, Morreau H, et al. Diagnostic approach and management of Lynch syndrome (hereditary nonpolyposis colorectal carcinoma): A guide for clinicians. CA Cancer J Clin. 2006;56:213-225.

Levin B, Lieberman DA, McFarland, et al. Screening and Surveillance for the Early Detection of Colorectal Cancer and Adenomatous Polyps, 2008: A Joint Guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. Published online March 5, 2008. CA Cancer J Clin. 2008;58.

National Colorectal Cancer Research Alliance. Colorectal Cancer Legislation Report Card. 2007. Available at: http://www.eifoundation.org/national/nccra/report_card. Accessed January 31, 2008.

Rex DK, Kaho CJ, Levin B, et al. Guidelines for colonoscopy surveillance after cancer resection: a consensus update by the American Cancer Society and US Multi-Society Task Force on Colorectal Cancer. CA Cancer J Clin. 2006;56:160-167.

Schernhammer ES, Laden F, Speizer FE, et al. Night-shift work and risk of colorectal cancer in the Nurses' Health Study. J Natl Cancer Inst. 2003;95:825-828.

Schrag D. The price tag on progress--chemotherapy for colorectal cancer. N Engl J Med. 2004;351:317-319.

Winawer, SJ, Zauber AG, Fletcher RH, et al. Guidelines for colonoscopy surveillance after polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer and the American Cancer Society. CA Cancer J Clin. 2006;56:143-159.

Revised: 03/05/2008