The colon and rectum are part of the large intestine. Colorectal cancer occurs when tumors form in the lining of the large intestine. It is common in both men and women. The risk of developing colorectal cancer rises after age 50. You're also more likely to get it if you have colorectal polyps, a family history of colorectal cancer, ulcerative colitis or Crohn's disease, eat a diet high in fat, or smoke.

Symptoms of colorectal cancer include

• Diarrhea or constipation
• A feeling that your bowel does not empty completely
• Blood (either bright red or very dark) in your stool
• Stools that are narrower than usual
• Frequent gas pains or cramps, or feeling full or bloated
• Weight loss with no known reason
• Fatigue
• Nausea or vomiting

Because you may not have symptoms at first, it's important to have screening tests. Everyone over 50 should get screened. Tests include colonoscopy and tests for blood in the stool. Treatments for colorectal cancer include surgery, chemotherapy, radiation, or a combination. Surgery can usually cure it when it is found early.

Colorectal cancer is cancer that occurs in the colon or rectum. Sometimes it is called colon cancer, for short. As the drawing shows, the colon is the large intestine or large bowel. The rectum is the passageway that connects the colon to the anus.

Sometimes abnormal growths, called polyps, form in the colon or rectum. Over time, some polyps may turn into cancer. Screening tests can find polyps so they can be removed before turning into cancer. Screening also helps find colorectal cancer at an early stage, when treatment works best.

Cancer is a disease in which cells in the body grow out of control. When cancer starts in the colon or rectum, it is called colorectal cancer. Sometimes it is called colon cancer, for short.

Of cancers that affect both men and women, colorectal cancer is the second leading cancer killer in the United States, but it doesn’t have to be. Colorectal cancer screening saves lives. Screening can find precancerous polyps—abnormal growths in the colon or rectum—that can be removed before they turn into cancer. Screening also helps find colorectal cancer at an early stage, when treatment works best. About nine out of every 10 people whose colorectal cancers are found early and treated appropriately are still alive five years later.

If you are 45 years old or older, get screened now. If you think you may be at increased risk for colorectal cancer, speak with your doctor about when to begin screening, which test is right for you, and how often to get tested.

What Is Colorectal Cancer?

Colorectal cancer is cancer that occurs in the colon or rectum. Sometimes it is called colon cancer, for short.

What Are the Risk Factors for Colorectal Cancer?

Your risk of getting colorectal cancer increases as you get older, and there are other risk factors.

What Can I Do to Reduce My Risk of Colorectal Cancer?

The most effective way to reduce your risk of colorectal cancer is by having regular colorectal cancer screening tests beginning at age 45.

What Are the Symptoms of Colorectal Cancer?

Colorectal cancer doesn't always cause symptoms, especially at first.

What Should I Know About Screening?

Screening tests can find precancerous polyps, so that they can be removed before they turn into cancer. Screening tests can also find colorectal cancer early, when treatment works best.

Questions to Ask Your Doctor

Several screening tests can be used to find polyps or colorectal cancer. The benefits and risks of these screening methods vary. Discuss with your doctor which test is best for you.

The Digestive System

The digestive system is like a long tube that runs from the mouth to the anus and includes organs that help the body digest and absorb food and nutrients. The organs that make up the digestive system include the mouth, esophagus, stomach, small intestine, large intestine (or colon), rectum, and anus. Inside these organs is a lining called the mucosa. The digestive tract also contains a layer of smooth muscle. The muscle moves food through the tract in a wavelike movement called peristalsis, helping to mix it and break it down.

The liver and the pancreas also belong to the digestive system. They produce digestive juices that empty into the small intestine through ducts. The gallbladder stores the liver's digestive juices.

Digestion begins in the mouth. Chewed food is swallowed and moves into the pharynx, and then is pushed down the esophagus into the stomach. There, food is churned by smooth muscle contractions and mixed with digestive juices produced by the stomach. The stomach slowly empties its contents into the small intestine, where food dissolves into juices secreted from the pancreas, liver, and intestine. As the digested food moves through the small intestine, its nutrients are absorbed into the intestinal wall and into the bloodstream, where it is transported throughout the body for distribution. The colon removes water from the digested matter and converts it into a mostly solid mass of waste material, consisting largely of indigestible elements of the food, called fiber, and older cells that have been shed from the mucosa. Waste material is then expelled as feces.

The Colon

The small intestine joins the large intestine, or colon, in the right lower abdomen. The colon is a muscular tube about 5 feet long. It's made up of four sections: the ascending colon, which extends upward on the right side of the abdomen; the transverse colon, which goes across the body from the right to the left side in the upper abdomen; the descending colon, which continues downward on the left side; and the sigmoid colon (called this because of its "S" or "sigmoid" shape). The sigmoid colon attaches to the rectum, which ends in the anus.

The colon is composed of a number of different layers of tissue:

• The mucosa, the innermost layer, includes a single layer of epithelial cells, a layer of connective tissue, and a thin muscle layer. It is lined with goblet cells, glands that secrete mucous to help the passage of material through the colon.
• The submucosa is a layer of connective tissue beneath the mucosa.
• The circular muscle is a band of muscle that wraps around the entire colon and helps move waste material through it.
• The longitudinal muscle runs lengthwise along the colon. It works in conjunction with the circular muscle to create the wavelike motion of peristalsis.
• The serosa is the outermost layer of the colon.

Colon Function

The major function of the colon is to extract water, salts, and nutrients from partially digested food, and to propel the residue to the rectum and anus for expulsion. When the contents of the small intestine reach the colon, they're liquid. By the time they are expelled as feces, they're solid. About 2 pints of liquid matter enter the colon each day; stool volume is about a third of a pint. The difference between these two amounts is what the colon has absorbed in the course of digestion. If the digested matter lacks enough water, the colon can also add water to it to soften the stool. Maintaining this balance is one of the colon's most important functions.

By the time the partially digested food enters the colon, most of its nutrients have been absorbed by the small intestine. However, the process of digestion isn't over. The colon contains large numbers of bacteria. The most important of these are the lactobacilli and bifidus bacteria, which live in a symbiotic (mutually beneficial) relationship with the colon. They ferment the soluble fiber in food, forming valuable short-chain fatty acids that nourish intestinal cells, help regulate production of cholesterol, and are thought to help prevent a variety of diseases (including cancer). Beneficial bacteria also help to keep harmful bacteria in check. In addition, intestinal bacteria synthesize vitamin K, important in blood clot formation.

Figure 23.21 Large Intestine The large intestine includes the cecum, colon, and rectum.

Rectal valve is one of three transverse folds in the rectum where feces is separated from flatus

Rectum is part of the large intestine between the sigmoid colon and anal canal

Rectum

Food residue leaving the sigmoid colon enters the rectum in the pelvis, near the third sacral vertebra. The final 20.3 cm (8 in) of the alimentary canal, the rectum extends anterior to the sacrum and coccyx. Even though rectum is Latin for "straight," this structure follows the curved contour of the sacrum and has three lateral bends that create a trio of internal transverse folds called the rectal valves. These valves help separate the feces from gas to prevent the simultaneous passage of feces and gas.

Large Intestine

The large intestine includes the cecum, colon, and rectum.

Absorption, Feces Formation, and Defecation

The small intestine absorbs about 90 percent of the water you ingest (either as liquid or within solid food). The large intestine absorbs most of the remaining water, a process that converts the liquid chyme residue into semisolid feces ("stool"). Feces is composed of undigested food residues, unabsorbed digested substances, millions of bacteria, old epithelial cells from the GI mucosa, inorganic salts, and enough water to let it pass smoothly out of the body. Of every 500 mL (17 ounces) of food residue that enters the cecum each day, about 150 mL (5 ounces) become feces.

Feces are eliminated through contractions of the rectal muscles. You help this process by a voluntary procedure called Valsalva's maneuver, in which you increase intra-abdominal pressure by contracting your diaphragm and abdominal wall muscles, and closing your glottis.The process of defecation begins when mass movements force feces from the colon into the rectum, stretching the rectal wall and provoking the defecation reflex, which eliminates feces from the rectum. This parasympathetic reflex is mediated by the spinal cord. It contracts the sigmoid colon and rectum, relaxes the internal anal sphincter, and initially contracts the external anal sphincter. The presence of feces in the anal canal sends a signal to the brain, which gives you the choice of voluntarily opening the external anal sphincter (defecating) or keeping it temporarily closed. If you decide to delay defecation, it takes a few seconds for the reflex contractions to stop and the rectal walls to relax. The next mass movement will trigger additional defecation reflexes until you defecate.If defecation is delayed for an extended time, additional water is absorbed, making the feces firmer and potentially leading to constipation. On the other hand, if the waste matter moves too quickly through the intestines, not enough water is absorbed, and diarrhea can result. This can be caused by the ingestion of foodborne pathogens. In general, diet, health, and stress determine the frequency of bowel movements. The number of bowel movements varies greatly between individuals, ranging from two or three per day to three or four per week.

Your risk of getting colorectal cancer increases as you get older. Other risk factors include having—

• Inflammatory bowel disease such as Crohn’s disease or ulcerative colitis.
• A personal or family history of colorectal cancer or colorectal polyps.
• A genetic syndrome such as familial adenomatous polyposis (FAP) or hereditary non-polyposis colorectal cancer (Lynch syndrome).

Lifestyle factors that may contribute to an increased risk of colorectal cancer include—

• Lack of regular physical activity.
• A diet low in fruit and vegetables.
• A low-fiber and high-fat diet, or a diet high in processed meats.
• Overweight and obesity.
• Alcohol consumption.
• Tobacco use.

Anyone can get colorectal cancer, but certain factors make you more likely to develop it:

• Being older; your risk of getting colorectal cancer increases as you age.
• Having a personal or family history of colorectal cancer.
• Having a history of adenomas. Adenomas are colorectal polyps (growths) that look abnormal under a microscope or are 1 centimeter or larger. Adenomas are not cancer, but they can sometimes turn into cancer over time.
• Having a genetic syndrome such as familial adenomatous polyposis (FAP) or Lynch syndrome (hereditary non-polyposis colorectal cancer).
• Having chronic ulcerative colitis or Crohn disease for 8 years or more.
• Having three or more alcoholic drinks per day.
• Smoking cigarettes.
• Being Black; Black people have an increased risk of colorectal cancer and death from colorectal cancer compared to other races.
• Having obesity.

Colorectal cancer happens when there are changes in your genetic material (DNA). These changes are also called mutations or variants. Often, the genetic changes that lead to colorectal cancer happen during your lifetime and the exact cause is unknown. But certain genetic changes that raise your risk for colorectal cancer are inherited, meaning that you are born with them.

Besides genetics, other factors, including your lifestyle and the environment, can affect your risk of colorectal cancer.

Familial colon cancer is a cluster of colon cancer within a family. Most cases of colon cancer occur sporadically in people with little to no family history of the condition. Approximately 3-5% of colon cancer is considered "hereditary" and is thought to be caused by an inherited predisposition to colon cancer that is passed down through a family in an autosomal dominant or autosomal recessive manner. In some of these families, the underlying genetic cause is not known; however, many of these cases are caused by changes (mutations) in the APC, MYH, MLH1, MSH2, MSH6, PMS2, EPCAM, PTEN, STK11, SMAD4, BMPR1A, NTHL1, POLE, and POLD1 genes (which are associated with hereditary cancer syndromes). An additional 10-30% of people diagnosed with colon cancer have a significant family history of the condition but have no identifiable mutation in a gene known to cause a hereditary predisposition to colon cancer. These clusters of colon cancer are likely due to a combination of gene(s) and other shared factors such as environment and lifestyle.

High-risk cancer screening and other preventative measures such as prophylactic surgeries are typically recommended in people who have an increased risk for colon cancer based on their personal and/or family histories.

Colorectal polyps and colorectal cancer don’t always cause symptoms, especially at first. Someone could have polyps or colorectal cancer and not know it. That is why getting screened regularly for colorectal cancer is so important.

If you have symptoms, they may include—

• A change in bowel habits.
• Blood in or on your stool (bowel movement).
• Diarrhea, constipation, or feeling that the bowel does not empty all the way.
• Abdominal pain, aches, or cramps that don’t go away.
• Losing weight and you don’t know why.

If you have any of these symptoms, talk to your doctor. They may be caused by something other than cancer. The only way to know what is causing them is to see your doctor.

Colorectal cancer may not always cause symptoms, especially at first. If you do have symptoms, they could include:

• A change in bowel habits that lasts more than a few days, such as:
  • Diarrhea
  • Constipation
  • Feeling that the bowel does not empty completely
  • Your stool is narrower or has a different shape than usual
• Blood (either bright red or very dark) in the stool
• Frequent gas pains, bloating, fullness, or cramps
• Weight loss for no known reason
• Fatigue

What Is Colorectal Cancer Screening?

A screening test is used to look for a disease when a person doesn’t have symptoms. (When a person has symptoms, diagnostic tests are used to find out the cause of the symptoms.)

Colorectal cancer almost always develops from precancerous polyps (abnormal growths) in the colon or rectum. Screening tests can find precancerous polyps, so that they can be removed before they turn into cancer. Screening tests can also find colorectal cancer early, when treatment works best.

Screening Guidelines

Regular screening, beginning at age 45, is the key to preventing colorectal cancer and finding it early. The U.S. Preventive Services Task Force (USPSTF) recommends that adults age 45 to 75 be screened for colorectal cancer. The Task Force recommends that adults age 76 to 85 ask their doctor if they should be screened.

The Task Force recommends several colorectal cancer screening strategies, including stool tests, flexible sigmoidoscopy, colonoscopy, and CT colonography (virtual colonoscopy).

When Should I Begin to Get Screened?

Most people should begin screening for colorectal cancer soon after turning 45, then continue getting screened at regular intervals. However, you may need to be tested earlier than 45, or more often than other people, if—

• You or a close relative have had colorectal polyps or colorectal cancer.
• You have an inflammatory bowel disease such as Crohn’s disease or ulcerative colitis.
• You have a genetic syndrome such as familial adenomatous polyposis (FAP) or hereditary non-polyposis colorectal cancer (Lynch syndrome).

If you think you are at increased risk for colorectal cancer, speak with your doctor about—

• When to begin screening.
• Which test is right for you.
• How often to get tested.

Insurance and Medicare Coverage

Most insurance plans and Medicare help pay for colorectal cancer screening for people who are 50 years old or older. Colorectal cancer screening tests may be covered by your health insurance policy without a deductible or co-pay. For more information about Medicare coverage, visit www.medicare.gov or call 1-800-MEDICARE (1-800-633-4227). TTY users should call 1 (877) 486-2048. Check with your insurance plan to find out what benefits are covered for colorectal cancer screening.

Because colorectal cancer may not cause symptoms at first, it's important to have screening tests for colorectal cancer. Screening tests look for signs of a disease before you have any symptoms. They can help find cancer early, when it may be easier to treat.

Most experts recommend that start screenings at 45 and continue until at least age 75. People over 75 and those who are at high risk should talk to their providers about how often you need screening and what type of test they should get.

The types of tests include different stool tests and procedures such as colonoscopies and flexible sigmoidoscopy. Talk with your provider about how often you need screening and what type of test you should get.

The U.S. Preventive Services Task Force recommends that adults age 45 to 75 be screened for colorectal cancer. The decision to be screened after age 75 should be made on an individual basis. If you are older than 75, ask your doctor if you should be screened. People at an increased risk of getting colorectal cancer should talk to their doctor about when to begin screening, which test is right for them, and how often to get tested.

Several screening tests can be used to find polyps or colorectal cancer. The Task Force outlines the following colorectal cancer screening strategies. It is important to know that if your test result is positive or abnormal on some screening tests (stool tests, flexible sigmoidoscopy, and CT colonography), a colonoscopy test is needed to complete the screening process. Talk to your doctor about which test is right for you.

Stool Tests

• The guaiac-based fecal occult blood test (gFOBT) uses the chemical guaiac to detect blood in the stool. It is done once a year. For this test, you receive a test kit from your health care provider. At home, you use a stick or brush to obtain a small amount of stool. You return the test kit to the doctor or a lab, where the stool samples are checked for the presence of blood.
• The fecal immunochemical test (FIT) uses antibodies to detect blood in the stool. It is also done once a year in the same way as a gFOBT.
• The FIT-DNA test (also referred to as the stool DNA test) combines the FIT with a test that detects altered DNA in the stool. For this test, you collect an entire bowel movement and send it to a lab, where it is checked for cancer cells. It is done once every one or three years.

Flexible Sigmoidoscopy

For this test, the doctor puts a short, thin, flexible, lighted tube into your rectum. The doctor checks for polyps or cancer inside the rectum and lower third of the colon.

How often: Every 5 years, or every 10 years with a FIT every year.

Colonoscopy

This is similar to flexible sigmoidoscopy, except the doctor uses a longer, thin, flexible, lighted tube to check for polyps or cancer inside the rectum and the entire colon. During the test, the doctor can find and remove most polyps and some cancers. Colonoscopy also is used as a follow-up test if anything unusual is found during one of the other screening tests.

How often: Every 10 years (for people who do not have an increased risk of colorectal cancer).

CT Colonography (Virtual Colonoscopy)

Computed tomography (CT) colonography, also called a virtual colonoscopy, uses X-rays and computers to produce images of the entire colon, which are displayed on a computer screen for the doctor to analyze.

How often: Every 5 years.

How Do I Know Which Screening Test Is Right for Me?

There is no single “best test” for any person. Each test has advantages and disadvantages. Talk to your doctor about the pros and cons of each test, and how often to be tested. Which test to use depends on—

• Your preferences.
• Your medical condition.
• The likelihood that you will get the test.
• The resources available for testing and follow-up.