Disclaimer: The information provided on this website is designed for educational purposes only.  It is not intended to substitute as a professional service or as medical advice.  If there is, or suspicion of, a health problem, a health care provider should be contacted.

Overview

 

 

The colon is the last portion of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body. The last 13 inches of the colon is called the rectum.  Cancer that starts in the colon is called colon cancer. Cancer that starts in the rectum is called rectal cancer. Cancer of the colon and rectum is also called colorectal cancer.

Globally, cancer of the colon and rectum is the third leading cause of cancer in males and the fourth leading cause of cancer in females. In the United States, it is the second leading cancer. 

Incidences of Colon Cancer Worldwide
(GLOBOcon 2002)

The frequency of colorectal cancer varies around the world. It is common in the Western world and is rare in Asia and Africa.  In countries where the people have adopted western diets, the incidence of colorectal cancer is increasing.

 

Distribution of Colon Cancer Worldwide
(GLOBOcon 2002)

Colon cancer begins as polyps or growths in the colon. Symptoms that a person has polyps can include bleeding and stomach pain. Between 30-50% of all people screened have polyps. The polyps can easily be removed – before they become cancer - by appropriate screenings.  Screening for polyps is recommended for people when they reach 50, have a family history or other health conditions.  

   

What are colon polyps?

The large intestine, also called the colon, is part of the digestive system.  It is a long, hollow tube at the end of the digestive tract where the body makes and stores stool.  A polyp is extra tissue that grows inside the body.  Colon polyps grow in the large intestine.

 

Illustration of the digestive tract.

Digestive tract

Colon

   

Are polyps dangerous?

Most polyps are not dangerous. Most are benign, which means they are not cancer. But over time, some types of polyps can turn into cancer. Usually, polyps that are smaller than a pea aren't harmful. But larger polyps could someday become cancer or may already be cancer. To be safe, doctors remove all polyps and test them.

Illustration showing two normal intestinal folds and one polyp.
Colon polyp

There are basically 4 types of polyps that commonly occur within the colon:

  • Inflammatory - Most often found in patients with ulcerative colitis or Crohn's disease. Often called "pseudopolyps" (false polyps), they are not true polyps, but just a reaction to chronic inflammation of the colon wall. They are not the type that turns to cancer. They are usually biopsied to verify type.
  • Hyperplastic - A common type of polyp which is usually very small and found in the rectum. They are considered to be low risk for cancer.
  • Tubular adenoma or adenomatous polyp - This is the most common type of polyp and the one referred to most often when a doctor speaks of colon polyps. About 70% of polyps removed are of this type. Adenomas carry a definite cancer risk which rises as the polyp grows larger. Adenomatous polyps usually cause no symptoms, but if detected early they can be removed during colonoscopy before any cancer cells form. The good news is that polyps grow slowly and may take years to turn into cancer. Patients with a history of adenomatous polyps must be periodically reexamined.
  • Villous adenoma or tubulovillous adenoma- About 15% of polyps removed are of this type. This is a much more serious type of polyp that has a very high cancer risk as it grows larger. Often they are larger and sessile and not on a stem making removal more difficult. Smaller ones can be removed in piecemeal fashion - sometimes over several colonoscopies. Larger sessile villous adenomas may require surgery for complete removal. Follow up depends on size and completeness of removal.
   

Who gets polyps?

Anyone can get polyps, but certain people are more likely than others. You may have a greater chance of getting polyps if

  • you're over 50. The older you get, the more likely you are to develop polyps.
  • you've had polyps before.
  • someone in your family has had polyps.
  • someone in your family has had cancer of the large intestine.
Two men talking

Find out if someone in your family has had polyps. You may also be more likely to get polyps if you

  • eat a lot of fatty foods
  • smoke
  • drink alcohol
  • don't exercise
  • weigh too much
   

What are the symptoms?

Most small polyps don't cause symptoms. Often, people don't know they have one until the doctor finds it during a regular checkup or while testing them for something else. But some people do have symptoms like these:

  • bleeding from the anus. You might notice blood on your underwear or on toilet paper after you've had a bowel movement.
  • constipation or diarrhea that lasts more than a week.
  • blood in the stool. Blood can make stool look black, or it can show up as red streaks in the stool.

If you have any of these symptoms, see a doctor to find out what the problem is.

   

How does the doctor test for polyps?

The doctor can use the following tests to check for polyps:

  • Sigmoidoscopy. With this test, the doctor can see inside your large intestine. The doctor puts a thin flexible tube into your rectum. The device is called a sigmoidoscope, and it has a light and a tiny video camera in it. The doctor uses the sigmoidoscope to look at the last third of your large intestine.
  • Colonoscopy. This test is like sigmoidoscopy, but the doctor looks at all of the large intestine. It usually requires sedation.
Illustration of women being tested.
Colonoscopy or sigmoidoscopy testing
   

Who should get tested for polyps?

Talk to your doctor about getting tested for polyps if

  • you have symptoms
  • you're 50 years old or older
  • someone in your family has had polyps or colon cancer
Women talking to men.
   

How are polyps treated?

The doctor will remove the polyp. Sometimes, the doctor takes it out during sigmoidoscopy or colonoscopy. Or the doctor may decide to operate through the abdomen. The polyp is then tested for cancer.  If you've had polyps, the doctor may want you to get tested regularly in the future.

Illustration of Polyp being removed by a Colonoscope.
Polyp removal
   

How can I prevent polyps?

Doctors don't know of any one sure way to prevent polyps. But you might be able to lower your risk of getting them if you

  • eat more fruits and vegetables and less fatty food
  • don't smoke
  • avoid alcohol
  • exercise every day
  • lose weight if you're overweight

Eating more calcium and folate can also lower your risk of getting polyps. Some foods that are rich in calcium are milk, cheese, and broccoli. Some foods that are rich in folate are chickpeas, kidney beans, and spinach.

Some doctors think that aspirin might help prevent polyps. Studies are under way.

Illustration of women walking and two men sitting on a bench eating.
   

Points to Remember

  • A polyp is extra tissue that grows inside the body. Most polyps are not harmful.
  • Symptoms may include constipation or diarrhea for more than a week or blood on your underwear, on toilet paper, or in your stool.
  • Many polyps do not cause symptoms.
  • Doctors remove all polyps and test them for cancer.
  • Talk to your doctor about getting tested for polyps if
    • you have any symptoms
    • you're 50 years old or older
    • someone in your family has had polyps or colon cancer
   

Glossary

Abdomen (AB-duh-men): The area between the chest and the hips. It contains the stomach, small intestine, large intestine, liver, gallbladder, pancreas, and spleen.

Anus (AY-nus): The opening through which stool leaves the body.

Benign (buh-NINE): Not cancerous.

Colonoscopy (koh-luh-NAW-skuh-pee): A test to look inside the entire large intestine. The doctor uses a flexible tube that contains a light and a tiny video camera. This device is called a colonoscope.

Large intestine: A long, hollow tube in your body that makes and stores stool. Also called the colon.

Polyp (PAH-lip): An extra piece of tissue that grows inside the body.

Rectum (REK-tum): The last section of the large intestine, leading to the anus.

Sigmoidoscopy (SIG-moy-DAW-skuh-pee): A test to look inside the lower section of the large intestine. The doctor uses a flexible tube that contains a light and a tiny video camera. The device is called a sigmoidoscope.

Stool: The solid waste that passes through the rectum as a bowel movement.

   

What is the recommended age for screenng?

Physicians recommend screening beginning at age 50, if there are no other risk factors, such as family history.  The incidence of colon cancer increases with age.  Ninety percent of colon cancer diagnoses are in people over the age of 50.

 
   

What if there is a family history?

Twenty percent of people who develop colon cancer who have other family members who have had the disease.  People with a first-degree relative (parent, sibling, or child) with colon  cancer or adenomatous polyps*  diagnosed before 60 years or two first-degree relatives (grandparent, aunt, or uncle) diagnosed at any age should begin screening at age 40 or 10 years before the youngest case in the immediate family, whichever is earlier.  People diagnosed with cancer and/or who have adenomatous polyps should notify other family members.

   

What if you had previous cancers, ulcerative coliis or Crohn's disease

Women with a history of breast, ovarian, or endometrium cancer face an increased risk of developing colorectal cancer, as do people with inflammatory bowel disease, including ulcerative colitis and Crohn's disease. .  People who have had colorectal cancer, even though it was completely removed and there was chemotherapy or radiation treatment, and people who have a history of adenomatous polyps, especially, if they were large or if there were many of them, also have an increased risk. 

   

What is the effect of lifestyle?

Women with a history of breast, ovarian, or endometrium cancer face an increased risk of developing colorectal cancer, as do people with inflammatory bowel disease, including ulcerative colitis and Crohn's disease. .  People who have had colorectal cancer, even though it was completely removed and there was chemotherapy or radiation treatment, and people who have a history of adenomatous polyps, especially, if they were large or if there were many of them, also have an increased risk. 

   

What are comment screening tests?

 

Common screening tests for colorectal cancer screening include fecal occult blood testing (FOBT), sigmoidoscopy, and colonoscopy. Fecal occult blood testing uses a chemical reaction to find traces of blood in stool. A positive result on FOBT should lead to colonoscopy. Sigmoidoscopy involves looking into the rectum and lower colon through a flexible tube-shaped instrument with a camera on its tip. Colonoscopy uses a similar but longer instrument to look at the entire colon. During colonoscopy, doctors can take samples of the colon (biopsies) and remove polyps.

 

Newer tests that may help to screen for colorectal cancer include computed tomography, colonography ("virtual colonoscopy"), and stool tests that use DNA-based technology. "Virtual colonoscopy" uses x-rays and computers to produce multiple thin-sliced images of the inside of the colon. It takes about 10 minutes and does not require sedation, but it requires that a patient take laxatives before the test, like regular colonoscopy, and also involves exposure to radiation. Abnormal results from virtual colonoscopy need to be followed up with regular colonoscopy. A screening method that is still under study, is the DNA-based stool test.  It  is more expensive than FOBT but might be more accurate.
   

What is a colonoscopy?

A colonoscopy (koh-luh-NAH-skuh-pee) allows a doctor to look inside the entire large intestine. The procedure enables the physician to see things such as inflamed tissue, abnormal growths, and ulcers. It is most often used to look for early signs of cancer in the colon and rectum. It is also used to look for causes of unexplained changes in bowel habits and to evaluate symptoms like abdominal pain, rectal bleeding, and weight loss.

   

What is the colon

The colon, or large bowel, is the last portion of your digestive tract, or gastrointestinal tract. The colon is a hollow tube that starts at the end of the small intestine and ends at the rectum and anus. The colon is about 5 feet long, and its main function is to store unabsorbed food waste and absorb water and other body fluids before the waste is eliminated as stool

Illustration of the digestive system with the colon and rectum highlighted.
Digestive Tract
   

Preparation

You will be given instructions in advance that will explain what you need to do to prepare for your colonoscopy. Your colon must be completely empty for the colonoscopy to be thorough and safe. To prepare for the procedure you will have to follow a liquid diet for 1 to 3 days beforehand. The liquid diet should be clear and not contain food colorings, and may include

  • fat-free bouillon or broth
  • strained fruit juice
  • water
  • plain coffee
  • plain tea
  • diet soda
  • gelatin

Thorough cleansing of the bowel is necessary before a colonoscopy. You will likely be asked to take a laxative the night before the procedure. In some cases you may be asked to give yourself an enema. An enema is performed by inserting a bottle with water and sometimes a mild soap in your anus to clean out the bowels. Be sure to inform your doctor of any medical conditions you have or medications you take on a regular basis such as

  • aspirin
  • arthritis medications
  • blood thinners
  • diabetes medication
  • vitamins that contain iron

The medical staff will also want to know if you have heart disease, lung disease, or any medical condition that may need special attention. You must also arrange for someone to take you home afterward, because you will not be allowed to drive after being sedated.

   

Procedure

For the colonoscopy, you will lie on your left side on the examining table. You will be given pain medication and a moderate sedative to keep you comfortable and help you relax during the exam. The doctor and a nurse will monitor your vital signs, look for any signs of discomfort, and make adjustments as needed.

The doctor will then insert a long, flexible, lighted tube into your rectum and slowly guide it into your colon. The tube is called a colonoscope (koh-LON-oh-skope). The scope transmits an image of the inside of the colon onto a video screen so the doctor can carefully examine the lining of the colon. The scope bends so the doctor can move it around the curves of your colon.

You may be asked to change positions at times so the doctor can more easily move the scope to better see the different parts of your colon. The scope blows air into your colon and inflates it, which helps give the doctor a better view. Most patients do not remember the procedure afterwards.

The doctor can remove most abnormal growths in your colon, like a polyp, which is a growth in the lining of the bowel. Polyps are removed using tiny tools passed through the scope. Most polyps are not cancerous, but they could turn into cancer. Just looking at a polyp is not enough to tell if it is cancerous. The polyps are sent to a lab for testing. By identifying and removing polyps, a colonoscopy likely prevents most cancers from forming.

The doctor can also remove tissue samples to test in the lab for diseases of the colon (biopsy). In addition, if any bleeding occurs in the colon, the doctor can pass a laser, heater probe, electrical probe, or special medicines through the scope to stop the bleeding. The tissue removal and treatments to stop bleeding usually do not cause pain. In many cases, a colonoscopy allows for accurate diagnosis and treatment of colon abnormalities without the need for a major operation.

During the procedure you may feel mild cramping. You can reduce the cramping by taking several slow, deep breaths. When the doctor has finished, the colonoscope is slowly withdrawn while the lining of your bowel is carefully examined. Bleeding and puncture of the colon are possible but uncommon complications of a colonoscopy.

A colonoscopy usually takes 30 to 60 minutes. The sedative and pain medicine should keep you from feeling much discomfort during the exam. You may feel some cramping or the sensation of having gas after the procedure is completed, but it usually stops within an hour. You will need to remain at the colonoscopy facility for 1 to 2 hours so the sedative can wear off.

Rarely, some people experience severe abdominal pain, fever, bloody bowel movements, dizziness, or weakness afterward. If you have any of these side effects, contact your physician immediately. Read your discharge instructions carefully. Medications such as blood-thinners may need to be stopped for a short time after having your colonoscopy, especially if a biopsy was performed or polyps were removed. Full recovery by the next day is normal and expected and you may return to your regular activities.

 
   

What tests are used to see if the caner cells have spread?

After colon cancer has been diagnosed by analyzing polyps that have been removed, tests are done to find out if cancer cells have spread within the colon or to other parts of the body. The process used to find out if cancer has spread within the colon or to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment. The following tests and procedures may be used in the staging process:

  • CT scan(CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
  • Lymph node biopsy: The removal of all or part of a lymph node. A pathologist views the tissue under a microscope to look for cancer cells.
  • Complete blood count (CBC): A procedure in which a sample of blood is drawn and checked for the following:
  • Carcinoembryonic antigen (CEA) assay: A test that measures the level of CEA in the blood. CEA is released into the bloodstream from both cancer cells and normal cells. When found in higher than normal amounts, it can be a sign of colon cancer or other conditions.
  • MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the colon. A substance called gadolinium is injected into the patient through a vein. The gadolinium collects around the cancer cells so they show up brighter in the picture. This procedure is also called nuclear magnetic resonance imaging (NMRI).

  • Chest x-ray: An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.

  • Surgery: A procedure to remove the tumor and see how far it has spread through the colon.
   

How does cancer spread in the body?

The three ways that cancer spreads in the body are:>

  • Through tissue. Cancer invades the surrounding normal tissue.
  • Through the lymph system. Cancer invades the lymph system and travels through the lymph vessels to other places in the body.
  • Through the blood. Cancer invades the veins and capillaries and travels through the blood to other places in the body.

When cancer cells break away from the primary (original) tumor and travel through the metastasis. The secondary (metastatic) tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the bones, the cancer cells in the bones are actually breast cancer cells. The disease is metastatic breast cancer, not bone cancer.

   

How is colon cancer staged?

As colon cancer progresses from Stage 0 to Stage IV, the cancer cells grow through the layers of the colon wall and spread to lymph nodes and other organs.

- Stage 0 cells are found in the innermost lining of the colon. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called carcinoma in situ.

- Stage I colon cancer has formed and spread beyond the innermost tissue layer of the colon wall to the middle layers. Stage I colon cancer is sometimes called Dukes A colon cancer.

- Stage II colon cancer is divided into stage IIA and stage IIB. Stage II colon cancer is sometimes called Dukes B colon cancer.

Recurrent colon cancer is cancer that has recurred (come back) after it has been treated. The cancer may come back in the colon or in other parts of the body, such as the liver, lungs, or both.

   

What treatment plans are used?

Treatment for colon cancer usually includes surgery followed by chemotherapy.  Rectal cancers - cancers found in the first 12 inches of the colon - usually includes radiation and chemotherapy, followed by surgery, followed by additional chemotherapy.

   

Acknowledgements