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Colon Screening - When it is recommended, and how can it change your life.

Colorectal Cancer Screening Tests

Adapted from Levin B., Lieberman DA., McFarland B. 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. Gastroenterology. 2008 May;134(5):1570-95.

Colonoscopy

This procedure involves the examination of the colon by use of a long, flexible, lighted tube called the colonoscope through which the doctor can view the entire colon and rectum for polyps or cancer and during the same exam remove pre-cancerous polyps. It is the test most gastroenterologists recommend as the single best screening exam for colorectal cancer. It is the only method that combines both screening and prevention (by removal of pre-cancerous polyps). The colonoscope has a camera at the end, which can project images on a screen. If a polyp is found, it can be removed by a wire loop that is passed through the colonoscope and hooked around the base of the polyp. The doctor sends an electric current through the loop, which severs the polyp from the colon wall and pulls it out of the colon. The polyp is then sent to a laboratory to be tested to determine whether it is cancerous. This procedure requires patients to be sedated and may take approximately 30 minutes. A colonoscopy can be performed safely in an ambulatory surgical center, an outpatient office or a hospital setting. Patients do not have to be hospitalized. Some pressure may be felt from the instrument's movements during the exam and there may be some cramping afterwards. Occasionally traces of blood will be seen in the stool after the procedure if a biopsy was taken or a polyp was removed. If you have more than a tablespoon of blood, you should call your doctor.

  • When to have this test: Recommended every 10 years after age 50 for average-risk individuals. Patients at higher risk for colorectal cancer, including those with a family history, or with polyps or other diseases, should talk to your gastroenterologist about appropriate screening intervals.
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  • Test preparation: Your doctor will prescribe a diet, often clear liquids, for the day prior to your examination. Laxatives and/or enemas will be required. For more information on colonoscopy, read the AGA Institute brochure on that topic in your gastroenterologist's office or visit www.gastro.org/patient.

Fecal Immunohistochemical Test (FIT)

FIT is a test that can detect blood in the stool with great accuracy. The test is available in a kit with which you can collect the stool samples at home and send them into a laboratory to test for blood coming from your colon. FIT is relatively easy to perform and inexpensive. It can only detect early cancers, not pre-cancerous polyps. You do not have to follow a special diet. If the FIT test is abnormal, you will require a regular colonoscopy for further evaluation.

When to have this test: It is recommended annually for persons beginning at age 50. If the test is positive, your doctor may recommend a colonoscopy examination.

Test preparation: FIT does not require a restricted diet.

Fecal Occult Blood Test (FOBT)

In this procedure, stool is tested in a laboratory for the presence of blood. The test is available in a kit with which you can collect the stool samples at home. You will need to follow a special diet when collecting your samples. This test, which is relatively easy and inexpensive, is designed to test for early cancers, but it does not detect pre-cancerous polyps. If the FOBT is abnormal, you will require a regular colonoscopy for further evaluation.

When to have this test: It is recommended annually for persons beginning at age 50. If the test is positive, your doctor may recommend a colonoscopy examination.

Test preparation: Avoid these items in your diet for two days prior to the test as they may affect the test results:

 

  • Cauliflower      
  • Cabbage
  • Horseradish     
  • Radishes
  • Turnips
  • Red meat
  • Vitamin C supplements
  • Foods containing iron
  • Aspirin, which can irritate the stomach

Sigmoidoscopy

Sigmoidoscopy is a test during which a doctor uses a short, flexible, lighted tube to check the rectum and the lower end of the colon for polyps and cancer. If a polyp or abnormality is found, you may require a regular colonoscopy for further evaluation. This test can be performed in a doctor's office and does not require anesthesia or sedation. You will need to take a cleansing enema prior to the procedure. Insertion of the flexible tube may be somewhat uncomfortable and some cramping may occur during the procedure, which takes about 10 minutes. After the test, there may be some mild abdominal gas pains. If the doctor took a biopsy, some traces of blood may be in the stool for a few days after the procedure.

  • When to have this test: This test is recommended every five years beginning at age 50 unless colonoscopies are being done.
  • Test preparation: One or two mild enemas are given prior to the test.

Computed Tomographic (CT) Colonography

This test involves an examination of your colon and rectum using a CT scanner to take pictures. A computer is used to combine the pictures creating both 2- and 3-dimensional views that allow a specially trained physician to "fly through" images of your colon and rectum to look for polyps and cancer. This procedure takes approximately 10 minutes and does not require sedation. You will need to take a preparation to cleanse your colon, much the same as for a regular colonoscopy, prior to the test. At the beginning of the test, a small flexible tube will be inserted into your rectum to introduce air into your colon. A CT colonography can be performed in an outpatient imaging center, an outpatient office or a hospital setting. If a polyp or other abnormality is discovered during the CT colonography, you will require a regular colonoscopy to biopsy or remove the abnormality.

  • When to have this test: Recommended every 5 years for average risk individuals. Patients at higher risk for colorectal cancer, including those with a family history, or with polyps or other diseases, should talk to your gastroenterologist about whether a regular colonoscopy may be a more appropriate screening method.
  • Test preparation: Your doctor will prescribe a diet, often clear liquids, for the day prior to your examination. Laxatives and/or enemas will be required just like the preparation for a regular colonoscopy.

Barium Enema

The procedure is an X-ray examination of the entire colon and rectum. It is an exam that is rarely performed any more because more accurate and comfortable tests are available. An enema is first given and then a soft, flexible tube is inserted into the rectum. A small amount of liquid called barium is inserted into the tube and is then removed. Air is injected into the colon. Special X-rays follow the flow of the barium in the colon and outline any lumps, polyps or abnormalities. A person may feel some cramping and a strong urge to move their bowels during the test. There may be some white or pinkish material in the bowel movements after the test. If a polyp or other abnormality is discovered on barium enema, you will require a regular colonoscopy to biopsy or remove the abnormality.

  • When to have this test: This test is part of the available options for screening, but is rarely performed.
  • Test preparation: A full 24 hours before the test, begin the special diet your doctor has prescribed. Eat or drink only clear liquids after midnight and during the morning before the test. Your doctor will prescribe a laxative to be taken the night before. The morning of the procedure, special enemas may be prescribed by your doctor.

Stool DNA (sDNA)

In this procedure, stool is tested in a laboratory to look for genetic DNA mutations. Colorectal cancer cells that contain altered DNA are shed into the large bowel and passed into the stool. The test is available using a special kit with which you collect the stool sample at home. You must have access to a working freezer as the stool specimen will need to be submitted back to the lab along with a specially designed ice pack. If the sDNA test is abnormal, you will require a regular colonoscopy for further evaluation.

  • When to have this test: All people over age 50 should be tested for colorectal cancer. If the test is positive, your doctor may recommend a colonoscopy examination. The screening interval for sDNA is unknown at this time and most insurance does not cover this test.
  • Test preparation: Since sDNA detects DNA in stool, preparaton does not require a restricted diet.

Digital Rectal Examination

A FOBT or FIT done during a digital rectal exam in the doctor's office is not adequate for screening.

Talk to your gastroenterologist to make an informed decision about which screening tests are right for you.

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Information Provided by Hattiesburg G.I. Associates, PLLC

American Gastroenterological Association. (April 23, 2010). Colorectal Cancer Prevention and Treatment.
From http://www.gastro.org/patient-center/digestive-conditions/colorectal-cancer web.