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Friday, September 10, 2010

Colonoscopy: What Patients Should Know

Roger Kao, MD

Published: November 10, 2009

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Colorectal cancer is the third most commonly diagnosed cancer and the third leading cause of cancer death in both men and women in the U.S., with approximately 150,000 new cases and 50,000 expected deaths each year.

All adults should undergo colorectal screening beginning at age 50 or earlier, depending upon the person's familial risk. Cancer detection tests (stool tests that detect blood or abnormal DNA) can help identify cancers at an early and possibly treatable stage. Cancer prevention tests (colonoscopy, CT colonography, flexible sigmoidoscopy) have the advantage of identifying abnormal growths called adenomatous polyps; these polyps can be removed before they become cancerous.

The American College of Gastroenterology, the American Society for Gastrointestinal Endoscopy and National Comprehensive Cancer Network each recommend colonoscopy as the preferred strategy for colon cancer screening. The major advantages of colonoscopy include that it is widely available, examines the entire colon, allows for diagnosis and removal of polyps in the same session, and is comfortable when carried out with sedation. Colonoscopy also has the longest rescreening interval of all forms of testing; if normal, the exam does not need to be repeated for 10 years. Unfortunately, only half of people aged 50 or older in the U.S. are being screened regularly.

Performing colonoscopy for colon cancer screening is a regular part of my gastroenterology practice and patients who require colonoscopy often have questions and concerns about the procedure.

What is a Colonoscopy?

A colonoscopy is an examination of the lower part of the gastrointestinal tract, which is called the colon or large intestine. The colonoscope, which is a flexible tube approximately the size of the index finger, is inserted into the rectum and advanced through the entire colon with careful examination of the lining upon withdrawal. Colonoscopy is a safe and effective procedure that provides information other tests may not be able to give. The procedure generally last between 15 to 45 minutes, although patients should plan on approximately two hours for waiting, preparation and recovery.

What are risk factors for colon cancer?

Increasing age — 90 percent of individuals diagnosed with colon cancer are older than 50 years of age. Risk increases with age throughout life.

Family history of colorectal cancer — Having colorectal cancer in a family member increases an individual's risk of cancer, especially if the family member is a first degree relative (a parent, brother or sister, or child), if several family members are affected, or if the cancers have occurred at an early age (before age 55 years).

A personal history of colorectal cancer or polyps — People who have previously had colorectal cancer have an increased risk of developing a new colorectal cancer. People who have had adenomatous polyps before the age of 60 years are also at increased risk for developing colorectal cancer.

Familial adenomatous polyposis — Familial adenomatous polyposis (FAP) is an uncommon inherited condition that increases a person's risk of colorectal cancer. Nearly 100 percent of people with this condition will develop colorectal cancer during their lifetime, and most of these cancers occur before the age of 50 years. FAP causes hundreds of polyps to develop throughout the colon.

Hereditary nonpolyposis colon cancer — Hereditary nonpolyposis colon cancer (HNPCC) is another inherited condition associated with an increased risk of colorectal cancer. HNPCC is suspected in those with a strong family history of colon cancer; several family members from different generations may have been affected, some of whom developed the cancer relatively early in life. People with HNPCC are also at risk for other types of cancer, including cancer of the uterus, stomach, bladder, kidney, and ovary.

Inflammatory bowel disease — People with Crohn's disease of the colon or ulcerative colitis have an increased risk of colorectal cancer. The amount of increased risk depends upon the amount of inflamed colon and the duration of disease; pancolitis (inflammation of the entire colon) and colitis of 10 years' duration or longer are associated with the greatest risk for colorectal cancer.

Lifestyle factors

Low-fiber, high-fat diet

Sedentary lifestyle

Obesity

Cigarette smoking

What are other reasons for performing colonoscopy?

In addition to screening for colorectal cancer, the other most common reasons for performing colonoscopy are to evaluate the following:

Blood in the stool or rectal bleeding

Dark/black stools

Persistent diarrhea

Iron deficiency anemia (a decrease in blood count due to loss of iron)

Surveillance in people with ulcerative colitis

For the medical management of chronic inflammatory bowel disease

Chronic, unexplained abdominal pain.

What preparation is required?

The colon must be completely cleaned of stool for the test results to be accurate and complete. This is accomplished by restricting what is eaten and by drinking a solution which flushes the colon clean. As a general rule, patients should not eat any solid food for the entire day before the examination. Only clear liquids such as black coffee, tea, soda, water, apple juice, cranberry juice, grape juice, Gatorade, clear broth, popsicles, and jello are recommended. Emptying the bowel of stool occurs by consuming a large volume of indigestible solution and special oral laxatives. Your doctor will tell you what dietary restrictions to follow and which specific preparation to use.

What happens during colonoscopy?

During a colonoscopy, the patient lies on their left side and a long, flexible tube (colonoscope) is inserted into the rectum and advanced through the entire colon and possibly a short distance into the small intestine. Medications will be administered through an intravenous line to help the patient better tolerate any discomfort. Most patients will receive a combination of a sedative (to help patients relax), and a narcotic (to prevent discomfort). Many people sleep during the examination while others are very relaxed, comfortable, and generally not aware of the examination. The vital signs are monitored before, during and after the examination. The entire lining of the colon is carefully examined as the colonoscope is slowly withdrawn. The procedure generally last between 15 to 45 minutes, although patient should plan on approximately two hours for waiting, preparation and recovery.

What are polyps and how are they removed?

Polyps are abnormal growths in the colon lining. Adenomatous polyps are thought to be the pre-cursors of colon cancer. They vary in size from a few millimeters to several inches. Polyps may be removed using a technique called snare polypectomy which involves passing a wire loop through the colonoscope and removing it from the intestinal wall using an electrical current. Smaller polyps are removed with biopsy instruments. Patients should feel no pain during the polyp removal.

What should I expect after the procedure?

After the colonoscopy, the patient will be observed until the effects of the sedative medication are gone. Your physician will explain the results of the examination to you, although biopsy or polyp tissue results will usually take a week to return. The most common discomfort after colonoscopy is a feeling of bloating and gas cramps. Patients may also feel groggy from the sedation medications. Patients should not return to work that day. Most patients are able to eat a regular diet after the examination.

Conclusion

Colonoscopy is the preferred strategy for colorectal screening because of its ability to identify and remove precancerous growths called polyps before they become cancer.

All patients at average risk should undergo colorectal screening beginning at age 50.

The colon must be completely clean for the tests results to be accurate and complete.

Colonoscopy is a safe, simple and effective test and patients are comfortable and relaxed during the entire examination.

References

1. Rex, DK, Johnson, DA, Anderson, JC, et al. American College of Gastroenterology guidelines for colorectal cancer screening 2008. Am J Gastroenterol 2009; 104:739. 2. Levin, B, Lieberman, DA, McFarland, B, et al. Screening and Surveillance for early detection of colorectal cancer and adenomatous polyps, 2008: A joint guideline from the American Cancer Society, The U.S. Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology, Ca, Cancer J Clin 2008. 3. Lieberman, DA, Weiss, DG, Bond, JH, et al. Use of colonoscopy to screen asymptomatic adults for colorectal cancer. Veterans Affairs Cooperative Study Group 380. N. Engl J Med 2000; 343:162. 4. Davila RE, Rajan E, Baron TH et al. ASGE guideline: colorectal cancer screening and surveillance. Gastrointest Endosc 2006; 63:546–557 Visit Roger's website.