Colonoscopy

Definition

Colonoscopy is an endoscopic medical procedure that uses a long, flexible, lighted tubular instrument called a colonoscope to view the rectum and the entire inner lining of the colon (large intestine).

Purpose

A colonoscopy is generally recommended when the patient complains of rectal bleeding, has a change in bowel habits, and/or has other unexplained abdominal symptoms. The test is frequently used to look for colorectal cancer, especially when polyps or tumor-like growths have been detected by a barium enema examination and other diagnostic imaging tests. Polyps can be removed through the colonoscope, and samples of tissue (biopsies) can be taken to detect the presence of cancerous cells. In addition, colonoscopy can also be used to remove foreign bodies, control hemorrhaging, and excise tumors.

The test also enables physicians to check for bowel diseases such as ulcerative colitis and Crohn's disease and is an essential tool for monitoring patients who have a past history of polyps or colon cancer. Colonoscopy is being used increasingly as a screening tool in both asymptomatic patients and patients at risk for colon cancer. It has been recommended as a screening test in all people 50 years or older.

Description

Colonoscopy can be performed either in a physician's office or in an endoscopic procedure room of a hospital. For otherwise healthy patients, colonoscopy is generally performed by a gastroenterologist or surgeon in an office setting; when performed on patients with other medical conditions requiring hospitalization, it is often performed in the endoscopy department of a hospital, where more intensive physiologic monitoring and/or general anesthesia can be better provided.

An intravenous line is inserted into a vein in the patient's arm to administer, in most cases, a sedative and a painkiller.

During the colonoscopy, patients are asked to lie on their sides with their knees drawn up towards the abdomen. The doctor begins the procedure by inserting a lubricated, gloved finger into the anus to check for any abnormal masses or blockage. A thin, well-lubricated colonoscope is then inserted into the anus and gently advanced through the colon. The lining of the intestine is examined through the colonoscope. The physician views images on a television monitor, and the procedure can be documented using a video recorder. Still images can be recorded and saved on a computer disk or printed out. Occasionally, air may be pumped through the colonoscope to help clear the path or open the colon. If excessive secretions, stool, or blood obstructs the viewing, they are suctioned out through the scope. The doctor may press on the abdomen or ask the patient to change position in order to advance the scope through the colon.

The entire length of the large intestine can be examined in this manner. If suspicious growths are observed, tiny biopsy forceps or brushes can be inserted through the colon and tissue samples can be obtained. Small polyps or inflamed tissue can be removed using tiny instruments passed through the scope. For excising tumors or performing other types of surgery on the colon during colonoscopy, an electrosurgical device or laser system may be used in conjunction with the colonoscope. To stop bleeding in the colon, a laser, heater probe, or electrical probe is used, or special medicines are injected through the scope. After the procedure, the colonoscope is slowly withdrawn and the instilled air is allowed to escape. The anal area is then cleansed with tissues. Tissue samples taken by biopsy are sent to a clinical laboratory, where they are analyzed by a pathologist.

The procedure may take anywhere from 30 minutes to two hours depending on how easy it is to advance the scope through the colon. Colonoscopy can be a long and uncomfortable procedure, and the bowel-cleansing preparation may be tiring and can produce diarrhea and cramping. During the colonoscopy, the sedative and the pain medications will keep the patient drowsy and relaxed. Some patients complain of minor discomfort and pressure from the colonoscope. However, the sedative and pain medication usually cause most patients to dose off during the procedure.

Patients who regularly take aspirin , nonsteroidal anti-inflammatory drugs (NSAIDs), blood thinners, or insulin should be sure to inform the physician prior to the colonoscopy. Patients with severe active colitis, extremely dilated colon (toxic megacolon), or severely inflamed bowel may not be candidates for colonoscopy. Patients requiring continuous ambulatory peritoneal dialysis are generally not candidates for colonoscopy due to a higher risk of developing intraperitoneal bleeding.

Diagnosis/Preparation

The physician should be notified if the patient has allergies to any medications or anesthetics, bleeding problems, or is pregnant. The doctor should be informed of all the medications the patient is taking and if he or she has had a barium enema x-ray examination recently. If the patient has had heart valves replaced, the doctor should be informed so that appropriate antibiotics can be administered to prevent infection. The risks are explained to the patient beforehand, and the patient is asked to sign a consent form.

The colon must be thoroughly cleansed before performing colonoscopy. Consequently, for two or more days before the procedure, considerable preparation is necessary to clear the colon of all stool. The patient is asked to refrain from eating any solid food for 24–48 hours before the test. Only clear liquid such as juices, broth, and gelatin are allowed. Red or purple juices should be avoided, since they can cause coloring of the colon that may be misinterpreted during the colonoscopy. The patient is advised to drink plenty of water to avoid dehydration. A day or two before the colonoscopy, the patient is prescribed liquid, tablet, and/or suppository laxatives by the physician. In addition, commercial enemas may be prescribed. The patient is given specific instructions on how and when to use the laxatives and/or enemas.

On the morning of the colonoscopy, the patient is not to eat or drink anything. Unless otherwise instructed by the physician, the patient should continue to take all current medications. However, vitamins with iron, iron supplements, or iron preparations should be discontinued for a few weeks prior to the colonoscopy because iron residue in the colon can inhibit viewing during the procedure. These preparatory procedures are extremely important to ensure a thoroughly clean colon for examination.

After the procedure, the patient is kept under observation until the medications' effects wear off. The patient has to be driven home and can generally resume a normal diet and usual activities unless otherwise instructed. The patient is advised to drink plenty of fluids to replace those lost by laxatives and fasting.

For a few hours after the procedure, the patient may feel groggy. There may be some abdominal cramping and a considerable amount of gas may be passed. If a biopsy was performed or a polyp was removed, there may be small amounts of blood in the stool for a few days. If the patient experiences severe abdominal pain or has persistent and heavy bleeding, this information should be brought to the physician's attention immediately.

For patients with abnormal results such as polyps, the gastroenterologist will recommend another colonoscopy, usually in another year or so.

Risks

The procedure is virtually free of any complications and risks. Rarely, (two in 1,000 cases) a perforation (a hole) may occur in the intestinal wall. Heavy bleeding due to the removal of the polyp or from the biopsy site occurs infrequently (one in 1,000 cases). Some patients may have adverse reactions to the sedatives administered during the colonoscopy, but severe reactions are very rare. Infections due to a colonoscopy are also extremely rare. Patients with artificial or abnormal heart valves are usually given antibiotics before and after the procedure to prevent an infection.

Normal results

The results are normal if the lining of the colon is a pale reddish pink and there are no masses that appear abnormal in the lining.

Abnormal results indicate polyps or other suspicious masses in the lining of the intestine. Polyps can be removed during the procedure, and tissue samples can be taken by biopsy. If cancerous cells are detected in the tissue samples, then a diagnosis of colon cancer is made. A pathologist analyzes the tumor cells further to estimate the tumor's aggressiveness and the extent of the disease. This is crucial before deciding on the mode of treatment for the disease. Abnormal findings could also be due to inflammatory bowel diseases such as ulcerative colitis or Crohn's disease. A condition called diverticulosis, which causes many small finger-like pouches to protrude from the colon wall, may also contribute to an abnormal result in the colonoscopy.

Morbidity and mortality rates

In 2003, an estimated 57,100 people will die from colorectal cancer. Although screening could find precancerous growths (polyps), which lead to colorectal cancer, screening rates in the United States remain low. Removing polyps before they turn into cancer could prevent the disease and potentially reduce deaths. Scientific evidence shows that more than one-third of deaths from colorectal cancer could be avoided if people aged 50 years and older were screened regularly.

Despite recent advances in screening and treatment for colon cancer, it is still one of the most common cancers among men and women in the United States. According to a report in the American Journal of Gastroenterology, there has been no improvement in colon cancer survival in the United States since the 1980s. As well, the number of patients surviving five years after their cancer diagnosis did not improve.

Recent National Cancer Institute-funded clinical trials show that taking daily aspirin for as little as three years could reduce the development of colorectal polyps by 19–35% in people at high risk for colorectal cancer.

The Center for Disease Control and Prevention recommends that everyone 50 years of age and over have one or a combination of the four recommended screening tests: fecal occult blood test, sigmoidoscopy , colonoscopy, or barium enema.

Alternatives

New research suggests that a simple blood test may identify people at risk of colorectal cancer. The blood test detects a genetic alteration that may identify people who are likely to develop the disease and who would benefit from additional screening; however, further research has to be done before this test becomes available.

Virtual colonoscopy is a new technique under development and evaluation for screening for colon polyps and cancer, and is undergoing continual improvement. One technique uses images from a magnetic resonance imaging (MRI) scan, and the other uses the x-ray images from a computerized tomography (CT) scan. They both provide views of the colon that are similar to those obtained in a colonoscopy. The images of the colon are produced by computerized manipulations rather than direct observation through the colonoscope.

While the CT scan technique is available in many radiology units, the MRI scan technique is still experimental. The colon is cleaned out using potent laxatives for both types of studies. A virtual image of the colon is formed after the scans are performed, and the images are analyzed and manipulated.

One benefit of the CT scan is that it can find polyps that occasionally are missed by colonoscopy because the polyps lie behind folds within the colon. Nevertheless, criticisms of the CT scan include:

• It cannot find small polyps (<0.2 in [5 mm] in size) that are easily seen in a colonoscopy.
• It is less able to find flat polyps compared to a colonoscopy.
• The procedure does not require patients to be sedated or put under anesthesia, and it can be performed in less than one minute, compared with about 30–60 minutes, plus recovery time required for standard colonoscopy.
• Small pieces of stool can look like polyps on the CT scan and lead to a diagnosis of polyp when there is none.
• If colonic polyps are found by virtual colonoscopy, then standard colonoscopy must be done to remove the polyps. As a result, the individual must undergo two procedures.

Although the CT scan is a good option for individuals who cannot or will not undergo standard colonoscopy, it has not been determined if it should be a primary screening tool for individuals at either normal risk or high risk for polyps or cancer.

Resources

books

Beers, Mark H. and Robert Berkow, eds. Merck Manual of Diagnosis and Therapy, 17th edition. Whitehouse Station, NJ: Merck & Co., 1999.

Dachman, Abraham H., (editor). Atlas of Virtual Colonoscopy. Berlin: Springer Verlag, 2003.

Dafnis, George. Colonoscopy: Introduction and Development, Completion Rates, Complications and Cancer Detection (Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, 1039). Uppsala, Sweden: Uppsala University, 2001.

Tierney, Lawrence M., Stephen J. McPhee, and Maxine A. Papadakis (editors). Current Medical Diagnosis & Treatment 2003. Stamford, CT: Appleton & Lange, 2002.

periodicals

Dominitz, J. A., et al. "Complications of Colonoscopy." Gastrointestinal Endoscopy 57, no 4 (April 2003): 441–5.

Isenberg, G. A., et al. "Virtual Colonoscopy." Gastrointestinal Endoscopy 57, no 4 (April 2003): 451–4.

Rabeneck, Linda, Hashem B. El-Serag, Jessica A. Davila, and Robert S. Sandler. "Outcomes of Colorectal Cancer in the United States: No Change in Survival (1986–1997)." The American Journal of Gastroenterology 98, no 2 (February 2003): 471–477.

organizations

American College of Gastroenterology (ACG). 4900-B South 31st Street, Arlington, VA 22206-1656. (703) 820-7400; Fax: (703) 931-4520. <http://www.acg.gi.org>.

Colorectal Cancer Network (CCNetwork). P.O. Box 182, Kensington, MD 20895-0182. (301) 879-1500; Fax: (301) 879-1901. <http://www.colorectal-cancer.net>.

International Foundation for Functional Gastrointestinal Disorders (IFFGD). P.O. Box 170864, Milwaukee, WI 53217. (888) 964-2001, (414) 964-1799; Fax: (414) 964-7176. Email: <iffgd@iffgd.org>. <http://www.iffgd.org>.

National Digestive Diseases Information Clearinghouse. 2 Information Way, Bethesda, MD 20892-3570. E-mail: <nddic@info.niddk.nih.gov>. <http://www.niddk.nih.gov>.

Society of American Gastrointestinal Endoscopic Surgeons (SAGES). 2716 Ocean Park Boulevard, Suite 3000, Santa Monica, CA 90405. (310) 314-2404; Fax: (310) 314-2585. <http://www.sages.org>.

Society of Gastroenterology Nurses and Associates Inc. 401 North Michigan Avenue, Chicago, IL 60611-4267. (800) 245-7462; Fax: (312) 527-6658. <http://www.sgna.org>.

other

Centers for Disease Control and Prevention. United States Department of Health and Human Services. Screen for Life. National Colorectal Cancer Action Campaign. 2003 [cited April 9, 2003] <http://www.cdc.gov/cancer/screen forlife/>.

Mayo Foundation for Medical Education and Research. Colorectal Cancer Screening Health Decision Guide. 2003 [cited April 4, 2003] <http://www.mayoclinic.com/invoke.cfm?objectid=B487B5A5-4F52-40E1-A76587E33E 0DD676>.

PDR Health (Thompson Healthcare). Colon Cancer: The Case For Early Detection. 2003 [cited April 2, 2003] <http://www.pdrhealth.com/content/lifelong_health/chapters/fgac31.shtml>.

Society of American Gastrointestinal Endoscopic Surgeons. Patient Information from Your Surgeon & SAGES. 2002 [cited April 9, 2003] <http://www.sages.org/pi_colonoscopy.html>.

Jennifer E. Sisk, MA Crystal H. Kaczkowski, MSc

Colonoscopy

Definition

Colonoscopy is a medical procedure during which a long, flexible, tubular instrument called the colonoscope is used to view the entire inner lining of the colon (large intestine) and the rectum.

Purpose

A colonoscopy is generally recommended when the patient complains of rectal bleeding or has a change in bowel habits or other unexplained abdominal symptoms. The test is frequently used to test for colorectal cancer, especially when polyps or tumor-like growths have been detected using the barium enema and other diagnostic tests. Polyps can be removed through the colonoscope and samples of tissue (biopsies) can be taken to test for the presence of cancerous cells.

The test also enables the physician to check for bowel diseases such as ulcerative colitis and Crohn's disease. It is a necessary tool in monitoring patients who have a past history of polyps or colon cancer . It may also be used as a screening tool for people at high risk of developing colon cancer, such as those with a strong family history of the disease.

Precautions

Patients who are pregnant or have a history of heart and lung disease and those with blood-clotting problems should tell the doctor about their health history before the procedure. Special precautions may be needed. For instance, a patient with artificial heart valves or a history of infection of the lining of the heart may need to take antibiotics to prevent infection. Patients also should tell the doctor about all medications they are taking. The doctor may want the patient to stop taking some drugs, such as aspirin, for a period of time before the procedure. Patients with some intestinal conditions should not have a colonoscopy. Examples of these conditions include acute diverticulitis, acute inflamatory bowel disease, a suspected perforation or break in the intestines, and recent abdominal surgery. Patients must be able to cooperate during the procedure.

Description

The procedure can be done either in the doctor's office or in a special procedure room of a local hospital. An intravenous (IV) line will be started in a vein in the arm. Through the IV line, the patient generally receives a sedative and a pain-killer if needed.

During the colonoscopy, the patient will be asked to lie on his/her left side with his/her knees drawn up toward the abdomen. The doctor begins the procedure by inserting a lubricated, gloved finger into the anus to check for any abnormal masses or blockage. A thin, well-lubricated colonoscope will then be inserted into the anus and it will be gently advanced through the colon. The lining of the intestine will be examined through the scope. Air is pumped through the colonoscope to help clear the path or make it easier to view the lining of the colon. If there are excessive secretions, stool or blood that obstruct the viewing, they will be suctioned out through the scope. The doctor may press on the abdomen or ask the patient to change his/her position in order to advance the scope through the colon.

The entire length of the large intestine can be examined in this manner. If suspicious growths are observed, tiny biopsy forceps or brushes can be inserted through the colonoscope and tissue samples can be obtained. Small polyps can also be removed through the colono-scope. Biopsies and the removal of polyps through the colonoscope are both painless procedures. After the procedure, the colonoscope is slowly withdrawn and the instilled air is allowed to escape. The anal area is then cleansed with tissues.

The procedure may take anywhere from 30 minutes to one hour, depending on how easy it is to advance the scope through the colon.

The bowel cleaning preparation may be tiring and often produces diarrhea and cramping. During the colonoscopy, the sedative will keep the patient drowsy and relaxed. Most patients complain of minor discomfort, such as cramping or a feeling of fullness. However, the procedure is not painful.

Preparation

The doctor should be notified if the patient has allergies to any medications or anesthetics, has any bleeding problems, or if a female patient is pregnant. The doctor should also be informed of all the medications that the patient is currently taking and if he or she has had a barium x-ray examination recently. The doctor may instruct the patient not to take certain medications, like aspirin and anti-inflammatory drugs that interfere with clotting, for a period of time prior to the procedure. If the patient has had heart valves replaced or a history of an inflammation of the inside lining of the heart, the doctor should be informed, so that appropriate antibiotics can be administered to prevent any chance of infection. The risks of the procedure will be explained to the patient before performing the procedure and the patient will be asked to sign a consent form.

It is important that the colon be thoroughly cleaned before performing the examination. Hence, before the examination, considerable preparation is necessary to clear the colon of all stool. The patient will be asked to refrain from eating any solid food for 24-48 hours before the test. Only clear liquids such as juices, broth, and gelatin are recommended. The patient is advised to drink plenty of water to avoid dehydration.

The day before the test, the patient will have to drink a special cleansing solution or take a strong laxative that the doctor has prescribed. The patient will also be given specific instructions as to how to use an enema, as a warm water enema may be necessary the next morning.

On the morning of the examination, one or two enemas of warm tap water may have to be taken. Generally, the procedure has to be repeated until the return from the enema is clear of stool particles. The patient is instructed not to eat or drink anything. The preparatory procedures are extremely important because the colon must be thoroughly clean for the exam to be performed.

Aftercare

After the procedure, the patient is kept under observation until the effects of the medications wear off. The patient will not be able to drive immediately after the procedure and can generally resume a normal diet and usual activities unless otherwise instructed. The patient will be advised to drink lots of fluids to replace those lost by laxatives and fasting.

For a few hours after the procedure, the patient may feel groggy. There may be some abdominal cramping and a considerable amount of gas may be passed. If a biopsy was performed or a polyp was removed, there may be small amounts of blood in the stool for a few days. If the patient experiences severe abdominal pain or has persistent and heavy bleeding, it should be brought to the doctor's attention immediately.

Risks

The procedure is considered safe. Very rarely (2 in 1, 000 cases) there may be a perforation (a hole) in the intestinal wall. Heavy bleeding due to the removal of the polyp or from the biopsy site occurs very infrequently (1 in 1, 000 cases). Infections due to a colonoscopy are also extremely rare. Patients with artificial or abnormal heart valves are usually given antibiotics before and after the procedure to prevent an infection.

Normal results

The results are said to be normal if the lining of the colon is a pale reddish pink and there are no abnormal looking masses that are found in the lining of the colon.

Abnormal results

Abnormal results would imply that polyps or other suspicious-looking masses were detected in the lining of the intestine. Polyps can be removed during the procedure and tissue samples can be biopsied. If cancerous cells are detected in the tissue samples, then a diagnosis of colon cancer is made. The pathologist analyzes the tumor cells further to estimate the aggressiveness of the tumor and the extent of spread of the disease.

Abnormal findings also could be due to inflammatory bowel diseases such as ulcerative colitis or Crohn's disease. A condition called diverticulosis, in which many small fingerlike pouches protrude from the colon wall, may also be identified.

Resources

BOOKS

Berkow, Robert et al., eds. Merck Manual of Diagnosis and Therapy, 17th edition. Rahway, NJ: Merck Publishing Group, 1999.

Fauci, Anthony S. "Gastrointestinal Endoscopy." In Harrison's Principles of Internal Medicine, 14th edition. New York, NY: The McGraw-Hill Companies, 2000.

Pfenninger, John L. Procedures for Primary Care Physicians, 2nd edition. St. Louis: Mosby, Inc. 2000.

Stauffer, Joseph and Joseph C. Segen. The Patient's Guide to Medical Tests. New York: Facts On File, 1997.

ORGANIZATIONS

American Cancer Society (National Headquarters). 1599Clifton Road, N.E. Atlanta, Georgia 30329. (800) 227-2345. <http://www.cancer.org>

American Gastroenterological Association. 7910 Woodmont Ave., Seventh Floor, Bethesda, MD 20814. Phone: (301) 654-2055. www.gastro.org.

Cancer Research Institute (National Headquarters). 681 Fifth Avenue, New York, N.Y. 10022. (800) 992-2623. <http://www.cancerresearch.org>

National Cancer Institute. 9000 Rockville Pike, Building 31, Room 10A31, Bethesda, Maryland, 20892. (800) 422-6237. <http://www.icic.nci.nih.gov>

Society of American Gastrointestinal Endoscopic Surgeons (SAGES). 2716 Ocean Park Boulevard, Suite 3000, Santa Monica, CA 90405. (310) 314-2404. <http://www.sages.org>

United Ostomy Association, Inc. (UOA). 19772 MacArthur Blvd., Suite 200, Irvine, CA 92612. (800) 826 0826. <http://www.uoa.org.>

Lata Cherath, Ph.D.

KEY TERMS

Barium enema

—An x-ray test of the bowel after giving the patient an enema of a white chalky substance that outlines the colon and the rectum.

Biopsy

—Removal of a tissue sample for examination under the microscope to check for cancer cells.

Colonoscope

—A thin, flexible, hollow, lighted tube that in inserted through the rectum into the colon to enable the doctor to view the entire lining of the colon.

Crohn's disease

—A chronic inflammatory disease resulting from the immune system attacking one's own body. The disease generally affects the gastrointestinal tract and may cause the formation of deep ulcers.

Diverticulosis

—A pouchlike section that bulges through the large intestine's muscular walls but is not inflamed. It may cause bleeding, stomach distress and excess gas.

Pathologist

—A doctor who specializes in the diagnosis of disease by studying cells and tissues under a microscope.

Polyps

—An abnormal growth that develops on the inside of a hollow organ such as the colon.

Ulcerative colitis

—A chronic condition where recurrent ulcers are found in the colon. It is manifested clinically by abdominal cramping, and rectal bleeding.

QUESTIONS TO ASK THE DOCTOR

• Did you see any abnormalities?
• How soon will you know the results of the biopsy (if one was done)?
• When can I resume any medications that were stopped?
• What future care will I need?

Colonoscopy

Definition

Colonoscopy is a medical procedure where a long, flexible, tubular instrument called the colonoscope is used to view the entire inner lining of the colon (large intestine) and the rectum.

Purpose

A colonoscopy is generally recommended when the patient complains of rectal bleeding or has a change in bowel habits and other unexplained abdominal symptoms. The test is frequently used to test for colorectal cancer, especially when polyps or tumor-like growths have been detected using the barium enema and other diagnostic tests. Polyps can be removed through the colonoscope and samples of tissue (biopsies) can be taken to test for the presence of cancerous cells.

The test also enables the physician to check for bowel diseases such as ulcerative colitis and Crohn's disease. It is a necessary tool in monitoring patients who have a past history of polyps or colon cancer.

Description

The procedure can be done either in the doctor's office or in a special procedure room of a local hospital. An intravenous (IV) line will be started in a vein in the arm. The patient is generally given a sedative and a pain-killer through the IV line.

During the colonoscopy, the patient will be asked to lie on his/her left side with his/her knees drawn up towards the abdomen. The doctor begins the procedure by inserting a lubricated, gloved finger into the anus to check for any abnormal masses or blockage. A thin, well-lubricated colonoscope then will be inserted into the anus and it will be gently advanced through the colon. The lining of the intestine will be examined through the scope. Occasionally air may be pumped through the colonoscope to help clear the path or open the colon. If there are excessive secretions, stool, or blood that obstruct the viewing, they will be suctioned out through the scope. The doctor may press on the abdomen or ask the patient to change his/her position in order to advance the scope through the colon.

The entire length of the large intestine can be examined in this manner. If suspicious growths are observed, tiny biopsy forceps or brushes can be inserted through the colon and tissue samples can be obtained. Small polyps also can be removed through the colonoscope. After the procedure, the colonoscope is slowly withdrawn and the instilled air is allowed to escape. The anal area is then cleansed with tissues.

The procedure may take anywhere from 30 minutes to two hours depending on how easy it is to advance the scope through the colon. Colonoscopy can be a long and uncomfortable procedure, and the bowel cleaning preparation may be tiring and can produce diarrhea and cramping. During the colonoscopy, the sedative and the pain medications will keep the patient very drowsy and relaxed. Most patients complain of minor discomfort and pressure from the colonoscope moving inside. However, the procedure is not painful.

A procedure called virtual colonoscopy has been developed but debate continues on whether or not it is effective as colonoscopy. Virtual colonoscopy refers to the use of imaging, usually with computed tomography (CT) scans or magnetic resonance imaging (MRI) to produce images of the colon. Studies in late 2003 showed that virtual colonoscopy was as effective as colonoscopy for screening purposes and it offered the advantage of being less invasive and less risky. However, many physicians were unwilling to accept it as a replacement for colonoscopy, particularly since some patients might still require the regular colonoscopy as a follow-up to the virtual procedure if a polyp or abnormality is found that requires biopsy.

Preparation

The doctor should be notified if the patient has allergies to any medications or anesthetics; any bleeding problems; or if the woman is pregnant. The doctor should also be informed of all the medications that the person is currently on and if he or she has had a barium x-ray examination recently. If the patient has had heart valves replaced, the doctor should be informed so that appropriate antibiotics can be administered to prevent any chance of infection. The risks of the procedure will be explained to the patient before performing the procedure and the patient will be asked to sign a consent form.

It is important that the colon be thoroughly cleaned before performing the examination. Before the examination, considerable preparation is necessary to clear the colon of all stool. The patient will be asked to refrain from eating any solid food for 24-48 hours before the test. Only clear liquids such as juices, broth, and gelatin are recommended. The patient is advised to drink plenty of water to avoid dehydration. The evening before the test, the patient will have to take a strong laxative that the doctor has prescribed. Several 1 qt enemas of warm tap water may have to be taken on the morning of the exam. Commercial enemas (e.g., Fleet) may be used.

The patient will be given specific instructions on how to use the enema and how many such enemas are necessary. Generally, the procedure has to be repeated until the return from the enema is clear of stool particles. On the morning of the examination, the patient is instructed not to eat or drink anything. The preparatory procedures are extremely important since, if the colon is not thoroughly clean, the exam cannot be done.

Aftercare

After the procedure, the patient is kept under observation until the effects of the medications wear off. The patient will have to be driven home by someone and can generally resume a normal diet and usual activities unless otherwise instructed. The patient will be advised to drink lots of fluids to replace those lost by laxatives and fasting.

For a few hours after the procedure, the patient may feel groggy. There may be some abdominal cramping and considerable amount of gas may be passed. If a biopsy was performed or a polyp was removed, there may be small amounts of blood in the stool for a few days. If the patient experiences severe abdominal pain or has persistent and heavy bleeding, it should be brought to the doctor's attention immediately.

Risks

The procedure is virtually free of any complications and risks. Very rarely (two in 1000 cases) there may be a perforation (a hole) in the intestinal wall. Heavy bleeding due to the removal of the polyp or from the biopsy site seldom occurs (one in 1000 cases). Infections due to a colonoscopy are also extremely rare. Patients with artificial or abnormal heart valves are usually given antibiotics before and after the procedure to prevent an infection.

Normal results

The results are said to be normal if the lining of the colon is a pale reddish pink and no abnormal looking masses are found in the lining of the colon.

Abnormal results

Abnormal results would imply that polyps or other suspicious-looking masses were detected in the lining of the intestine. Polyps can be removed during the procedure and tissue samples can be biopsied. If cancerous cells are detected in the tissue samples, then a diagnosis of colon cancer is made. The pathologist analyzes the tumor cells further to estimate the aggressiveness of the tumor and the extent of spread of the disease. This is crucial before deciding on the mode of treatment for the disease. Abnormal findings could also be due to inflammatory bowel diseases such as ulcerative colitis or Crohn's disease. A condition called diverticulosis, where many small fingerlike pouches protrude from the colon wall, may also contribute to an abnormal result in the colonoscopy.

Resources

PERIODICALS

"Professional Organization Recommends Standard Colonoscopy Over Virtual." Biotech Week December 31, 2003.

"Study Shows Virtual Colonoscopy as Effective as Traditional Colonoscopy." Biotech Week Dec. 31, 2003.

ORGANIZATIONS

American Cancer Society. 1599 Clifton Rd., NE, Atlanta, GA 30329-4251. (800) 227-2345. 〈http://www.cancer.org〉.

Cancer Research Institute. 681 Fifth Ave., New York, N.Y. 10022. (800) 992-2623. 〈http://www.cancerresearch.org〉.

National Cancer Institute. Building 31, Room 10A31, 31 Center Drive, MSC 2580, Bethesda, MD 20892-2580. (800) 422-6237. 〈http://www.nci.nih.gov〉.

United Ostomy Association, Inc. (UOA). 19772 MacArthur Blvd., Suite 200, Irvine, CA 92612-2405. (800) 826-0826. 〈http://www.uoa.org〉.

KEY TERMS

Barium enema— An x-ray test of the bowel after giving the patient an enema of a white chalky substance that outlines the colon and the rectum.

Biopsy— Removal of a tissue sample for examination under the microscope to check for cancer cells.

Colonoscope— A thin, flexible, hollow, lighted tube that in inserted through the rectum into the colon to enable the doctor to view the entire lining of the colon.

Crohn's disease— A chronic inflammatory disease where the immune system starts attacking one's own body. The disease generally starts in the gastrointestinal tract.

Diverticulosis— A condition where pouchlike sections that bulge through the large intestine's muscular walls but are not inflamed occur. They may cause bleeding, stomach distress, and excess gas.

Pathologist— A doctor who specializes in the diagnosis of disease by studying cells and tissues under a microscope.

Polyps— Abnormal growths that develop on the inside of a hollow organ such as the colon.

Ulcerative colitis— A chronic condition where recurrent ulcers are found in the colon. It is manifested clinically by abdominal cramping, and rectal bleeding.

colonoscopy (koh-lŏn-os-kŏpi) n. a procedure for examining the interior of the entire colon and rectum using a flexible illuminated fibreoptic instrument (colonoscope) introduced through the anus.

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