colonoscopy

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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.

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 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. Occasionally air may be pumped through the colono-scope 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 can also 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 After the procedure, the colonoscope is slowly withdrawn and the instilled air is allowed to escape.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.

— Lata Cherath, PhD

Examination of the colon with a colonoscope. Also called coloscopy.

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." GastrointestinalEndoscopy 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 CaseFor 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

Key Terms: Barium enema, Biopsy, Colonoscope, Crohn's disease, Diverticulosis, Pathologist, Polyps.

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 also may 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 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. 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 also can be removed through the colonoscope. 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.

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, 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. 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 (two 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 seldom occurs (one 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 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.

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?

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., editors. Merck Manual of Diagnosis and Therapy. 17th ed. Rahway, NJ: Merck Publishing Group, 1999.

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

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

Periodicals

"Professional Organization Recommends Standard Colonoscopy Over Virtual." Biotech Week December 31, 2003: 422.

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

Organizations

American Cancer Society (National Headquarters). 1599 Clifton Road, N.E. Atlanta, Georgia 30329. (800) 227-2345. .

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

Cancer Research Institute (National Headquarters). 681 Fifth Avenue, New York, N.Y. 10022. (800) 992-2623. .

National Cancer Institute. 9000 Rockville Pike, Building 31, Room 10A31, Bethesda, Maryland, 20892. (800) 422-6237. .

Society of American Gastrointestinal Endoscopic Surgeons (SAGES). 2716 Ocean Park Boulevard, Suite 3000, Santa Monica, CA 90405. (310) 314-2404. .

United Ostomy Association, Inc. (UOA). 19772 MacArthur Blvd., Suite 200, Irvine, CA 92612. (800) 826 0826. .

—Lata Cherath, Ph.D.; Teresa G. Odle

Endoscopic examination of the colon, either transabdominally during laparotomy, or transanally by means of a colonoscope.

Intervention: Colonoscopy
ICD-10 code:
ICD-9 code:	45.23
MeSH	D003113
Other codes:

Colonoscopy is the endoscopic examination of the large colon and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It may provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy or removal of suspected lesions.

Virtual colonoscopy, which uses 2D and 3D imagery reconstructed from computed tomography (CT) scans or from nuclear magnetic resonance (MR) scans, is also possible, as a totally non-invasive medical test, although it is not standard and still under investigation regarding its diagnostic abilities. Furthermore, virtual colonoscopy does not allow for therapeutic maneuvers such as polyp/tumor removal or biopsy nor visualization of lesions smaller than 5 millimeters. If a growth or polyp is detected using CT colonography, a standard colonoscopy would still need to be performed.

Colonoscopy can remove polyps as small as one millimeter or less. Once polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not.

Colonoscopy is similar to but not the same as sigmoidoscopy, the difference being related to which parts of the colon each can examine. While colonoscopy allows an examination of the entire colon (measuring four to five feet in length), sigmoidoscopy allows doctors to view only the final two feet of the colon. A sigmoidoscopy is often used as a screening procedure for a full colonoscopy, in many instances in conjunction with a fecal occult blood test (FOBT), which can detect the formation of cancerous cells throughout the colon. Other times, a sigmoidoscopy is preferred to a full colonoscopy in patients having an active flare of ulcerative colitis or Crohn's disease to avoid perforation of the colon. Additionally, surgeons have lately been using the term pouchoscopy to refer to a colonoscopy of the ileo-anal pouch.

Contents 1 Reasons for procedure 2 Procedure 2.1 Preparation 2.2 The investigation 2.3 Ultrasound Duodenography and Ultrasound Colonography 2.4 Risks 2.5 Results 3 See also 4 References 5 External links

Reasons for procedure

Indications for colonoscopy include gastrointestinal hemorrhage, unexplained changes in bowel habit or suspicion of malignancy. Colonoscopies are often used to diagnose colon cancer, but are also frequently used to diagnose inflammatory bowel disease. In older patients (sometimes even younger ones) an unexplained drop in hematocrit (one sign of anemia) is an indication to do a colonoscopy, usually along with an esophagogastroduodenoscopy (EGD), even if no obvious blood has been seen in the stool (feces).

Fecal occult blood is a quick test which can be done to test for microscopic traces of blood in the stool. A positive test is almost always an indication to do a colonoscopy. In most cases the positive result is just due to hemorrhoids; however, it can also be due to diverticulosis, inflammatory bowel disease (Crohn's disease, ulcerative colitis), colon cancer, or polyps. However--since its development by Dr. Hiromi Shinya and Dr. William I. Wolff in the 1960s--polypectomy has become a routine part of colonoscopy, allowing for quick and simple removal of polyps without invasive surgery.^[1]

Due to the high mortality associated with colon cancer and the high effectivity and low risks associated with colonoscopy, it is now becoming a routine screening test for people 40 years of age or older. Subsequent rescreenings are then scheduled based on the initial results found, with a five- or ten-year recall being common for colonoscopies that produce normal results.^[2]

A study published in the New England Journal of Medicine (September 18, 2008) has found that among people who have had an initial colonoscopy that found no polyps, the risk of developing colorectal cancer within five years is extremely low. Therefore, there's no need for those people to have another colonoscopy sooner than five years after the first screening.^[3][4]

Procedure

Preparation

The colon must be free of solid matter for the test to be performed properly. For one to three days, the patient is required to follow a low fibre or clear-fluid only diet. Examples of clear fluids are apple juice, bouillon, lemon-lime soda or sports drink, and water. It is very important that the patient remains hydrated. Orange juice, prune juice, and milk containing fibre, should not be consumed, nor should liquids dyed red, orange, purple, or brown, however cola is allowed. In most cases black coffee is allowed.

The day before the colonoscopy, the patient is either given a laxative preparation (such as Bisacodyl, phospho soda, sodium picosulfate, or sodium phosphate and/or magnesium citrate) and large quantities of fluid or whole bowel irrigation is performed using a solution of polyethylene glycol and electrolytes.

Since the goal of the preparation is to clear the colon of solid matter, the patient should plan to spend the day at home in comfortable surroundings with ready access to toilet facilities. The patient may also want to have at hand moist toilettes or a bidet for cleaning the anus. A soothing salve such as petroleum jelly applied after cleaning the anus will improve patient comfort.

The patient may be asked to skip aspirin and aspirin-like products such as salicylate, ibuprofen, and similar medications for up to ten days before the procedure to avoid the risk of bleeding if a polypectomy is performed during the procedure. A blood test may be performed before the procedure.^[5][6]

The investigation

During the procedure the patient is often given sedation intravenously, employing agents such as fentanyl or midazolam. Although meperidine (Demerol) may be used as an alternative to fentanyl, the concern of seizures has relegated this agent to second choice for sedation behind the combination of fentanyl and midazolam. The average person will receive a combination of these two drugs, usually between 25 to 100 µg IV fentanyl and 1-4 mg IV midazolam. Sedation practices vary between practitioners and nations; in some clinics in Norway, sedation is rarely administered.^[7][8]

Some endocoscopists are experimenting with, or routinely use, alternative or additional methods such as nitrous oxide^[9][10] and propofol,^[11] which have advantages and disadvantages relating to recovery time (particularly the duration of amnesia after the procedure is complete), patient experience, and the degree of supervision needed for safe administration. This sedation is called "twilight anesthesia" and for some patients it doesn't take and they are indeed awake for the procedure and watch the inside of their colon on the color monitor. Substituting propofol for midazolam, which gives the patient quicker recovery, is gaining wider use, but requires closer monitoring of respiration.

The first step is usually a digital rectal examination, to examine the tone of the sphincter and to determine if preparation has been adequate. The endoscope is then passed through the anus up the rectum, the colon (sigmoid, descending, transverse and ascending colon, the cecum), and ultimately the terminal ileum. The endoscope has a movable tip and multiple channels for instrumentation, air, suction and light. The bowel is occasionally insufflated with air to maximize visibility. Biopsies are frequently taken for histology.

In most experienced hands, the endoscope is advanced to the junction of where the colon and small bowel join up (cecum) in under 10 minutes in 95% of cases. Due to tight turns and redundancy in areas of the colon that are not "fixed", loops may form in which advancement of the endoscope creates a "bowing" effect that causes the tip to actually retract. These loops often result in discomfort due to stretching of the colon and its associated mesentery. Maneuvers to "reduce" or remove the loop include pulling the endoscope backwards while torquing the instrument. Alternatively, body position changes and abdominal support from external hand pressure can often "straighten" the endoscope to allow the scope to move forward. In a minority of patients, looping is often cited as a cause for an incomplete examination. Usage of alternative instruments leading to completion of the examination has been investigated, including use of pediatric colonoscope, push enteroscope and upper GI endoscope variants.^[12]

For screening purposes, a closer visual inspection is then often performed upon withdrawal of the endoscope over the course of 20 to 25 minutes. Lawsuits over missed cancerous lesions have recently prompted some institutions to better document withdrawal time as rapid withdrawal times may be a source of potential medical legal liability.^[13] This is often a real concern in private practice settings where high throughput of cases have been postulated as a financial incentive to complete colonoscopies as quickly as possible.

Suspicious lesions may be cauterized, treated with laser light or cut with an electric wire for purposes of biopsy or complete removal polypectomy. Medication can be injected, e.g. to control bleeding lesions. On average, the procedure takes 20-30 minutes, depending on the indication and findings. With multiple polypectomies or biopsies, procedure times may be longer. As mentioned above, anatomic considerations may also affect procedure times.

After the procedure, some recovery time is usually allowed to let the sedative wear off. Outpatient recovery time can take an estimate of 30-60 minutes. Most facilities require that patients have a person with them to help them home afterwords (again, depending on the sedation method used).

One very common aftereffect from the procedure is a bout of flatulence and minor wind pain caused by air insufflation into the colon during the procedure.

An advantage of colonoscopy over x-ray imaging or other, less invasive tests, is the ability to perform therapeutic interventions during the test. A polyp is a growth of excess of tissue that can develop into cancer. If a polyp is found, for example, it can be removed by one of several techniques. A snare can be placed around a polyp for removal. Even if the polyp is flat on the surface it can often be removed. For example, the following shows a polyp removed in stages:

Polyp is identified	A sterile solution is injected under the polyp to lift it away from deeper tissues.	A portion of the polyp is now removed.	The polyp is fully removed.

Ultrasound Duodenography and Ultrasound Colonography

duodenography and colonography are performed like a standard abdominal examination using B-mode and color flow Doppler ultrasonography using a low frequency transducer for example a 2.5 MHz and a high frequency transducer for example a 7.5 MHz probe. Detailed examination of duodenal walls and folds, colonic walls and haustra was performed using a 7.5 MHz probe. Deeply located abdominal structures were examined using 2.5 MHz probe. All ultrasound examinations are performed after overnight fasting (for at least 16 hours) using standard scanning procedure. Subjects are examined with and without water contrast. Water contrast imaging is performed by having adult subjects take at least one liter of water prior to examination. Patients are examined in the supine, left posterior oblique, and left lateral decubitus positions using the intercostal and subcostal approaches. The liver, gall bladder, spleen, pancreas, duodenum, colon, and kidneys are routinely evaluated in all patients. With patient lying supine, the examination of the duodenum with high frequency ultrasound duodenography is performed with 7.5 MHz probe placed in the right upper abdomen, and central epigastric successively; for high frequency ultrasound colonography, the ascending colon, is examined with starting point usually midway of an imaginary line running from the iliac crest to the umbilicus and proceeding cephalid through the right mid abdomen; for the descending colon, the examination begins from the left upper abdomen proceeding caudally and traversing the left mid abdomen and left lower abdomen, terminating at the sigmoid colon in the lower pelvic region. Color flow Doppler sonography is used to examine the localization of lesions in relation to vessels. All measurements of diameter and wall thickness are performed with built-in software. Measurements are taken between peristaltic waves ^[14].

The abdominal quadrants scanned in the order.	The duodenal tri-band wall with folds of Kerckring, showing floaters with water contrast.	A high resolution view of colonic haustration.

Risks

This procedure has a low (0.35%) risk of serious complications.^[15][16]

The most serious complication generally is a tear or hole in the lining of the colon called a gastrointestinal perforation, which is life-threatening and requires immediate major surgery for repair; however, the rate of perforation is less than 1 in 2000 colonoscopies.

Bleeding complications may be treated immediately during the procedure by cauterization via the instrument. Delayed bleeding may also occur at the site of polyp removal up to a week after the procedure and a repeat procedure can then be performed to treat the bleeding site. Even more rarely, splenic rupture can occur after colonoscopy because of adhesions between the colon and the spleen.

As with any procedure involving anaesthesia, other complications would include cardiopulmonary complications such as temporary drop in blood pressure and oxygen saturation, usually the result of overmedication and easily reversed. In rare cases, more serious cardiopulmonary events such as a heart attack, stroke, or even death may occur; these are extremely rare except in critically ill patients with multiple risk factors.

Oral sodium phosphates for bowel preparation prior to colonoscopy carry a risk of acute renal failure under the form of phosphate nephropathy.^[17]

On very rare occasions, intracolonic explosion may occur.

High frequency ultrasound duodenography and colonography carry no risks associated with the procedures.

Results

A recent study published in the Annals of Internal Medicine^[18] implies that colonoscopy screening prevents approximately two thirds of the deaths due to colorectal cancers on the left side of the colon, and is not associated with a significant reduction in deaths from right-sided disease.^[19] This study examined people with colon cancer diagnosed between 1996 and 2001 in Ontario who died of colon cancer by 2003, and hence studied colonoscopies done in the early to mid 1990s. (Since the procedure continues to evolve, more recent colonoscopies may be more effective). The summary result, according to table 3 of the report, show approximately a 37% reduction in the death rate from colorectal cancer, with a significantly lower reduction in death for "incomplete" colonoscopies.

See also

• Anal probe
• Bow and arrow sign
• Rectal examination
• Sigmoidoscopy
• Polypectomy
• Virtual colonoscopy

References

1. ^ Sivak, Jr., Michael V. (2004-12). "Polypectomy: Looking Back". Gastrointestinal Endoscopy 60 (6): 977–982. doi:10.1016/S0016-5107(04)02380-6. ISSN 1097-6779. http://linkinghub.elsevier.com/retrieve/pii/S0016510704023806. 
2. ^ Rex, Douglas K.; Bond,John H.; Winawer,Sidney; Levin,Theodore R.; Burt,Randall W.; Johnson,David A.; Kirk,Lynne M.; Litlin,Scott; Lieberman,David A.; Waye,Jerome D.; Church,James; Marshall,John B.; Riddell,Robert H. (June 2002). "Quality in the technical performance of colonoscopy and the continuous quality improvement process for colonoscopy: recommendations of the U.S. Multi-Society Task Force on Colorectal Cancer". The American Journal of Gastroenterology 97 (6): 1296–1308. ISSN 0002-9270. http://dx.doi.org/10.1111/j.1572-0241.2002.05812.x. 
3. ^ "Five-Year Risk of Colorectal Neoplasia after Negative Screening Colonoscopy.". N Engl J Med 359: 1218–1224doi=10.1056/NEJMoa0803597. 2008. doi:10.1056/NEJMoa0803597. http://content.nejm.org/cgi/content/abstract/359/12/1218. Retrieved on 2008-09-17. 
4. ^ No Need to Repeat Colonoscopy Until 5 Years After First Screening Newswise, Retrieved on September 17, 2008.
5. ^ Decker, Joe (15 November 2006). "Preparation: Diet" (Blog). Colonoscopy Blog. Blogger.com. http://colonoscopyblog.blogspot.com/2006/11/details-of-preparation.html. Retrieved on 2007-06-12. 
6. ^ "Colyte/Trilyte Colonoscopy Preparation" (PDF). Palo Alto Medical Foundation. June 2006. http://www.pamf.org/gastroenterology/ColyteColon.pdf. Retrieved on 2007-06-12. 
7. ^ Bretthauer, M; Hoff G, Severinsen H, Erga J, Sugar J, Huppertz-Hauss G (20 May 2004). "[Systematic quality control programme for colonoscopy in an endoscopy centre in Norway]" (in Norwegian) (Abstract). Tidsskrift for den Norske laegeforening 124 (10): 1402–1405. ISSN 0029-2001. PMID 15195182. 
8. ^ The article PMID 20514160 was cited here, but this UID appears to be incorrect.
9. ^ Rikshospitalet University Hospital (April 2006). "Clinical Trial: Nitrous Oxide for Analgesia During Colonoscopy". ClinicalTrials.gov. http://www.clinicaltrials.gov/ct/show/NCT00318825. Retrieved on 2007-06-12. 
10. ^ Forbes, GM; Collins BJ (March 2000). "Nitrous oxide for colonoscopy: a randomized controlled study". Gastrointestinal Endoscopy 51 (3): 271–277. doi:10.1016/S0016-5107(00)70354-3. PMID 10699770. 
11. ^ Clarke, Anthony C; Louise Chiragakis, Lybus C Hillman and Graham L Kaye (18 February 2002). "Sedation for endoscopy: the safe use of propofol by general practitioner sedationists". Medical Journal of Australia 176 (4): 158–161. PMID 11913915. http://www.mja.com.au/public/issues/176_04_180202/cla10751.html. Retrieved on 2007-06-12. 
12. ^ Lichtenstein, Gary R.; Peter D. Park, William B. Long, Gregory G. Ginsberg, Michael L. Kochman (18 August 1998). "Use of a Push Enteroscope Improves Ability to Perform Total Colonoscopy in Previously Unsuccessful Attempts at Colonoscopy in Adult Patients". The American Journal of Gastroenterology 94 (1): 187. doi:10.1111/j.1572-0241.1999.00794.x. PMID 9934753.  Note:Single use PDF copy provided free by Blackwell Publishing for purposes of Wikipedia content enrichment.
13. ^ Barclay RL, Vicari JJ, Doughty AS, et al. (2006). Colonoscopic withdrawal times and adenoma detection during screening colonoscopy. 355. pp. 2533–41. 
14. ^ Njemanze, P. C., Njemanze J., Skelton A., Akudo A., Akagha O., Chukwu A. A., Peters C., Maduka O. (2008). High-frequency ultrasound imaging of the duodenum and colon in patients with symptomatic giardiasis in comparison to amebiasis and health subjects. Journal of Gastroenterology and Hepatology, Vol 23, No. 7 (2), e34-e42.
15. ^ "Colonoscopy Risks". January 16, 2008. http://ibdcrohns.about.com/od/colonoscopy/p/colonoscopy.htm. Retrieved on 2008-07-18. 
16. ^ J. A. Dominitz, et al., American Society for Gastrointestinal Endoscopy, "Complications of Colonsocopy", Gastrointestinal Endoscopy, Vol 57, No. 4, 2003, pp. 441-445
17. ^ Lien YH (September 2008). "Is bowel preparation before colonoscopy a risky business for the kidney?". Nat Clin Pract Nephrol 4: 606. doi:10.1038/ncpneph0939. PMID 18797448. 
18. ^ N.N. Baxter, M.A. Goldwasser, L.F. Paszat, R. Saskin, D.R. Urbach, and L. Rabeneck, "Association of Colonoscopy and Death from Colorectal Cancer: A Population-Based, Case–Control Study," Annals of Internal Medicine, Volume 150 Issue 1, 6 January 2009 article; (see also summary version, Effectiveness of Colonoscopy for Prevention of Mortality From Colorectal Cancer accessed December 22, 2009)
19. ^ "Real-world colonoscopy benefit seen more limited". Reuters. December 16, 2008. http://uk.reuters.com/article/healthNewsMolt/idUKTRE4BF6LJ20081216?pageNumber=1&virtualBrandChannel=0. 

External links

• LearnColoRectalSurgery.com - Colonoscopy pictures
• Colonoscopy. Based on public-domain NIH Publication No. 02-4331, dated February 2002.
• Patient Education Brochures. American Society for Gastrointestinal Endoscopy information

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