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).


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.


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.


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.


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.


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:

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.



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.


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.


American College of Gastroenterology (ACG). 4900-B South 31st Street, Arlington, VA 22206-1656. (703) 820-7400; Fax: (703) 931-4520. .

Colorectal Cancer Network (CCNetwork). P.O. Box 182, Kensington, MD 20895-0182. (301) 879-1500; Fax: (301) 879-1901. .

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: .

National Digestive Diseases Information Clearinghouse. 2 Information Way, Bethesda, MD 20892-3570. E-mail: .

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

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


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] forlife/ .

Mayo Foundation for Medical Education and Research. Colorectal Cancer Screening Health Decision Guide. 2003 [cited April 4, 2003] 0DD676 .

PDR Health (Thompson Healthcare). Colon Cancer: The Case For Early Detection. 2003 [cited April 2, 2003] .

Society of American Gastrointestinal Endoscopic Surgeons. Patient Information from Your Surgeon & SAGES. 2002 [cited April 9, 2003] .

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

Also read article about Colonoscopy from Wikipedia

User Contributions:

My husband will be having a colonoscopy in a week. Should he avoid taking any Iron supplements? I am confused if he should stop the Iron supplements or the E supplements. Would appreicate your advice, thanks for your help.
Does a colonoscopy risk increase if a woman had a vertical cesarean section, 36 years ago?
this is to help with your paper for freshman orientation
What is the name of the liquid taken prior to having a colonoscopy--not "go lightly" but another one that is in a small bottle that you follow with water. It is sort of fizzy. Thanks.
im doinga' project about this but i was woundering would u send me more informantion about this on my e mail
I've had Crohn's for over 20 years and had a colonscopy at that time as well. At that time I had a fistula. They surgically removed 1/3 of my large intestine and 22 inches of my small. When I had a colonoscopy a few months ago they could not get the scope past swelling and scar tissue, thus not able to inspect all of the intestine. Is this normal to not be able to complete this type of test?
Wayne Brady
I found this article very helpful. The operation has a high success rate of finding polyps, and is a very safe procedure if done by a professional. I personally am trying to figure out just how helpful they are, and if they're worth all the trouble. amazing tool though, none the less.
the most painful experience i have ever had is a colonoscopy. it felt like being murdered. in fact i was once beaten and left for dead and it was nowhere this painful. i've had broken bones, broken hand, broken ribs, stepped on a knife and it passed through my foot, infections by aggressive microbes. botched surgery, frostbite, migraine, phlebitis, all less painful. 3 times. twice in the VA. once in a private hospital in Turkey. it feels like razor blades insides. why do no MD websites mention the pain.
I had my first colonoscopy today without medication ( my request). All I can say is wow, horrible incredible pain!! They had to abort it half way through, and I doubt I will do another one. I do not want their amnesia causing drugs, and hate to be out of maybe I will ask for a barium enema instead!! even that sounds like more fun! I was prepared for some pain and discomfort, but that was off the charts!
If polyps are found during a colonoscopy, how long will it take to do biopsy and get results?
I went to have what is considered a regular colonoscopy procedure. This would have been my frist one. The person that did the procedure went through and when he came out he procedure my colon was punched. They had to call in a surgent to rush me to surgery and during surgery they fixed my colon found that I had a Hernia they fixed it and I awoke in a hospital room What should of only took 2hr. I spent 4 days. He sat with my family telling them how sorry he was. The surgery was 4 hours that he sat with them. He came to my room twice to apologize to me.
I need to know if there is any medical explanation for extreme pain in my vagina following a "routine" colonoscopy procedure. I had a procedure before with polyps removed and did not have this problem, and only mild discomfort. The doctor said he found no major problems during this colonoscopy and it was a "routine procedure".

So why would I wind up with such burning pain in my vagina that I could barely walk and was back at the emergency room that night. It took almost 6 months to heal. Can that ever happen without something being inserted in my vagina? The only other explanation of course is that I was raped under total sedation as I was completely knocked out in three seconds, and did not come to until I was alone in the recovery area. Thank you for your research on my behalf.

Thank you for your reply.
linda tozer
can one have a MRI SCAN on the NHS? FOR THIS PROCEDURE.
Michael Izzi
I have had colonoscopies since 1985 and have never experienced the post procedure gas pains and bloating as I have after my last one. Could this be due to improper extraction of the scope without following proper procedure to allow enough time for the air to escape?
The day after my colonoscopy, I am having intense vaginal pain and pressure. I get why the previous person pondered rape. I DO NOT believe that is what happened, as there were way too many people in the room, about 5. Hubby and I had an argument shortly after the procedure and I woke up the following morning feeling this intense pressure. I guess it's worth noting I had a partial hysterectomy for years ago.
Woke up with labial irritation and an annul tear. Not explanation. 30 days post op and I am on pain killers. Not even getting a call back from local doctors. Gastro didn't call back today, either. Will never have a colonoscopy again!
I had colonoscope done yesterday. they gave me a sedative to put me to sleep for the procedure but I woke up half way through. I saw everything on the tv screen and heard the doctor saying that I may need an operation, then the pain in my stomach. it was pretty bad. after about 5 minutes the doctor finished and took out the scope. the pain didn't go away. the doctor said it's because of the air that was pumped in. the pain went away after a while and passing a lot of gas. the doctor said he was concerned about a small section that was flat. I asked if it was cancer and he said he didn't know. ?? so now I have to go do it again at the hospital.
Venice Miro
My father blood count is 56 so the doctor advice as for blood transfusion immediately. (3 bags) . I just want to know if its okey to undergo colonoscopy if the patient is in bleeding condition. Is there risk for that?
I am 72 and recently had a colonoscopy. I was so nervous and had put this one off for 14 plus years. My doctor and the staff was fantastic. I am that it is over with and everything went well. Please have a positive attitude when going thru a procedure. Always read and find out about the procedure, know and trust you doctor and the staff.
Lawrence Mitten
I had colon polyps removed 25 days ago and I am still in pain Is this normal.

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