Colonoscopy

Colonoscopy allows a doctor to look at the interior lining of the large intestine (rectum and colon) through a thin, flexible viewing instrument called a colonoscope. The colonoscope helps the doctor detect polyps, tumors, and areas of inflammation or bleeding. During a colonoscopy, tissue samples can be collected (for biopsy) and abnormal growths can be removed. Colonoscopy can also be used as a screening test to identify and remove precancerous and cancerous growths in the colon.

The colonoscope is a thin, flexible scope that ranges from 48 in. (121.92 cm) to 72 in. (182.88 cm) long. A small video camera is attached to the colonoscope so that photographic, electronic, or videotaped images of the large intestine can be made. In some cases, the colonoscope may use fiber optics. However, digital video technology has generally replaced fiber optics. The colonoscope can be used to view the entire colon as well as a small portion of the lower small intestine. Another test called sigmoidoscopy shows only the rectum and the lower third of the colon (see Sigmoidoscopy test).

Why It Is Done

Colonoscopy is done to:

• Detect problems or diseases of the anus, rectum, or large intestine (colon). These tests are often done to investigate symptoms such as unexplained bleeding from the rectum, prolonged diarrhea or constipation, obvious or hidden (occult) blood or pus in the stool (feces), or lower abdominal pain.
• Evaluate abnormal results from a barium enema test (see Barium Enema test).
• Screen for colon cancer or polyps.
• The American Gastroenterological Association recommends that people over age 50 who are at average risk for colon cancer undergo regular screening that includes yearly fecal occult blood testing (FOBT) combined with flexible sigmoidoscopy testing every five years (see the medical tests Sigmoidoscopy and Home Fecal Occult Blood Test for Colorectal Cancer). If results from either FOBT or sigmoidoscopy are abnormal, a follow-up colonoscopy with double-contrast barium enema is recommended (see Barium Enema test).
• The American Gastroenterological Association recommends that people at increased risk for colon cancer start FOBT and sigmoidoscopy screening at age 40, with a follow-up colonoscopy plus double-contrast barium enema if results from either FOBT or sigmoidoscopy are abnormal. Factors that increase a person's risk of developing colon cancer include a family history of the disease, a personal history of colon polyps or ulcerative colitis, or both. High-fat and low-fiber diets have also been linked to colorectal cancer.

Colonoscopy may also be done to:

• Screen for recurrence of colon cancer in people who have had surgical treatment for colon cancer.
• Monitor the growth of polyps that cannot be completely removed.
• Monitor treatment of inflammatory bowel disease.
• Remove polyps or take tissue samples (for biopsy) when colon cancer or other bowel disease is suspected.

How to Prepare

Before you have a colonoscopy, tell your doctor if:

• You are taking any medications.
• You are allergic to any medications, including anesthetics.
• You have had bleeding problems or are taking blood-thinning medications (such as Coumadin or medications that contain aspirin).
• You have a history of heart disease.
• Within the past 4 days, you have had an X-ray test using barium contrast material (such as a barium enema).
• You are or might be pregnant.

You will be asked to sign a form (consent form) that says you understand the risks of colonoscopy and agree to have the test done. As you read the consent form, you should ask your doctor any questions you have about the test and discuss any worries you may have about the need for the test, the risks of the test, or how it will be done.

Before this exam, you will need to clean out your colon. Your doctor's ability to see inside your colon depends on how thoroughly it has been cleared of stool (feces). Your doctor will give you specific instructions before your exam that take into consideration your health, age, and other medical conditions you may have. If you are taking medications for heart problems or arthritis, check with your doctor about which medications you need to take on the day of your exam.

The following information helps give you a general idea of how you might prepare for a colonoscopy.

• One to two days before a colonoscopy, you will need to stop eating solid foods and drink only clear liquids, such as water, tea, coffee, clear juices, clear broths, and gelatin (such as Jell-O). Do not eat or drink red food items such as red juice or red Jell-O.
• Your doctor may have you take a prescription laxative tablet or a laxative solution the day before the exam.
• You may need to drink a laxative solution prescribed by your doctor (such as Nulytely or Golytely) the evening before your colonoscopy. This solution will be given to you as a powder that you will mix with 1 gal (3.8 L) of water. You are often encouraged to drink this laxative solution over 1 to 2 hours. This solution may taste very salty and may make you feel nauseated. Each time you drink the solution, you may drink some water or clear liquids (like apple juice) to help cleanse the taste from your mouth.
• Continue to drink plenty of clear liquids to avoid dehydration and to help clean out your colon completely.
• Do not eat any solid foods after drinking the laxative solution.
• Stop drinking clear liquids 6 hours before the test.

You will need to have someone drive you home after the exam because you will be given medicine during the exam that will usually make you feel drowsy and may make it unsafe for you to drive.

How It Is Done

Colonoscopy may be done in a doctor's office or a hospital. The test is most often performed by a doctor who specializes in problems of the digestive system (gastroenterologist). The doctor may also have an assistant. Some family doctors, internists, and surgeons are also trained to do colonoscopy.

During the procedure, you may receive a pain medication (such as meperidine or Demerol) and a sedative (such as midazolam hydrochloride or Versed) through an intravenous (IV) line, usually in a vein in your arm or hand. These medications reduce pain and will make you feel relaxed and drowsy during the procedure.

You will need to take off most of your clothes. You will be given a cloth or paper covering to use during the test.

You will lie on your left side with your knees drawn up toward your abdomen. Once you are in position, the doctor will gently insert a gloved finger into your anus to check for tenderness or blockage. Then the thin, well-lubricated colonoscope is gently inserted and advanced while the intestinal lining of the colon is examined through the scope. In some settings, the doctor may also view your abdomen on an X-ray screen (fluoroscope) to check the position of the colonoscope.

You may feel the urge to have a bowel movement while the scope is in your colon. You may also feel some cramping. Try to breathe deeply and slowly through your mouth to relax your abdominal muscles and ease any discomfort. You will probably feel and hear some air escape around the scope. There is no need to be embarrassed about it. The passing of air is expected. You may be asked to change your position during the test.

Your doctor will try to examine the entire length of your large intestine. As the colonoscope is slowly withdrawn, extra care will be taken to examine the entire inner lining of your colon. The doctor may also insert tiny instruments (forceps, loops, swabs) through the colonoscope to collect tissue samples (biopsy) or remove growths. (The biopsy procedure is completely painless.) The colonoscope is then slowly withdrawn and the air is allowed to escape. After the scope is removed, your anal area will be cleaned with tissues. If you are having cramps, passing gas may help relieve them.

The procedure usually takes about 30 minutes, but it may take longer, depending upon what is found and what is done during the procedure.

After the test, you will be observed for 1 to 2 hours until the medications given to you during the exam wear off. When you are fully recovered, you can go home. You will not be able to drive or operate machinery for 12 hours after the exam. Your doctor will tell you when you can resume your usual diet and activities. Drink lots of liquids after the exam to replace the fluids you may have lost while you were taking the laxative solution.

How It Feels

This exam can be embarrassing and uncomfortable. Knowing what to expect can help eliminate fears and ease discomfort. The bowel cleaning preparation, especially the strong laxatives taken the day before, can produce diarrhea and cramping, which may keep you in the bathroom for the better part of the night.

During the exam, you may feel very drowsy and relaxed from the sedative and pain medications. You may have cramping or a feel brief, sharp pain when the scope is advanced or air is blown into your colon. As the scope is moved up the colon, you may feel the urge to have a bowel movement and expel gas. If you are experiencing pain, tell your doctor.

The suction machine used to remove stool (feces) and secretions may be noisy but does not cause pain. The removal of biopsy specimens and polyps is also painless, since the lining of your intestine does not contain nerves that detect pain.

You will feel groggy after the procedure until the medication wears off, usually in a few hours. Many people report that they remember very little of the exam because of the sedative given before and during the procedure.

After the procedure, you may have crampy gas pains and may need to pass some gas. If a biopsy was done or a polyp removed, you may have traces of blood in your stool (feces) for a few days. If polyps were removed, you may be instructed to avoid taking aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) for 7 to 14 days after the procedure. If you have heavy rectal bleeding, severe abdominal pain, or fever after the procedure, notify your doctor immediately.

Risks

Complications from colonoscopy are rare. There is a slight risk of puncturing the colon (less than 1 in 1,000) or causing severe bleeding by damaging the wall of the colon (less than 3 in 1,000). There is also a slight risk of causing a colon infection.

People who have certain types of heart murmurs, artificial heart valves, or previous infections of a heart valve will need antibiotics before and after the test to prevent infection. An irregular heartbeat may occur during the test but nearly always subsides on its own without treatment.

Results

If a sample of tissue was collected during the colonoscopy, it will be sent to a lab for further analysis.

• Samples of colon tissue are usually sent to a pathology lab, where they are examined under a microscope for evidence of certain diseases or infection.
• Other samples of colon tissue may be sent to a microbiology lab to determine if certain kinds of infection are present.

Your doctor may be able to discuss some of the findings with you immediately after the procedure. Other results are usually available in 2 to 4 days. Tests for certain infections may take several weeks.

What Affects the Test

• A barium enema done within a week before colonoscopy may make it difficult or impossible to get accurate test results. The presence of barium in the colon or rectum can block the view of the colon and may interfere with test results.
• Stool (feces) in the colon, a colon that has many turns, prior surgery on the colon, or extreme discomfort of the person being tested may make a thorough exam difficult or impossible.
• Taking iron supplements may make the stool turn black and may make it difficult to cleanse the colon adequately. Avoid taking iron supplements for several days before a colonoscopy exam.
• Red liquids or red gelatin ingested before a colonoscopy can discolor gastrointestinal secretions, and may be mistaken for blood.

What to Think About

• In general, pregnant women or people who have severe heart disease, an abdominal infection, or diverticulitis should not have a colonoscopy unless there is an important reason for it.
• Colonoscopy is a more expensive procedure than a barium enema and other endoscopic colon exams (such as proctoscopy or sigmoidoscopy). Colonoscopy may also involve greater risk and inconvenience to the person than sigmoidoscopy, and not all colonoscopy exams allow the doctor to view the whole colon. See the Sigmoidoscopy test for more information.
• The use of colonoscopy for people over age 50 who are at average risk for colon cancer is debated among doctors. Some recommend that individuals in this population undergo colonoscopy every ten years to screen for colon cancer. The American Gastroenterological Association recommends that people over age 50 who are at average risk for colon cancer undergo regular screening that includes yearly fecal occult blood testing (FOBT) combined with flexible sigmoidoscopy testing every five years (see Home Fecal Occult Blood Test for Colorectal Cancer and Sigmoidoscopy tests). If results from either FOBT or sigmoidoscopy are abnormal, a follow-up colonoscopy with double-contrast barium enema is recommended (see Barium Enema test).
• The American Gastroenterological Association recommends that people at increased risk for colon cancer start FOBT and sigmoidoscopy screening at age 40, with a follow-up colonoscopy plus double-contrast barium enema if results from either FOBT or sigmoidoscopy are abnormal. Factors that increase a person's risk of developing colon cancer include a family history of the disease, a personal history of colon polyps or ulcerative colitis, or both. High-fat and low-fiber diets have also been linked to colorectal cancer.
• A sigmoidoscopy plus a barium enema is an alternative method of screening for colon cancer and disease when a person refuses colonoscopy or when it is not feasible or safe for a person to undergo the procedure (see Sigmoidoscopy test).
• Virtual colonoscopy is an experimental technique that uses CT or MRI scanning to take three-dimensional images of the colon. Unlike conventional colonoscopy, virtual colonoscopy is noninvasive, takes less time, and may be less expensive. However, virtual colonoscopy may not be as accurate as conventional colonoscopy