What Is A Colonoscopy?

A colonoscopy is a special test that allows your doctor to inspect the lining of your lower gastrointestinal (GI) tract, or rectum and colon. In order to see these areas, your doctor will insert a long, flexible, narrow tube with a light and tiny camera attached to it (colonoscope), through your anus and into the rectum and colon. During the test, tissue can be biopsied from any area that looks abnormal and polyps, or abnormal growths, can be removed.

The procedure can either be done in a hospital or at an outpatient center.

Why Do I Need A Colonoscopy?

A colonoscopy is an important screening test for colorectal cancer, the second leading cause of cancer deaths in the US. While most people have a colonoscopy as part of routine cancer screening, it may also be used to evaluate any of the following:

  • Blood in your stool
  • Rectal bleeding
  • Changes in bowel habits
  • Persistent abdominal pain
  • Follow up of an abnormal result from a CT scan, MRI, barium enema, or stool test
  • Iron deficiency anemia (low blood count because of low iron)

How Do I Prepare For A Colonoscopy?

Your colon must be completely cleaned out before you have a colonoscopy. This gives your doctor the best chance of finding any abnormal areas that you may have in your colon. To clean your colon, your doctor will give you a laxative regimen to take at home before your test, along with specific instructions to follow about how to take it. The laxative will cause significant watery diarrhea, so you will need to remain close to a bathroom after you take it.

Also, it is common for your doctor to ask you to limit your diet to clear liquids (water, clear juice, clear broth, etc.) the day before your test. You will then need to stop drinking anything 6 to 8 hours before your procedure, unless your doctor instructs you otherwise.

 While most medications are safe to take before your test, you may be asked to stop taking certain medications. In order for your doctor to decide if any of your medications need to be stopped, it is essential that you let them know all of the medications you are taking, including supplements and herbal remedies.

You won't be able to drive yourself home after the colonoscopy, so it is important that you have someone go with you to the outpatient center or hospital.

If you think you could be pregnant you need to notify your doctor before the colonoscopy.

What Can I Expect During A Colonoscopy?

Before your colonoscopy, your doctor will review your medical history and all of the medications you are taking. The procedure will be explained to you and you will be asked to sign a consent form allowing your doctor to perform the colonoscopy. If you have any questions about the test now is the time to ask them.

You will also have an IV started that allows your doctor to give you light sedation and medication to prevent pain. If your procedure is expected to be long or complex, you may have an anesthesiologist give you heavy sedation.

When you are taken into the procedure room, you will be asked to lie on your side with your knees pulled up to your abdomen. Once your doctor starts the test, you are likely to be asleep and you won't feel anything. If you do notice anything, you may feel like you need to have a bowel movement when the scope is put in. You may also notice some cramping.

The entire test usually takes less than an hour.

What Can I Expect Immediately Following A Colonoscopy?

After your colonoscopy, you will be monitored in the recovery area until your sedation wears off. You are likely to feel tired and have problems concentrating for the rest of the day. Because of this, it is recommended that you go home and rest until you feel back to your normal self.

You may feel a bit bloated or have crampy gas pains that are relieved by passing gas but this should go away pretty quickly. If you had a biopsy or a polyp was removed, you may notice traces of blood in your stool for a few days.

You should be able to eat shortly after the procedure is finished, but your doctor may limit your diet and activities for a few days, depending on how the procedure went.

When you are sent home, you will be given a list of instructions on how to care for yourself after the colonoscopy. It is important to follow these instructions.

How Long Will It Take To Get The Results Of The Procedure?

Some of the results from your colonoscopy will be available right away. Once your sedation has worn off, your doctor will discuss the results of the procedure with you. However, you may not remember the conversation very well because of the sedation, so you may want a friend or family member to hear the results too.

If you had a biopsy taken or a polyp removed, the doctor will send the tissue to the laboratory for an examination. These results can take a few days or more to come back. Once your doctor has a chance to review the results, they may call you to discuss the results or ask you to schedule an appointment to discuss what needs to be done next.

What Are The Complications Of A Colonoscopy?

A colonoscopy is a safe procedure and serious complications are rare. Complications that can occur are infection or bleeding. Rarely, a small hole or tear in the rectum or colon can occur that requires immediate surgery to repair. Some people may have a reaction to a medication used during the procedure.

You should call your doctor right away if you experience any of the following:

  • Severe abdominal pain
  • Fever greater than 100.4 F
  • Rectal bleeding
  • Vomiting

Where Can You Get More Information About Colonoscopy?

This information was developed by the Publications Committee of the American Society for Gastrointestinal Endoscopy (ASGE). For more information about ASGE, visit

This information is intended only to provide general guidance. It does not provide definitive medical advice. It is important that you consult your doctor about your specific condition.

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In a colonoscopy, the physician passes the endoscope through your rectum and into the colon to examine the tissue of the colon wall for abnormalities such as polyps.

What is a colonoscopy?

Colonoscopy lets your doctor examine the lining of your large intestine (colon) for abnormalities by inserting a thin flexible tube, as thick as your finger, into your anus and slowly advancing it into the rectum and colon. This instrument, called a colonoscope, has its own lens and light source and it allows your doctor to view images on a video monitor.

Why is colonoscopy recommended?

Colonoscopy may be recommended as a screening test for colorectal cancer. Colorectal cancer is the third leading cause of cancer deaths in the United States. Annually, approximately 150,000 new cases of colorectal cancer are diagnosed in the United States and 50,000 people die from the disease. It has been estimated that increased awareness and screening would save at least 30,000 lives each year. Colonoscopy may also be recommended by your doctor to evaluate for symptoms such as bleeding and chronic diarrhea.

The endoscope is a thin, flexible tube with a camera and a light on the end of it. During the procedure, images of the colon wall are simultaneously viewed on a monitor.

What preparations are required?

Your doctor will tell you what dietary restrictions to follow and what cleansing routine to use. In general, the preparation consists of limiting your diet to clear liquids the day before and consuming either a large volume of a special cleansing solution or special oral laxatives. The colon must be completely clean for the procedure to be accurate and comprehensive, so be sure to follow your doctor's instructions carefully.

Can I take my current medications?

Most medications can be continued as usual, but some medications can interfere with the preparation or the examination. Inform your doctor about medications you're taking, particularly aspirin products, arthritis medications, anticoagulants (blood thinners such as warfarin or heparin), clopidogrel, insulin or iron products. Also, be sure to mention allergies you have to medications.

What happens during colonoscopy?

A colonoscope is a medical device used by expert physicians to look inside the colon and rectum. The expert physician controls the movement of the flexible tube using the endoscope handle.

Colonoscopy is well-tolerated and rarely causes much pain. You might feel pressure, bloating or cramping during the procedure. Typically, your doctor will give you a sedative or painkiller to help you relax and better tolerate any discomfort. You will lie on your side or back while your doctor slowly advances a colonoscope along your large intestine to examine the lining. Your doctor will examine the lining again as he or she slowly withdraws the colonoscope. The procedure itself usually takes less than 45 minutes, although you should plan on two to three hours for waiting, preparation and recovery. In some cases, the doctor cannot pass the colonoscope through the entire colon to where it meets the small intestine. Your doctor will advise you whether any additional testing is necessary.

What if the colonoscopy shows something abnormal?

If your doctor thinks an area needs further evaluation, he or she might pass an instrument through the colonoscope to obtain a biopsy (a small sample of the colon lining) to be analyzed. Biopsies are used to identify many conditions, and your doctor will often take a biopsy even if he or she doesn't suspect cancer. If colonoscopy is being performed to identify sites of bleeding, your doctor might control the bleeding through the colonoscope by injecting medications or by cauterization (sealing off bleeding vessels with heat treatment) or by use of small clips. Your doctor might also find polyps during colonoscopy, and he or she will most likely remove them during the examination. These procedures don't usually cause any pain.

Polyps are abnormal growths in the colon lining that are usually benign (noncancerous). They vary in size from a tiny dot to several inches.

What are polyps and why are they removed?

Polyps are abnormal growths in the colon lining that are usually benign (noncancerous). They vary in size from a tiny dot to several inches. Your doctor can't always tell a benign polyp from a malignant (cancerous) polyp by its outer appearance, so he or she will usually remove polyps for analysis. Because cancer begins in polyps, removing them is an important means of preventing colorectal cancer.

How are polyps removed?

Your doctor may destroy tiny polyps by fulguration (burning) or by removing them with wire loops called snares or with biopsy instruments. Your doctor will use a technique called "snare polypectomy" to remove larger polyps. Your doctor will pass a wire loop through the colonoscope and remove the polyp from the intestinal wall using an electrical current. You should feel no pain during the polypectomy.

What happens after a colonoscopy?

You will be monitored until most of the effects of the sedatives have worn off. You might have some cramping or bloating because of the air introduced into the colon during the examination. This should disappear quickly when you pass gas. Your physician will explain the results of the examination to you, although you'll probably have to wait for the results of any biopsies performed. If you have been given sedatives during the procedure, someone must drive you home and stay with you. Even if you feel alert after the procedure, your judgment and reflexes could be impaired for the rest of the day. You should be able to eat after the examination, but your doctor might restrict your diet and activities, especially after polypectomy. Your doctor will advise you on this.

What are the possible complications of colonoscopy?

Colonoscopy and polypectomy are generally safe when performed by doctors who have been specially trained and are experienced in these procedures. One possible complication is a perforation, or tear, through the bowel wall that could require surgery. Bleeding might occur at the site of biopsy or polypectomy, but it's usually minor. Bleeding can stop on its own or be controlled through the colonoscope; it rarely requires follow-up treatment. Some patients might have a reaction to the sedatives or complications from heart or lung disease. Although complications after colonoscopy are uncommon, it's important to recognize early signs of possible complications. Contact your doctor if you notice severe abdominal pain, fever and chills, or rectal bleeding. Note that bleeding can occur several days after the procedure.

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Important Reminder: This information is intended only to provide general guidance. It does not provide definitive medical advice. It is very important that you consult your doctor about your specific condition.

Since its founding in 1941, the American Society for Gastrointestinal Endoscopy (ASGE) has been dedicated to advancing patient care and digestive health by promoting excellence in gastrointestinal endoscopy. ASGE, with more than 11,000 members worldwide, promotes the highest standards for endoscopic training and practice, fosters endoscopic research, and is the foremost resource for endoscopic education.

This patient education brochure was developed by the Publications Committee of the American Society for Gastrointestinal Endoscopy. This information is the opinion of and provided by the American Society for Gastrointestinal Endoscopy.

American Society for Gastrointestinal Endoscopy and

Copyright ©2010. American Society for Gastrointestinal Endoscopy. All rights reserved. This information may not be reproduced without express written permission by ASGE. For permission requests, please contact the ASGE Communications Department at 630-673-0600.
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