If your doctor has determined that you should have a colonoscopy, you may have some questions and concerns about the procedure. This handout will provide information about colonoscopy and answers to questions that patients often ask.

Colonoscopy is a safe procedure that gives your doctor information other tests may not be able to give. A colonoscopy is an examination of the lower part of the gastrointestinal tract, which is called the colon or large intestine (bowel). It is performed by an endoscopist, a doctor with special training in endoscopy procedures. The colonoscope is inserted into the anus and advanced through to the end of the colon (the cecum) and possibly a short distance into the small intestine. The procedure generally takes from twenty minutes to an hour.


The most common reasons for colonoscopy are to evaluate the following:


Your doctor will provide specific instructions on how to prepare for the examination. The instructions are designed to maximize your safety during and after the examination, minimize possible complications, and provide the endoscopist with the best look at your colon.

It is important for you to read the instructions ahead of time and follow them carefully. Call your doctor or the endoscopy unit if you have questions.

The prep

The inside lining of your colon must be cleaned of stool to permit the endoscopist to obtain a thorough examination. This is accomplished in two ways:

What to eat

As a general rule, you should not eat any solid food for at least one day before the examination. You should drink only clear liquids (such as juices without pulp, bouillon, ginger ale) and eat only clear Jell-O. Your doctor's office or the endoscopy unit will supply you with a list of fluids that are allowed.


There are two main methods commonly used to purge the bowel of stool. The first involves drinking about one gallon of an undigestible solution that gives you temporary diarrhea. It comes in several flavors, which, unfortunately, only partially mask a somewhat unpleasant taste. Refrigerating the solution may make it more palatable. Do not add your own flavoring to the solutions. Many patients say that drinking the purgative solution was the most unpleasant part of the examination, but don't worry, you'll get through it.

The second method involves taking a solution called "Fleet's Phospho-soda" along with several cups of liquid. This preparation is easier to consume than the purgative described above. However, the solution contains a great deal of phosphorus, which may be a problem for people with heart or kidney conditions. You should check with your doctor.


Some medications, such as aspirin and iron preparations, should be discontinued for one to two weeks before the examination. Aspirin and pain killers such as Motrin® (which contains ibuprofen) slightly increase the risk of bleeding. If you take a blood thinning medication, consult with your doctor as to when you should stop taking it. Ask your doctor about medications for diabetes, heart or lung disease, high blood pressure, or seizure disorders. Your doctor may not want you to stop some of your medicines, and many of them can be taken even the day of the examination. If you take antibiotics before dental procedures, ask your doctor if you need them before colonoscopy.

An escort

You will be instructed to arrange for a responsible person to escort you safely home after the examination. Even though you will be awake by the time you are discharged, the medications used to sedate you will cause changes in your reflexes and judgment that will leave you feeling well but will interfere with your ability to make decisions coherently, similar to the effect of alcohol.


Prior to the colonoscopy, a nurse will prepare you for the examination. The nurse will take a history to determine what you already know about the procedure and whether you understand why the examination is being done. Other questions that you should be prepared to answer include:

The nurse will start an intravenous line (put a needle in a vein in your arm) to administer medications to help you relax and keep you comfortable during the examination. This is just a pin prick, no worse than having your blood drawn. Your vital signs will be monitored during the examination and for a time after the colonoscopy is over. The nurse will check your blood pressure and pulse either manually or with a machine that continuously monitors your heart rate and rhythm, your oxygen level, and blood pressure. The monitoring machines are not painful. You may also be given oxygen during the examination.


A doctor will review the examination with you, including possible complications, and will ask you to sign a consent form. He will answer any questions you may have about the examination.


The colonoscopy will be performed with you lying on your left side. Medications will be administered through the intravenous line. Most endoscopy units administer a combination of a sedative, to help you relax, and a narcotic, to diminish any unpleasant sensations. Many people sleep during the examination and others are very relaxed, comfortable, and generally not very aware of the examination.

The colonoscope is a flexible tube, approximately the size of your index finger. It has a lens and a light source that allows the endoscopist to look into the scope or at a TV monitor. The image on the TV monitor is magnified many times so the endoscopist can see minute changes in tissue.

The endoscope contains channels that allow the endoscopist to obtain biopsies (small pieces of tissue), remove polyps and to introduce or withdraw fluid or air. Neither of these hurt since the lining of the colon does not have that type of pain sensation.

Air is introduced through the scope to open up the colon so that the scope can be moved forward and to allow the endoscopist to see. You may experience a feeling of bloating or gas cramps from the air as it distends the colon. Do not be embarrassed about releasing the air through your rectum if you can. Importantly, let the doctor know if you are uncomfortable.


Polyps are extra growths of tissue that can range in size from the tip of a pen to several inches (doctors measure them in millimeters and centimeters). Most polyps are benign (not cancerous) but can turn into cancers if left to grow for a very long time. As a result, they are usually removed so they can be analyzed under the microscope. You should consult with your doctor after the examination for results of any polyps that were removed.


After the colonoscopy, you will be kept for a time for observation while some of the medicine wears off. The most common discomfort after the examination is a feeling of bloating and gas cramps. You may also be very groggy from the sedation medications or you may have difficulty concentrating. It is usually advised that you not to return to work that day. Unless you are given other instructions, you should be able to eat a regular diet after the examination. You should ask your doctor when it is safe to restart aspirin or blood thinning medications.


Colonoscopy is a safe procedure and complications are rare, but can occur:

The following symptoms should be reported immediately:


Although patients worry about discomforts of the examination, most people tolerate it very well and feel fine afterwards. Some fatigue after the examination is common. You should plan to take it easy and relax the rest of the day.

You should contact your doctor about the results of your test if you have any questions and especially if biopsies were taken. The endoscopy team can give you some guidelines as to when your doctor should have all the results and whether further treatment will be necessary. Most patients who had polyps removed will require a repeat colonoscopy within three to five years.