- Three Rivers Endoscopy Center
Three Rivers Endo Patient Education Having a Scope Test Quality Data

Preparing for Colonoscopy

So you are going to have a colonoscopy. The first reaction we hear from most people is, "Do I have to drink that stuff?" When the test is over most people are surprised how easy and painless it is, but almost all say, maybe by the next time I have to have this done you guys will come up with another way to clean me out. Indeed, there are more choices for colonoscopy preparation now than there were in the past, and the more a patient knows about each prep, the more they will be able to help their doctor pick the right one for them.

All preps are divided into two parts. The patent must modify their diet and then take a cleansing solution. Ideally for a prep to be affective it must incorporate several elements. It must be convenient with simple instructions that are easy to follow. It must be well tolerated with relatively good flavor and the least amount of volume possible. It should be safe with minimal side effects. And, finally, it must be effective. The last thing either the doctor or the patient want is a bad prep. Indeed, a bad prep is more difficult for the doctor, typically more uncomfortable for the patient since the test takes longer and more air must be used, and poor preps have a higher chance of missing important lesions.

In the following paragraphs we will discuss the main preps that are used with the hopes of helping you choose the one that would be best for you. All preps have pros and cons and not all preps are suitable for each person. For exact details on each prep please visit our website.


    These are one of the preferred methods of prepping the colon. Typically these preps use a balanced electrolyte solution with polyethylene glycol (PEG) and work by flushing out the bowel. A clear liquid diet is recommended the day before the procedure and the prep is typically taken until the recommended amount of solution is consumed or the liquid coming out is a clear yellow (almost like urine).

    We typically use one of three lavage preps. One involves drinking an entire 4-liter bottle of PEG solution. The other involves taking an 8 oz bottle of citrate of magnesia first then following this with 2 liters of PEG solution. We also use a prep that combines Gatorade with a PEG powder.

    Advantages of these preps include:

    1. They do not cause any damage to the lining of the colon. Some preps can cause the colonic lining to look abnormal which may be confusing to the doctor.

    2. These preps are typically preferred in patients with active lower GI bleeding since they typically give a better prep in these individuals and allow a more exact identification of the source of bleeding.

    3. Even though patients are required to drink a large volume of liquid it is not absorbed and causes less fluid and electrolyte shifts. Therefore, it is safe to use these preps in patients on a fluid restriction such as those with congestive heart failure, renal failure on dialysis, cirrhosis, or chronic electrolyte abnormalities.

    The major disadvantage of this prep is the large volume of liquid (up to 4 liters) that must be consumed and the marginal taste of the solution. Patients may experience nausea, vomiting, bloating or abdominal cramping at times. Your doctor may be able to prescribe medication that can provide some relief. For example, an anti nausea medicine can be given or a medication that improves the movement of the intestine can be used in some people to help get the fluid through the intestine more quickly.

    There are also several things that the patient can do to make the prep go better. We typically recommend using a flavored prep or mixing Crystal Light with the PEG solution to improve the taste. Also if you experience nausea, vomiting or significant bloating you should slow down in drinking or even stop for one or two hours before resuming and finishing the prep.


    These are laxatives that contain magnesium or phosphate. Since they are poorly absorbed they draw and hold water in the small intestine, which then flushes out through the colon. These come in two basic forms: liquid and tablet. The tablet form is called Visicol and requires the patent to take 32 tablets in divided doses the night before and the day of the colonoscopy along with several glasses of water. The liquid form comes as a prepackaged kit called Accu-prep or in a bottle called oral fleets phospha soda, which the patients must divide and mix themselves. The total amount of liquid prep solution required is only a few ounces plus some additional water.

    The major advantages of these preps are their ease of administration since they come as pills or small volume liquids. These preps have been shown to work just as well as the lavage solutions. The major drawback of this form of preparation is the fluid and electrolyte shifts that can occur in some patients. For this reason these preps should not be used in people with congestive heart failure, kidney disease, cirrhosis or certain electrolyte problems and should be used with caution in patient on diuretics (water pills). Your doctor may require you to get a blood test prior to using this prep. We have also seen some patients who have developed low calcium levels while taking these preps. This usually causes a tingling in the fingers or toes, muscle cramps or spasms, or chest tightness and occasionally requires intravenous calcium to be given prior to the procedure. If you experience any unusual symptoms while taking these preps you should tell your doctor. These preps can be more expensive than the lavage solutions and are typically not covered by insurance, requiring greater out of pocket expense from the patient.

In summary, the preparation for a colonoscopy is a very important part of the test. Several choices exist and are described above, each with pros and cons. Remember to follow the directions on the prep you choose carefully. Avoid red dyes in clear liquids (such as red Jell-O) the day before your procedure as these may look like blood in the colon and be confusing to the doctor. Typically you should stop iron supplements 5 days before the procedure to improve the prep. Your doctor may also recommend that you stop certain medications prior to the test to reduce the risk of bleeding. Check with your doctor about these details.



Questions or Comments: Three Rivers Endoscopy Center
© 1997-2004 Three Rivers Endoscopy Center All Rights Reserved. Terms and Conditions Privacy Policy