Colonoscopy preparation, commonly referred to as the prep, may be the most dreaded component of this invaluable screening test. Proper colonoscopy preparation makes your colon squeaky clean, allowing the doctor to visualize the inner lining. Leftover stool or fluids can camouflage a tiny polyp or a section of irregular flat tissue within the colon. The cleaner your colon is, the better your doctor will be able to see.
You Can Do It
Why is the prep so horrible? Probably because you will spend the majority of your prep in or near the bathroom evacuating your bowels. The prep consists of taking laxatives and substances that force a bowel movement (or many of them).
No Prep, No Test
If you do not follow the prep instructions, there is a chance your test will be canceled. Let your doctor know right away if you cannot complete the prep; this may help you avoid "no-show" charges when your colonoscopy is canceled, or worse – having to repeat the procedure. In some cases, there is even a chance that the leftover stool may be confused for unhealthy tissue.
Every doctor orders a slightly different version of the colonoscopy prep, which will vary according to his or her preferences and your health. Some preps may begin with a liquid diet days before your test; others could involve using an enema and laxatives at home the night prior. If you have questions, do not wait until the last minute – call the doctor’s office and get clarification.
Colonoscopy preps come in the form of pills, liquids to drink (solutions), enemas to use rectally – or a combination of the three along with dietary modifications. You may hear the word cathartic, which is another term for laxative or any substance that cleans you out.
Oral laxatives come in the form of a pill or a liquid to drink and are commonly used in conjunction with a clear liquid diet. Some commonly prescribed pills and solutions include:
- Dulcolax (bisacodyl) tablets
- Magnesium citrate tablets or solution
- Senakot (senna) tablets
- GoLYTELY solution
- NuLYTELY solution
- TriLyte solution
- Glycolax solution
- CoLyte solution
- MiraLax solution
- TriLyte solution
- Fleet Phospho Soda (sodium biphosphate and sodium phosphate) solution or tablets
Preparation and Directions
These solutions may come in individual bottles or as do-it-yourself powders that need to be mixed. You should receive instruction on how to use the solution from your doctor. You will need to know exactly how much to drink and how often to drink it. Most of the older solutions, such as the GoLYTELY prep, are still reliable and widely used, but require drinking a vast amount of fluids (up to four liters). Newer solutions may require less formula to drink, but you will still need to drink plenty of water to flush the colon clean.
The bitter and salty taste of some solutions can stop the prep in its tracks. However, many of the newer formulas are sulfate-free, which means they don’t have a salty aftertaste. If you can’t tolerate the solution there is little chance you will drink all four liters. Ask your doctor about the pre-flavored mix options, which may include cherry, lemon-lime or even a pineapple taste additive. If your taste-buds are still offended, ask your doctor if you can add a powdered commercial drink prep, like Crystal Light or Gatorade, to mitigate the flavor.
Enemas are sometimes ordered to complete the colon cleansing prep, but can only clean out a small section at the end of the colon. Your doctor may order a tap-water or Fleet enema for the night before or the morning of your colonoscopy. You will have to stay close to a bathroom after using the enema; they usually work very quickly (within 10 minutes or less).
Some colonoscopy preps may include a dietary change for one to four days before the procedure. This diet will consist of clear liquids only – if you can see through it, you can probably eat or drink it. Some favorites on the clear liquid diet include beef or chicken broth, clear sodas, white grape or apple juices and a lot of gelatin. Avoid red gelatin or red sports drinks, as they can tint the colon. Unless otherwise advised, you can continue to drink tea or coffee, but hold the cream or milk. If you are getting hungry on your clear liquid diet consider drinking a tall glass of water with every "meal."
Prior to, or in lieu of, a clear liquid diet you may be put on the low-residue diet. This diet consists of meal replacement shakes, soups or bars, which are mostly protein and calories with very little fiber (residue). You should not eat any fruits, vegetables or grains on the low-residue diet.
The colonoscopy prep has one more concerning issue: the side effects of rapidly discharging the colon. The cathartics and substances used to clean your bowels may stimulate some unpleasant side effects, such as explosive gas and nausea. Your doctor may prescribe medications to help with these symptoms:
- Reglan (metaclopramide) – Helps move the cathartics through the stomach quickly, which can help alleviate nausea and heartburn.
- Mylicon, Gas-X, Mylanta (simethicone) – Helps break up gas so that it can be passed more comfortably.
Take another proactive step toward comfort and invest in some quality toilet paper before your prep (no kidding). Cheaper brands tend to be more abrasive and can irritate the skin around your anus after multiple trips to the toilet. Talk to your doctor if you have hemorrhoids; prepare accordingly with soothing baths, soaks and creams as directed.
Other side effects, although uncommon, may include a fluid and electrolyte shift. Your body is constantly working to keep a balance between the fluids in your cells and the fluids in your bloodstream with the help of electrolytes, such as sodium or potassium. If you lose a lot of fluids at once (think frequent, watery stools) your fluid and electrolytes can get out of whack and cause uncomfortable symptoms, like a headache. Abdominal discomfort and vomiting are also uncommon, but possible. If discomfort or symptoms are keeping you from completing the colonoscopy prep, call your doctor. He or she may have some suggestions to help increase your comfort level.
American Cancer Society. (2006). Complete guide to colorectal cancer. Atlanta: American Cancer Society Health Promotions.
American Society for Gastrointestinal Endoscopy. (2006). A Consensus Document on Bowel Preparation Before Colonoscopy. Gastrointestinal Endoscopy; 63, 558-565. Accessed December 4, 2011.