Cleaning out the colon, or tips on surviving the bowel prep.


As a patient, you only have control over a few parts of your colonoscopy.  Usually you have a choice of which doctor does the procedure.  You have a choice of showing up on the day of the procedure vs. running in the other direction.  And finally, you have control on how well you are “prepped” for the procedure.

Various bowel preps that are optimized for split-dosing.

Various bowel preps that are optimized for split-dosing.

Bowel preparation (“prep” for short) is the most important patient-controlled part of the colonoscopy.  Done properly, the inside of the colon looks as clean as the inside of a mouth.  Ideally, after taking the prep, there is no stool or residue left behind, and the endoscopist can get a good view of everything.  If there are polyps or other issues present, a good prep allows the doctor to see and address these findings.  The procedure is usually shorter because less time is wasted trying to washing out the colon while you are under anesthesia.  The procedure is safer because the doctor can see better.  You are usually more comfortable at the end of the test because the doctor didn’t have to pump in as much gas during prolonged efforts to clean out the remaining debris in the colon.

The opposite of a good prep is a poor prep.  In a poor prep, either thick liquid stool and particles, or solid stool are still present in the colon.  This cannot just be flushed away during the exam, and therefore there will usually be one of two outcomes: the procedure will be aborted due to not being able to see anything meaningful; or the next colonoscopy will be recommended at an earlier date (e.g., in less than six months).  Either way, you (the patient) are exposed to all the inconveniences of a colonoscopy (the day off work, the anesthesia, the risks, the cost, etc.) and none of the benefits (preventing colon cancer, or finding what was causing bleeding/symptoms, etc.)

There are several ways to maximize your chances of successfully completing the bowel prep.  In no particular order, here they are:

  • Follow the printed instructions from the doctors office regarding the prep and diet to follow before your colonoscopy.  Read this a few days before the procedure, not after lunch the day before the procedure!
  • Make sure you have all required prep materials in the house: the actual prep from the pharmacy, any over-the-counter stuff you need (e.g., dulcolax, magnesium citrate), and any clear liquids you may need.
  • Plan ahead and refrigerate the prep if possible to make it easier to drink.
  • Tell your doctor if you have had a problem with the prep in the past, there may be another alternative prep or schedule you can use.
  • Split-dose bowel prep is both easier to tolerate, and gives a better prep.  If your doctor hasn’t prescribed the prep this way, ask him or her why not.
  • Don’t think that since you are having diarrhea after only finishing half of the prep, that the second half is optional…it’s not! The second half is actually more important than the first and needs to be completed.  This is the part that really washes out all the “debris” that sticks to the walls of the colon.
  • The prep can make some people nauseated, and vomiting can be common if you try to drink the prep too rapidly.  If you are feeling full or nauseous, just slow down.  Give yourself a break for a half-hour and try again.  Don’t be a hero and try to “chug” the prep as fast as possible and then end up vomiting up the whole thing!
  • If you have questions or issues regarding the prep, don’t be afraid to call the doctor’s office the day or night before the procedure.  I would rather you call than have a poor prep and have to then repeat the colonoscopy!

Remember that the goal of a screening colonoscopy is to prevent colon cancer, so give yourself the best chance possible by doing a good job with the prep!

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