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    Laxatives for Bowel Prep and Colonoscopy

    Enduring bowel prep during the days leading up to your colonoscopy procedure is usually the some burdensome part of the colon cancer screening process. It is crucial that the entirety of the large intestine be emptied before a colonoscopy, so that your gastroenterologist (GI doctor) does not mistake any residual fecal matter in the colon for an abnormality that may signal that you have or will develop colon cancer, or worse yet – miss a flat cancer lesion under the area of unprepped colon. Improper bowel prep can lead to false results and possibly a need for re-examination. Bowel prep entails a complete emptying of the colon through the use of laxatives and by avoiding solid foods for 1 or 2 days before your colonoscopy procedure. Any beverages consumed should be clear, such as water or apple juice.  Most bowel preparations will require ingestion of at least 4 liters of liquid the day prior to the colonoscopy procedure.  The reason for this is to adequately cleanse the colon without causing dehydration or electrolyte shifts.  Historically, phosphosoda preps were available which provided bowel cleansing with ingestion of a single small dose of medication; however, these have been found to b e unsafe and cause serious electrolyte shifts which can result in kidney damage or cardiac events.

    What is a Laxative?

    A laxative is a substance increases the frequency that a person has bowel movements. Unfortunately, laxatives can also trigger diarrhea and abdominal pain. They are often used to treat constipation, defined as difficult or infrequent bowel movements. If you are having trouble passing stool, please contact a colonoscopy specialist for advice on how to encourage regular bowel movements or to schedule a colon cancer screening to examine underlying conditions that may be cause for the constipation.

    Some foods high in fiber such as fruits and vegetables can act as natural laxatives in a person’s body. Natural laxatives are usually consumed while medical laxatives are consumed. Typically, there are 4 types of medical laxatives available to patients:

    Bulking Agents—bulking agents make the intestines absorb fluid more easily, which makes the stool held in a patient’s bowels bigger. The idea is that bigger stool will give you stronger urges to have a bowel movement. Bulking agents can be used regularly (and often are used by women and aging individuals, who more commonly suffer from constipation).

    Stool Softeners—stool softeners use lubrication to make stool already located in the large intestine soft and easier to pass. These laxatives require the user to drink plenty of water while taking the laxative, to encourage the softening process as well as to replenish any hydration lost during the over-absorption of fluid by the stool.

    Osmotic Laxatives—osmotic laxatives work similarly to stool softeners, as they encourage fluid absorption by the stool, which softens stool and makes it easier to pass. However, the fluid generally comes from other areas of body tissue and blood vessels. Patients should still drink a lot of water to compensate for lost fluid elsewhere in the body.

    Stimulant Laxatives—also called irritants, stimulant laxatives will speed up the frequency of bowel movements by irritating the lining of the gastrointestinal (GI) tract. It is dangerous to use stimulant or irritant laxatives for long periods of time, as the process is counter-intuitive to the natural process of absorption by the intestines. Using stimulant laxatives on a regular basis can also make a patient dependent on them to pass stool.

    If you require frequent laxative use for treatment of constipation, you should consult with a gastroenterologist for further evaluation, as although generally safe, unmonitored long term use of laxatives can be damaging to your body.  As with any health condition, you should not start or stop any long term medication without consulting with your physician.

    If you need advice on taking laxatives before a colon cancer screening test, one of our colonoscopy specialists will be happy to help. Don’t let bowel prep prevent you from maintaining your colorectal health.

    Reviewed 12/12/2011 by David M. Nolan, M.D.
    Diplomate of the American Board of Internal Medicine, 2011
    Currently a Fellow of Gastroenterology, at UCI 2011-2014