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Making the most of currently available bowel preparations for colonoscopy

Cleveland Clinic Journal of Medicine. 2010 May;77(5):317-326 | 10.3949/ccjm.77a.09122
May 1, 2010|Cleveland Clinic Journal of Medicine
Ashish Atreja, MD, MPH, FACP;Sansrita Nepal, MD;Bret A. Lashner, MD, MPH
Author and Disclosure Information

Ashish Atreja, MD, MPH, FACP
Digestive Diseases Institute, Cleveland Clinic; Clinical instructor, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University

Sansrita Nepal, MD
Department of Medicine, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India

Bret A. Lashner, MD, MPH
Professor of Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University; Director, Gastroenterology Fellowship Program; and Director, Center for Inflammatory Bowel Disease, Department of Gastroenterology and Hepatology, Digestive Disease Institute, Cleveland Clinic

Address: Ashish Atreja, MD, MPH, Digestive Diseases Institute, A31, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195; e-mail atrejaa@ccf.org

Dr. Lashner has disclosed that he has received honoraria from the Salix corporation for teaching and speaking.

ABSTRACTAdequate bowel preparation is essential before colonoscopy. Choosing an agent can be confusing, since many are available. The authors review the available regimens, offer an algorithm for choosing an appropriate regimen, and provide bowel preparation instructions for patients.

KEY POINTS

  • Polyethylene glycol solutions are fast, effective, and preferred for cleansing the colon.
  • Use of split dosing, a low-volume solution, or both can increase patient acceptability without compromising efficacy.
  • Sodium phosphate can be prescribed for patients who cannot tolerate polyethylene glycol solutions, provided they are not at risk of electrolyte or fluid imbalances.
  • Enemas, bisacodyl, magnesium citrate, and metoclopramide (Reglan) can be useful as adjuncts to polyethylene glycol but by themselves are inadequate for cleansing the entire colon.
  • Educating patients about bowel preparation instructions, including correct dosing and adequate hydration, helps reduce the risk of adverse events and serious adverse events.

OTHER CONSIDERATIONS

Patient education

The importance of patient education for successful bowel preparation cannot be overemphasized. Patients need to be informed about why they need to undergo colonoscopy, the importance of bowel preparation, the side effects of agents used, and the exact preparation instructions. An interactive educational tutorial about colonoscopy for patients is available at Medline Plus at https://www.nlm.nih.gov/medlineplus/tutorials/colonoscopy/htm/index.htm.

In a prospective study, an education program reduced the rate of preparation failure from 26% to 5%.31 Many endoscopy centers provide education about colonoscopy and give patients clear, written instructions at the time an appointment for colonoscopy is made. Table 2 details bowel preparation instructions for split-dose polyethylene glycol regimens. Similar instructions for bowel preparation are also available online at https://clevelandclinic.org/bowelprep.

Role of hydration

A commonly held misconception is that patients taking 4 L of polyethylene glycol do not need additional hydration, since they are already ingesting such a large volume of fluid. Given that bowel preparations induce diarrhea and, in some instances, nausea and vomiting, all patients taking bowel preparations are at risk of dehydration.32 In fact, the fluid loss during bowel preparation may exceed 2 to 3 L. It is not surprising that many safety issues associated with bowel preparation agents are related to dehydration and its complications.

Hence, patients should be advised to consume at least 64 oz (approximately 2 L) of clear fluid on the day before the colonoscopy. According to the American Society of Anesthesiologists, clear liquids can be safely ingested up until 2 hours before receiving anesthesia.33 Patients should contact their physicians if they experience vomiting or cannot comply with clear liquid volume instructions prior to colonoscopy. Metoclopramide has been found useful in many cases of nausea or vomiting associated with bowel preparation agents.18 In addition, patients should also be reminded to keep drinking extra fluids after the procedure is completed to reduce the risk of dehydration and its complications (Table 2).

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