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Bowel preparation for colonoscopy and flexible sigmoidoscopy in adults

Yousif I A-Rahim, MD, PhD
Myron Falchuk, MD
Section Editor
John R Saltzman, MD, FACP, FACG, FASGE, AGAF
Deputy Editor
Kristen M Robson, MD, MBA, FACG


A successful colonoscopy or flexible sigmoidoscopy requires clear visualization of the mucosal surface of the colon, and the degree of bowel cleansing is a critical factor in determining the quality, difficulty, speed, and completeness of the examination [1].

This topic will review the most frequently used methods for bowel preparation for colonoscopy and flexible sigmoidoscopy and will provide recommendations for addressing commonly encountered problems. An overview of colonoscopy in adults is discussed separately. (See "Overview of colonoscopy in adults".)

The recommendations that follow are generally consistent with a 2014 guideline from the US Multi-Society Task Force on Colorectal Cancer and a 2015 guideline from the American Society of Gastrointestinal Endoscopy [2,3].


Patient instructions, medications, and diet — Patients should be provided with written instructions that are simple, easy to follow, and in a language the patient understands. Patients should also be instructed to read the instructions at least a week prior to the colonoscopy since medication and dietary changes are often required several days prior to the examination.

Medications — Most medications may be continued up to the time of colonoscopy and are taken with a small sip of water the day of the colonoscopy. Some medications may need to be adjusted prior to colonoscopy, such as metformin and insulin. Oral iron should also be stopped at least five days before the colonoscopy since it makes the residual feces black, viscous, and difficult to clear.


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Literature review current through: Apr 2017. | This topic last updated: Sep 14, 2016.
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