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 .
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".)
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.
Decisions regarding the management of antiplatelet agents or anticoagulants must weigh the risks of bleeding from the procedure with the probability of a thromboembolic event occurring while the antithrombotic medication is interrupted (table 1 and table 2) . Furthermore, the urgency of the procedure and the availability of alternative tests must be evaluated (eg, a bleeding scan in a patient with acute lower gastrointestinal bleeding). Whenever possible, management decisions about antithrombotic agents should be made following discussion with the patient and the clinician prescribing the medication. Aspirin and nonsteroidal anti-inflammatory drugs in standard doses may be continued safely in patients undergoing colonoscopy, including in those who require polypectomy. (See "Management of anticoagulants in patients undergoing endoscopic procedures" and "Management of antiplatelet agents in patients undergoing endoscopic procedures" and "Endoscopic procedures in patients with disorders of hemostasis".)