Bowel preparation before colonoscopy

This is one of a series of documents discussing the use of GI endoscopy in common clinical situations. The Standards of Practice Committee of the American Society for Gastrointestinal Endoscopy prepared this document that updates a previously issued consensus statement and a technology status evaluation report on this topic.1,2 In preparing this guideline, a search of the medical literature was performed by using PubMed between January 1975 and March 2014 by using the search terms “colonoscopy,” “bowel preparation,” “intestines,” and “preparation.” Additional references were obtained from the bibliographies of the identified articles and from recommendations of expert consultants. When limited or no data exist from well-designed prospective trials, emphasis is given to results from large series and reports from recognized experts. Recommendations for appropriate use of endoscopy are based on a critical review of the available data and expert consensus at the time that the documents are drafted. Further controlled clinical studies may be needed to clarify aspects of recommendations contained in this document. This document may be revised as necessary to account for changes in technology, new data, or other aspects of clinical practice. 

 The strength of individual recommendations is based both on the aggregate evidence quality and an assessment of the anticipated benefits and harms. Weaker recommendations are indicated by phrases such as “we suggest,” whereas stronger recommendations are typically stated as “we recommend.”

This guideline is intended to be an educational device to provide information that may assist endoscopists in providing care to patients. It is not a rule and should not be construed as establishing a legal standard of care or as encouraging, advocating, requiring, or discouraging any particular treatment. Clinical decisions in any particular case involve a complex analysis of the patient’s condition and available courses of action. Therefore, clinical considerations may lead an endoscopist to take a course of action that varies from these recommendations and suggestions.

Colonoscopy is the current standard method for imaging the mucosa of the entire colon. Large-scale reviews have shown rates of incomplete colonoscopy, defined as the inability to achieve cecal intubation and mucosal visualization effectively,4,5 between 10% and 20%,4 well over targets recommended by the U.S. Multi-Society Task Force on Colorectal Cancer.6 The diagnostic accuracy and therapeutic safety of colonoscopy depends, in part, on the quality of the colonic cleansing or preparation.7 Inadequate bowel preparation can result in failed detection of prevalent neoplastic lesions and has been linked to an increased risk of procedural adverse events.1,8 Sidhu et al9 performed an audit of all colonoscopies performed between April 2005 and 2010 at the Royal Liverpool University. Of the 8910 colonoscopies performed, 693 were incomplete (7.8%; 58% women; mean age, 61 years), and inadequate bowel preparation was the most common reason for incomplete colonoscopy, accounting for nearly 25% of failed colonoscopies in their series.

Numerous investigations designed to identify predictors of inadequate colonoscopy bowel preparation6-8 have found that inadequate preparation is more common in patients with the following characteristics: previous inadequate bowel preparation, non-English speaking, Medicaid insurance, single and/or inpatient status, polypharmacy (especially with constipating medications such as opiates), obesity, advanced age, male sex, and comorbidities such as diabetes mellitus, stroke, dementia, and Parkinson’s disease.1,10,11 Poor adherence to preparation instructions, erroneous timing of bowel purgative administration, and longer appointment wait times for colonoscopy have also been associated with poor bowel preparation.10,11 Thus, it is important for clinicians to understand the numerous modifiable physician- and patient-related factors that can lead to colonoscopy failure to reduce its incidence and provide patients with improved outcomes. 

The ideal preparation for colonoscopy should reliably empty the colon of all fecal material in a rapid fashion with no gross or histologic alteration of the colonic mucosa. The preparation should not cause patient discomfort or shifts in fluids or electrolytes. The preparation should be safe, convenient, tolerable, and inexpensive.12 Unfortunately, none of the currently available preparations have all of these characteristics. This document updates a previous consensus document and a technology status evaluation report on bowel preparation1,2 and reviews the available evidence regarding bowel preparation before colonoscopy.