Colorectal cancer is the second leading cause of cancer death in the United States. Colonoscopy is the gold standard for evaluating the colon. Adequate bowel preparation before colonoscopy is essential for an optimal colonoscopy. The American College of Gastroenterology (ACG), American Gastroenterological Association (AGA), and the American Society for Gastrointestinal Endoscopy (ASGE) recently published an update on bowel preparation for colonoscopy.
The guideline for ACG/AGA/ASGE Optimizing Adequacy of Bowel Cleansing for Colonoscopy Guideline was published March 4, 2025 in Gastroenterology (full text available here). Recommendations in this guideline apply to ambulatory patients at low risk for inadequate bowel preparation unless otherwise noted. Some of the key changes include limiting diet modifications to the day before colonoscopy, recommendations for split-dose low volume bowel preparation purgatives, the use of simethicone as a bowel preparation adjunct, and an increase in quality measures for bowel preparation adequacy from 85% to 90% or more. During this Guidelines Timeline article, we will take a look at these and other key changes in bowel preparation for colonoscopy. We encourage readers to review the full guidelines provided below for a more comprehensive understanding.
Guidelines Referenced
Similarities from 2014-2025
The 2014 and 2025 guidelines agree and/or offer addition support in the following areas:
- Patient education and navigation
- Tailoring of bowel preparation regimen to the individual patient
- Timing for split dose regimens
- The use of the term “adequate bowel preparation” after adequate cleaning and suctioning has been completed
- Same day salvage maneuvers
- Repeat colonoscopies for patients with inadequate, non-salvageable bowel preparations
Changes and Key Takeaways from 2014-2025
Dietary Modifications
- It is now recommended that diet modifications be limited to the day before colonoscopy.
- For patients using split-dose preparations, the updated guideline adds low-fiber foods to the recommended diet modifications for early and midday meals the day before colonoscopy.
Choice of Bowel Preparation Purgative
- The use of lower volume 2 L preparation regimens instead of 4 L regimens are now suggested.
- It is now recommended that hyperosmotic solutions NOT be used for bowel preparation.
Bowel Purgative | FDA-Approval as of 2025 | Important Considerations |
|---|---|---|
| Polyethylene glycol-electrolyte lavage solution (PEG-ELS) | approved | 2 L PEG-based regimens provide similar quality bowel preparation with better tolerability compared to 4 L regimens |
| PEG-ELS (2 L) + ascorbate | approved | Contraindicated in patients with phenylketonuria or glucose-6-phosphate dehydrogenase deficiency; should not be used in patients with reduced creatinine clearance or patients with congestive heart failure; purgative is hypertonic, hydration with additional water is recommended |
| PEG-ELS (1L) + ascorbate | FDA-approved | Similar adenoma detection rates compared to other bowel preparations |
| PEG-ELS (2L) + citrate | FDA-approved | Improved patient tolerability due to improved taste |
| PEG-3350 (2L) + bisacodyl | NOT FDA-approved | Widely used, but not FDA-approved. Associated with rare occurrences of ischemic colitis |
| Sodium picosulfate + magnesium citrate | FDA-approved | Contraindicated for patients with congestive heart failure, hypermagnesemia, and severe renal failure |
| Sodium picosulfate + magnesium oxide + citrate | FDA-approved | Potential for fluid and electrolyte shifts |
| Oral sulfate solution | FDA-approved | Increased risk of nausea and vomiting compared to PEG-ELS + ascorbate, Increased adenoma detection rate compared to 2 L PEG-ELS regimens |
Dosing and Timing of Bowel Preparation Regimen
- Split-dose preparations are now preferred for all patients regardless of preparation volume.
- The new recommendations add that same-day regimens are an inferior alternative to split dosing for patients having a morning colonoscopy.
Adjuncts to Help with Bowel Preparation
- Oral simethicone is now suggested for bowel preparation.
Assessment of Bowel Preparation
- The previous guideline did not comment on patient report of incomplete bowel preparation. The new guideline suggests colonoscope insertion to the sigmoid colon to confirm adequacy of preparation before aborting the procedure.
Improving Bowel Preparation Quality After Colonoscope Insertion
- The routine use of irrigation pumps to assist with bowel preparation during colonoscopy is suggested now.
Bowel Preparation Adequacy Rate as a Quality Measure
- The new guideline adds tracking the rate of adequate bowel preparation at the endoscopy unit level, in addition to the level of the individual endoscopist.
- The recommended rate of bowel preparation adequacy has increased from at least 85% to at least 90%.
Management of Patients With Inadequate and Non-Salvageable Bowel Preparations
- Modifications of bowel preparation instructions should include one of the following:
- Increased attention to communication of bowel preparation instructions
- Increased use of patient navigation
- Restricting intake of vegetable and legumes for 2 to 3 days before colonoscopy
- Allowing only clear liquids on the day before colonoscopy
- Adding in promotility agents
- Treating underlying constipation
- Temporary cessation of anticholinergic, opioid, or other constipating medications
- Use of high-volume bowel preparation regimens.
Bowel Preparation Regimen for Individuals at High Risk for Inadequate Preparation
- Bowel preparation regimens should be modified for patients at high risk for inadequate bowel preparation. Modifications should be similar to the modifications for patients who previously have had inadequate bowel preparation quality.
- The following regimen is suggested for patients at high risk for inadequate bowel preparation:
- Split-dose 4 L PEG-ELS + 15 mg bisacodyl the afternoon before colonoscopy
- Low-residue diet 3 and 2 days before colonoscopy
- Clear liquid diet the day before colonoscopy
| Bowel Preparation | 2025 Recommendations | 2014 Recommendations | Key Takeaways |
|---|---|---|---|
| Patient Education and Navigation | Should give verbal and written patient instructions. Suggests use of some form of patient navigation to improve bowel preparation adequacy. | Same as 2025 recommendations. | Verbal and written patient instructions and use of patient navigation can improve bowel preparation adequacy. |
| Dietary Modifications | Should be limited to the day before colonoscopy. | Limits diet modifications to improve compliance and tolerability. | |
| Should include low-residue and low-fiber or full liquids for early and midday meals the day before colonoscopy (for patients using a split-dose regimen). | Should include either low-residue or full liquid until the evening before colonoscopy (for patients using a split-dosing regimen). | Diet modification now includes low-fiber foods. | |
| Choice of Bowel Preparation Purgative | Suggests that 2 L regimens be used over 4 L regimens. | Low volume bowel cleansing was associated with greater willingness to repeat the regimen; split-dose 4 L PEG-ELS provides high quality bowel preparation; In healthy unconstipated patients, a 4 L PEG-ELS formulation produces bowel cleansing quality that is not superior to a lower volume PEG formulation. | Decreased volume of purgative leads to better tolerance with similar bowel preparation quality. |
| No recommendation for one bowel preparation purgative as superior to others for preparation adequacy. | See table on bowel purgatives for more information. | ||
| Selection of a bowel-cleansing regimen should take into consideration the patient's medical history, medications, and, when available, the adequacy of bowel preparation reported from prior colonoscopies | Same as the 2025 recommendation. | Choice of bowel-cleansing regimen should be tailored to the individual patient. | |
| Recommends that hyperosmotic regimens NOT be used | Recommends 4 L PEG-ELS based cleansing agents. | Consider the risk for fluid shift in at-risk patients. | |
| Dosing and Timing of Bowel Preparation Regimens | Split-dose regimens are recommended for all patients. | Split-dose regimens recommended for elective colonoscopy; split-dose bowel cleansing was associated with greater willingness to repeat the regimen. | Split-dose regimens are preferred . |
| Second dose of split preparation should begin 4 to 6 hours before the time of colonoscopy with completion of the last dose at least 2 hours before the procedure. | Same as the 2025 recommendation. | ||
| Same-day regimens are an acceptable alternative for patients undergoing an afternoon colonoscopy, but are an inferior alternative to split-dose regimens for patients undergoing a morning colonoscopy. | Same-day regimen is an acceptable alternative to split dosing, especially for patients undergoing an afternoon examination. | Updated recommendations note that same-day regimens are inferior to split-dose regimens in patients having a morning examination. | |
| Adjuncts for Bowel Preparation | Suggests oral simethicone | Recommended adjunctive agents NOT be used. | If endoscopists opt to use simethicone a dose of 320 mg should be used. |
| Suggests that non-simethicone adjuncts NOT be used routinely. | |||
| Assessing Bowel Preparation | Suggest insertion of the colonoscope to the sigmoid colon to confirm inadequacy before aborting the procedure in patients who report inadequate adherence to preparation or statement suggesting their bowel preparation may not be adequate like dark bowel effluent. | No guidance regarding patient reports of inadequate bowel preparation. | May mitigate unnecessary cancellations, since patient-reported inadequacy of bowel preparation is unreliable. |
| Improving Bowel Preparation Qualify After Colonoscope Insertion | New recommendation to routinely use irrigation pumps to assist with bowel preparation. | No recommendations regarding the use of irrigation pumps. | Routine use of irrigation pumps during colonoscopy can be used to improve bowel preparation adequacy. |
| Bowel Preparation Adequacy Rate as a Quality Measure | Track rate of adequate bowel preparation at the endoscopy unit level and the individual endoscopist level. | Track rate of adequate bowel preparation at the level of the individual endoscopist. | Increases tracking to include the endoscopy unit. |
| Recommends preparation adequacy rate of at least 90%. | Recommended preparation adequacy rate of at least 85% | Increase recommended bowel preparation adequacy rate. | |
| Management of Patients With Inadequate and Non-Salvageable Bowel Preparation | Modification of bowel preparation: increased attention to communication of preparation regimen, increased use of patient navigation, restricting intake of vegetables and legumes for 2 to 3 days before colonoscopy, allowing only clear liquids the day before colonoscopy, adding promotility agents, treatment of underlying constipation, temporary cessation of anticholinergic, opioid, or other constipating medications, and/or use of high-volume bowel preparation regimens. | No recommendations | New guidance regarding bowel preparation regimens for patients with previous inadequate and non-salvageable bowel preparation. |
| Bowel Preparation Regimen for Patients at High Risk for Inadequate Preparation | Patients at high risk for inadequate bowel preparation should be managed like patients with prior inadequate bowel preparation | Recommends considering additional bowel purgatives. | Updated guideline suggests specific modifications to bowel preparation regimens for patients at risk of inadequate bowel preparation. |
| Suggested preparation regimen: split-dose 4 L PEG-ELS + 15 mg bisacodyl the afternoon before colonoscopy, low-residue diet 3 and 2 days before colonoscopy, clear-liquid diet the day before colonoscopy. | |||
| Selection of Bowel Preparation in Specific Populations | Updated guidelines make specific recommendations for bowel preparation modification in patients at risk for inadequate bowel preparation as detailed above. No recommendations were made regarding other specific patient populations. | Elderly: Insufficient evidence to recommend a specific bowel preparation regimen, however sodium phosphate preparations should be avoided. Children and adolescents: Insufficient evidence to recommend a specific bowel preparation regimen, however sodium phosphate preparations should not be used in children younger than 12 years of age or in those with risk factors for complications from this.Patients at risk for inadequate bowel preparation: Additional bowel purgatives should be considered in patients with risk factors for inadequate preparation (history of inadequate preparation, constipation, use of opioids, or other constipating medications, prior colon resection, diabetes mellitus, or spinal cord injury). After bariatric surgery: low-volume preparations or extended time delivery for high-volume preparations are recommended. Pregnant women: tap water enemas should be used to prepare the colon for sigmoidoscopy. Spinal cord injuries: Insufficient evidence to recommend specific regimens. |
That concludes our Guidelines Timeline post covering the 2025 update for Optimizing Bowel Preparation Quality for Colonoscopy. We value your feedback and would like to hear your suggestions for future topics. Please feel free to contact us with any ideas or questions you may have.
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