The levels of evidence (I–V) and strength of recommendations (A–D) are defined at the end of the "Major Recommendations" field.
Regimens For Colonic Cleansing Before Colonoscopy
Diet
Dietary modifications alone, such as a clear liquid diet, are inadequate for colonoscopy. However they have proven to be a beneficial adjunct to other mechanical cleansing methods (Grade IIB).
Enemas
Use enemas in patients who present to endoscopy with a poor distal colon preparation and in patients with a defunctionalized distal colon.
High-Volume Gut Lavage
Neither high-volume nor unbalanced solutions, such as mannitol, should be used for colonic preparation (Grade IA). In addition, caution should be taken when using nasogastric tubes for the administration of any bowel preparation infusion (Grade VD).
Rectal Pulsed Irrigation
Rectal pulsed irrigation administered immediately before the procedure combined with magnesium citrate given the evening before the procedure is a reasonable alternative to full-volume (4-liters) polyethylene glycol (PEG) in those individuals who cannot tolerate per oral administration of PEG (Grade IIB).
PEG (Electrolyte Lavage Solution)
PEG is a faster, more effective, and better-tolerated method for cleansing the colon than a restricted diet combined with cathartics, high-volume gut lavage, or mannitol (Grade IA). PEG is safer than osmotic laxatives/sodium phosphate (NaP) for patients with electrolyte or fluid imbalances, such as renal or liver insufficiency, congestive heart failure, or liver failure and is, therefore, preferable in these patient groups (Grade IA). Divided-dose PEG regimens (2–3 liters given the night before the colonoscopy and 1–2 liters on the morning of procedure) are acceptable alternative regimens that enhance patient tolerance (Grade IIB). Cleansing preparations for colonoscopies performed in the afternoon should instruct that at least part of the PEG solution be given the morning before the procedure (Grade IIB). Enemas, bisacodyl, and metoclopramide as adjuncts to the full volume of PEG have not been demonstrated to improve colonic cleansing or patient tolerance and are, therefore, unnecessary (Grade IIB).
Sulfate-Free PEG (SF-PEG)
SF-PEG is comparable to PEG in terms of safety, effectiveness, and tolerance. SF-PEG is better tasting, but still requires the consumption of 4 liters in its standard regimen. SF-PEG is an acceptable alternative lavage solution when a PEG-based lavage solution is required (Grade IIB).
Low-Volume PEG/PEG-3350 and Bisacodyl Delayed-Release Tablets
Two-liter PEG regimens combined with bisacodyl (i.e., HalfLytely®) or magnesium citrate are equally effective compared with standard 4-liter PEG regimens but appear to be better tolerated and therefore a more acceptable alternative to the 4 liter PEG regimens (Grade IA). However, the safety of the reduced dose PEG in patients who may not tolerate fluids is still unknown. Additional studies comparing 2-liter regimens with NaP would be beneficial.
Low-Volume PEG-3350 and Bisacodyl Delayed-Release Tablets
Two-liter PEG 3350 regimens combined with bisacodyl (i.e., Miralax®) are equally effective compared with standard 4-liter PEG (Grade IA).
Aqueous NaP
Aqueous NaP colonic preparation is an equal alternative to PEG solutions except for pediatric and elderly patients, patients with bowel obstruction, and other structural intestinal disorders, gut dysmotility, renal failure, congestive heart failure, or liver failure (Grade IA). Dosing of aqueous NaP should be 45 mL in divided doses, 10 to 12 hours apart with one of the doses taken on the morning of the procedure (Grade IIB). Aqueous NaP is the preferable form of NaP at this time (Grade IIB). Apart from anecdotal reports, the addition of adjuncts to the standard NaP regimen has not demonstrated any dramatic effect on colonic cleansing preparation. Carbohydrate-electrolyte solutions such as E-Lyte® may improve safety and tolerability.
Tablet NaP
The improved taste and palatability of tablet NaP compared with aqueous NaP has not translated into improved overall patient tolerance (Grade IA). The reduced amount of microcrystalline cellulose allows for better visualization of the colonic mucosa with less need for colonic irrigation (Grade IVB). Efficacy is maintained despite decreasing the number of tablets required to complete the preparation (Grade IIB), significantly improving patient tolerance.
Adjuncts to Colonic Cleansing Before Colonoscopy
See the original guideline document for information about adjuncts to colonic cleansing before colonoscopy, including
- Flavoring
- Nasogastric/orogastric tube administration of colonic preparations
- Carbohydrate-electrolyte solutions
- Enemas
- Metoclopramide
- Simethicone
- Bisacodyl
- Saline Laxatives
- Senna
Special Considerations
Inadequate Bowel Preparation
Inadequate bowel preparation for colonoscopy can result in missed lesions, cancelled procedures, increased procedural time, and a potential increase in complication rates. One study examined the possible causes for poor preparations. Surprisingly, less than 20 percent of patients with an inadequate colonic preparation reported a failure to adequately follow preparation instructions. Independent predictors of an inadequate colon preparation included a later colonoscopy starting time, failure to follow preparation instructions, inpatient status, procedural indication of constipation, use of tricyclic antidepressants, male gender, and a history of cirrhosis, stroke, or dementia. Anecdotally, a poor preparation after a PEG preparation is usually liquid and more easily managed than a preparation after NaP, which tends to be thick and tenaciously adhered to the mucosa. There is no published information on the management of the patient who has received a colonoscopy preparation that has been deemed inadequate. Regardless of the preparation selected, the patient and physician must be aware of potential financial obligations of a repeat colonoscopy and preparation. Specifically, the patient may be required to pay an additional co-pay for each examination and the financial intermediary may deem one or both examinations unnecessary. In these instances, the patient may be responsible for payment in full for both examinations. The following are recommendations (Grade VD) on management of this clinical predicament. Identify whether or not the patient has consumed the preparation as prescribed. If not, it would be reasonable to repeat the same preparation, although not within 24 hours using NaP because of the risk of toxicity. If the patient has properly consumed the preparation, reasonable options include repeating the preparation with a longer interval of dietary restriction to clear liquids, switching to an alternate but equally effective preparation (if the patient received PEG, change to NaP or vice versa), adding another cathartic, such as magnesium citrate, bisacodyl, or senna, to the previous regimen, or double administration of the preparation during a two-day period (with the exception of NaP). Combining preparations, for example PEG solution and NaP solution, also has been described with some success.
Selection of Bowel Preparation Based on Comorbidities
Elderly Patients
Elderly patients tend to have poorer preparations, although one study found no difference in the adequacy of the colonic preparation between PEG and NaP solutions. They are at an increased risk for phosphate intoxication because of decreased kidney function, concomitant medication use, and systemic and gastrointestinal diseases. Administration of NaP causes a significant rise in serum phosphate, even in patients with normal creatinine clearance. Hypokalemia is more prevalent in frail patients. However, NaP preparations may be safe in selected healthy elderly patients.
Possible Underlying Inflammatory Bowel Disease
NaP preparations may cause mucosal abnormalities that mimic Crohn's disease. However, the frequency of this problem is rare and may not mitigate against using NaP. This caveat is most important in the initial colonoscopic evaluation of patients with symptoms suspect for colitis.
Diabetes Mellitus
One study showed that patients with diabetes have significantly poorer preparations with PEG solutions than patients without diabetes, although there is no evidence that NaP preparations are superior in this group.
Pregnancy
The need for colonoscopy is uncommon during pregnancy, therefore, the safety and efficacy of colonoscopy in these individuals is not well studied. However, invasive procedures are justified when it is clear that by not doing so could expose the fetus and/or mother to harm. The safety of PEG electrolyte isotonic cathartic solutions has not been studied in pregnancy. PEG solutions are Food and Drug Administration (FDA) Category C for use in pregnancy, as defined in the FDA Current Category for Drug Use in Pregnancy, wherein no adequate and well-controlled studies have been undertaken in pregnant females and a limited number of animal studies have shown an adverse effect. The common use of PEG solutions, such as Miralax®, to manage constipation associated with pregnancy supports its safety as a bowel preparation. NaP preparations, which are also FDA Category C, may cause fluid and electrolyte abnormalities and should be used with caution.
Recommendations. If the potential benefit of colonoscopy outweighs the small but potential risks, patients may be cleansed with PEG solutions or, in select patients, a NaP preparation may be used (Grade VD).
Pediatric Population
Although there are no "national standards" per se for pediatric bowel preparations for colonoscopy, review of the literature documents the three most commonly used preparations. The least commonly used preparation is the administration of two pediatric Fleet® enemas and X-Prep® (for age). A more widely used preparation includes Miralax® at 1.25 mg/kg per day for four days, the last day of which the child is maintained on clear liquids. This regimen is mild, well tolerated, and relatively simple to administer. The simplest preparation, both for the parents and the child, is the administration of a sugar-free, clear-liquid diet the day before and then nil by mouth for eight hours before the colonoscopy. This regimen is combined with Fleet® Phospho-soda® at a dosage of 1.5 tablespoons for children weighing less than 15 kg and 3 tablespoons for children weighing 15 kg or more, the afternoon and then again the evening before the colonoscopy. Each of these preparations is safe and will adequately prepare the child's colon for colonoscopy (Grade IA).
Definitions:
Levels of Evidence
- Meta-analysis of multiple well-designed, controlled studies, randomized trials with low-false positive and low-false negative errors (high power)
- At least one well-designed experimental study; randomized trials with high false-positive or high false-negative errors or both (low power)
- Well-designed, quasi experimental studies, such as nonrandomized, controlled, single-group, preoperative-postoperative comparison, cohort, time, or matched case-control series
- Well-designed, nonexperimental studies, such as comparative and correlational descriptive and case studies
- Case reports and clinical examples
Recommendation Grades
- Evidence of Type I or consistent findings from multiple studies of Type II, III, or IV
- Evidence of Type II, III, or IV and generally consistent findings
- Evidence of Type II, III, or IV but inconsistent findings
- Little or no systematic empirical evidence
