REVIEWS Optimal bowel preparation—a practical guide for clinicians Douglas K. Rex Abstract | High-quality bowel preparation is essential for effective colonoscopy. Bowel preparations are judged by their safety, efficacy and tolerability. Between efficacy and tolerability, efficacy is the clinical priority because inadequate preparations are disruptive and costly. Achieving high rates of adequate preparation depends first on using split-dose or same-day dosing. Patients who have medical predictors of inadequate preparation quality (for example chronic constipation) should be prescribed more aggressive preparations and patients who have factors that predict they are less likely to follow the instructions (such as English not being their first language) should receive intensified education. On the day of the procedure, patients with persistent brown effluent should be considered for large-volume enemas or additional oral preparation before proceeding with colonoscopy. During the procedure, preparation quality should be graded after the clean-up has been completed. Rex, D. K. Nat. Rev. Gastroenterol. Hepatol. 11, 419–425 (2014); published online 1 April 2014; doi:10.1038/nrgastro.2014.35

Introduction The critical role of bowel cleansing in effective colonoscopy is increasingly recognized.1–3 From the patient’s perspective, bowel cleansing is most likely to be the worst part of the procedure,4–7 especially in an increasing era of deep sedation for colonoscopy, at least in the USA. The patient is often focused on the volume and poor taste of many of the commercially available preparations. Typically, patients are incompletely aware of the essential role of preparation quality in identifying precancerous lesions in the colon, ensuring that the procedure won’t have to be repeated sooner than necessary, and making the examination as efficient and as safe as possible. For colonoscopists, complaints about tolerability necessitate repeated instruction to patients about the value of taking enough preparation for adequate cleansing. This Review presents one colonoscopist’s perspective in describing elements of a bowel preparation programme that enhance high-quality colon cleansing with acceptable tolerability.

How bowel preparations are judged

Indiana University School of Medicine, Department of Medicine, 550 University Boulevard, Indianapolis, IN 46202, USA. [email protected]

Clinicians evaluate and select bowel preparations on the basis of their understanding of three criteria: efficacy, tolerability and safety. A fourth criterion for some patients is out-of-pocket costs, which generally should be discussed with patients before choosing a preparation. Safety from serious, specific organ toxicity is a prerequisite for bowel preparations. Although bowel preparations based on sodium phosphate have relatively favourable profiles for both efficacy and tolerability, the Competing interests D.K.R. declares that he is a member of the speakers’ bureau and has received research support from Ferring Pharmaceuticals and Braintree Laboratories.

occurrence of rare but serious renal injury 8,9 has virtually eliminated their use in the USA. Complications related to electrolyte imbalance, vomiting and dehydration are common to all types of preparation. Hyperosmotic preparations might place patients who are at high risk of fluid shifts (including patients with congestive heart failure, chronic renal insufficiency or cirrhosis with ascites) at an even greater risk; polyethylene glycol-electrolyte lavage solution (PEG-ELS) preparations are often selected for these populations. With safety from specific organ toxicity presumed, the choice of preparation revolves around efficacy versus tolerability. Reduced tolerability of bowel preparations is associated with high volume, bad taste and increased abdominal symptoms, particularly vomiting. In general, preparations that require a low volume of active in­gredient to be ingested tend to be better tolerated.10–12 Of the commercially available preparations, 4 l PEG-ELS is probably the worst tolerated, and a substantial fraction of patients assigned this preparation fail to ingest the entire volume.13 However, 4 l PEG-ELS given in split doses is still the gold standard for efficacy.14 A goal is to balance efficacy and tolerability using a regimen tailored to the patient’s medical status. Both efficacy and tolerability are important, and they are related. If preparations are poorly tolerated, then some patients will be unable to complete ingestion, reducing efficacy. Furthermore, poorly tolerated preparations increase the likelihood that patients will be unwilling to repeat procedures,4–7 which, in turn, increases the risk of colon cancer. By contrast, the consequences of using preparations that are ineffective are particularly problematic (Box 1).1–3,15,16 Often under-recognized is the sub­stantial contribution of inadequate bowel preparation

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REVIEWS Key points ■■ Efficacy and tolerability of bowel preparations are each important and are related to one another; as inadequate preparation has disruptive and costly consequences, efficacy is the more important clinical goal ■■ Several medical factors including previous inadequate preparation, chronic constipation, use of opioids and obesity predict an increased risk of inadequate preparation; such patients should receive a more aggressive bowel preparation regimen ■■ As patient factors such as having Medicaid insurance and English not being their first language predict failure to follow bowel preparation instructions, intensified education or patient navigation are indicated ■■ Split-dose and same-day-dose bowel preparation regimens are more effective than dosing either the day or evening before; all preparations can be given as split doses ■■ Brown rectal effluent on presentation predicts suboptimal preparation in 50% of patients, so large-volume enemas or additional oral preparation should be considered prior to attempting colonoscopy ■■ During colonoscopy, bowel preparation quality should be described after cleaning efforts are completed; washing and suctioning to improve preparation quality are part of the expected effort of most colonoscopies

Box 1 | Adverse consequences of ineffective bowel preparation ■■ Increased costs (repeat procedures)15 ■■ Impaired detection of large and small adenomas1–3 

■■ Impaired detection of flat lesions16  ■■ Patients lost to follow-up1  ■■ Longer procedural times3

Box 2 | Patient factors associated with failure to follow preparation instructions ■■ Medicaid insurance28  ■■ English not first language27 ■■ Lower educational level24 

■■ Low ‘healthy literacy’27,29  ■■ Low ‘patient activation’34  ■■ Longer waiting time on schedule24

to the overall costs of delivering colonoscopy.15 Given that the goal of colonoscopy is to prevent colon cancer, and that optimizing that goal requires adequate preparation, efficacy should be the primary goal, which will sometimes require the sacrifice of tolerability. Therefore, patients will sometimes have to undergo a preparation that will be difficult to complete, but which will enable the endoscopist to achieve the primary goal of an effective examination. Some patients will require education about the importance of preparation and motivational measures to succeed.17–20 Over the past decade, investigators have repeatedly reported rates of inadequate preparation of 20–40% in clinical practice. 1–3,21–26 There has been reluctance to set thresholds in guidelines for rates of adequate bowel preparation because rates of achievable adequate prep­ aration vary according to patient population factors such as average socioeconomic status. In general, bowel preparation quality is worse in populations with poor socioeconomic status, such as those in safety-net hospitals.27–29 Patients in these hospitals might have no insurance or only public insurance (Medicaid), and have lower rates of ‘health literacy’. It therefore seemed unfair to expect physicians practicing in these settings to achieve minimum thresholds of adequate preparation. However, the increasingly recognized adverse consequences of poor preparation have resulted in the consensus that all endoscopy units should seek to achieve quite high rates 420  |  JULY 2014  |  VOLUME 11

of adequate preparation. Efficacy is thus the first priority, and tolerability the second.

Predictors of inadequate preparation As rates of inadequate bowel preparation of 20–40% are still being reported, it is logical to ask which patients are failing and why? Are some patients more difficult to prepare and, if so, who are they? The approach to prescribing bowel preparations for colonoscopy is often more simplistic than the pharmacological approach to other problems. Many gastroenterology groups use only one or two preparations, with no adjustments made for age, gender, weight or bowel movement frequency. In fact, the literature suggests that these factors, among others, predict inadequate preparation.21,25,26,30,31 Predictors of inadequate preparation fall into two broad categories. The first category encompasses medical factors, including prior inadequate preparation, chronic constipation, use of constipating medications (such as opioids and tricyclic anti-depressants), prior colon resection, obesity and diabetes mellitus.21,25,26,30–32 When these factors are present, it would be reasonable to consider a more aggressive cleansing regimen. Segmental colon resection, which intuitively would predict that bowel cleansing would be easier, is actually a predictor of inadequate preparation. The most reliable predictor is the patient who has had a previously inadequate bowel preparation for colonoscopy. Such patients will almost certainly require some modification of a commercially available preparation, such as the addition of magnesium citrate, or even doubling the dose of a preparation, that is giving the entire preparation not once, but twice, over the course of 48 h. Anecdotally, I saw a patient with a very redundant colon who had to remain on clear liquids and drink 4 l of PEG-ELS on five consecutive days to achieve adequate colon cleansing.33 The second category of predictors of inadequate preparation are non-medical patient factors. These factors are associated with difficulty in following the instructions (listed in Box 2). ‘Health literacy’ refers to the patient’s cognitive skills and ‘patient activation’ refers to how engaged the patient is in their health care. Of note, a patient can have a high level of health literacy and a low level of patient activation. Unfortunately, there are no simple tools in clinical practice to predict health literacy and patient activation. Two simple and useful predictors of patients not following the instructions are having Medicaid insurance and English not being the patient’s primary language.27,28 When these factors are present, the solution is to intensify education, motivate the patient through education and employ reminders.17–20 Several simple educational pieces have appeared in the literature that facilitate education.18–20 The ultimate expression of managing these predictors is ‘patient navigation’, in which an educator who speaks the patient’s language meets with and guides the patient through the preparation process. In safety-net hospitals, patient navigators have been shown to increase attendance rates for colono­ scopy, increase rates of adequate preparation and to be highly cost-effective.34–37



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REVIEWS Box 3 | Summary of recent evidence on bowel preparation cleansing efficacy ■■ Split dosing is more effective than evening-before dosing13 ■■ Split dosing is better tolerated than evening-before dosing13 ■■ Same-day dosing is as (or more) effective and causes less disruption to work the day before colonoscopy than split dosing and is well tolerated40–42 ■■ 4 l split-dose PEG-ELS remains the gold standard for efficacy14 ■■ Oral sulphate solution and 2 l PEG-ELS with ascorbate have comparable efficacy56 ■■ Oral sulphate solution is more effective than sodium-picosulfate plus magnesium citrate (Prepopik®)57 ■■ Day-before ingestion of low-residue or fibre-free foods results in equal or better cleansing and improved tolerability compared with clear liquids only51–55

Selecting a bowel preparation An ideal bowel preparation would fully evacuate the colon and not produce continued watery bowel movements after the debris has been evacuated. Unfortunately, mg/kg or volume per kg dosing either does not work in bowel preparation or has seldom been tried. The currently available approach is to use a more aggressive preparation when medical predictors of an i­nade­ quate preparation are present (discussed above). The literature indicates that the most effective of the commercially-based prep­arations is 4 l PEG-ELS given in split doses (although split dosing is not an FDA-approved regimen for 4 l PEG-ELS [single dosing is approved]).13 Head-to-head comparisons of 4 l split-dose PEG-ELS with split-dose oral sulphate solution are warranted. Most studies of 4 l PEG-ELS have split the dose to 2 l in the evening before and 2 l on the day of the examination, but 3 l in the evening and 1 l on the day of the examination has also been studied and is effective.13 With regard to efficacy, an important rule to follow is that all preparations can be either split or given on the day of the procedure. Splitting is more effective than eveningbefore dosing and is better tolerated.13 In a meta-analysis of five randomized trials (including 1,232 patients) comparing split-dose PEG-ELS with evening-before dosing, satisfactory preparations were increased with split dosing (OR 3.70; 95% CI 2.79–4.91), as was willingness to repeat the same preparation (OR 1.76; 95% CI 1.06–2.91). 13 Split dosing resulted in fewer preparation discontinuations (OR 0.53; 95% CI 0.28–0.98) and a lower rate of nausea (OR 0.55; 95% CI 0.38–0.79) than evening-before dosing.13 Thus far, split dosing has not been demonstrated to be safer than evening-before dosing, although there is a clear rationale to believe that split dosing would be safer in certain situations. Most cases of phosphate nephro­ pathy have occurred with evening-before dosing.8,9 Peak serum phosphate levels occur 4–6 h after the dose, so when both doses are taken the evening before, the second dose is ingested just as the serum phosphate levels from the first dose are peaking. Splitting is typically associated with separation of the doses by at least 10–12 h, permitting serum phosphate levels to return to normal after the first dose. Similarly, in a report of PEG 3350-induced hyponatraemia cases, all of the cases occurred when the entire preparation was ingested the evening before, and none of the reported cases occurred with split dosing.38 Regardless of the preparation, electrolyte disturbances induced by the preparation could be reasonably expected

to be mitigated by ingesting part of the preparation and then waiting before ingesting the other part so that preparation-induced electrolyte changes do not move as far out of the normal range. As stated above, however, at this time, there is no proof that split dosing is actually safer than evening-before or same-day dosing. Resistance of clinicians to recommending split dosing is declining as evidence of its profound benefit mounts. Given the level of evidence supporting split dosing,13,3940 and same-day dosing 41,42 and its endorsement in screening guidelines,43 in my opinion it’s reasonable to ask whether endoscopists who continue with administering all doses the day before colonoscopy are serious about detecting pre-cancerous lesions during colonoscopy.44 Concerns about patient inconvenience should be alleviated by the demonstration that patients are willing to get up and take preparation for early morning appointments if they understand the importance of split dosing to cleansing quality,45 as well as surveys showing that patients seldom have faecal incontinence en route to the endoscopy unit after split dosing.46 Although anaesthesia specialists still sometimes argue against split dosing owing to concerns about aspiration, the American Society of Anesthesiologists guidelines permit ingestion of clear liquids up to 2 h before sedation,47 and two studies have found that residual gastric volumes are virtually unaffected by split dosing compared with evening-before dosing.48,49 Colonoscopy is certainly associated with a risk of aspiration, and that risk is increased by the use of anaesthesia specialists and propofol.50 How­ever, the risk is associated with the greater depth of sedation achieved when anaesthesia specialists participate in colonoscopy,50 and not because of split-dosing or same-day dosing. All bowel preparations can, and therefore should, be given with split-dosing or same-day-dosing regimens. Scientific advances in our knowledge of bowel prep­ aration with regard to efficacy are summarized in Box 3. In the past 10 years, several studies have shown that ingesting a low-residue or fibre-free diet rather than clear liquids on the day prior to colonoscopy results in cleansing quality that is either better, or at least not impaired, as well as improved tolerability and patient satisfaction.51–55 Thus, these diets are now a viable alternative to clear liquids, although some clinicians remain concerned that some patients who are allowed to eat the day before colono­scopy will stray from the recommended amounts and types of foods. At least in theory, patients who are at increased risk of complications from fluids shifts might do better with PEG-ELS preparations compared with hyperosmotic preparations (as discussed above). Thus, in our own practice, we use PEG-ELS preparations in patients who report congestive heart failure, chronic renal insufficiency and liver disease accompanied by ascites. In our practice, we use some purely anecdotal rules for assigning preparations to patients. For example, PEG‑3350 prepared in the sports drink Gatorade® is given to many non-constipated patients without risk factors for inadequate preparation. This decision is based

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REVIEWS Triage process

Congestive heart failure Liver disease with ascites Chronic renal failure PEG-ELS only Continue triage

No

Medical predictors of inadequate preparation Yes

No

More agressive preparation (e.g. 4 l PEG-ELS or low-volume preparation plus magnesium citrate)

Low-volume preparations

Patient predictors of poor compliance Yes

Intensify education; navigation if available

Verbal and written instructions for split-dose or same-day dosing Day of procedure Query effluent

Brown

Clear or yellow Colonoscopy: rate preparation quality after clean up Measure adequacy rate based on preparation description and interval recommendations

Consider additional oral preparation or enemas

Figure 1 | An algorithm addressing key considerations in selecting bowel preparations. Abbreviation: PEG-ELS, polyethylene glycol-electrolyte lavage solution. Reproduced with permission from Elsevier © Rex, D. Clin. Gastroenterol. Hepatol. 12, 458–462 (2014).

on little evidence. Essentially, we find that PEG‑3350based preparation is very well tolerated and generally effective in patients without risk factors for inadequate prep­aration as well as being inexpensive and easy to prepare. However, constant harping from pharmaceutical representatives about the lack of FDA approval and the potential medical–legal risks of using PEG‑3350 have caused us to restrict its use to patients aged ≤70 years, unless approved by the colonoscopist.38 The rationale is simply that the elderly are more likely to have almost any complication from a preparation, and so this policy leaves us less likely to incur an electrolyte-related complication from PEG‑3350. Also, we do not give magnesium citrate or Prepopik®(sodium picosulfate plus magnesium oxide and anhydrous citric acid; Ferring Pharmaceuticals, Hoofddorp, Netherlands) to patients undergoing dialysis, although it’s not clear that the magnesium either in one bottle of magnesium citrate or in one Prepopik®kit is enough to harm a patient un­dergoing dialysis. Few studies have directly compared low-volume preparations to each other (Box 3). Oral sulphate solution (960 ml) and PEG-ELS with ascorbate have comparable efficacy.56 In a randomized controlled trial in 337 patients, oral sulphate solution was more effective than Prepopik®.57 Anecdotally, we have more failures with Prepopik®and PEG‑3350 than other preparations, and we now avoid these preparations in patients with predictors of inadequate preparation. Again, Prepopik®and PEG‑3350 are well tolerated,58–62 but efficacy is the priority. 422  |  JULY 2014  |  VOLUME 11

For patients who have predictors of inadequate preparation, we often use split dose 4 l sulphate-free ELS (NuLYTELY, Braintree Labs, Braintree, MA, USA). If patients have very severe constipation or if they have failed to adequately prepare for a previous colonoscopy, we often use 8 l of NuLYTELY spread over 2 days. This regimen is not FDA-approved, but it’s essential to design some regimen to deal with hard-to-prepare patients. An alternative that I have anecdotally found useful is to give a bottle of magnesium citrate with or without bisacodyl ~24 h prior to colonoscopy and then administer standard split doses of oral sulphate solution. For the rare patients who cannot tolerate liquid oral preparation in any form, one approach is to use repeated doses of bisacodyl over 2–3 days (some caution is needed with bisacodyl dosing because on rare occasions it can precipitate ischaemic colitis63) followed by colonic hydrotherapy or just large-volume enemas until the effluent is clear. A second approach is oral bisacodyl, followed by an initial colonoscopy with infusion of PEG-ELS or other laxatives into the right colon.64,65 A final approach that is rarely needed is to schedule the patient for same day upper endoscopy and colonoscopy. The upper endoscopy is performed in the early morning using a colonoscope. The colonoscope is passed beyond the ligament of Treitz, and the bowel preparation is infused into the small bowel via the scope. During the infusion, it might be wise to give intravenous prokinetics and to periodically withdraw into the stomach and check for excessive entero-gastric reflux of the infusion. The patient is then allowed to wake up and the colonoscopy is performed after the rectal effluent is clear. Figure 1 displays a general approach for selecting bowel preparations.32 The algorithm is not meant to represent a proven sequence of steps to follow, but rather to emphasize specific categories of issues that should be addressed by endoscopy units when designing preparation protocols. Some steps might be more or less a­ppropriate for specific patient populations.

On presentation to the unit When the patient presents to the endoscopy unit, they should be asked about the colour of their effluent. If the effluent is either clear or yellow, the patient generally is ready for colonoscopy, although work might still be needed to complete the preparation. If the effluent is still brown, the likelihood of suboptimal preparation is ~50%.25 Depending on how many bowel movements the patient has had and how runny they are, it might be appropriate to administer a large-volume enema64 or to administer more oral preparation. If there is still substantial solid stool in the effluent, more oral preparation is often the best approach. We usually have the patient drink PEG-ELS in the unit and report to the nurses when the effluent becomes clear. We then wait at least 2 h and proceed with colonoscopy. An alternative approach when the effluent is still brown is to proceed with colonoscopy as in 50% of cases the preparation is adequate25 and even poor preparations can sometimes be salvaged with extensive work. Specific devices are available to help clean up poor



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REVIEWS preparations.66–68 The MedJet™ (MedJet Ltd, Tel Aviv, Israel) device consists of a catheter passed through the colonoscope working channel that delivers a controlled but high power jet of saline and carbon dioxide gas. The jet clears debris off the mucosa and breaks up small particles. In 32 patients who had poor preparation no complications were reported, improved bowel cleansing was achieved, and 18 adenomas and a colon cancer were said to be uncovered by the device.66 The JetPrep™ system (JetPrep Ltd, Herzliya, Israel) is a catheter with a showerhead nozzle at the tip that provides a high power wash and was safe and superior to syringe-based flushing in improving poor preparations.68 Although such devices are useful, the need for them portends an inefficient colonoscopy, and an important goal is to minimize the need for all special intraprocedural measures by using effective pre-procedure cleansing protocols. Finally, there continues to be publication of new ‘tricks’ to improve efficacy. For example, regular use of menthol sugar-free sweets during PEG-ELS ingestion improves the ability of patients to ingest PEG-ELS and improves cleansing.69

During the colonoscopy During the colonoscopy, the colonoscopist should work at the cleansing process so that whenever possible the findings of the examination will be sufficiently reliable that the appropriate screening or surveillance recommendations can be followed. According to the US Multi-Society Task Force (MSTF), if cleaning can occur to the point where lesions larger than 5 mm can be reliably detected, then the preparation is adequate.70 Bubbles and mucus should be washed down using the colonoscope water jet. Pools of semi-solid debris can generally be removed by a process of continuous irrigation with the water jet combined with suctioning. If seeds or solid particles continue to get in the way, placing a Savary wire down the instrument until the spring section has fully exited the scope might enable the clean-up to continue without faecal material jamming the channel. Temporarily removing the suction valve and suctioning with the fingertip directly over the suction opening in the control head can help to prevent clogging the instrument when removing particulate debris. If the preparation can be improved to the point where only one or a few small areas of semisolid material cannot be suctioned, the mucosa under these areas can often be adequately viewed by rotating the patient and watching the mucosa become visible as gravity moves the residual pools. The central point is that cleaning up is part of colono­ scopy and is necessary to one degree or another in most examinations, even if in many cases that simply means washing down bubbles and mucus. The quality of the bowel preparation should be judged after the cleaning process has occurred since only that level of cleansing reflects on the adequacy of mucosal inspection.

might be able to salvage the procedure by administering an enema through the colonoscope (and then allowing the patient to awaken, pass the enema and then trying the procedure again), or by allowing the patient to awaken and drink more oral preparation followed by another attempt at colonoscopy. In some cases, these measures are not logistically feasible for a given patient or endo­ scopy unit. It is very appropriate for an endoscopist to abort a procedure as soon as it is evident that the prep­ aration cannot be made adequate, particularly when the indication is screening or surveillance and therefore has polyp detection as the primary goal. Colonoscopists should be aware that poor preparation is associated with longer insertion times3 and thus probably more gas insufflation. On the basis of an anecdotal review of malpractice cases, I am convinced that proceeding with an attempt at caecal intubation in a poorly prepared colon increases the risk of barotrauma injury to the right colon, including perforation. Gas insufflation should be judicious when a decision is made to proceed with caecal intubation in a poorly prepared left colon, particularly if the sigmoid has severe diverticulosis, which can result in gas trapping between the sigmoid and caecum. In this setting, conversion to carbon dioxide insufflation or water immersion might help to prevent distention, and abdominal distention should be monitored during insertion by frequent abdominal inspection and palpation. When the procedure is aborted because of preparation quality and cannot be salvaged on the same day or the following day (when the patient takes more preparation at home and returns the next day) then the patient should be scheduled at the next available appointment after additional education and consideration of a more aggressive preparation regimen. If the procedure is complete to the caecum, but the preparation does not meet the MSTF criteria for adequacy,70 the MSTF now recommends that the procedure be repeated within 1 year.71 An interval shorter than 1 year is appropriate when advanced neoplasia is discovered and the preparation is inadequate. Photographs of poorly prepared areas should be obtained to document the need for an early repeat examination.

Overview of the evidence Split dosing and same-day dosing are the most important advances in bowel preparation science in the past two decades. Medical factors that predict inadequate bowel preparation should be reviewed prior to prescribing the preparation and when present should lead to a more aggressive preparation. Predictors of noncompliance with preparation instructions should be reviewed and identification of such factors should lead to additional efforts at patient education, motivation and in some settings navigation. In safety-net hospitals, navigation is cost-effective.

When all measures fail

Conclusions

As noted above, when a preparation is determined to be inadequate during the colonoscopy, colonoscopists

The modern colonoscopist considers efficacy, tolerability and safety when selecting bowel preparations.

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REVIEWS Safety from specific organ toxicity is a prerequisite of bowel preparations and between efficacy and tolerability, efficacy should be the priority. The individuals who are selecting preparations for patients must be well informed and use a flexible approach. The patient should receive written and verbal instructions. On the day of the examination, large-volume enemas or additional oral preparation should be considered in patients who still have brown effluent. Effective colonoscopists work during the procedure to improve preparation quality to

1.

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the point that screening and surveillance guidelines can be followed. Review criteria A literature search was conducted using the databases MEDLINE and EMBASE and the search terms “bowel preparation” and “colonoscopy”, with the final search performed on 30 October 2013. Reference lists were searched for relevant articles when appropriate.

cleansing. Am. J. Gastroenterol. 98, 2187–2191 (2003). Kilgore, T. W. et al. Bowel preparation with splitdose polyethylene glycol before colonoscopy: a meta-analysis of randomized controlled trials. Gastrointest. Endosc. 73, 1240–1245 (2011). Enestvedt, B. K. et al. 4‑Liter split-dose polyethylene glycol is superior to other bowel preparations, based on systematic review and meta-analysis. Clin. Gastroenterol. Hepatol. 10, 1225–1231 (2012). Rex, D. K. et al. Impact of bowel preparation on efficiency and cost of colonoscopy. Am. J. Gastroenterol. 97, 1696–1700 (2002). Parra-Blanco, A. et al. The timing of bowel preparation before colonoscopy determines the quality of cleansing, and is a significant factor contributing to the detection of flat lesions: a randomized study. World J. Gastroenterol. 12, 6161–6166 (2006). Liu, X. et al. Telephone-based re-education on the day before colonoscopy improves the quality of bowel preparation and the polyp detection rate: a prospective, colonoscopist-blinded, randomised, controlled study. Gut 63, 125–130 (2014). Rosenfeld, G. et al. The impact of patient education on the quality of inpatient bowel preparation for colonoscopy. Can. J. Gastroenterol. 24, 543–546 (2010). Tae, J. W. et al. Impact of patient education with cartoon visual aids on the quality of bowel preparation for colonoscopy. Gastrointest. Endosc. 76, 804–811 (2012). Spiegel, B. M. et al. Development and validation of a novel patient educational booklet to enhance colonoscopy preparation. Am. J. Gastroenterol. 106, 875–883 (2011). Ness, R. M. et al. Predictors of inadequate bowel preparation for colonoscopy. Am. J. Gastroenterol. 96, 1797–1802 (2001). Hendry, P. O., Jenkins, J. T. & Diament, R. H. The impact of poor bowel preparation on colonoscopy: a prospective single centre study of 10,571 colonoscopies. Colorectal Dis. 9, 745–748 (2007). Chung, Y. W. et al. Patient factors predictive of inadequate bowel preparation using polyethylene glycol: a prospective study in Korea. J. Clin. Gastroenterol. 43, 448–452 (2009). Chan, W. K. et al. Appointment waiting times and education level influence the quality of bowel preparation in adult patients undergoing colonoscopy. BMC Gastroenterol. 11, 86 (2011). Fatima, H., Johnson, C. S. & Rex, D. K. Patients’ description of rectal effluent and quality of bowel preparation at colonoscopy. Gastrointest. Endosc. 71, 1244–1252 (2010). Borg, B. B. et al. Impact of obesity on bowel preparation for colonoscopy. Clin. Gastroenterol. Hepatol. 7, 670–675 (2009).



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VOLUME 11  |  JULY 2014  |  425

Optimal bowel preparation--a practical guide for clinicians.

High-quality bowel preparation is essential for effective colonoscopy. Bowel preparations are judged by their safety, efficacy and tolerability. Betwe...
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