Updates Surg DOI 10.1007/s13304-015-0295-2
REVIEW ARTICLE
Improving the view during flexible sigmoidoscopy: a systematic review of published randomized, controlled trials comparing the use of oral bowel preparation versus enema bowel preparation Muhammad Shafique Sajid1 • Jennifer F. Caswell1 • Mustafa A. Q. Abbas1 Mirza K. Baig1 • Malcolm R. McFall1
•
Received: 17 December 2014 / Accepted: 27 March 2015 Ó Italian Society of Surgery (SIC) 2015
Abstract To systematically analyse the published randomized, controlled trials (RCTs) comparing the use of oral bowel preparation (OBP) versus enema bowel preparation (EBP) for diagnostic or screening flexible sigmoidoscopy. Published RCTs, comparing the use of OBP versus EBP, were analysed using RevManÒ, and the combined outcomes were expressed as odds ratios (OR). Eight RCTs evaluating 2457 patients were retrieved from the standard electronic databases. There was significant heterogeneity among included trials. The compliance of the patients (p = 0.32) and the acceptability of both bowel preparation regimens (OR, 1.42; 95 % CI, 0.67, 2.99; z = 0.92; p = 0.36) were similar in both groups. In addition, the incidence of adverse reactions (OR, 0.87; 95 % CI, 0.54, 1.41; z = 0.57; p = 0.57), the risk of incomplete procedure due to poor bowel preparation (p = 0.18) and the incidence of poor bowel preparation (OR, 1.21; 95 % CI, 0.63, 2.33; z = 0.59; p = 0.56) were also similar in both groups. EBP and OBP were equally effective for bowel preparation in patients undergoing flexible sigmoidoscopy. Although this study failed to demonstrate the superiority of EBP, at least equivalent efficacy for bowel cleansing may be extrapolated. Keywords Flexible sigmoidoscopy Colorectal cancer Bowel preparation Enema preparation Bowel cleansing tools
& Muhammad Shafique Sajid [email protected] 1
Department of General, Endoscopic and Laparoscopic Colorectal Surgery, Western Sussex Hospitals NHS Foundation Trust, Worthing Hospital, Washington Suite, North Wing, Worthing, West Sussex BN11 2DH, UK
Introduction Diagnostic, screening and surveillance flexible sigmoidoscopy (FS) is of utmost importance for the evaluation of symptoms and optimum management of colorectal disorders such as benign polyps, malignant polyps, colorectal cancer, diverticular disease and inflammatory bowel disease [1, 2]. Adequate bowel preparation can have a significant influence on the length of procedure, risk of complication and the rate of adenoma detection [3, 4]. Approaches to bowel preparation involved dietary preparation, laxatives, enemas, whole gut irrigation via nasogastric tube and the use of mannitol solution during the preceding days to procedure [5–10]. Whilst these preparations were shown to produce acceptable bowel cleansing, they required many hours or days of dietary modification and were found to be uncomfortable and poorly tolerated by the patients. A major advance came with the development of polyethylene-glycol (PEG) lavage solution that resulted in less electrolyte or fluid disturbances than its counterparts and was reported safe and effective in practice [11, 12]. Despite its apparent clinical success, major drawback was again poor patient compliance, with up to 15 % of patients failing to complete the preparation [13]. Oral sodium phosphate solution was introduced as a major competitor to PEG solution due to much better tolerance and compliance [14, 15]. However, over time, concerns emerged regarding the use of oral phosphate preparations over their propensity to cause significant electrolyte imbalance [16–22]. Enema bowel preparations (EBP) have been suggested to be advantageous over oral solution in FS as they quickly clear the bowel and do not require dietary preparation [23]. Furthermore, their tendency to avoid the aforementioned complications of oral bowel preparations (OBP) increases their favourability. Preliminary studies
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have shown good outcomes with enema preparations [24, 25]. However, so far, in the literature a consensus on preferred bowel cleansing strategy for FS is not reported, with many studies demonstrating conflicting results. The objective of this article is to analyse the randomized, controlled trials comparing the effectiveness of OBP versus EBP in patients undergoing FS.
narrow and widen the results of potentially usable studies. The titles of the published articles from the search results were examined closely and assessed for suitability for potential inclusion. The reference lists from selected articles were also examined as a further search tool to find additional trials. Selection criteria for included trials
Methods Electronic data sources and their search planning In order to obtain appropriate studies, a search of medical electronic databases such as MEDLINE, EMBASE, and the Cochrane library for randomized, controlled trials was conducted and screened according to the PRISMA flow chart (Fig. 1). The MeSH terms published in the Medline library relevant to OBP versus EBP were used to retrieve the relevant randomized, controlled trials. No limits for language, gender, sample size and place of study origin were entered for the search in the search engine. Boolean operators (AND, OR, NOT) were additionally used to
For inclusion in this meta-analysis, a study had to fulfil the following criteria: (1) randomized, controlled trial; (2) comparison between OBP and EBP in patients undergoing flexible sigmoidoscopy; (3) evaluation of bowel preparation quality, number of incomplete procedures secondary to poor preparation, patient acceptance or compliance and adverse events. Data abstraction from included trials Two independent reviewers using a predefined meta-analysis form extracted relevant data from each study which resulted in a satisfactory inter-observer agreement. The extracted data contained name of the publishing authors,
Idenficaon
Fig. 1 PRISMA flow diagram Records idenfied through database searching (n = 51 )
Addional records idenfied through other sources (n = 0 )
Eligibility
Screening
Records aer duplicates removed (n = 51 )
Records screened (n = 13 )
Full-text arcles assessed for eligibility (n = 10)
Included
Studies included in qualitave synthesis (n = 8)
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Studies included in quantave synthesis (meta-analysis) (n = 8)
Records excluded (n = 38 ) Causes: irrelevant
Full-text arcles excluded, with reasons (n = 3 ) Causes: Other reviews Other technique reviews Duplicate data
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title of the published study, journal in which the study was published, country and year of the study, intervention protocol in both limbs of the trial, testing sample size (with sex differentiation if applicable), the number of patients receiving each regimen and within each group the number of patients who succeeded and the number of patients who failed the allocated preparation, the patient compliance rate in each group, the number of patients reporting complications and the number of patients with absence of complications in each arm of the trial. After completing the data extraction the two independent reviewers discussed the data-related results and, if discrepancies were present, a consensus was reached. Statistical analysis The software package RevMan 5.3.1 [25, 26], provided by the Cochrane Collaboration, was used for the statistical analysis. The odds ratio (OR) with a 95 % confidence interval (CI) was calculated for binary data. The random effects model [27, 28] was used to calculate the combined outcomes of both binary variables. Heterogeneity was explored using the v2 test, with significance set at p \ 0.05, and was quantified [29] using I2, with a maximum value of 30 % identifying low heterogeneity [30]. The Mantel– Haenszel method was used for the calculation of OR under the random effect models [31]. In a sensitivity analysis, 0.5 was added to each cell frequency for trials in which no event occurred in either the treatment or control group, according to the method recommended by Deeks et al. [32]. If the standard deviation was not available, then it was calculated according to the guidelines of the Cochrane Collaboration [25]. This process involved assumptions that both groups had the same variance, which may not have been true, and variance was either estimated from the range or from the p value. The estimate of the difference between both techniques was pooled, depending upon the effect weights in results determined by each trial estimate variance. A forest plot was used for the graphical display of the results. The square around the estimate stood for the accuracy of the estimation (sample size), and the horizontal line represented the 95 % CI. The methodological quality of the randomized, controlled trials was assessed using the published guidelines of Jaddad et al. and Chalmers et al. [33, 34]. Based on the quality of the included randomized, controlled trials, the strength and summary of the evidence were further evaluated by GradeProÒ [35], a tool provided by the Cochrane Collaboration. Outcomes Quality of preparation was analysed as the primary endpoint in this study. Secondary endpoints included incomplete
examinations secondary to poor preparation, acceptability, compliance, and experience of adverse effects.
Results The PRISMA flow chart to explain the literature search strategy and trial selection is given in Fig. 1. Eight randomized, controlled trials [36–43] on 2457 patients undergoing FS were retrieved from the search of standard medical electronic databases. There were 1280 patients in the EBP group and 1177 patients in the OBP group. Two trials were excluded from the combined analysis due to inadequate data reporting for translation from a foreign language [44] and comparison of groups that did not meet our analysis protocol [45]. Two trials were split for subgroup analysis into one or two doses of EBP compared to OBP [39, 42]. The characteristics of the included trials are given in Table 1. The salient features and treatment protocols adopted in the included randomized, controlled trials are given in Table 2. Methodological quality of included randomized, controlled trials Based upon the scoring of the included trials according to the guidelines published by Jaddad et al. and Chalmers et al. [33, 34], the quality of the majority of included trials was good to moderate attributable to the satisfactory utilization of randomization techniques. In addition, there was adequate reporting of power calculation and allocation concealment (Table 3). However, the majority of the trials did not report an ITT analysis. Based on the quality of included randomized, controlled trials, the strength and summary of evidence analysed on the GradeProÒ [35] are given in Fig. 2. Incidence of poor bowel preparation As shown in Fig. 3, there was significant heterogeneity [s2 = 0.80, v2 = 51.37, df = 9, (p = 0.00001); 2 I = 82 %] among included trials. In the random effects model (OR, 1.21; 95 % CI, 0.63, 2.33; z = 0.59; p = 0.56), the incidence of poor bowel preparation was statistically similar following the use of both types of bowel cleansing remedies in patients undergoing flexible sigmoidoscopy. Compliance of patients As shown in Fig. 4, there was significant heterogeneity [s2 = 0.65, v2 = 44.90, df = 5, (p = 0.00001); I2 = 89 %] among included trials. In the random effects model (OR, 1.45; 95 % CI, 0.70, 3.01; z = 0.99; p = 0.32), the compliance of the patients for both types of bowel cleansing strategies was statistically similar.
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Updates Surg Table 1 Characteristics of included trials Trial
Year
Country
Age in years
Gender M:F
Atkin et al. [36] EBP
2000
UK 60
45 % M
OBP
61
49 % M
66.4 ± 9.4
98.4 % M
66.2 ± 8.4
98.4 %
EBP
58 (43–72)
Not reported
OBP
58 (43–72)
Bini et al. [37]
2000
USA
EBP OBP Drew et al. [38]
Fincher et al. [39] a
1997
1999
UK
USA
EBP OBP Fincher et al. [39] b
1999
OBP 1990
OBP 1999
60.1
50.5 % M
60.0
46.3 % M
56 (18–74)
8:11
57 (24–79)
12:8
UK
EBP Manoucheri et al. [41]
49.5 % M 46.3 % M
USA
EBP Hickson et al. [40]
59.6 60.0
USA
EBP
66.5 ± 11.9
37:39
OBP
65.7 ± 12
48:29
62
45 % F
65
37 % F
Osgard et al. [42] a
1998
USA
EBP OBP Osgard et al. [42] b
1998
USA
EBP
64
43 % F
65
37 % F
EBP
65.2 ± 7.3
Male only
OBP
62.8 ± 8.9
OBP Sharma et al. [43]
1997
USA
Acceptability of patients As shown in Fig. 5, there was significant heterogeneity [s2 = 0.98, v2 = 44.55, df = 8, (p = 0.00001); 2 I = 82 %] among included trials. In the random effects model (OR, 1.42; 95 % CI, 0.67, 2.99; z = 0.92; p = 0.36), the acceptability of the patients for both types of bowel preparations was also statistically similar.
Follow up (months)
Indication for procedure
Following day
Screening
Same day
Screening
Same day
Diagnostic
Same day
Diagnostic screening
Same day
Diagnostic screening
Same day
Diagnostic
Same day
Diagnostic screening
Immediately after procedure
Diagnostic screening
Immediately after procedure
Diagnostic screening
Same day
Screening
Risk of incomplete procedure due to poor preparation As shown in Fig. 7, there was significant heterogeneity [s2 = 1.36, v2 = 48.58, df = 5, (p = 0.00001); 2 I = 90 %] among included trials. In the random effects model (OR, 2.03; 95 % CI, 0.73, 5.65; z = 1.35; p = 0.18), the risk of incomplete procedure due to poor preparation was similar in both groups.
Adverse reactions As shown in Fig. 6, there was significant heterogeneity [s2 = 0.34, v2 = 31.08, df = 8, (p = 0.0001); I2 = 74 %] among included trials. In the random effects model (OR, 0.87; 95 % CI, 0.54, 1.41; z = 0.57; p = 0.57), the risk of adverse reactions was similar in both groups of bowel preparation.
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Discussion This meta-analysis demonstrates that EBP and OBP were equally effective in terms of quality of bowel preparation, compliance and acceptability in patients undergoing FS. Furthermore, no significant difference in adverse effects
Updates Surg Table 2 Treatment protocol adopted in included trials Trial
Enema preparation group
Oral preparation group
Atkin et al. [36]
Self-administered phosphate enema an hour before leaving home with subsequent fasting
Picolax one sachet either 2 pm or 6 pm a day before oral depending upon next day am or pm list
If preparation was poor, sigmoidoscopy was repeated after administration of an enema in the unit
Fasting thereafter until after examination
Bini et al. [37]
Oral Dulcolax 5 pm day before and then self-administering two fleet enemas an hour before leaving home on the day of Endoscopy
Oral Dulcolax at 5 pm a day before followed 1 h later by 45 ml of oral sodium phosphate solution with 16 oz of water
Drew et al. [38]
Self administration of one fleet enema two hours before leaving home on the day of Endoscopy
Oral Picolax one sachet at 7 pm a day before
Fincher et al. [39]
Oral magnesium citrate taken at 6:00 pm the night before the procedure in combination with:
Oral magnesium citrate taken at 6:00 pm the night before the procedure in combination with:
Group I: one fleet enema administered 1 h before procedure
Cross over was allowed in terms of change of preparation as well as change of place of enema or Picolax intake
Oral bisacodyl at 6:00 pm the night before the procedure
Group II: one fleet enema administered 2 h before procedure and another enema 1 h before Hickson et al. [40]
2 9 Klyx (docusate sodium and sorbitol) enema preparation 2–3 h before procedure without any dietary restrictions
Picolax 1 and sachet in 500 ml water at 7 pm a day before orally 2–3 h before procedure without any dietary restrictions
Manoucheri et al. [41]
Group A: light breakfast and one fleet phosphate enema administered 2 h before the procedure, followed by another enema 1 h later
Group C: clear liquid meal on evening before the examination. Later in evening to drink 1.5 oz fleet phosphor-soda oral saline laxative in half a glass of water followed immediately by 8 oz of water. Fasting from midnight. Self-administered one fleet enema 2 h before procedure, followed by another 1 h later
Group B: clear liquid meal on the evening before procedure, with fasting from midnight. Self-administered one fleet enema 2 h before examination, followed by another enema 1 h later
Group D: identical instructions to group C, with the exception that they were to administer only one fleet enema 1 h before the examination
Group I: one fleet enema 1 h before procedure
Two enemas as per group II and magnesium citrate taken orally the night before
Osgard et al. [42]
Group II: two Fleet enemas given at 2 h and 1 h before procedure Sharma et al. [43]
Magnesium citrate and two Dulcolax tablets at 6 pm on the evening before procedure
Two fleet enemas on arrival to endoscopy suite. Light breakfast on morning of procedure
Light breakfast on morning of procedure
Table 3 Quality variable of included trials Study
Randomization
Power calculations
ITT
Blinding
Concealment
Atkin et al. [36]
Computer generated block randomization
Yes
Yes
Yes: endoscopist and nurse
Reported
Bini et al. [37]
Computer generated block randomization
Yes
Not reported
Yes: endoscopist
Not reported
Drew et al. [38]
Random number generator
Not reported
Not reported
Yes: endoscopist and nurse
Not reported
Fincher et al. [39]
Computer generated
Yes
Yes
Yes
Not reported
Hickson et al. [40]
Not reported
Not reported
Not reported
Not reported
Not reported
Manoucheri et al. [41]
Computer generated random sequential order
Yes
Not reported
Yes: endoscopist
Not reported
Osgard et al. [42]
Computer generated
Yes
Yes
Yes: endoscopist
Reported
Sharma et al. [43]
Computer generated
Yes
Yes
Yes
Reported
was identified between the two groups. Atkin et al. [36] reported a higher quality of bowel preparation in 76 % of patients using EBP versus 52.2 % using oral Picolax.
Conversely, Bini et al. [37] found that bowel preparation was good or excellent in 86.5 % of OBP patients versus 57.3 % in the EBP group. However, this combined analysis
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Fig. 2 Strength and summary of the evidence analysed on GradeProÒ
Fig. 3 Forest plot for poor preparation in each type of bowel preparation. Odds ratios are shown with 95 % confidence intervals. EBP enema bowel preparation, OBP oral bowel preparation
of eight RCTs shows that the EBP and OBP were equally effective for bowel preparation in patients undergoing FS. The risk of incomplete procedure and incidence in poor bowel preparation was similar in both analysis arms.
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Whilst neither bowel cleansing regime demonstrated superiority, at least equivalent efficacy may be inferred. A study published on a postal questionnaire of patients that had experienced both types of preparation reported that
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Fig. 4 Forest plot for compliance for each type of bowel preparation. Odds ratios are shown with 95 % confidence intervals. EBP enema bowel preparation, OBP oral bowel preparation
Fig. 5 Forest plot for acceptability for each type of bowel preparation. Odds ratios are shown with 95 % confidence intervals. EBP enema bowel preparation, OBP oral bowel preparation
61 % preferred OBP compared to 39 % preferring EBP [46]. This review article finds no significant difference in compliance or acceptability between EBP and OBP. Bowel evacuation with EBP is more rapid and can be administered on the day of the procedure. OBP administered on the days preceding the investigation fundamentally prolongs the duration that associated symptoms are endured, compared with the short action of EBP. Therefore, in cases where patients are able to self-administer EBP, this may be a favourable alternative. Adverse effects of OBP have been well reported in colonoscopy. OBP in FS is often administered in smaller doses which may reduce the experience of significant adverse effects. A study published by Gidwani et al. [45] reported no difference in the experience of abdominal cramps in the EBP group versus a combined
EBP and OBP cohort which is consistent with the findings of this article. This article is the first ever reported systematic review exploring the role of most commonly used OBP and EBP for FS. The included RCTs evaluated preparation quality either as primary or secondary outcomes according to the pre-trial analysis strategy. The use of preparation quality as a primary or secondary endpoint is well targeted because bowel preparation quality is central to adequacy of FS and noted by the endoscopist during each procedure. Furthermore, the secondary outcome measures reporting compliance, acceptability and adverse events are relevant factors that may influence the successful completion of FS and can be a source of morbidity affecting patient experience and satisfaction. Notably, only 50 % of the included trials
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Fig. 6 Forest plot for adverse effects of each type of bowel preparation. Odds ratios are shown with 95 % confidence intervals. EBP enema bowel preparation, OBP oral bowel preparation
Fig. 7 Forest plot for incomplete procedure due to poor preparation for each type of bowel preparation. Odds ratios are shown with 95 % confidence intervals. EBP enema bowel preparation, OBP oral bowel preparation
reported their data using an intention to treat analysis. GradeProÒ analysis demonstrated a moderate strength of evidence based on the quality of included RCTs [35]. Limitations of this study reflect the large degree of heterogeneity between the trials. There were multiple causes of heterogeneity which can be attributed to clinical or methodological factors. Different study protocols comparing OBP and EBP were used with significant methodological differences, particularly relating to timing of administration and use of different oral and enema agents. Primary and secondary outcomes were recorded using a variety of grading scales for preparation quality, patient compliance and acceptability, which resulted in the lack of a uniform and standardised measuring tool. Adverse effects
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reporting criteria also differed significantly between trials. Various clinical indications, such as diagnostic, screening and symptomatic patients, were included in the trials. Notably, patients with significant constipation may have affected the performance of the selected bowel cleansing regimes. In addition, operator experience and equipment variability may be confounding factors when considering the quality of bowel preparation and ability to complete the procedure. Furthermore, studies included in the review that recruited small numbers of patients may not have had sufficient power to reveal small differences in outcomes. However, despite these limitations, it is reasonable to infer that minimal and clinically significant differences between the two groups were observed in overall quality,
Updates Surg
compliance, acceptability and adverse events in case of both types of bowel preparations. EBP is an equally favourable alternative to OBP that can be administered within close proximity to the procedure time and reduce the prolonged duration of OBP. Future research with larger prospective randomized, controlled trials exercising improved methodology is required to fully identify an optimal bowel preparation for flexible sigmoidoscopy. Authors propose the conduction of new trials using novice endoscopy technology, new oral and per rectal bowel preparation formulations and following the CONSORT guidelines for the internal and external validity of trial methods to achieve reliable and stronger evidence on this subject. In addition, the use of an internationally agreed tool to define the quality of bowel preparation should also be developed and incorporated into the trial methodology to achieve optimum outcome of any new trial. Conflict of interest
None to declare.
Compliance with Ethical Standards All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional or/and national research committee and with the 1964 Helsinki declaration and its later amendments or comparable standards. Research involving human participants and/or animals This article does not contain any studies with animals performed by any of the authors. Informed consent Informed consent was obtained from all individual participants included in published trials used for this review.
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REVIEW ARTICLE
Improving the view during flexible sigmoidoscopy: a systematic review of published randomized, controlled trials comparing the use of oral bowel preparation versus enema bowel preparation Muhammad Shafique Sajid1 • Jennifer F. Caswell1 • Mustafa A. Q. Abbas1 Mirza K. Baig1 • Malcolm R. McFall1
•
Received: 17 December 2014 / Accepted: 27 March 2015 Ó Italian Society of Surgery (SIC) 2015
Abstract To systematically analyse the published randomized, controlled trials (RCTs) comparing the use of oral bowel preparation (OBP) versus enema bowel preparation (EBP) for diagnostic or screening flexible sigmoidoscopy. Published RCTs, comparing the use of OBP versus EBP, were analysed using RevManÒ, and the combined outcomes were expressed as odds ratios (OR). Eight RCTs evaluating 2457 patients were retrieved from the standard electronic databases. There was significant heterogeneity among included trials. The compliance of the patients (p = 0.32) and the acceptability of both bowel preparation regimens (OR, 1.42; 95 % CI, 0.67, 2.99; z = 0.92; p = 0.36) were similar in both groups. In addition, the incidence of adverse reactions (OR, 0.87; 95 % CI, 0.54, 1.41; z = 0.57; p = 0.57), the risk of incomplete procedure due to poor bowel preparation (p = 0.18) and the incidence of poor bowel preparation (OR, 1.21; 95 % CI, 0.63, 2.33; z = 0.59; p = 0.56) were also similar in both groups. EBP and OBP were equally effective for bowel preparation in patients undergoing flexible sigmoidoscopy. Although this study failed to demonstrate the superiority of EBP, at least equivalent efficacy for bowel cleansing may be extrapolated. Keywords Flexible sigmoidoscopy Colorectal cancer Bowel preparation Enema preparation Bowel cleansing tools
& Muhammad Shafique Sajid [email protected] 1
Department of General, Endoscopic and Laparoscopic Colorectal Surgery, Western Sussex Hospitals NHS Foundation Trust, Worthing Hospital, Washington Suite, North Wing, Worthing, West Sussex BN11 2DH, UK
Introduction Diagnostic, screening and surveillance flexible sigmoidoscopy (FS) is of utmost importance for the evaluation of symptoms and optimum management of colorectal disorders such as benign polyps, malignant polyps, colorectal cancer, diverticular disease and inflammatory bowel disease [1, 2]. Adequate bowel preparation can have a significant influence on the length of procedure, risk of complication and the rate of adenoma detection [3, 4]. Approaches to bowel preparation involved dietary preparation, laxatives, enemas, whole gut irrigation via nasogastric tube and the use of mannitol solution during the preceding days to procedure [5–10]. Whilst these preparations were shown to produce acceptable bowel cleansing, they required many hours or days of dietary modification and were found to be uncomfortable and poorly tolerated by the patients. A major advance came with the development of polyethylene-glycol (PEG) lavage solution that resulted in less electrolyte or fluid disturbances than its counterparts and was reported safe and effective in practice [11, 12]. Despite its apparent clinical success, major drawback was again poor patient compliance, with up to 15 % of patients failing to complete the preparation [13]. Oral sodium phosphate solution was introduced as a major competitor to PEG solution due to much better tolerance and compliance [14, 15]. However, over time, concerns emerged regarding the use of oral phosphate preparations over their propensity to cause significant electrolyte imbalance [16–22]. Enema bowel preparations (EBP) have been suggested to be advantageous over oral solution in FS as they quickly clear the bowel and do not require dietary preparation [23]. Furthermore, their tendency to avoid the aforementioned complications of oral bowel preparations (OBP) increases their favourability. Preliminary studies
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have shown good outcomes with enema preparations [24, 25]. However, so far, in the literature a consensus on preferred bowel cleansing strategy for FS is not reported, with many studies demonstrating conflicting results. The objective of this article is to analyse the randomized, controlled trials comparing the effectiveness of OBP versus EBP in patients undergoing FS.
narrow and widen the results of potentially usable studies. The titles of the published articles from the search results were examined closely and assessed for suitability for potential inclusion. The reference lists from selected articles were also examined as a further search tool to find additional trials. Selection criteria for included trials
Methods Electronic data sources and their search planning In order to obtain appropriate studies, a search of medical electronic databases such as MEDLINE, EMBASE, and the Cochrane library for randomized, controlled trials was conducted and screened according to the PRISMA flow chart (Fig. 1). The MeSH terms published in the Medline library relevant to OBP versus EBP were used to retrieve the relevant randomized, controlled trials. No limits for language, gender, sample size and place of study origin were entered for the search in the search engine. Boolean operators (AND, OR, NOT) were additionally used to
For inclusion in this meta-analysis, a study had to fulfil the following criteria: (1) randomized, controlled trial; (2) comparison between OBP and EBP in patients undergoing flexible sigmoidoscopy; (3) evaluation of bowel preparation quality, number of incomplete procedures secondary to poor preparation, patient acceptance or compliance and adverse events. Data abstraction from included trials Two independent reviewers using a predefined meta-analysis form extracted relevant data from each study which resulted in a satisfactory inter-observer agreement. The extracted data contained name of the publishing authors,
Idenficaon
Fig. 1 PRISMA flow diagram Records idenfied through database searching (n = 51 )
Addional records idenfied through other sources (n = 0 )
Eligibility
Screening
Records aer duplicates removed (n = 51 )
Records screened (n = 13 )
Full-text arcles assessed for eligibility (n = 10)
Included
Studies included in qualitave synthesis (n = 8)
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Studies included in quantave synthesis (meta-analysis) (n = 8)
Records excluded (n = 38 ) Causes: irrelevant
Full-text arcles excluded, with reasons (n = 3 ) Causes: Other reviews Other technique reviews Duplicate data
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title of the published study, journal in which the study was published, country and year of the study, intervention protocol in both limbs of the trial, testing sample size (with sex differentiation if applicable), the number of patients receiving each regimen and within each group the number of patients who succeeded and the number of patients who failed the allocated preparation, the patient compliance rate in each group, the number of patients reporting complications and the number of patients with absence of complications in each arm of the trial. After completing the data extraction the two independent reviewers discussed the data-related results and, if discrepancies were present, a consensus was reached. Statistical analysis The software package RevMan 5.3.1 [25, 26], provided by the Cochrane Collaboration, was used for the statistical analysis. The odds ratio (OR) with a 95 % confidence interval (CI) was calculated for binary data. The random effects model [27, 28] was used to calculate the combined outcomes of both binary variables. Heterogeneity was explored using the v2 test, with significance set at p \ 0.05, and was quantified [29] using I2, with a maximum value of 30 % identifying low heterogeneity [30]. The Mantel– Haenszel method was used for the calculation of OR under the random effect models [31]. In a sensitivity analysis, 0.5 was added to each cell frequency for trials in which no event occurred in either the treatment or control group, according to the method recommended by Deeks et al. [32]. If the standard deviation was not available, then it was calculated according to the guidelines of the Cochrane Collaboration [25]. This process involved assumptions that both groups had the same variance, which may not have been true, and variance was either estimated from the range or from the p value. The estimate of the difference between both techniques was pooled, depending upon the effect weights in results determined by each trial estimate variance. A forest plot was used for the graphical display of the results. The square around the estimate stood for the accuracy of the estimation (sample size), and the horizontal line represented the 95 % CI. The methodological quality of the randomized, controlled trials was assessed using the published guidelines of Jaddad et al. and Chalmers et al. [33, 34]. Based on the quality of the included randomized, controlled trials, the strength and summary of the evidence were further evaluated by GradeProÒ [35], a tool provided by the Cochrane Collaboration. Outcomes Quality of preparation was analysed as the primary endpoint in this study. Secondary endpoints included incomplete
examinations secondary to poor preparation, acceptability, compliance, and experience of adverse effects.
Results The PRISMA flow chart to explain the literature search strategy and trial selection is given in Fig. 1. Eight randomized, controlled trials [36–43] on 2457 patients undergoing FS were retrieved from the search of standard medical electronic databases. There were 1280 patients in the EBP group and 1177 patients in the OBP group. Two trials were excluded from the combined analysis due to inadequate data reporting for translation from a foreign language [44] and comparison of groups that did not meet our analysis protocol [45]. Two trials were split for subgroup analysis into one or two doses of EBP compared to OBP [39, 42]. The characteristics of the included trials are given in Table 1. The salient features and treatment protocols adopted in the included randomized, controlled trials are given in Table 2. Methodological quality of included randomized, controlled trials Based upon the scoring of the included trials according to the guidelines published by Jaddad et al. and Chalmers et al. [33, 34], the quality of the majority of included trials was good to moderate attributable to the satisfactory utilization of randomization techniques. In addition, there was adequate reporting of power calculation and allocation concealment (Table 3). However, the majority of the trials did not report an ITT analysis. Based on the quality of included randomized, controlled trials, the strength and summary of evidence analysed on the GradeProÒ [35] are given in Fig. 2. Incidence of poor bowel preparation As shown in Fig. 3, there was significant heterogeneity [s2 = 0.80, v2 = 51.37, df = 9, (p = 0.00001); 2 I = 82 %] among included trials. In the random effects model (OR, 1.21; 95 % CI, 0.63, 2.33; z = 0.59; p = 0.56), the incidence of poor bowel preparation was statistically similar following the use of both types of bowel cleansing remedies in patients undergoing flexible sigmoidoscopy. Compliance of patients As shown in Fig. 4, there was significant heterogeneity [s2 = 0.65, v2 = 44.90, df = 5, (p = 0.00001); I2 = 89 %] among included trials. In the random effects model (OR, 1.45; 95 % CI, 0.70, 3.01; z = 0.99; p = 0.32), the compliance of the patients for both types of bowel cleansing strategies was statistically similar.
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Updates Surg Table 1 Characteristics of included trials Trial
Year
Country
Age in years
Gender M:F
Atkin et al. [36] EBP
2000
UK 60
45 % M
OBP
61
49 % M
66.4 ± 9.4
98.4 % M
66.2 ± 8.4
98.4 %
EBP
58 (43–72)
Not reported
OBP
58 (43–72)
Bini et al. [37]
2000
USA
EBP OBP Drew et al. [38]
Fincher et al. [39] a
1997
1999
UK
USA
EBP OBP Fincher et al. [39] b
1999
OBP 1990
OBP 1999
60.1
50.5 % M
60.0
46.3 % M
56 (18–74)
8:11
57 (24–79)
12:8
UK
EBP Manoucheri et al. [41]
49.5 % M 46.3 % M
USA
EBP Hickson et al. [40]
59.6 60.0
USA
EBP
66.5 ± 11.9
37:39
OBP
65.7 ± 12
48:29
62
45 % F
65
37 % F
Osgard et al. [42] a
1998
USA
EBP OBP Osgard et al. [42] b
1998
USA
EBP
64
43 % F
65
37 % F
EBP
65.2 ± 7.3
Male only
OBP
62.8 ± 8.9
OBP Sharma et al. [43]
1997
USA
Acceptability of patients As shown in Fig. 5, there was significant heterogeneity [s2 = 0.98, v2 = 44.55, df = 8, (p = 0.00001); 2 I = 82 %] among included trials. In the random effects model (OR, 1.42; 95 % CI, 0.67, 2.99; z = 0.92; p = 0.36), the acceptability of the patients for both types of bowel preparations was also statistically similar.
Follow up (months)
Indication for procedure
Following day
Screening
Same day
Screening
Same day
Diagnostic
Same day
Diagnostic screening
Same day
Diagnostic screening
Same day
Diagnostic
Same day
Diagnostic screening
Immediately after procedure
Diagnostic screening
Immediately after procedure
Diagnostic screening
Same day
Screening
Risk of incomplete procedure due to poor preparation As shown in Fig. 7, there was significant heterogeneity [s2 = 1.36, v2 = 48.58, df = 5, (p = 0.00001); 2 I = 90 %] among included trials. In the random effects model (OR, 2.03; 95 % CI, 0.73, 5.65; z = 1.35; p = 0.18), the risk of incomplete procedure due to poor preparation was similar in both groups.
Adverse reactions As shown in Fig. 6, there was significant heterogeneity [s2 = 0.34, v2 = 31.08, df = 8, (p = 0.0001); I2 = 74 %] among included trials. In the random effects model (OR, 0.87; 95 % CI, 0.54, 1.41; z = 0.57; p = 0.57), the risk of adverse reactions was similar in both groups of bowel preparation.
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Discussion This meta-analysis demonstrates that EBP and OBP were equally effective in terms of quality of bowel preparation, compliance and acceptability in patients undergoing FS. Furthermore, no significant difference in adverse effects
Updates Surg Table 2 Treatment protocol adopted in included trials Trial
Enema preparation group
Oral preparation group
Atkin et al. [36]
Self-administered phosphate enema an hour before leaving home with subsequent fasting
Picolax one sachet either 2 pm or 6 pm a day before oral depending upon next day am or pm list
If preparation was poor, sigmoidoscopy was repeated after administration of an enema in the unit
Fasting thereafter until after examination
Bini et al. [37]
Oral Dulcolax 5 pm day before and then self-administering two fleet enemas an hour before leaving home on the day of Endoscopy
Oral Dulcolax at 5 pm a day before followed 1 h later by 45 ml of oral sodium phosphate solution with 16 oz of water
Drew et al. [38]
Self administration of one fleet enema two hours before leaving home on the day of Endoscopy
Oral Picolax one sachet at 7 pm a day before
Fincher et al. [39]
Oral magnesium citrate taken at 6:00 pm the night before the procedure in combination with:
Oral magnesium citrate taken at 6:00 pm the night before the procedure in combination with:
Group I: one fleet enema administered 1 h before procedure
Cross over was allowed in terms of change of preparation as well as change of place of enema or Picolax intake
Oral bisacodyl at 6:00 pm the night before the procedure
Group II: one fleet enema administered 2 h before procedure and another enema 1 h before Hickson et al. [40]
2 9 Klyx (docusate sodium and sorbitol) enema preparation 2–3 h before procedure without any dietary restrictions
Picolax 1 and sachet in 500 ml water at 7 pm a day before orally 2–3 h before procedure without any dietary restrictions
Manoucheri et al. [41]
Group A: light breakfast and one fleet phosphate enema administered 2 h before the procedure, followed by another enema 1 h later
Group C: clear liquid meal on evening before the examination. Later in evening to drink 1.5 oz fleet phosphor-soda oral saline laxative in half a glass of water followed immediately by 8 oz of water. Fasting from midnight. Self-administered one fleet enema 2 h before procedure, followed by another 1 h later
Group B: clear liquid meal on the evening before procedure, with fasting from midnight. Self-administered one fleet enema 2 h before examination, followed by another enema 1 h later
Group D: identical instructions to group C, with the exception that they were to administer only one fleet enema 1 h before the examination
Group I: one fleet enema 1 h before procedure
Two enemas as per group II and magnesium citrate taken orally the night before
Osgard et al. [42]
Group II: two Fleet enemas given at 2 h and 1 h before procedure Sharma et al. [43]
Magnesium citrate and two Dulcolax tablets at 6 pm on the evening before procedure
Two fleet enemas on arrival to endoscopy suite. Light breakfast on morning of procedure
Light breakfast on morning of procedure
Table 3 Quality variable of included trials Study
Randomization
Power calculations
ITT
Blinding
Concealment
Atkin et al. [36]
Computer generated block randomization
Yes
Yes
Yes: endoscopist and nurse
Reported
Bini et al. [37]
Computer generated block randomization
Yes
Not reported
Yes: endoscopist
Not reported
Drew et al. [38]
Random number generator
Not reported
Not reported
Yes: endoscopist and nurse
Not reported
Fincher et al. [39]
Computer generated
Yes
Yes
Yes
Not reported
Hickson et al. [40]
Not reported
Not reported
Not reported
Not reported
Not reported
Manoucheri et al. [41]
Computer generated random sequential order
Yes
Not reported
Yes: endoscopist
Not reported
Osgard et al. [42]
Computer generated
Yes
Yes
Yes: endoscopist
Reported
Sharma et al. [43]
Computer generated
Yes
Yes
Yes
Reported
was identified between the two groups. Atkin et al. [36] reported a higher quality of bowel preparation in 76 % of patients using EBP versus 52.2 % using oral Picolax.
Conversely, Bini et al. [37] found that bowel preparation was good or excellent in 86.5 % of OBP patients versus 57.3 % in the EBP group. However, this combined analysis
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Fig. 2 Strength and summary of the evidence analysed on GradeProÒ
Fig. 3 Forest plot for poor preparation in each type of bowel preparation. Odds ratios are shown with 95 % confidence intervals. EBP enema bowel preparation, OBP oral bowel preparation
of eight RCTs shows that the EBP and OBP were equally effective for bowel preparation in patients undergoing FS. The risk of incomplete procedure and incidence in poor bowel preparation was similar in both analysis arms.
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Whilst neither bowel cleansing regime demonstrated superiority, at least equivalent efficacy may be inferred. A study published on a postal questionnaire of patients that had experienced both types of preparation reported that
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Fig. 4 Forest plot for compliance for each type of bowel preparation. Odds ratios are shown with 95 % confidence intervals. EBP enema bowel preparation, OBP oral bowel preparation
Fig. 5 Forest plot for acceptability for each type of bowel preparation. Odds ratios are shown with 95 % confidence intervals. EBP enema bowel preparation, OBP oral bowel preparation
61 % preferred OBP compared to 39 % preferring EBP [46]. This review article finds no significant difference in compliance or acceptability between EBP and OBP. Bowel evacuation with EBP is more rapid and can be administered on the day of the procedure. OBP administered on the days preceding the investigation fundamentally prolongs the duration that associated symptoms are endured, compared with the short action of EBP. Therefore, in cases where patients are able to self-administer EBP, this may be a favourable alternative. Adverse effects of OBP have been well reported in colonoscopy. OBP in FS is often administered in smaller doses which may reduce the experience of significant adverse effects. A study published by Gidwani et al. [45] reported no difference in the experience of abdominal cramps in the EBP group versus a combined
EBP and OBP cohort which is consistent with the findings of this article. This article is the first ever reported systematic review exploring the role of most commonly used OBP and EBP for FS. The included RCTs evaluated preparation quality either as primary or secondary outcomes according to the pre-trial analysis strategy. The use of preparation quality as a primary or secondary endpoint is well targeted because bowel preparation quality is central to adequacy of FS and noted by the endoscopist during each procedure. Furthermore, the secondary outcome measures reporting compliance, acceptability and adverse events are relevant factors that may influence the successful completion of FS and can be a source of morbidity affecting patient experience and satisfaction. Notably, only 50 % of the included trials
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Fig. 6 Forest plot for adverse effects of each type of bowel preparation. Odds ratios are shown with 95 % confidence intervals. EBP enema bowel preparation, OBP oral bowel preparation
Fig. 7 Forest plot for incomplete procedure due to poor preparation for each type of bowel preparation. Odds ratios are shown with 95 % confidence intervals. EBP enema bowel preparation, OBP oral bowel preparation
reported their data using an intention to treat analysis. GradeProÒ analysis demonstrated a moderate strength of evidence based on the quality of included RCTs [35]. Limitations of this study reflect the large degree of heterogeneity between the trials. There were multiple causes of heterogeneity which can be attributed to clinical or methodological factors. Different study protocols comparing OBP and EBP were used with significant methodological differences, particularly relating to timing of administration and use of different oral and enema agents. Primary and secondary outcomes were recorded using a variety of grading scales for preparation quality, patient compliance and acceptability, which resulted in the lack of a uniform and standardised measuring tool. Adverse effects
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reporting criteria also differed significantly between trials. Various clinical indications, such as diagnostic, screening and symptomatic patients, were included in the trials. Notably, patients with significant constipation may have affected the performance of the selected bowel cleansing regimes. In addition, operator experience and equipment variability may be confounding factors when considering the quality of bowel preparation and ability to complete the procedure. Furthermore, studies included in the review that recruited small numbers of patients may not have had sufficient power to reveal small differences in outcomes. However, despite these limitations, it is reasonable to infer that minimal and clinically significant differences between the two groups were observed in overall quality,
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compliance, acceptability and adverse events in case of both types of bowel preparations. EBP is an equally favourable alternative to OBP that can be administered within close proximity to the procedure time and reduce the prolonged duration of OBP. Future research with larger prospective randomized, controlled trials exercising improved methodology is required to fully identify an optimal bowel preparation for flexible sigmoidoscopy. Authors propose the conduction of new trials using novice endoscopy technology, new oral and per rectal bowel preparation formulations and following the CONSORT guidelines for the internal and external validity of trial methods to achieve reliable and stronger evidence on this subject. In addition, the use of an internationally agreed tool to define the quality of bowel preparation should also be developed and incorporated into the trial methodology to achieve optimum outcome of any new trial. Conflict of interest
None to declare.
Compliance with Ethical Standards All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional or/and national research committee and with the 1964 Helsinki declaration and its later amendments or comparable standards. Research involving human participants and/or animals This article does not contain any studies with animals performed by any of the authors. Informed consent Informed consent was obtained from all individual participants included in published trials used for this review.
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