Dig Dis Sci DOI 10.1007/s10620-014-3125-3
ORIGINAL ARTICLE
Rescue Bowel Preparation: Same Day 2 L Polyethylene Glycol Addition, Not Superior to Bisacodyl Addition 7 Days Later Jong Wook Kim • Jeung Hye Han • Sun-Jin Boo • Ock Bae Ko • Soo-Kyung Park Sang Hyoung Park • Dong-Hoon Yang • Kee Wook Jung • Kyung-Jo Kim • Byong Duk Ye • Seung-Jae Myung • Suk-Kyun Yang • Jin-Ho Kim • Jeong-Sik Byeon
•
Received: 23 December 2013 / Accepted: 18 March 2014 Ó Springer Science+Business Media New York 2014
Abstract Background The optimal colon-cleansing method after failure of bowel preparation (BP) for colonoscopy has not been established. Aims We aimed to compare BP rescue methods after failed initial BP and to identify risk factors for rescue BP failure. Methods Eighty-five patients with BP failure after 4 L polyethylene glycol (PEG) ingestion were prospectively enrolled from March 2008 to March 2012. A second colonoscopy was performed either on the same day after ingestion of another 2 L PEG (group A) or 1 week later
Jong Wook Kim and Jeung Hye Han contributed equally to this work. J. W. Kim Department of Internal Medicine, Inje University Ilsan Paik Hospital, Goyang, Korea J. H. Han Asan Health Screening and Promotion Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea S.-J. Boo Department of Internal Medicine, Jeju National University School of Medicine, Jeju, Korea O. B. Ko S. H. Park D.-H. Yang K. W. Jung K.-J. Kim B. D. Ye S.-J. Myung S.-K. Yang J.-H. Kim J.-S. Byeon (&) Department of Gastroenterology, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro 43-gil, Songpa-gu, Seoul, Korea e-mail: [email protected] S.-K. Park Department of Internal Medicine, Digestive Disease Center and Research Institute, Soonchunhyang University College of Medicine, Bucheon, Korea
after ingestion of 4 L PEG plus 20 mg oral bisacodyl (group B). Differences between groups in terms of BP quality and risk factors for a poor BP on the second colonoscopy were investigated. Results Median patient age was 59 years, 45 were male (52.9 %), and 17 (20 %) had poor BP on the second colonoscopy. For group B, the multivariable-adjusted odds ratio (OR) for poor BP on the second colonoscopy relative to group A was 0.68 (95 % confidence interval [CI], 0.16–2.95). Adequately ingested PEG during the initial colonoscopy was associated with poor BP on the second colonoscopy (OR 4.05; 95 % CI 1.04–15.75). The two groups had similar patient discomfort rates during the second BP. Conclusions The two groups did not differ in rescue BP failure rate. Initial BP failure after adequate consumption of 4 L PEG may be a risk factor for rescue BP failure. A stricter BP regimen should be considered for these patients. Keywords Colonoscopy Bowel preparation Polyethylene glycol Bisacodyl Abbreviations BP Bowel preparation CI Confidence interval IQR Interquartile range OR Odds ratio PEG Polyethylene glycol
Introduction Colonoscopy is considered to be the gold standard method for assessing the colonic mucosa. Its diagnostic accuracy depends on the quality of bowel preparation (BP) [1, 2]. The frequency of BP failure for colonoscopy varies from 5 to
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30 % [3, 4]. Several studies have demonstrated that older age, male gender, prior abdominal surgery, presence of diabetes mellitus, and history of constipation associate with an increased risk of BP failure. Medications such as antidepressants or calcium antagonists and a later colonoscopy start time after the end of BP are also risk factors of BP failure [5–7]. Although BP failure is not uncommon and its risk factors are well recognized, optimal rescue BP methods remain to be clearly established. The recent European Society of Gastrointestinal Endoscopy (ESGE) guideline recommends that to rescue BP failure, intensive BP methods (including endoscopic irrigation pumps) should be used or the colonoscopy should be repeated on the following day [8]. However, such methods are often cumbersome and the level of evidence for their use in the guideline was of low quality. Therefore, an optimal rescue BP method after failure of the initial BP for colonoscopy remains to be established. Some physicians consider that repeating colonoscopy on the same day after ingestion of more polyethylene glycol (PEG) is better than repeating the colonoscopy several days later because they believe that the additional PEG will eliminate the residual feces. However, for this, the patients must stay longer in the hospital for the examination. In addition, some patients may not be willing to ingest more PEG. An alternative approach is to use adjuvant products such as bisacodyl, which may reduce the amount of PEG needed during repeat BP and thus may enhance the bowel cleansing when consumed with the routine 4 L of PEG [9]. However, to date, there has been little direct comparison of the various rescue BP strategies. Therefore, the present study assessed the efficacy of two rescue BP methods in patients who failed initial BP consisting of 4 L PEG ingestion. These methods involved either the additional ingestion of 2 L PEG on the same day or the ingestion of 4 L PEG plus bisacodyl 1 week later. Analyses to identify risk factors for rescue BP failure were also performed.
Methods Patients and Study Design In this parallel-arm, single-center, prospective study, patients were allocated to receive the BP rescue method of their choice after being informed about their risks and benefits. Patients found to have BP failure on the index colonoscopy after a standard BP with 4 L of PEG solution after 3 days of a low-residue diet were eligible for inclusion in the study. For the index colonoscopy, initial BP was done as follows: When the index colonoscopies were scheduled in the morning, 2 L PEG was given the night before and the remaining 2 L was given at 4 a.m. on the examination day. Both 2 L doses of PEG solution had to be
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ingested within 2 h: For the colonoscopies that were scheduled in the afternoon, the entire 4 L of PEG was ingested within 4 h during the morning of the examination day. The Aronchick scale was used to grade the quality of colon cleansing as follows: (1) excellent (there was a small volume of clear liquid or [95 % of the surface could be seen); (2) good (there was a large volume of clear liquid covering 5–25 % of the surface but [90 % of the surface could be seen); (3) fair (there was some semisolid stool that could be suctioned or washed away but [90 % of the surface could be seen); (4) poor (there was semisolid stool that could not be suctioned or washed away and \90 % of the surface could be seen); and (5) inadequate (repeat BP and colonoscopy needed) [10]. For agreement on the Aronchick scale, only four experienced endoscopists performed the rescue colonoscopies during the study period. All patients were prospectively enrolled between March 2008 and March 2012 at a tertiary referral center in Seoul, Korea (Asan Medical Center). The consecutive patients who exhibited BP failure (Aronchick scale of 5) at the index colonoscopy were assigned to groups A or B on the basis of the preference of the individual patients. Group A received another 2 L of PEG on the same day of the index colonoscopy and then underwent a rescue colonoscopy 2 h or more after the PEG ingestion was completed. Group B, who underwent the rescue colonoscopy after 1 week of a lowresidue diet, ingested 20 mg of bisacodyl at 7 p.m. the day before the colonoscopy and ingested 4 L PEG as described above. For patient tolerability in group B, we did not increase the total dosage of PEG. The degree of bowel cleansing after the rescue BP methods was also scored by using the Aronchick scale [10]. Rescue BP failure was defined as an Aronchick BP scale score of ‘‘poor’’ or ‘‘inadequate’’ [5]. Before the rescue colonoscopy was started, the examinees completed a questionnaire to assess the degree of discomfort during the rescue BP methods. Thus, the magnitude of discomfort was graded by using a visual analog scale of 0–10. Patients who had undergone prior major abdominal surgery (including colorectal resection) were less than 18 years of age or had inflammatory bowel disease or colorectal cancer were excluded. The study protocol was approved by the Institutional Review Board of Asan Medical Center (IRB No. 2009-0733). Data Collection The following variables were recorded by the endoscopist at the end of the index colonoscopy: date, age, gender, main indication for colonoscopy, history of constipation, comorbidities, previous medication history, and adequacy of BP solution ingestion. During the rescue colonoscopy, the tolerability of the rescue regimen (as assessed by the patient-reported 10-point visual analog scale) and the
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Aronchick BP score were recorded. Tolerability parameters included nausea/vomiting, abdominal distension, and overall discomfort. Adequate ingestion of PEG solution was defined as both adequate timing and ingestion of C75 % of the required PEG solution.
Table 1 Baseline clinical characteristics of the patients in groups A and B Group A: addition of 2 L PEG on the same day (n = 42)
Statistical Analysis Age (years)
The baseline clinical characteristics of the patients were summarized by using number (%) for categorical variables and median (interquartile range, IQR) for continuous variables. Pearson’s chi-square test and the Mann–Whitney U test were used to compare the differences between the groups. Variables that were found to be statistically significant in the bivariate analysis in predicting poor BP during the rescue colonoscopy were entered into the multivariate logistic regression model by forward selection. In the final model, a p value \0.05 was considered to be statistically significant. All statistical analyses were performed by using Stata version 12.1 (StataCorp, TX, USA).
Results Comparison Between Groups A and B Baseline Characteristics of the Patients During the study period, 87 patients met the inclusion criteria and proceeded to the rescue BP. There were 43 patients in group A and 44 in group B. In both groups, one patient failed to complete the rescue BP. Thus, 85 patients (42 patients in group A and 43 in group B) were finally included in the per protocol analysis. Groups A and B did not differ significantly in terms of gender, age, comorbidities, or prevalence of constipation. However, group A had a significantly shorter interval between the completion of rescue PEG ingestion and the rescue colonoscopy (median [IQR], 194 min [155–223] vs. 372 min [321–463]; p \ 0.001). Table 1 summarizes the baseline characteristics of both groups. With regard to the adequacy of PEG ingestion during the rescue BP, 40 of the 42 group A patients (95.2 %) showed adequate ingestion of the additional 2 L of PEG, while 40 of the 43 group B patients (93.0 %) reported adequate ingestion of the 4 L of PEG. Rescue BP-Related Variables The quality of the rescue BP was similar for the two groups (Table 2). The two BP methods did not differ significantly in terms of patient-reported discomfort grade (Table 3): 15 patients in group A (35.7 %) did not complain of any discomfort (including nausea/vomiting and abdominal
Male BMI (kg/m2)
58 (50–66)
Group B: 4 L PEG plus bisacodyl (20 mg) 1 week later (n = 43) 59 (48–68)
0.768
20 (47.6 %)
25 (58.1 %)
0.331
23.4 (21.1–25.8)
23.6 (20.8–25.5)
Indication for colonoscopy Screening
0.989 0.439
23 (54.8 %)
18 (41.9 %)
Lower GI symptomsa
5 (11.9 %)
4 (9.3 %)
Constipation
8 (19.0 %)
9 (20.9 %)
Postpolypectomy surveillance
6 (14.3 %)
12 (27.9 %)
Comorbidities Diabetes mellitus
p value
9 (21.4 %)
8 (18.6 %)
0.745
Hypertension
4 (9.5 %)
2 (4.7 %)
0.433
Adequate initial PEG intake
27 (64.3 %)
23 (53.5 %)
0.312
Time since completion of rescue PEG ingestion (min)
194 (155–223)
372 (321–463)
\0.001
The data are expressed as median (interquartile range) or n (%) BMI; body mass index, PEG; polyethylene glycol, GI; gastrointestinal a Lower GI symptoms include rectal bleeding, significant loose stool, lower abdominal pain, and abdominal discomfort
distension), and a similar rate was observed in group B (12 patients, 27.9 %; p = 0.440). Rescue BP Failure Rate and Risk Factors Risk Factors for BP Failure There were 17 cases (20 %) of rescue BP failure. The patients who showed rescue BP failure were significantly older than those whose rescue BP was successful (66 years [IQR, 55–69] vs. 57 years [IQR, 48–65]; p = 0.023, Table 4). Rescue BP failure was significantly more likely in the patients who ingested PEG adequately during the index colonoscopy (82.4 %) than in the patients who did not ingest the initial PEG dose adequately (52.9 %; p = 0.031). Male gender was also associated with a higher rate of rescue BP failure (76.5 vs. 47.1 %; p = 0.034). However, the type of rescue BP method did not influence the rescue BP failure rate: While group B had a slightly lower rescue BP failure rate (6/43, 14.0 %) than group A (11/42, 26.2 %), this did not achieve statistical significance (p = 0.158).
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Dig Dis Sci Table 2 Quality of the rescue bowel preparation in groups A and B Excellent
Good
Fair
Poor
Inadequate
Group A
0
14 (33.3 %)
17 (40.5 %)
11 (26.2 %)
0
Group B
0
19 (44.2 %)
18 (41.9 %)
5 (11.6 %)
Rescue BP method
p value 0.229
1 (2.3 %)
BP; bowel preparation
Table 3 Grades of patient-reported discomfort during rescue bowel preparation p value
Covariate
0 (0–3)
0.912
Rescue BP method Group A 42
0 (0–2)
0.363
Rescue BP group A
Rescue BP group B
Nausea and/or vomiting
0 (0–2)
Abdominal distension
0 (0–4)
Overall discomforta, n (%) No Yes
0.440
35
1
Yes
50
4.05
Rescue BP success (n = 68, 80 %)
Age (years)
66 (55–69)
57 (48–65)
0.023
Male
13 (76.5 %)
32 (47.1 %)
0.034
22.6 (20.9–25.9)
23.6 (20.8–25.6)
0.981
Constipation
7 (41.2 %)
14 (20.6 %)
0.114
Diabetes mellitus
6 (35.3 %)
11 (16.2 %)
0.096
Hypertension
3 (17.7 %)
3 (4.4 %)
0.091
14 (82.4 %)
36 (52.9 %)
0.031
213 (178–413)
280 (198–403)
0.464
Group A
11 (26.2 %)
31 (73.8 %)
Group B
6 (14.0 %)
37 (86.0 %)
p value
Comorbidities
Time since completion of rescue PEG ingestion (min) Rescue BP method
0.158
BMI; body mass index, BP; bowel preparation, PEG; polyethylene glycol
Multivariable-adjusted analysis showed that the group B method had a lower odds for rescue BP failure compared to the group A method (odds ratio [OR] 0.68, 95 %
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0.68
No
Rescue BP failure (n = 17, 20 %)
p value
0.16–2.95
0.605
Adequate PEG ingestion before index colonoscopya
31 (72.1 %)
Table 4 Bivariate analysis of factors associated with rescue bowel preparation failure
95 % CI
1
43
12 (27.9 %)
Overall discomfort was regarded as ‘‘Yes’’ when the nausea/vomiting score was 1 or more and/or the abdominal distension score was 1 or more
Adequate initial PEG intake
OR
27 (64.3 %)
a
BMI (kg/m )
Group B
n
15 (35.7 %)
The data are expressed as median (interquartile range) scores of selfreported discomfort, as measured by using a visual analog scale of 0–10 BP; bowel preparation
2
Table 5 Multivariable-adjusted logistic regression analysis of risk factors for rescue bowel preparation failure
1.04–15.75
0.044
Covariates included in the model are time since the completion of the rescue PEG ingestion, adequacy of PEG ingestion for the index colonoscopy, and rescue BP method BP; bowel preparation, CI; confidence interval, OR; odds ratio, PEG; polyethylene glycol a
PEG ingestion before index colonoscopy was defined as adequate if enough PEG was ingested (C75 % of 4 L PEG) and ingestion was completed within the specified time
Table 6 Subgroup analysis of the influence of rescue bowel preparation method on rescue bowel preparation failure in patients who ingested the polyethylene glycol for the index colonoscopy adequately (n = 50) Rescue BP failure n
Adjusted ORa
Group A
27
1.00
Group B
23
0.51
95 % CI
Rescue BP method 0.13–2.02
BP; bowel preparation, CI; confidence interval, OR; odds ratio a
Adjusted for age
confidence interval [CI] 0.16–2.95), but this again did not achieve statistical significance (p = 0.605; Table 5). Adequate PEG ingestion during the index colonoscopy was associated with increased risk of rescue BP failure (OR 4.05, 95 % CI 1.04–15.75; p = 0.044). Subgroup Analyses Fifty patients ingested the PEG for the index colonoscopy adequately. Of these, 14 (28 %) showed rescue BP failure. Subgroup analysis of these 50 patients revealed that of the 27 group A patients who adequately ingested PEG for the index
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colonoscopy, nine (33.3 %) showed rescue BP failure. This did not differ significantly from the rescue BP failure rate of group B (5/23 [21.7 %]; p = 0.363), which implies rescue BP methods may not be a risk factor for rescue BP failure even in those who ingested adequate amount of PEG for the index colonoscopy. Table 6 shows the adjusted analysis results.
Discussion In this prospective observational study, the two rescue BP methods [i.e., an additional 2 L ingested on the same day and 4 L PEG plus bisacodyl (20 mg) 1 week later] did not differ in terms of rescue BP failure rate. This suggests that the patients can choose the rescue BP method without any restrictions. Interestingly, adequate PEG ingestion for the index colonoscopy was predictive of rescue BP failure. Thus, more attention should be paid to patients who show BP failure despite adequate ingestion of PEG because these patients seem to comprise the high-risk group for rescue BP failure. Bowel cleansing is important for detecting colonic lesions and results in lower rates of adverse events during colonoscopy examinations. However, despite the importance of BP, BP failure occurs commonly. Repeat BP failure is also relatively common: A retrospective analysis in a tertiary referral center demonstrated that of 235 patients whose first colonoscopy failed because of inadequate BP, the repeat colonoscopy also failed because of unsatisfactory BP in 54 (23 %) [3, 5, 7, 11]. This rescue BP failure rate is substantial and warrants the development of an adequate rescue BP method. In the present study, the rescue BP failure rate was 20 % in overall, which is similar to the rate of 23 % in the aforementioned study [3]. The analysis of the two rescue BP methods revealed that although the bisacodyl/4 L PEG/7 days later method had a smaller rescue BP failure rate (14.0 %), it was not significantly different from the rescue BP failure rate of the additional 2 L PEG/same-day method (26.2 %, p = 0.158). This suggests that the efficacy of both rescue BP regimens in our study was not satisfactorily high and further efforts to identify an optimal rescue BP method are warranted. This also indicates that at this point in time, given the lack of consensus regarding the bowel cleansing of individuals who have experienced a suboptimal bowel cleansing, the patients’ preference may be the most important basis for the choice of rescue BP method. One may reason that adding more PEG on the same day in patients with an initial inadequate BP would lead to good bowel cleansing because it would remove the presumed small amount of residual feces relatively easily. However, the present study showed that this approach was not associated with a good rescue BP rate. Indeed, its successful rescue
BP rate was numerically lower than that of the bisacodyl/4 L PEG/7 days later approach. The reason for this disparity is not clear, but several factors may have contributed. First, it may reflect the high rate of adequate ingestion of 4 L PEG in group B (40/43, 93 %). Second, the addition of bisacodyl may have improved the bowel cleansing rate because bisacodyl stimulates colonic peristalsis, which is a different mechanism from PEG, and thus may act in an adjunctive fashion in bowel cleansing. However, the contribution of bisacodyl should be investigated further because bisacodyl, when used with PEG, has demonstrated no significant difference in BP quality [12]. Third, the low-residue diet for a prolonged period might have contributed to the tendency for a lower rate of BP failure in group B. A previous study also showed that following a low-residue diet for 5 days was associated with a higher likelihood of acceptable BP in the repeat colonoscopy [3, 5, 7, 11]. However, because we did not accurately assess the degree to which the patients restricted their dietary fiber intake, the impact of a prolonged low-residue diet on the rate of rescue BP failure should be studied further in the future. Although not assessed in this study, the risk of falling and aspiration from over-sedation for two colonoscopy examinations on the same day in group A seems to be present. In addition, the group A regimen may not be a feasible option for the afternoon BP failure cases because long additional time is required for withdrawal of the initial sedation, drinking additional PEG, and readministration of the second sedation. Therefore, routine recommendation of same day repeat colonoscopy may not be advisable. The rescue BP failure rate of patients who took an adequate amount of PEG for the index colonoscopy was significantly higher than that of those who did not (14/50, 28.0 % vs. 3/35 8.6 %; p = 0.031). This association continued to be significant on multivariable analysis. Since this subgroup appears to be the most resistant to good BP, these patients should be seen as being at high risk of rescue BP failure and thus their rescue BP should be more intensive: For example, all of the 4 L of PEG during the rescue BP should be ingested within the specified time limit, the time interval between the completion of PEG intake and colonoscopy should be adequate, adding adjunctive laxatives like bisacodyl could be considered, and prolonged and stringent adherence to a low-residue diet before rescue colonoscopy should be recommended. In addition, the mechanism behind the high risk of rescue BP failure in this subgroup should be investigated so that the rescue BP protocol in these patients can be customized and optimized. For example, if the reason for the rescue BP failure in this subgroup is delayed colon transit, one could consider adding prokinetics for several days before performing the rescue BP. Further studies addressing this issue are warranted.
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The proportion of patients who complained of any discomfort related to the rescue BP was 64.3 and 72.1 % in the group A and B, respectively. However, the actual median scores of nausea and abdominal distension were both 0 in both groups. This implies that our rescue BP methods-related discomfort may be frequent, but usually mild. In the present study, the rate of inadequate initial PEG ingestion was high (n = 35, 41.2 %). Since the adequacy of the initial PEG ingestion could have influenced our analysis of the rescue BP failure rate, we performed a subgroup analysis that included only the patients who had ingested PEG adequately at the index colonoscopy. In this subgroup, the two rescue BP methods did not differ significantly in rescue BP failure rate. This allows us to state with more confidence that the rescue BP method may not influence the rescue BP failure or success. This study had several limitations. First, the time between completion of PEG ingestion and colonoscopy was around 6 h in group B. Since the time interval between the last dose of bowel preparation agents and the colonoscopy start time has been recommended to be no longer than 4 h [13–15], such a time lag in group B may have increased the number of poor BP patients. Second, the power of the study may be limited due to the relatively small sample size. The absence of BP quality difference between groups in this study might have been due to type II error. Therefore, it will be necessary to perform a larger multicenter study before the findings of this study can be generalized to the wider population. Third, this study was not randomized, which limits the comparability of the two groups although the baseline characteristics were not significantly different between both groups. Lastly, we did not analyze the effect of the split-dose BP (where half of the PEG dose is consumed the night before and the other half on the morning of the colonoscopy), although some patients in our study underwent this procedure. Several studies showed that a split-dose BP may be more effective in cleansing the colon than a regimen in which the whole PEG solution is consumed the day before. Moreover, the split-dose regimen may also be more tolerable [16–18]. In future studies, the dosing of PEG should be kept constant if possible, or the influence of the dosing method should be analyzed along with other variables. Despite these limitations, our study has two strengths. First, it is the first prospective comparison of two different rescue BP methods. Second, it allowed a subgroup of patients who are at high risk of rescue BP failure to be identified. In conclusion, the two rescue BP methods analyzed in this study did not differ in terms of rescue bowel cleansing quality. Endoscopists should be aware of the high rate of rescue BP failure of patients who ingested the initial PEG dose adequately.
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Conflict of interest
None.
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Dig Dis Sci 16. Aoun E, Abdul-Baki H, Azar C, et al. A randomized single-blind trial of split-dose PEG-electrolyte solution without dietary restriction compared with whole dose PEG-electrolyte solution with dietary restriction for colonoscopy preparation. Gastrointest Endosc. 2005;62:213–218. 17. Chiu HM, Lin JT, Wang HP, Lee YC, Wu MS. The impact of colon preparation timing on colonoscopic detection of colorectal
neoplasms—a prospective endoscopist-blinded randomized trial. Am J Gastroenterol. 2006;101:2719–2725. 18. Parra-Blanco A, Nicolas-Perez D, Gimeno-Garcia 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. 2006;12:6161–6166.
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ORIGINAL ARTICLE
Rescue Bowel Preparation: Same Day 2 L Polyethylene Glycol Addition, Not Superior to Bisacodyl Addition 7 Days Later Jong Wook Kim • Jeung Hye Han • Sun-Jin Boo • Ock Bae Ko • Soo-Kyung Park Sang Hyoung Park • Dong-Hoon Yang • Kee Wook Jung • Kyung-Jo Kim • Byong Duk Ye • Seung-Jae Myung • Suk-Kyun Yang • Jin-Ho Kim • Jeong-Sik Byeon
•
Received: 23 December 2013 / Accepted: 18 March 2014 Ó Springer Science+Business Media New York 2014
Abstract Background The optimal colon-cleansing method after failure of bowel preparation (BP) for colonoscopy has not been established. Aims We aimed to compare BP rescue methods after failed initial BP and to identify risk factors for rescue BP failure. Methods Eighty-five patients with BP failure after 4 L polyethylene glycol (PEG) ingestion were prospectively enrolled from March 2008 to March 2012. A second colonoscopy was performed either on the same day after ingestion of another 2 L PEG (group A) or 1 week later
Jong Wook Kim and Jeung Hye Han contributed equally to this work. J. W. Kim Department of Internal Medicine, Inje University Ilsan Paik Hospital, Goyang, Korea J. H. Han Asan Health Screening and Promotion Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea S.-J. Boo Department of Internal Medicine, Jeju National University School of Medicine, Jeju, Korea O. B. Ko S. H. Park D.-H. Yang K. W. Jung K.-J. Kim B. D. Ye S.-J. Myung S.-K. Yang J.-H. Kim J.-S. Byeon (&) Department of Gastroenterology, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro 43-gil, Songpa-gu, Seoul, Korea e-mail: [email protected] S.-K. Park Department of Internal Medicine, Digestive Disease Center and Research Institute, Soonchunhyang University College of Medicine, Bucheon, Korea
after ingestion of 4 L PEG plus 20 mg oral bisacodyl (group B). Differences between groups in terms of BP quality and risk factors for a poor BP on the second colonoscopy were investigated. Results Median patient age was 59 years, 45 were male (52.9 %), and 17 (20 %) had poor BP on the second colonoscopy. For group B, the multivariable-adjusted odds ratio (OR) for poor BP on the second colonoscopy relative to group A was 0.68 (95 % confidence interval [CI], 0.16–2.95). Adequately ingested PEG during the initial colonoscopy was associated with poor BP on the second colonoscopy (OR 4.05; 95 % CI 1.04–15.75). The two groups had similar patient discomfort rates during the second BP. Conclusions The two groups did not differ in rescue BP failure rate. Initial BP failure after adequate consumption of 4 L PEG may be a risk factor for rescue BP failure. A stricter BP regimen should be considered for these patients. Keywords Colonoscopy Bowel preparation Polyethylene glycol Bisacodyl Abbreviations BP Bowel preparation CI Confidence interval IQR Interquartile range OR Odds ratio PEG Polyethylene glycol
Introduction Colonoscopy is considered to be the gold standard method for assessing the colonic mucosa. Its diagnostic accuracy depends on the quality of bowel preparation (BP) [1, 2]. The frequency of BP failure for colonoscopy varies from 5 to
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30 % [3, 4]. Several studies have demonstrated that older age, male gender, prior abdominal surgery, presence of diabetes mellitus, and history of constipation associate with an increased risk of BP failure. Medications such as antidepressants or calcium antagonists and a later colonoscopy start time after the end of BP are also risk factors of BP failure [5–7]. Although BP failure is not uncommon and its risk factors are well recognized, optimal rescue BP methods remain to be clearly established. The recent European Society of Gastrointestinal Endoscopy (ESGE) guideline recommends that to rescue BP failure, intensive BP methods (including endoscopic irrigation pumps) should be used or the colonoscopy should be repeated on the following day [8]. However, such methods are often cumbersome and the level of evidence for their use in the guideline was of low quality. Therefore, an optimal rescue BP method after failure of the initial BP for colonoscopy remains to be established. Some physicians consider that repeating colonoscopy on the same day after ingestion of more polyethylene glycol (PEG) is better than repeating the colonoscopy several days later because they believe that the additional PEG will eliminate the residual feces. However, for this, the patients must stay longer in the hospital for the examination. In addition, some patients may not be willing to ingest more PEG. An alternative approach is to use adjuvant products such as bisacodyl, which may reduce the amount of PEG needed during repeat BP and thus may enhance the bowel cleansing when consumed with the routine 4 L of PEG [9]. However, to date, there has been little direct comparison of the various rescue BP strategies. Therefore, the present study assessed the efficacy of two rescue BP methods in patients who failed initial BP consisting of 4 L PEG ingestion. These methods involved either the additional ingestion of 2 L PEG on the same day or the ingestion of 4 L PEG plus bisacodyl 1 week later. Analyses to identify risk factors for rescue BP failure were also performed.
Methods Patients and Study Design In this parallel-arm, single-center, prospective study, patients were allocated to receive the BP rescue method of their choice after being informed about their risks and benefits. Patients found to have BP failure on the index colonoscopy after a standard BP with 4 L of PEG solution after 3 days of a low-residue diet were eligible for inclusion in the study. For the index colonoscopy, initial BP was done as follows: When the index colonoscopies were scheduled in the morning, 2 L PEG was given the night before and the remaining 2 L was given at 4 a.m. on the examination day. Both 2 L doses of PEG solution had to be
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ingested within 2 h: For the colonoscopies that were scheduled in the afternoon, the entire 4 L of PEG was ingested within 4 h during the morning of the examination day. The Aronchick scale was used to grade the quality of colon cleansing as follows: (1) excellent (there was a small volume of clear liquid or [95 % of the surface could be seen); (2) good (there was a large volume of clear liquid covering 5–25 % of the surface but [90 % of the surface could be seen); (3) fair (there was some semisolid stool that could be suctioned or washed away but [90 % of the surface could be seen); (4) poor (there was semisolid stool that could not be suctioned or washed away and \90 % of the surface could be seen); and (5) inadequate (repeat BP and colonoscopy needed) [10]. For agreement on the Aronchick scale, only four experienced endoscopists performed the rescue colonoscopies during the study period. All patients were prospectively enrolled between March 2008 and March 2012 at a tertiary referral center in Seoul, Korea (Asan Medical Center). The consecutive patients who exhibited BP failure (Aronchick scale of 5) at the index colonoscopy were assigned to groups A or B on the basis of the preference of the individual patients. Group A received another 2 L of PEG on the same day of the index colonoscopy and then underwent a rescue colonoscopy 2 h or more after the PEG ingestion was completed. Group B, who underwent the rescue colonoscopy after 1 week of a lowresidue diet, ingested 20 mg of bisacodyl at 7 p.m. the day before the colonoscopy and ingested 4 L PEG as described above. For patient tolerability in group B, we did not increase the total dosage of PEG. The degree of bowel cleansing after the rescue BP methods was also scored by using the Aronchick scale [10]. Rescue BP failure was defined as an Aronchick BP scale score of ‘‘poor’’ or ‘‘inadequate’’ [5]. Before the rescue colonoscopy was started, the examinees completed a questionnaire to assess the degree of discomfort during the rescue BP methods. Thus, the magnitude of discomfort was graded by using a visual analog scale of 0–10. Patients who had undergone prior major abdominal surgery (including colorectal resection) were less than 18 years of age or had inflammatory bowel disease or colorectal cancer were excluded. The study protocol was approved by the Institutional Review Board of Asan Medical Center (IRB No. 2009-0733). Data Collection The following variables were recorded by the endoscopist at the end of the index colonoscopy: date, age, gender, main indication for colonoscopy, history of constipation, comorbidities, previous medication history, and adequacy of BP solution ingestion. During the rescue colonoscopy, the tolerability of the rescue regimen (as assessed by the patient-reported 10-point visual analog scale) and the
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Aronchick BP score were recorded. Tolerability parameters included nausea/vomiting, abdominal distension, and overall discomfort. Adequate ingestion of PEG solution was defined as both adequate timing and ingestion of C75 % of the required PEG solution.
Table 1 Baseline clinical characteristics of the patients in groups A and B Group A: addition of 2 L PEG on the same day (n = 42)
Statistical Analysis Age (years)
The baseline clinical characteristics of the patients were summarized by using number (%) for categorical variables and median (interquartile range, IQR) for continuous variables. Pearson’s chi-square test and the Mann–Whitney U test were used to compare the differences between the groups. Variables that were found to be statistically significant in the bivariate analysis in predicting poor BP during the rescue colonoscopy were entered into the multivariate logistic regression model by forward selection. In the final model, a p value \0.05 was considered to be statistically significant. All statistical analyses were performed by using Stata version 12.1 (StataCorp, TX, USA).
Results Comparison Between Groups A and B Baseline Characteristics of the Patients During the study period, 87 patients met the inclusion criteria and proceeded to the rescue BP. There were 43 patients in group A and 44 in group B. In both groups, one patient failed to complete the rescue BP. Thus, 85 patients (42 patients in group A and 43 in group B) were finally included in the per protocol analysis. Groups A and B did not differ significantly in terms of gender, age, comorbidities, or prevalence of constipation. However, group A had a significantly shorter interval between the completion of rescue PEG ingestion and the rescue colonoscopy (median [IQR], 194 min [155–223] vs. 372 min [321–463]; p \ 0.001). Table 1 summarizes the baseline characteristics of both groups. With regard to the adequacy of PEG ingestion during the rescue BP, 40 of the 42 group A patients (95.2 %) showed adequate ingestion of the additional 2 L of PEG, while 40 of the 43 group B patients (93.0 %) reported adequate ingestion of the 4 L of PEG. Rescue BP-Related Variables The quality of the rescue BP was similar for the two groups (Table 2). The two BP methods did not differ significantly in terms of patient-reported discomfort grade (Table 3): 15 patients in group A (35.7 %) did not complain of any discomfort (including nausea/vomiting and abdominal
Male BMI (kg/m2)
58 (50–66)
Group B: 4 L PEG plus bisacodyl (20 mg) 1 week later (n = 43) 59 (48–68)
0.768
20 (47.6 %)
25 (58.1 %)
0.331
23.4 (21.1–25.8)
23.6 (20.8–25.5)
Indication for colonoscopy Screening
0.989 0.439
23 (54.8 %)
18 (41.9 %)
Lower GI symptomsa
5 (11.9 %)
4 (9.3 %)
Constipation
8 (19.0 %)
9 (20.9 %)
Postpolypectomy surveillance
6 (14.3 %)
12 (27.9 %)
Comorbidities Diabetes mellitus
p value
9 (21.4 %)
8 (18.6 %)
0.745
Hypertension
4 (9.5 %)
2 (4.7 %)
0.433
Adequate initial PEG intake
27 (64.3 %)
23 (53.5 %)
0.312
Time since completion of rescue PEG ingestion (min)
194 (155–223)
372 (321–463)
\0.001
The data are expressed as median (interquartile range) or n (%) BMI; body mass index, PEG; polyethylene glycol, GI; gastrointestinal a Lower GI symptoms include rectal bleeding, significant loose stool, lower abdominal pain, and abdominal discomfort
distension), and a similar rate was observed in group B (12 patients, 27.9 %; p = 0.440). Rescue BP Failure Rate and Risk Factors Risk Factors for BP Failure There were 17 cases (20 %) of rescue BP failure. The patients who showed rescue BP failure were significantly older than those whose rescue BP was successful (66 years [IQR, 55–69] vs. 57 years [IQR, 48–65]; p = 0.023, Table 4). Rescue BP failure was significantly more likely in the patients who ingested PEG adequately during the index colonoscopy (82.4 %) than in the patients who did not ingest the initial PEG dose adequately (52.9 %; p = 0.031). Male gender was also associated with a higher rate of rescue BP failure (76.5 vs. 47.1 %; p = 0.034). However, the type of rescue BP method did not influence the rescue BP failure rate: While group B had a slightly lower rescue BP failure rate (6/43, 14.0 %) than group A (11/42, 26.2 %), this did not achieve statistical significance (p = 0.158).
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Dig Dis Sci Table 2 Quality of the rescue bowel preparation in groups A and B Excellent
Good
Fair
Poor
Inadequate
Group A
0
14 (33.3 %)
17 (40.5 %)
11 (26.2 %)
0
Group B
0
19 (44.2 %)
18 (41.9 %)
5 (11.6 %)
Rescue BP method
p value 0.229
1 (2.3 %)
BP; bowel preparation
Table 3 Grades of patient-reported discomfort during rescue bowel preparation p value
Covariate
0 (0–3)
0.912
Rescue BP method Group A 42
0 (0–2)
0.363
Rescue BP group A
Rescue BP group B
Nausea and/or vomiting
0 (0–2)
Abdominal distension
0 (0–4)
Overall discomforta, n (%) No Yes
0.440
35
1
Yes
50
4.05
Rescue BP success (n = 68, 80 %)
Age (years)
66 (55–69)
57 (48–65)
0.023
Male
13 (76.5 %)
32 (47.1 %)
0.034
22.6 (20.9–25.9)
23.6 (20.8–25.6)
0.981
Constipation
7 (41.2 %)
14 (20.6 %)
0.114
Diabetes mellitus
6 (35.3 %)
11 (16.2 %)
0.096
Hypertension
3 (17.7 %)
3 (4.4 %)
0.091
14 (82.4 %)
36 (52.9 %)
0.031
213 (178–413)
280 (198–403)
0.464
Group A
11 (26.2 %)
31 (73.8 %)
Group B
6 (14.0 %)
37 (86.0 %)
p value
Comorbidities
Time since completion of rescue PEG ingestion (min) Rescue BP method
0.158
BMI; body mass index, BP; bowel preparation, PEG; polyethylene glycol
Multivariable-adjusted analysis showed that the group B method had a lower odds for rescue BP failure compared to the group A method (odds ratio [OR] 0.68, 95 %
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0.68
No
Rescue BP failure (n = 17, 20 %)
p value
0.16–2.95
0.605
Adequate PEG ingestion before index colonoscopya
31 (72.1 %)
Table 4 Bivariate analysis of factors associated with rescue bowel preparation failure
95 % CI
1
43
12 (27.9 %)
Overall discomfort was regarded as ‘‘Yes’’ when the nausea/vomiting score was 1 or more and/or the abdominal distension score was 1 or more
Adequate initial PEG intake
OR
27 (64.3 %)
a
BMI (kg/m )
Group B
n
15 (35.7 %)
The data are expressed as median (interquartile range) scores of selfreported discomfort, as measured by using a visual analog scale of 0–10 BP; bowel preparation
2
Table 5 Multivariable-adjusted logistic regression analysis of risk factors for rescue bowel preparation failure
1.04–15.75
0.044
Covariates included in the model are time since the completion of the rescue PEG ingestion, adequacy of PEG ingestion for the index colonoscopy, and rescue BP method BP; bowel preparation, CI; confidence interval, OR; odds ratio, PEG; polyethylene glycol a
PEG ingestion before index colonoscopy was defined as adequate if enough PEG was ingested (C75 % of 4 L PEG) and ingestion was completed within the specified time
Table 6 Subgroup analysis of the influence of rescue bowel preparation method on rescue bowel preparation failure in patients who ingested the polyethylene glycol for the index colonoscopy adequately (n = 50) Rescue BP failure n
Adjusted ORa
Group A
27
1.00
Group B
23
0.51
95 % CI
Rescue BP method 0.13–2.02
BP; bowel preparation, CI; confidence interval, OR; odds ratio a
Adjusted for age
confidence interval [CI] 0.16–2.95), but this again did not achieve statistical significance (p = 0.605; Table 5). Adequate PEG ingestion during the index colonoscopy was associated with increased risk of rescue BP failure (OR 4.05, 95 % CI 1.04–15.75; p = 0.044). Subgroup Analyses Fifty patients ingested the PEG for the index colonoscopy adequately. Of these, 14 (28 %) showed rescue BP failure. Subgroup analysis of these 50 patients revealed that of the 27 group A patients who adequately ingested PEG for the index
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colonoscopy, nine (33.3 %) showed rescue BP failure. This did not differ significantly from the rescue BP failure rate of group B (5/23 [21.7 %]; p = 0.363), which implies rescue BP methods may not be a risk factor for rescue BP failure even in those who ingested adequate amount of PEG for the index colonoscopy. Table 6 shows the adjusted analysis results.
Discussion In this prospective observational study, the two rescue BP methods [i.e., an additional 2 L ingested on the same day and 4 L PEG plus bisacodyl (20 mg) 1 week later] did not differ in terms of rescue BP failure rate. This suggests that the patients can choose the rescue BP method without any restrictions. Interestingly, adequate PEG ingestion for the index colonoscopy was predictive of rescue BP failure. Thus, more attention should be paid to patients who show BP failure despite adequate ingestion of PEG because these patients seem to comprise the high-risk group for rescue BP failure. Bowel cleansing is important for detecting colonic lesions and results in lower rates of adverse events during colonoscopy examinations. However, despite the importance of BP, BP failure occurs commonly. Repeat BP failure is also relatively common: A retrospective analysis in a tertiary referral center demonstrated that of 235 patients whose first colonoscopy failed because of inadequate BP, the repeat colonoscopy also failed because of unsatisfactory BP in 54 (23 %) [3, 5, 7, 11]. This rescue BP failure rate is substantial and warrants the development of an adequate rescue BP method. In the present study, the rescue BP failure rate was 20 % in overall, which is similar to the rate of 23 % in the aforementioned study [3]. The analysis of the two rescue BP methods revealed that although the bisacodyl/4 L PEG/7 days later method had a smaller rescue BP failure rate (14.0 %), it was not significantly different from the rescue BP failure rate of the additional 2 L PEG/same-day method (26.2 %, p = 0.158). This suggests that the efficacy of both rescue BP regimens in our study was not satisfactorily high and further efforts to identify an optimal rescue BP method are warranted. This also indicates that at this point in time, given the lack of consensus regarding the bowel cleansing of individuals who have experienced a suboptimal bowel cleansing, the patients’ preference may be the most important basis for the choice of rescue BP method. One may reason that adding more PEG on the same day in patients with an initial inadequate BP would lead to good bowel cleansing because it would remove the presumed small amount of residual feces relatively easily. However, the present study showed that this approach was not associated with a good rescue BP rate. Indeed, its successful rescue
BP rate was numerically lower than that of the bisacodyl/4 L PEG/7 days later approach. The reason for this disparity is not clear, but several factors may have contributed. First, it may reflect the high rate of adequate ingestion of 4 L PEG in group B (40/43, 93 %). Second, the addition of bisacodyl may have improved the bowel cleansing rate because bisacodyl stimulates colonic peristalsis, which is a different mechanism from PEG, and thus may act in an adjunctive fashion in bowel cleansing. However, the contribution of bisacodyl should be investigated further because bisacodyl, when used with PEG, has demonstrated no significant difference in BP quality [12]. Third, the low-residue diet for a prolonged period might have contributed to the tendency for a lower rate of BP failure in group B. A previous study also showed that following a low-residue diet for 5 days was associated with a higher likelihood of acceptable BP in the repeat colonoscopy [3, 5, 7, 11]. However, because we did not accurately assess the degree to which the patients restricted their dietary fiber intake, the impact of a prolonged low-residue diet on the rate of rescue BP failure should be studied further in the future. Although not assessed in this study, the risk of falling and aspiration from over-sedation for two colonoscopy examinations on the same day in group A seems to be present. In addition, the group A regimen may not be a feasible option for the afternoon BP failure cases because long additional time is required for withdrawal of the initial sedation, drinking additional PEG, and readministration of the second sedation. Therefore, routine recommendation of same day repeat colonoscopy may not be advisable. The rescue BP failure rate of patients who took an adequate amount of PEG for the index colonoscopy was significantly higher than that of those who did not (14/50, 28.0 % vs. 3/35 8.6 %; p = 0.031). This association continued to be significant on multivariable analysis. Since this subgroup appears to be the most resistant to good BP, these patients should be seen as being at high risk of rescue BP failure and thus their rescue BP should be more intensive: For example, all of the 4 L of PEG during the rescue BP should be ingested within the specified time limit, the time interval between the completion of PEG intake and colonoscopy should be adequate, adding adjunctive laxatives like bisacodyl could be considered, and prolonged and stringent adherence to a low-residue diet before rescue colonoscopy should be recommended. In addition, the mechanism behind the high risk of rescue BP failure in this subgroup should be investigated so that the rescue BP protocol in these patients can be customized and optimized. For example, if the reason for the rescue BP failure in this subgroup is delayed colon transit, one could consider adding prokinetics for several days before performing the rescue BP. Further studies addressing this issue are warranted.
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The proportion of patients who complained of any discomfort related to the rescue BP was 64.3 and 72.1 % in the group A and B, respectively. However, the actual median scores of nausea and abdominal distension were both 0 in both groups. This implies that our rescue BP methods-related discomfort may be frequent, but usually mild. In the present study, the rate of inadequate initial PEG ingestion was high (n = 35, 41.2 %). Since the adequacy of the initial PEG ingestion could have influenced our analysis of the rescue BP failure rate, we performed a subgroup analysis that included only the patients who had ingested PEG adequately at the index colonoscopy. In this subgroup, the two rescue BP methods did not differ significantly in rescue BP failure rate. This allows us to state with more confidence that the rescue BP method may not influence the rescue BP failure or success. This study had several limitations. First, the time between completion of PEG ingestion and colonoscopy was around 6 h in group B. Since the time interval between the last dose of bowel preparation agents and the colonoscopy start time has been recommended to be no longer than 4 h [13–15], such a time lag in group B may have increased the number of poor BP patients. Second, the power of the study may be limited due to the relatively small sample size. The absence of BP quality difference between groups in this study might have been due to type II error. Therefore, it will be necessary to perform a larger multicenter study before the findings of this study can be generalized to the wider population. Third, this study was not randomized, which limits the comparability of the two groups although the baseline characteristics were not significantly different between both groups. Lastly, we did not analyze the effect of the split-dose BP (where half of the PEG dose is consumed the night before and the other half on the morning of the colonoscopy), although some patients in our study underwent this procedure. Several studies showed that a split-dose BP may be more effective in cleansing the colon than a regimen in which the whole PEG solution is consumed the day before. Moreover, the split-dose regimen may also be more tolerable [16–18]. In future studies, the dosing of PEG should be kept constant if possible, or the influence of the dosing method should be analyzed along with other variables. Despite these limitations, our study has two strengths. First, it is the first prospective comparison of two different rescue BP methods. Second, it allowed a subgroup of patients who are at high risk of rescue BP failure to be identified. In conclusion, the two rescue BP methods analyzed in this study did not differ in terms of rescue bowel cleansing quality. Endoscopists should be aware of the high rate of rescue BP failure of patients who ingested the initial PEG dose adequately.
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Conflict of interest
None.
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