Increased adenoma detection rate with system-wide implementation of a split-dose preparation for colonoscopy

ORIGINAL ARTICLE: Clinical Endoscopy

Increased adenoma detection rate with system-wide implementation of a split-dose preparation for colonoscopy Suryakanth R. Gurudu, MD, Francisco C. Ramirez, MD, M. Edwyn Harrison, MD, Jonathan A. Leighton, MD, Michael D. Crowell, PhD Scottsdale, Arizona, USA

Background: Recent studies using split-dose preparations (SDPs) suggest a significant improvement in the quality of preparation and patient compliance. However, the effects of SDP on other quality indicators of colonoscopy, such as cecal intubation and adenoma detection rates, have not been previously reported, to our knowledge. Objective: The primary objective of this study was to compare polyp detection rates (PDRs) and adenoma detection rates (ADRs) before and after the implementation of an SDP as the preferred bowel preparation. The secondary objectives were to compare the quality of the preparation and colonoscopy completion rates before and after implementation of the SDP. Design: Retrospective study. Setting: Tertiary care medical center. Patients: Patients undergoing colonoscopy for screening and surveillance of colon polyps and cancer. Interventions: System-wide implementation of SDP. Results: A total of 3560 patients in the pre-SDP group and 1615 patients in the post-SDP group were included in the study. SDP use increased significantly from 9% to 74% after implementation. In comparison with the pre-SDP group, both PDRs (44.1%-49.5%; P ⬍ .001) and ADRs (26.7%-31.8%; P ⬍ .001) significantly improved in the post-SDP group. The colonoscopy completion rate significantly increased from 93.6% to 95.5% in the post-SDP group (P ⫽ .008). Bowel preparation quality also improved significantly (P ⬍ .001) in the post-SDP group. Limitations: Retrospective design; not all endoscopists were the same in both periods. Conclusions: System-wide implementation of an SDP as the primary choice for colonoscopy significantly improved both PDRs and ADRs, overall quality of the preparation, and colonoscopy completion rates. (Gastrointest Endosc 2012;76:603-8.)

Abbreviations: ADR, adenoma detection rate; PDR, polyp detection rate; PEG, polyethylene glycol; SDP, split-dose preparation; SSA, sessile serrated adenoma.

Copyright © 2012 by the American Society for Gastrointestinal Endoscopy 0016-5107/$36.00 http://dx.doi.org/10.1016/j.gie.2012.04.456

DISCLOSURE: The following author disclosed financial relationships relevant to this publication: M. D. Crowell is a consultant for Ethicon Inc. and statistical editor of the American Journal of Gastroenterology. All other authors disclosed no financial relationships relevant to this publication.

Received January 4, 2012. Accepted April 19, 2012.

See CME section; p. 621.

Use your mobile device to scan this QR code and watch the author interview. Download a free QR code scanner by searching ‘QR Scanner’ in your mobile device’s app store. www.giejournal.org

Current affiliations: Division of Gastroenterology, Mayo Clinic Arizona, Scottsdale, Arizona, USA. Presented at American College of Gastroenterology annual meeting, Washington DC, October 28-November 2, 2011 (Am J Gastroenterol 2011; 106(Suppl 2):S417-8). Reprint requests: Suryakanth R. Gurudu, MD, Division of Gastroenterology and Hepatology, Mayo Clinic Arizona, 13400 East Shea Blvd, Scottsdale, AZ 85259. If you would like to chat with an author of this article, you may contact Dr Suryakanth at [email protected].

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A good-quality bowel preparation is essential for colonoscopy to be effective. Inadequate bowel preparation can result in incomplete procedures, missed lesions, higher complication rates, and increased costs resulting from repeated procedures.1-5 The ideal preparation reliably and rapidly clears the colon of all fecal material, leaving no gross or histologic alterations in the mucosa. It should be palatable and well tolerated by patients with minimal adverse GI symptoms1,6 to enhance compliance. The polyethylene glycol (PEG) solution is commonly used as a cleansing bowel preparation because it is safe and does not cause major fluid and electrolyte shifts. However, a major disadvantage is the large volume required to be taken over a short time that may result in patient intolerance and poor compliance, leading to a poor preparation. Recent studies have explored new approaches in administering PEG solutions to improve patient tolerability, compliance, and efficacy. Splitting the preparation is such an approach. Patients are advised to consume 2 or 3 L the night before and 1 or 2 L the morning of the procedure. A recent meta-analysis of randomized studies7 using splitdose preparations (SDPs) suggested a significant improvement in the quality of preparation and patient compliance. However, the effects of SDP on other quality indicators of colonoscopy, such as cecal intubation and adenoma detection rates, have not been evaluated, to our knowledge. The primary aim of this study was to compare polyp detection rates (PDRs) and adenoma detection rates (ADRs) before and after implementation of an SDP as the preferred bowel preparation in a tertiary GI practice. Secondary goals were to compare the quality of the preparation and cecal intubation rates before and after implementation of the SDP.

METHODS The institutional review board of Mayo Clinic approved the study. Electronic medical records of all the patients who underwent colonoscopy from January 2009 to December 2009 (before SDP) and from October 2010 to March 2011 (after SDP) were reviewed. All patients who underwent colonoscopy for screening and surveillance were included in the study. We excluded patients with incomplete data, prior colon resection, and those who had colonoscopy performed for indications of bleeding, anemia, and inflammatory bowel disease. Repeated colonoscopy in the same patient during the study period, after an initial colonoscopy detected adenomas, was also excluded. Patient demographics, indication for procedure, type of bowel preparation, quality of bowel preparation, completion of colonoscopy, total time of procedure and withdrawal time were recorded. Colonoscopy was performed by a gastroenterologist or by a GI fellow under direct supervision of the gastroenterologist. Complete colonoscopy was defined as intubation of the cecum, with identification of the appen604 GASTROINTESTINAL ENDOSCOPY Volume 76, No. 3 : 2012

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Take-home Message ●

System-wide implementation of a split-dose preparation for colonoscopy improves adenoma detection rate, quality of the preparation, and colonoscopy completion rate.

diceal orifice and the ileocecal valve. The PDR was defined as the percentage of colonoscopies in which at least 1 polyp was detected per colonoscopy. The ADR was defined as the percentage of colonoscopies in which at least 1 adenoma was detected per colonoscopy. Sessile serrated adenomas and advanced adenomas were included in the analysis for measurement of ADR. The quality of bowel preparation was rated by endoscopists on the basis of 5 prespecified criteria as follows: “excellent,” “good,” “fair-adequate,” “inadequate,” or “poor” (modified Aronchick scale8) (Appendix A, available online at www.giejournal.org). Standard high-definition colonoscopes (Olympus PCF-Q180AL, CF-Q180AL; Olympus America, Center Valley, PA; and Fujinon EC-530HL, EC530LS; Fujinon Endoscopy, Wayne, NJ) were used for all procedures. Colonoscopy was performed primarily with the patients under moderate sedation by using intravenous midazolam in combination with either fentanyl or meperidine. Monitored anesthesia care or general anesthesia was used in a minority of patients when indicated.

Preparation instructions The bowel preparation choices for split dosing were 4L PEG electrolyte solution or MoviPrep (Salix Pharmaceuticals Inc., Raleigh, NC). Before the procedure, printed information regarding the bowel preparation protocol was provided to all patients by the scheduling staff. Patients were instructed to avoid eating a high-fiber diet for 2 days before taking the bowel preparation and to drink only clear liquids for the entire day before colonoscopy. With the 4-L PEG solutions, patients were instructed to drink 3 L the night before, starting at 6 pm, and 1 L at least 4 hours before the scheduled procedure time on the day of the procedure. Patients using MoviPrep (after preparing the solution according to manufacturer’s specifications) were instructed to drink half of the volume the night before colonoscopy, starting at 6 pm, and the other half at least 4 hours before the scheduled procedure time on the day of the procedure. All patients were instructed to take nothing by mouth for at least 3 hours before the procedure. Patients who had an early morning procedure or long travel time to the endoscopy unit were offered the option of taking the entire preparation the night before (nonsplit dose).

Statistical analysis Data were entered manually and statistically assessed by using the Statistical Package for the Social Sciences www.giejournal.org

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(IBM SPSS version 19.0, Chicago, IL). Normality of data sets was evaluated by using the SPSS Explore and Descriptive functions. Stem-and-leaf plots and histograms were used to evaluate the distributions and to assess outliers. Normality plots were used to display normal probability and detrended normal probability plots. Where appropriate, the Kolmogorov-Smirnov statistic, with a Lilliefors significance level, was used for testing normality.9 Comparisons between groups were made by using either parametric t tests or nonparametric Mann-Whitney U tests as indicated. Tests for proportionality between groups were made by using the ␹2 tests with the Mantel-Haenszel statistic. Binary logistic regression was used to estimate unadjusted odds ratios and 95% confidence intervals. Multivariable logistic regressions were completed by using generalized estimating equations to adjust error estimates caused by data clustering among endoscopists.10,11 Point estimates and interval estimates were reported for all descriptive data and are presented as means or proportions and the standard deviation or 95% confidence intervals. The results of multivariate logistic regression are presented as odds ratios and 95% confidence intervals. Statistical significance was defined as P ⬍ .05.

Split-dose preparation for colonoscopy

TABLE 1. Patient demographics

Number of patients Age: mean (SD) y 2

BMI: mean (SD) kg/m Female sex (%)

Before split dose

After split dose

P value

3560

1615

—

62 (12)

61 (12)

.457

27 (5)

28 (5)

.579

50

50

.969

BMI, Body mass index.

Sample size estimate A primary goal of the proposed study was to test the null hypothesis that the ADR was identical before and after implementation of the SDP for colonoscopy. The criterion for significance (alpha) was set at 0.05 with a 2-tailed test. With a minimum sample size of 1500 in either of the 2 groups, the study would have ⬎80% power to detect a statistically significant result with a difference in proportions of at least 5% (approximately 25% vs 30%). The availability of larger samples would increase the power to detect group differences. The effect size was estimated on the basis of previous ADR studies and the smallest effect size that was considered important to detect. A second goal of this study was to estimate the difference in ADR between the 2 study populations. Based on these assumptions, the study would enable us to report the difference in proportions with a 95% confidence level of approximately plus/minus 3%.

RESULTS

Figure 1. Quality of the preparation before and after SDP periods.

from 9% in the pre-SDP period to 74% during the post-SDP period.

Quality of bowel preparation Overall bowel preparation quality improved significantly (P ⬍ .001) in the post-SDP group (Figure 1). The improvement was noted mainly in patients rated with good to excellent preparations (34.9%-53.9%), at the expense of those rated with fair to adequate preparations (54.3%-37.8%), and to a lesser degree in those with poor to inadequate preparations (10.6%-8.3%). The quality of bowel preparation after the implementation of SDP improved in both men and women, but the effect was statistically significant only in women; poor preparation decreased from 11.4% to 7.8% (P ⬍ .002) in women and from 11.3% to 10.1% (P ⫽ .4) in men.

Cecal intubation rate Colonoscopy was completed in 5492 patients in the pre-SDP period (12 months) and 2523 patients in the post-SDP period (6 months) for all indications. After the application of exclusion criteria, there were 3560 patients in the pre-SDP group and 1615 patients in the postSDP group. The pre-SDP and post-SDP patient groups were similar in age, body mass index, and sex (Table1). The mean (SD) ages of patients were 62 (12) and 61 (12) years, respectively, in the pre-SDP and post-SDP groups (Table 1). As expected, SDP use increased significantly www.giejournal.org

The cecal intubation rate (colonoscopy completion rate) increased from 93.6% in the pre-SDP group to 95.5% in the post-SDP group (P ⫽ .008). As expected, a significantly higher proportion of patients with incomplete colonoscopy had a poor preparation (32.8% vs 9.2%, P ⫽ .001) compared with those with complete colonoscopy.

Polyp and adenoma detection rates The PDR improved significantly in the post-SDP group compared with the pre-SDP group (44.1%-49.5%; P ⬍ Volume 76, No. 3 : 2012 GASTROINTESTINAL ENDOSCOPY 605

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TABLE 2. Colonoscopy quality measures

TABLE 3. ADR for each endoscopist present in both study periods

Before After split P split dose dose value Endoscopist

Before splitdose ADR % (n) 1 year

After splitdose ADR % (n) 6 months

% change

8.3

A

17.5 (10/57)

47.6 (20/42)

⫹ 30.1

54.5

37.8

B

17.7 (11/62)

22.7 (10/44)

⫹ 5.0

Good/excellent

34.9

53.9

C

13 (3/23)

36.1 (13/36)

⫹ 23.1

Colonoscopy completion rate (%)

93.6

95.5

D

31.1 (69/222)

26.4 (29/110)

⫺ 4.7

E

20.3 (40/197)

33.3 (14/42)

⫹ 13.0

F

21.1 (50/237)

19.1 (13/68)

⫺ 2.0

G

39.9 (143/358)

46.2 (54/117)

⫹ 6.3

H

21.5 (72/335)

30.4 (51/168)

⫹ 8.9

I

21.5 (31/144)

24.3 (9/37)

⫹ 2.8

J

33.2 (91/274)

41.7 (58/139)

⫹ 8.5

K

21.8 (34/156

28.8 (30/104)

⫹ 7.0

L

40.4 (136/337)

37.8 (79/209)

⫺ 2.6

M

28% (7/25)

12.9% (4/31)

⫺ 15.1

Preparation quality (%)

—

—

Poor/inadequate

10.6

Adequate

⬍ .001

.008

Withdrawal time (min)

11.6 (7.7) 15.3 (11.1) ⬍ .001

Total colonoscopy time (min)

20.6 (11.6) 21.0 (10.5)

.265

44.1

49.5

⬍ .001

Men

52.0

53.4

.5

Women

36.1

45.6

⬍ .001

26.7

31.8

⬍ .001

Men

33

36

.15

Women

20

28

⬍ .001

Patients with at least 1 adenoma 10 mm or more (%)

6.7

8.2

.04

Patients with at least 1 SSA (%)

3.3

Polyp detection rate total (%)

Adenoma detection rate total (%)

3.4

.9

SSA, Sessile serrated adenoma.

.001). Likewise, the ADR increased from 26.7% in the pre-SDP group to 31.8% in the post-SDP group (P ⬍ .001). Although PDR and ADR both improved numerically, the effect was significant only in women (Table 2). After sex, age, and body mass index were controlled for, the odds of detecting an adenoma in the post-SDP group were significantly higher than in the pre-SDP group (OR 1.32; 95% CI 1.16, 1.51). The proportion of patients with at least 1 large adenoma (10 mm or more in size) improved from 6.7% to 8.2% (P ⫽ .04) after the implementation of SDP. The proportion of patients with at least 1 sessile serrated adenoma was similar in the pre-SDP and post-SDP periods (3.3%-3.4%, P ⫽ .9). Three endoscopists from the pre-SDP period left the institution and were replaced by 5 other endoscopists in the post-SDP period. Table 3 summarizes the ADRs of the 13 endoscopists who were present for both the pre-SDP and post-SDP periods; 9 showed an improvement in their ADRs in the post-SDP period. The mean ADR of these 13 endoscopists improved from 26.6% to 32% (P ⬍ .001; odds ratio 1.30; 95% confidence interval 1.13, 1.49) after imple606 GASTROINTESTINAL ENDOSCOPY Volume 76, No. 3 : 2012

ADR, Adenoma detection rate.

TABLE 4. ADR for each endoscopist present in only 1 study period Before split-dose ADR (%)

After split-dose ADR (%)

N

18.7

—

O

24.7

—

P

27.2

—

Q

—

19.5

R

—

33.0

S

—

24.6

T

—

27.1

U

—

37.8

Endoscopist

ADR, Adenoma detection rate.

mentation of SDP. Table 4 summarizes the ADRs of endoscopists who were present during only 1 study period.

Quality measures between first and last 6 months of pre-SDP period The quality of the preparation and the ADR were not different in patients undergoing colonoscopy in the first and the last 6 months of the pre-SDP period; however, the PDR was lower in patients undergoing colonoscopy in the last 6 months of the pre-SDP period (Table 5). www.giejournal.org

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TABLE 5. Quality measures between first and last 6 months of pre-SDP period First 6 Last 6 P months months value Poor/inadequate preparation 11.9%

10.7%

.2

Adenoma detection rate

25.4%

24.4%

.4

Polyp detection rate

43.7%

40.5%

.03

SDP, Split-dose preparation.

Quality measures between patients taking split versus nonsplit preparation after implementation of SDP After implementation of the SDP regimen, 74% (n ⫽ 1165) of patients consumed the 4 L PEG (72%) or MoviPrep (28%) following the SDP instructions, and 26% (n ⫽ 411) of patients consumed the entire preparation the night before during the study period. A majority (76%) of patients who took the nonsplit preparation underwent colonoscopy in the morning. The quality of preparation was significantly better (P ⬍ .001) in patients who took the SDP than in patients who had not. Specifically, the proportion of patients with good to excellent preparations increased from 45.5% to 57.3%. In addition, patients with a poor or inadequate preparation decreased from 12.4% to 6.6%, and those with a fair to adequate preparation decreased from 42.1% to 36.1%. However, the colonoscopy completion rates (95.6%-95.5%, P ⫽ .9), PDR (48.4%49.6%, P ⫽ .6), and ADR (29.9%-49.6%, P ⫽ .4) were not significantly different between these groups.

DISCUSSION Colonoscopy is the best tool to inspect the colonic mucosa and is considered the criterion standard for screening and surveillance of colorectal cancer. In spite of the success of screening colonoscopy in reducing the rates of colorectal cancer, there is growing concern about missed lesions on colonoscopy, especially on the right side of the colon. This concern has been fueled by reports in recent years suggesting the development of “interval cancers” after colonoscopy caused by missed lesions12,13 and by reports of decreased protection from proximal colon cancer mortality.14 In response, considerable efforts have been made to improve the effectiveness of colonoscopy. Measures of quality have been developed, including withdrawal time, PDR, and, most importantly, ADR.15,16 Endoscopists increasingly are provided feedback and education to improve their performance in colonoscopy by these measures.17,18 However, all of these efforts are dependent on effective bowel preparation. Good-quality bowel preparation is necessary to allow thorough inspection of the colonic mucosa and reliable detection of mucosal lesions. www.giejournal.org

Several randomized studies and a recent metaanalysis7,19,20 have found that SDP improved the quality of bowel preparation and patient compliance compared to with standard PEG bowel preparations. Our study strengthens these findings by demonstrating a significant improvement in overall quality of the bowel preparation after the initiation of an SDP protocol. Interestingly, however, the effects of SDP on other quality indicators of colonoscopy have not been reported. To our knowledge, this study is the first to demonstrate significant improvement in colonoscopy completion rate, PDR, and ADR after the system-wide implementation of an SDP as the primary choice in an active colonoscopy practice. The implementation of SDP thereby has the potential to improve both the quality and the effectiveness of colonoscopy. The significant increase in ADR observed after SDP in our study was largely due to a larger effect in women (20% vs 28%, P ⬍ .001). Although ADR increased in men, the difference did not reach statistical significance in our study (33% vs 36%, P ⫽ .15). The smaller effect on ADR in men might be associated with a higher baseline ADR or the smaller improvements in bowel preparations with SDP in men. It is worth noting that our overall ADRs for men (33%) and women (20%) were above the published benchmarks (25% in men and 15% in women) before implementation of the SDP. We also found significantly increased withdrawal time in the post-SDP period, whereas total colonoscopy time remained the same. The increase in withdrawal time might be explained by the increased detection of polyps in the post-SDP period and by the resultant additional time taken to remove polyps. It is also possible that the endoscopists became more aware of the importance of withdrawal time after the implementation of SDP. The primary goal of our study was to evaluate the outcomes related to system-wide implementation of SDP for colonoscopy in a practice setting. The actual use of SDP was individualized to the patients’ particular needs; therefore, 26% of patients did not use SDP. The common reasons for not using SDP during the study period were long-distance travel, early-morning colonoscopy, and conflicting appointments. This observation emphasizes the importance of patient-specific factors in the system-wide implementation of bowel preparations in a practice setting. The majority (76%) of patients who did not use SDP had their colonoscopy in the morning, which may be one reason for the lack of difference in colonoscopy completion rates, PDRs, and ADRs despite improvement in the overall quality of the preparation in the SDP group compared with the non-SDP group. Other investigators have reported higher rates of colonoscopy completion and adenoma detection in the morning colonoscopies.21,22 Unlike prior SDP regimens using 4-L PEG solutions, in which patients were instructed to take half of the solution the night before and the other half on the morning of the procedure,19,20,23,24 we used a modified schedule to reduce Volume 76, No. 3 : 2012 GASTROINTESTINAL ENDOSCOPY 607

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the inconvenience to the patient in the morning. With this modified SDP regimen, patients were instructed to take 3 L of solution the night before and a lower volume (1 L) the morning of the procedure. The favorable results of our study support the benefits of this modified SDP regimen adopted at our institution. The limitations of our study include the following: the design was retrospective, not all endoscopists were the same for both periods, and the study was conducted over 2 different time periods. It is possible that endoscopists in the post-SDP period better understood the importance of withdrawal time, polyp detection, and right-sided flat lesions, which might have played a role in improved polyp and adenoma detection rates. However, no feedback was given to endoscopists regarding their completion rates and ADRs during either of the study periods. Furthermore, a lack of any improvement in the quality measures from the first to the last 6 months of the pre-SDP period and a significant improvement in these measures after the implementation of SDP supports the role of SDP in improving these outcomes.

CONCLUSIONS We have demonstrated, for the first time to our knowledge, that system-wide implementation of an SDP as the primary choice for colonoscopy significantly improved both PDRs and ADRs as well as colonoscopy completion rates. These results confirm the benefit of an SDP and the importance of bowel preparation in the detection of colon polyps. REFERENCES 1. Hawes RH, Lowry A, Deziel D. A consensus document on bowel preparation before colonoscopy: prepared by task force from the American Society of Colon Rectal Surgeons (ASCRS), the American Society for Gastrointestinal endoscopy (ASGE), and the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES). Gastrointest Endosc 2006; 63:894-909. 2. Rex DK, Imperiale TF, Latinovich DR, et al. Impact of bowel preparation on efficiency and cost of colonoscopy. Am J Gastroenterol 2002;97: 1696-700. 3. Rex DK, Petrini JL, Baron TH, et al. Quality indicators of colonoscopy. Am J Gastroenterol 2006;101:873-85. 4. Harewood GC, Sharma VK, de Garmo P. Impact of colonoscopy preparation quality on detection of suspected colonic neoplasia. Gastrointest Endosc 2003;58:76-9. 5. Ben-Horin S, Bar-Meir S, Avidan B. The impact of colon cleanliness assessment on endoscopists’ recommendations for follow-up colonoscopy. Am J Gastroenterol 2007;102:2680-5.

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6. Rex DK, Johnson DA, Anderson JC, et al. American College of Gastroenterology guidelines for colorectal cancer screening 2009. Am J Gastroenterol 2009;104:739-50. 7. Kilgore TW, Abdinoor AA, Szary NM, et al. Bowel preparation with splitdose polyethylene glycol before colonoscopy: a meta-analysis of randomized controlled trials. Gastrointest Endosc 2011;73:1240-5. 8. Aronchick CA, Lipshutz WH, Wright SH, et al. A novel tableted purgative for colonoscopic preparation: efficacy and safety comparisons with Colyte and Fleet Phospho-Soda. Gastrointest Endosc 2000;52:346-52. 9. Lilliefors HW. On the Kolmogorov-Smirnov tests for normality with mean and variance unknown. J Am Stat Assoc 1967;62:399-402. 10. Liang KY, Zeger SL. Longitudinal data analysis using generalized linear models. Biometrika 1986;73:13-22. 11. Hanley JA, Negassa A, Edwardes MD, et al. Statistical analysis of correlated data using generalized estimating equations: an orientation. Am J Epidemiol 2003;157:364-75. 12. Bressler B, Paszat LF, Chen Z, et al. Rates of new or missed colorectal cancers after colonoscopy and their risk factors: a population-based analysis. Gastroenterology 2007;132:96-102. 13. Singh H, Nugent Z, Demers AA, et al. Rate and predictors of early/missed colorectal cancers after colonoscopy in Manitoba: a population based study. Am J Gastroenterol 2010;105:2588-96. 14. Baxter NN, Goldwasser MA, Paszat LF, et al. Association of colonoscopy and death from colorectal cancer. Ann Intern Med 2009;150:1-8. 15. Rex DK. Maximizing detection of adenomas and cancers during colonoscopy. Am J Gastroenterol 2006;101:2866-77. 16. Kaminski MF, Regula J, Kraszewska E, et al. Quality indicators for colonoscopy and the risk of interval cancer. N Eng J Med 2010;362:1795-803. 17. Harewood GC, Petersen BT, Ott BJ, et al. Prospective assessment of the impact of feedback on colonoscopy performance. Aliment Pharmacol Ther 2006;24:313-8. 18. Barclay RL, Vicari JJ, Greenlaw RL, et al. Effect of a time-dependent colonoscopic withdrawal protocol on adenoma detection during screening colonoscopy. Clin Gastroenterol Hepatol 2008;6:1091-8. 19. 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;62:213-8. 20. Marmo E, Rotondano G, Riccio G, et al. Effective bowel cleansing before colonoscopy: a randomized study of split-dosage versus non-split dosage regimens of high-volume versus low-volume polyethylene glycol solutions. Gastrointest Endosc 2010;72:313-20. 21. Sanaka MR, Shah N, Mullen KD, et al. Afternoon colonoscopies have higher failure rates than morning colonoscopies. Am J Gastroenterol 2006;101:2726-30. 22. Sanaka MR, Deepinder F, Thota PN, et al. Adenomas are detected more often in morning than in afternoon colonoscopy. Am J Gastroenterol 2009;104:1659-64. 23. Abdul-Baki H, Hashash JG, Elhajj II, et al. A randomized, controlled, double-blind trial of the adjunct use of tegaserod in whole-dose or split dose polyethylene glycol electrolyte solution for colonoscopy preparation. Gastrointest Endosc 2008;68:294-300. 24. Park SS, Sinn DH, Kim YH, et al. Efficacy and tolerability of split-dose magnesium citrate: low-volume (2 liters) polyethylene glycol vs. single-or split-dose polyethylene glycol for bowel preparation for morning colonoscopy. Am J Gastroenterol 2010;105:1319-26.

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Appendix A. Bowel Cleansing Scale Definitions: Modified Aronchick scale Rating

Description

Poor

Repreparation required - Large amount of fecal residue precludes a complete examination.

Inadequate

Inadequate but examination completed - Enough feces or turbid fluid to prevent a reliable examination, less than 90% mucosa seen.

Fair Adequate

Moderate amount of stool that can be cleared with suctioning permitting adequate evaluation of entire colonic mucosa, greater than 90% mucosa seen.

Good

Small amount of turbid fluid without feces not interfering with examination, greater than 90% mucosa seen.

Excellent

Small amount of clear liquid with clear mucosa seen, greater than 95% mucosa seen.

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