Download One small step for colonoscopy, one giant leap for bowel preparation

EDITORIAL
One small step for colonoscopy, one giant leap for bowel preparation
The adenoma is the target lesion of screening colonoscopy. In fact, adenoma detection is thought to be the
most important indicator of high-quality colonoscopy.
This belief is based on data demonstrating that the adenoma detection rate (ADR) is a valid measure of the effectiveness of colonoscopy in colorectal cancer prevention.
In a study of screening colonoscopy that used a highquality national database, Kaminski et al1 demonstrated
that endoscopists with an ADR less than 20% were more
likely to observe an interval cancer arise after screening
colonoscopy than were endoscopists with an ADR of 20%
or more. The wide variability in ADRs among endoscopists, as much as 10-fold, is proof that there is room for
meaningful improvement in the performance of colonoscopy. For example, studies from diverse settings indicate
that colonoscopy is less effective in the prevention of
proximal cancers compared with distal cancers.2 Furthermore, although the mortality rate from colorectal cancer in
the National Polyp Study was reduced by 53% during a
median followup time of almost 16 years, 12 patients died
of colorectal cancer while under surveillance.3 An improvement in our understanding of the reasons for such
variance in ADRs should make possible further improvements in the quality and effectiveness of colonoscopy.
From an operational perspective, ADR may be affected
by endoscopist-related, technical, and patient-related factors. A well-designed study from Berlin used a 2-level
mixed linear model to more sharply define the characteristics that affect ADR.4 A total of 12,134 consecutive
colonoscopies, performed by 21 experienced colonoscopists during an 18-month period, were prospectively
assessed. Cecal intubation rates and the number of
continuing medical education points were the only
endoscopist-related variables that correlated with the
ADR, whereas the annual volume of screening colonoscopies, withdrawal time, and lifetime experience performing
colonoscopy did not correlate with the ADR. Relative to
instrument technology, no difference in ADR was observed between the latest generation of instruments and
those 1 generation removed, although the use of older
colonoscopes did result in lower ADRs. Among patientrelated variables, age, sex, and the quality of bowel preparation were significantly correlated with ADR.
Copyright © 2012 by the American Society for Gastrointestinal Endoscopy
0016-5107/$36.00
http://dx.doi.org/10.1016/j.gie.2012.05.017
www.giejournal.org
The observation that polyp and adenoma detection are
affected by the quality of bowel preparation comes as little
surprise to most endoscopists. Two recent studies examined the effect of an inadequate bowel preparation on
missed lesions.5,6 These investigators retrospectively analyzed the findings of repeated colonoscopies performed
within 3 years of index examinations that were incomplete
because of poor preparation. Lesions detected only during
the second examination were deemed “missed lesions.”
The per-patient rates of missed adenomas were 25% and
33%, respectively. More impressive, however, were the
per-adenoma miss rates of 42% and 48%, respectively.
Considering that nearly 1 in 4 colonoscopies have a bowel
preparation that is adjudged to be inadequate, it is likely
that many adenomas are missed because of poor-quality
bowel preparation.
Considering that nearly 1 in 4 colonoscopies
have a bowel preparation that is adjudged to
be inadequate, it is likely that many adenomas
are missed because of poor-quality bowel
preparation.
The concept of a split-dose bowel preparation was first
proposed in the mid-1990s by Church, who questioned
the time-tested tradition of completing the bowel preparation on the evening before examination and speculated
that there is a window of time after gut lavage for optimal
cleansing of the bowel.7 Today, there is considerable evidence that a split-dose preparation, with at least part of
the preparation consumed within several hours of the
examination, provides ideal bowel cleansing, especially
within the proximal colon, where flat adenomas and
serrated lesions are easily obscured by small amounts
of residual debris. A meta-analysis of 5 randomizedcontrolled trials involving polyethylene glycol (PEG)based preparations found that split dosing resulted in
improved colon cleansing and patient satisfaction when
compared with a preparation taken the day before examination.8 Additionally, several studies have demonstrated
increased rates of detection for flat and neoplastic lesions
with a split-dose regimen compared with the same purgative administered the day before colonoscopy (also described as a 1-day regimen).9,10 It remained unproven,
Volume 76, No. 3 : 2012 GASTROINTESTINAL ENDOSCOPY 609
Editorial
however, whether a split-dose regimen would improve
ADRs compared with a standard bowel preparation.
Accordingly, in this month’s issue of Gastrointestinal
Endoscopy, Gurundu et al11 report the results of a retrospective analysis of an endoscopic database from an academic center that compared ADRs in 2 patient cohorts.
Group 1, composed of 3560 patients, underwent colonoscopy after a 1-day bowel preparation during a 12-month
period in 2009. Group 2 was composed of 1615 patients
who received a split-dose bowel preparation and underwent colonoscopy during a 6-month period that ended in
March 2011. It is noteworthy that the study periods were
noncontemporaneous. Furthermore, although all patients
received PEG lavage, some individuals within each group
received 4 L of PEG solution, whereas others were given 2
L of PEG mixed with ascorbate and sodium sulfate
(MoviPrep, Salix Pharmaceuticals, Morrisville, NC). Patients assigned to the 1-day arm were instructed to complete their preparation, either 4 L or 2 L of PEG, the
evening before colonoscopy. Patients in the split-dose
group drank part of their preparation, either 3 L or 1 L of
PEG, starting at 6 PM the evening before examination and
they completed the preparation at least 4 hours before the
procedure. A total of 21 endoscopists performed examinations: 13 who were present for both study periods, 3
who participated only during period 1 (1-day preparation), and 5 who participated only during period 2 (splitdose preparation). High-definition colonoscopes were
standard during all procedures, and most procedures were
performed under moderate sedation.
The study’s primary endpoints were polyp detection
rates and ADRs, and the secondary goals were quality of
the preparation and cecal intubation rates. The results
showed that the polyp detection rates (44.1% vs 49.5%,
P ⬍ .0010) and ADR (26.7% vs 31.8%, P ⬍ .001) were
significantly greater during period 2 (split-dose) than during period 1 (1 day). Of the 13 endoscopists who were
present for both study periods, the mean ADR improved
from 26.6% to 32% (P ⬍ .001, odds ratio 1.3, 95% confidence interval 1.13-1.49) after the split-dose regimen was
implemented, and 9 endoscopists showed an improvement in their individual ADR during the split-dose period.
The overall bowel preparation quality as well as the cecal
intubation rate improved after the introduction of a splitdose preparation.
Because this was a retrospective study, there are several
limitations to the study’s findings. For instance, it is impossible to know whether the improvement in ADR between
periods 1 and 2 might have resulted from an improvement
in endoscopic skills, longer withdrawal times, greater
awareness of flat and serrated lesions, or some combination of these factors. In addition, the turnover among
participating endoscopists could have affected the observed ADRs. Although these and other issues require
evaluation in subsequent studies, the study by Gurundu et
610 GASTROINTESTINAL ENDOSCOPY Volume 76, No. 3 : 2012
Cohen
al provides further proof of the benefits of split-dose
bowel preparation.
Several investigators have attempted to quantify the
ideal time interval between the last dose of purgative and
the start of colonoscopy. In an observational study, the
best bowel preparations were observed in study participants who consumed their second dose of preparation 3
to 5 hours before colonoscopy.12 Similar findings were
observed in a prospective study that observed betterquality bowel preparations among those who began their
preparation less than 7 hours and completed their preparation less than 4 hours before colonoscopy.13 On the
basis of the findings of these and other published studies,
it seems reasonable to conclude that the ideal window of
opportunity for achieving an optimal bowel preparation is
4 to 7 hours before the start of examination.
Few important advances in the area of bowel preparation have occurred during the past 30 years. Arguably, the
most notable advance was the development of an
electrolyte-balanced lavage solution.14 The split-dose
bowel regimen warrants recognition because it improves
the quality of colonoscopy with little additional effort or
expense. Some endoscopists have been reluctant to implement a split-dose regimen, however, because of concerns over patient tolerance, patient unwillingness to
awaken at night to complete the preparation, longdistance traveling by patients between home and the endoscopy center, or preprocedure fasting guidelines. Randomized studies and a meta-analysis confirm that patient
tolerance is greater with a split-dose regimen than with a
1-day regimen.15 Anectodotally, we have observed that
compliance with a split-dose regimen is excellent when
patients understand that its purpose is to improve the
quality of examination. There will always be some patients
who are unwilling to awaken from sleep to complete their
preparation. In fact, 26% of patients assigned to the splitdose group in the study by Gurundu et al11 consumed
their entire preparation the evening before the colonoscopy. As expected, the quality of the bowel preparation
was significantly better in patients who completed the
split-dose regimen than in patients who took the entire
preparation the evening before examination. The best
option for patients who are either unable or unwilling to
complete a split-dose preparation during the night is to
schedule them for afternoon colonoscopy. With regard
to a split-dose bowel regimen and precolonoscopy fasting,
the American Society of Anesthesiology guidelines stipulate that a patient must be fasting at least 2 hours for clear
liquids.16 Consequently, patients should begin their second dose 4 to 7 hours before examination and should be
fasting for at least 2 hours.
If your patients are like mine, you’re accustomed to
hearing them ask, “If they can put a man on the moon,
why can’t they make a better bowel preparation?” I usually
respond by explaining that although preparations have
improved, the changes may not be evident to them. The
www.giejournal.org
Cohen
Editorial
split-dose bowel regimen is a case in point. Although its
importance pales by comparison with the legendary first
walk on the moon by Neil Armstrong almost 50 years ago,
the split-dose regimen represents a significant advance for
colonoscopy and colon cancer prevention. The study by
Gurundu et al11 confirms that shortening the “runway
time” enhances adenoma detection, thereby reducing the
risk of an interval carcinoma. The time has come for all
endoscopists to assess the quality of their colonoscopies
and to decide whether a split-dose bowel regimen might
help to improve their ADRs.
5.
6.
7.
8.
9.
DISCLOSURE
The author has disclosed no financial relationships
relevant to this publication.
Lawrence B. Cohen, MD
Department of Medicine (Gastroenterology)
The Mount Sinai School of Medicine
New York, New York, USA
Abbreviations: ADR, adenoma detection rate; PEG, polyethylene glycol.
10.
11.
12.
13.
REFERENCES
14.
1. Kaminski MF, Regula J, Kraszewska E, et al. Quality indicators for colonoscopy and the risk of interval cancer. N Engl J Med 2010;362:1795-803.
2. Baxter NN, Goldwasser MA, Paszat LF, et al. Association of colonoscopy
and death from colorectal cancer. Ann Intern Med 2009;150:1-8.
3. Zauber AG, Winawer SJ, O’Brien MJ, et al. Colonoscopic polypectomy
and long-term prevention of colorectal-cancer deaths. N Engl J Med
2012;366:687-96.
4. Adler A, Wegscheider K, Lieberman DA, et al. Factors determining the
quality of screening colonoscopy: a prospective study on adenoma de-
www.giejournal.org
15.
16.
tection rates, from 12,134 examinations (Berlin colonoscopy project 3,
CECOP-3). Gut 2012; ePub.
Lebwohl B, Kastrinos F, Glick M, et al. The impact of suboptimal bowel
preparation on adenoma miss rates and the factors associated with
early repeat colonoscopy. Gastrointest Endosc 2011;73:1207-14.
Chokshi RV, Hovis CE, Hollander T, et al. Prevalence of missed adenomas
in patients with inadequate bowel preparation on screening colonoscopy. Gastrointest Endosc 2012;75:1197-203.
Church JM. Effectiveness of polyethylene glycol antegrade gut lavage
bowel preparation for colonoscopy: timing is the key! Dis Colon Rectum
1998;41:1223-5.
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.
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 trial. World J Gastroenterol 2006;12:6161-6.
Chiu HM, Lin JT, Wang HP, et al. The impact of colon preparation timing
on colonoscopic detection of colorectal neoplasms: a prospective
endoscopist-blinded randomized trial. Am J Gastroenterol 2006;101:
2719-25.
Gurundu SR, Ramirez FC, Harrison E, et al. Increased adenoma detection
rate with system-wide implementation of a split-dose preparation for
colonoscopy. Gastrointest Endosc 2012;76:603-8.
Seo EH, Kim TO, Park MJ, et al. Bowel preparation with split-dose polyethylene glycol before colonoscopy: a meta-analysis of randomized
controlled trials. Gastrointest Endosc 2012;75:583-90.
Eun CS, Han DS, Hyun YS, et al. The timing of bowel preparation is more
important than the timing of colonoscopy in determining the quality of
bowel cleansing. Dig Dis Sci 2011;56:539-44.
Davis GR, Santa Ana CA, Morawski SG, et al. Development of a lavage
solution associated with minimal water and electrolyte absorption or
secretion. Gastroenterology 1980;78:991-5.
Cohen LB. Split dosing of bowel preparations for colonoscopy: an analysis of its efficacy, safety, and tolerability. Gastrointest Endosc 2010;72:
406-12.
Apfelbaum JL, Caplan RA, Connis RT, et al. Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of
pulmonary aspiration: application to healthy patients undergoing elective procedures. Anesthesiology 2011;114:495-511.
Volume 76, No. 3 : 2012 GASTROINTESTINAL ENDOSCOPY 611