Quality of bowel cleansing for afternoon colonoscopy is influenced by time of administration.

Abstract

Afternoon colonoscopies have higher failure rates, due primarily to poor bowel cleansing. Hypothesizing that the time of administration influences the quality of bowel cleansing, we compared the quality of bowel cleansing for afternoon colonoscopies in patients completing the preparation on the same day vs. the day before colonoscopy.
Data on afternoon colonoscopies performed between July 2008 and April 2009 were obtained from our endoscopy database. Bowel-preparation options were 4L polyethylene glycol (PEG) or 2L PEG plus four bisacodyl tablets. Patients could take the preparation on the same day as the procedure or the day prior, or consume half the day prior and half the same day. Bowel-cleansing quality was reported as excellent, good, fair-adequate, inadequate, or poor. Multivariate logistic regression analysis evaluated the association between quality of bowel cleansing and time of preparation administration.
Bowel cleansing was reported as poor or inadequate in 7% of patients, adequate in 63%, and good or excellent in 30%. Afternoon colonoscopies using the same-day 4L PEG preparation were 3.14 times more likely to have fair-adequate cleansing and 7.03 times more likely to have good or excellent cleansing when compared with the other options.
Same-day 4L PEG preparation for afternoon colonoscopy confers better-quality cleansing than prior-day preparation.

Full text

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Introduction
Colonoscopy is a valuable diagnostic and therapeutic clinical
examination and is routinely performed in both the morning
and the afternoon. Availability of the procedure throughout the
work day allows efficient deployment of expensive equipment,
health-care facilities, and the entire health-care team. Recently,
studies have reported higher failure rates and lower sensitivity
for the detection of adenomas among patients who performed
their bowel preparation the day prior to their colonoscopy and
who underwent colonoscopy in the afternoon of the following
day (1,2). Poor bowel preparation is considered to be the main
reason for these results (1–3). Among the many factors involved
in successful completion of a colonoscopy, the quality of bowel
preparation, the timing of colonoscopy, and the training of the
endoscopist are the three modifiable factors that might improve
the successful completion of the study (4–9). We have previously
reported that afternoon colonoscopy was associated with poor-
quality bowel preparations and lower cecal intubation rates com-
pared with colonoscopy performed in the morning (10).
Mixed results have emerged from several small studies that have
evaluated the quality of bowel preparation completed on the day
prior to colonoscopy compared with bowel preparation completed
on the same day as colonoscopy (3,11,12). No large studies have been
reported comparing the efficacy of same-day vs. prior-day bowel
cleansing for afternoon colonoscopy. Thus, we performed a large ret-
rospective review of our patient population to evaluate the quality of
colon preparation, cecal intubation rates, and polyp detection rates
in patients who underwent same-day bowel preparation and after-
noon colonoscopy, compared with patients who underwent bowel
preparation on the previous day. We hypothesized that the same-day
bowel preparation would be associated with improved quality of
the bowel preparation for afternoon colonoscopy as compared with
bowel preparation completed on the day prior to colonoscopy.
Quality of Bowel Cleansing for Afternoon
Colonoscopy Is Influenced by Time of
Administration
Suryakanth R. Gurudu, MD1, Shiva Ratuapli, MD1, Russell Heigh, MD1, John DiBaise, MD1, Jonathan Leighton, MD1 and Michael Crowell, PhD1
objectives:
Afternoon colonoscopies have higher failure rates, due primarily to poor bowel cleansing.
Hypothesizing that the time of administration influences the quality of bowel cleansing, we compared
the quality of bowel cleansing for afternoon colonoscopies in patients completing the preparation on
the same day vs. the day before colonoscopy.
methods:
Data on afternoon colonoscopies performed between July 2008 and April 2009 were obtained from
our endoscopy database. Bowel-preparation options were 4L polyethylene glycol (PEG) or 2L PEG plus
four bisacodyl tablets. Patients could take the preparation on the same day as the procedure or the
day prior, or consume half the day prior and half the same day. Bowel-cleansing quality was reported
as excellent, good, fair–adequate, inadequate, or poor. Multivariate logistic regression analysis
evaluated the association between quality of bowel cleansing and time of preparation administration.
results:
Bowel cleansing was reported as poor or inadequate in 7% of patients, adequate in 63%, and good or
excellent in 30%. Afternoon colonoscopies using the same-day 4L PEG preparation were 3.14 times
more likely to have fair–adequate cleansing and 7.03 times more likely to have good or excellent
cleansing when compared with the other options.
conclusions: Same-day 4L PEG preparation for afternoon colonoscopy confers better-quality cleansing than prior-
day preparation.
Am J Gastroenterol 2010;105:2318–2322; doi:10.1038/ajg.2010.235
1division of Gastroenterology and hepatology, mayo clinic Arizona, scottsdale, Arizona, usA. Correspondence: suryakanth r. Gurudu, md, division of
Gastroenterology and hepatology, mayo clinic Arizona, 13400 east shea boulevard, scottsdale, Arizona 85259, usA. e-mail: Gurudu.suryakanth@mayo.edu

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preparation was rated by endoscopists on the basis of five pre-
specified criteria: excellent, good, fair–adequate, inadequate, and
poor (Table 1).
Statistical comparisons were planned a priori to address the
primary hypothesis that same-day bowel cleansing would be
associated with improved quality of bowel preparation for after-
noon colonoscopy compared with bowel preparation completed
on the day prior to colonoscopy. We tested the hypothesis using
multivariable logistic regression analyses controlling for sex, age,
body mass index (BMI), and total quantity of bowel preparation
consumed by the patient. Demographics and clinical character-
istics between groups were evaluated by χ2 tests and unadjusted
univariate logistic regression to evaluate the strength of associa-
tion between each predictor and the criterion variables.
Point estimates and interval estimates are reported for all
descriptive data and presented as means or proportions and the
s.d. or 95% confidence interval (CI). Results of univariate and
multivariate logistic regression are presented as odds ratios (ORs)
and 95% CIs. Statistical significance was defined as P <0.05. All
analyses were conducted with the SPSS software package (version
15; SPSS, Chicago, IL).
Results
Baseline characteristics. Afternoon colonoscopy was completed
in 1,345 patients. The mean age of the sample was 61 (s.d. 14)
years, and 52% were male. The quality of the bowel preparation
was not significantly different across sexes or ages. A significant
inverse linear effect was found between quality of bowel prepa-
ration and BMI (Table 2). The most common indications for
colonoscopy were screening or surveillance (61%), anemia/bleed-
ing (11%), diarrhea (8%), abdominal pain (4%), colitis (3%), con-
stipation (2%), and other (11%). The bowel-cleansing regimens
included 4L PEG am in 226 patients (17%), 2L PEG am in 39
patients (3%), 2L PEG pm/am (split dose) in 48 patients (3.5%), 2L
PEG pm in 656 patients (48.5%), and 4L PEG pm in 376 patients
(28%). The recommended quantity of preparation was ingested by
95% of patients (1,276/1,345). No episodes of bronchoaspiration
Methods
The protocol was approved by the Institutional Review Board at
Mayo Clinic. The electronic medical records of all endoscopies
performed at Mayo Clinic Arizona from July 2008 to April 2009
were evaluated to identify consecutive patients who underwent
afternoon colonoscopy. Afternoon colonoscopy was defined as
those procedures that were performed after 1:00 pm. All colonos-
copies were performed by the attending gastroenterologists or by
the fellows under direct supervision of the attending gastroen-
terologist. Each attending performed colonoscopies in half-day
blocks, with the afternoon block starting at 1:00 pm. All colonos-
copies, both complete and incomplete, were included regardless
of indication. Colonoscopy was determined as complete when
the cecum was intubated and the appendiceal orifice and ileoce-
cal valve were identified.
Data on patient demographics, indication for colonoscopy,
type of bowel preparation used, timing of completed prepara-
tion, time of procedure, quality of bowel cleansing, extent of
examination (cecal intubation), and number of polyps detected
were obtained and analyzed.
Before the procedure, verbal and printed information regard-
ing the bowel-preparation protocol was provided to the patients
by the scheduling staff. Patients were instructed to avoid eat-
ing a high-fiber diet for 2 days before taking the bowel prepa-
ration and to drink only clear liquids for the entire day prior
to colonoscopy. The bowel-preparation options were 4L poly-
ethylene glycol (PEG) electrolyte solution (GoLYTELY, Colyte,
NuLYTELY) or 2L PEG (HalfLytely) plus four bisacodyl tablets.
Patients were given the option of taking the preparation on the
same day as the procedure or the day prior to the procedure, or,
if the 4L PEG were selected, to split the dose, consuming half
the day prior and the remaining half the same day as the pro-
cedure. Ingestion of preparation was started at 7:00 pm for the
prior-day bowel-preparation schedule, and at 5:00 am for the
same-day schedule, and the patients were instructed to drink
8 ounces of the preparation every 15 minutes until completion.
The resulting bowel-cleansing regimens included same-day
morning 4L PEG (4L PEG am), same-day morning 2L PEG plus
4 bisacodyl (2L PEG am), split dose (2L PEG pm/am), prior-day
evening 2L PEG plus 4 bisacodyl (2L PEG pm), and prior-day
evening 4L PEG (4L PEG pm). The endoscopy nurse preparing
the patient for the procedure documented the type and timing
of the colonoscopy bowel cleansing.
Patients were allowed to drink clear liquids up to 3 hours
before the procedure, after which they were kept NPO (noth-
ing by mouth). All procedures were carried out with the patient
under conscious sedation, and none required administration
of general anesthesia. The medications used for sedation were
midazolam, meperidine, and fentanyl; the choice and dosing of
the medication varied according to the endoscopist’s preference.
The quality of bowel cleansing seen during colonoscopy was
rated and recorded immediately after the colonoscopy, by the
performing endoscopist. The modified Aronchick scale was used
to document the quality of preparation (13). The quality of bowel
Table 1. Bowel-cleansing scale definitions: modified Aronchick
scale
Rating
Poor
Description
re-preparation 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 suc-
tioning permitting adequate evaluation of entire colonic
mucosa; more than 90% mucosa seen
Goodsmall amount of turbid fluid without feces not interfer-
ing with examination; more than 90% mucosa seen
excellentsmall amount of clear liquid with clear mucosa seen;
more than 95% mucosa seen

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preparation provides superior-quality bowel cleansing compared
with previous-day bowel preparation for afternoon colonoscopy.
Importantly, the association remained robust after adjustment for
important clinical variables such as age, BMI, sex, and the quan-
tity of preparation taken. The polyp detection rate did not differ
among bowel-cleansing regimens. We speculate that the lack of
differences in polyp detection may be due to the high rate of ade-
quate bowel preparations with all five regimens.
We found no difference in the quality of bowel preparation using
a split dose preparation compared to the 4L prior evening regi-
men; however, the number of patients electing this bowel cleans-
ing regimen was quite small. In contrast, two previous studies have
shown that using a split-dose preparation resulted in better quality
bowel cleansing along with higher compliance. (14, 15).
Whereas our study showed improved quality of prepara-
tion with same day administration compared with previous-day
administration, as did several other studies using different types
of bowel preparation (3,12,16–18), Gupta and associates did not
show significant differences in bowel-preparation quality (11). All
of the above-mentioned studies are limited by the relatively small
numbers of patients included. Despite the mixed findings on the
effects of these two regimens on the quality of bowel preparation,
the polyp detection rate in the majority of these studies was con-
sistent with our findings.
were recorded, including in the procedures performed in patients
taking same-day bowel preparation.
Preparation quality vs. type of preparation. A significant unad-
justed association was found between quality of bowel preparation
and type of cleansing regimen used that suggested more frequent
adequate to good/excellent preparations in the 4L PEG am group
(P = 0.005) (Figure 1). Multivariable logistic regression adjusted
for age, sex, BMI, and total preparation consumed showed that
afternoon colonoscopy following 4L PEG am was approximately
three times as likely to have fair–adequate cleansing (OR 3.14; 95%
CI, 1.19–8.31; P = 0.02) and more than seven times as likely to have
good or excellent cleansing when compared with 4L PEG pm (OR
7.03; 95% CI, 2.57–19.22; P < 0.001). No significant differences
were noted for the other bowel-cleansing regimens compared with
4L PEG pm (Table 3). A subsequent analysis demonstrated that
when all preparations were combined, bowel preparations com-
pleted on the same day as colonoscopy were more likely to have
good or excellent cleansing compared to previous-day adminis-
tration (OR 3.42; 95% CI, 1.81–6.47; P < 0.001). No significant
differences were noted between adequate cleansing and poor/
inadequate cleansing with respect to bowel-preparation day (OR
0.70; 95% CI, 0.38–1.30; P = 0.26).
Adenoma detection and colonoscopy completion. Colonoscopy
was completed successfully in 92% (1,237/1,345) of all patients.
Completion rates for all bowel preparations exceeded 90% except
for the 2L PEG am (83%). No statistically significant association was
found between preparation regimen and completeness of colonos-
copy. In addition, no significant differences in adenoma-detection
rates were found for either same-day vs. prior-day preparation dos-
ing (OR 1.17; 95% CI, 0.94–1.45; P = 0.16) or preparation quality
(OR 1.01; 95% CI, 0.84–1.22; P = 0.93).
Discussion
The existing literature on the quality of bowel preparation com-
pleted on the day prior to colonoscopy compared with bowel
preparation completed on the same day as colonoscopy has yielded
mixed results, in part because of small sample sizes (3,11,12).
The current study used a large sample size from a standardized
database. Our data demonstrate that same-day 4L PEG bowel
Preparation Type
4L PEG PM
4L PEG AM
SPLIT 2L PEG AM
2L PEG PM
0%
20%
40%
30%
50%
60%
70%
80%
90%
100%
10%
Good/excellent/adequatePoor/inadequate
Proportion of patients
Figure 1. comparison of preparation quality by type of preparation.
Table 2. Quality of bowel preparation across age, body mass index, and sex
Preparation quality
Poor/Inadequate AdequateGood/ExcellentP value
Age (y), mean (s.d.) 59 (13)62 (13)59 (15) 0.62
bmi (kg/m2), mean (s.d.)29.47 (5.52) 28.43 (5.50)27.26 (5.60) <0.001
sex0.05
Female n (%) 42 (7%)395 (61%)213 (33%)
male n (%)53 (8%)456 (66%) 186 (27%)
bmI, body mass index.

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colon. Hence, a shorter interval between completion of the bowel
preparation and the colonoscopy start time leads to better bowel-
preparation quality (12).
There are limitations to our study. First, the retrospective design
of the study is subject to confounding factors, even though efforts
were made to eliminate these by statistical methods. Second, the
quality of bowel cleansing was rated on the basis of a modification
of the Aronchick scale and, as such, has not been fully validated;
but this measurement was used consistently across preparation
groups. Third, the number of patients receiving different types of
bowel preparations was not distributed equally. This difference
was adjusted statistically. Fourth, the inclusion of both inpatient
and outpatient populations may affect bowel-preparation quality
because of the severity of underlying medical illnesses. Fifth, our
practice pattern of endoscopists performing only half-day blocks of
procedures may not be applicable to all practices. Sixth, tolerance
of the bowel preparation was not assessed and compared between
the two timing regimens. Finally, the effects of other known fac-
tors affecting colonoscopy, such as diverticulosis, chronic consti-
pation, and medications (calcium channel blockers, opioids), were
not controlled.
In conclusion, results from our study suggest that the quality
of bowel cleansing for afternoon colonoscopies is dependent on
the quantity and timing of administration of the regimen used.
Patients receiving same-day 4L PEG preparation for afternoon
colonoscopy have significantly better-quality cleansing than
patients receiving prior-day preparations. Continued efforts to
improve the quality of bowel preparation for afternoon colonos-
copy are needed to increase the effectiveness of colonoscopy.
CONFLICT OF INTEREST
Guarantor of article: Suryakanth R. Gurudu, MD.
Chiu et al. found a significant increase in adenoma detection
rate using a same-day bowel preparation (16). Parra-Blanco et
al. (18) found that the detection of flat lesions was higher when
same-day preparation was used, but that the overall adenoma
detection rate was the same. In contrast to our study, and several
other studies addressing the timing of bowel-preparation admin-
istration, Chiu et al. (16) studied patients undergoing a second
colonoscopy after an adenoma had already been detected at the
first colonoscopy. The resulting higher prevalence of adenomas
in the study population of Chiu et al. might explain the observed
differences in adenoma detection in comparison with our study.
Several other studies (19,20) showed an increased adenoma
detection rate when bowel-preparation quality was improved in
general, without differentiating between same-day and previous-
evening preparation regimens.
Another significant finding of our study was the negative effect
of obesity on the quality of bowel preparation. Several studies have
shown that obesity is a significant factor affecting the quality of
bowel preparation (21). The quality of bowel preparation in our
study became increasingly poor with rising BMI (Table 2) which
was a significant factor that correlated with bowel-preparation
results regardless of which option was chosen.
The quality of bowel cleansing is dependent on the effective
removal of fecal material and gastrointestinal secretions (succus
entericus), which are the two main components of colonic debris.
Polyethylene glycol is an osmotically balanced bowel preparation
that promotes bowel cleansing through ingestion of a large vol-
ume of nonabsorbable fluid, which induces a liquid stool within a
short period of time (22). Constant secretion of gastric, intestinal,
pancreatic, and biliary fluids continues even during and after the
cleansing of the bowel with PEG. These fluids then flow into the
large bowel, making the colon dirty again, starting with the right
Table 3. Adjusted logistic regression comparing preparation quality of four bowel-preparation regimens against prior-day evening 4L
polyethylene glycol
Adequate vs. poor/inadequate
(n = 946)
Good/excellent vs. poor/inadequate
(n = 494)
Cleansing regimena (n) Point estimate 95% CI (lower–upper)Point estimate 95% CI (lower–upper)
4l PeG pm
(n = 376)
ref. ref.
4l PeG am
(n = 226)
3.141.19–8.317.03 2.57–19.22
2l PeG am
(n = 48)
0.58 0.21–1.660.46 0.14–1.54
2l PeG pm/am
(n = 39)
0.910.25–3.26 2.450.68–8.83
2l PeG pm
(n = 656)
1.240.77–20.1 0.950.56–0.96
CI, confidence interval; PeG, polyethylene glycol.
abowel-cleansing regimens included same-day morning 4l PeG (4l PeG am), same-day morning 2l PeG plus 4 bisacodyl (2l PeG am), split dose (2l PeG pm/am),
prior-day evening 2l PeG plus 4 bisacodyl (2l PeG pm), and prior-day evening 4l PeG (4l PeG pm).

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Specific author contributions: Suryakanth R. Gurudu designed
the study. Shiva Ratuapli collected data and drafted the paper.
Michael Crowell designed and performed statistical analysis,
along with drafting the paper. Suryakanth R. Gurudu, Russell
Heigh, and Jonathan Leighton conceived and drafted the study.
Michael Crowell and John DiBaise revised the paper. All the
authors approved the final version of the paper.
Financial support: None.
Potential competing interests: None.
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