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| Journal of the New Zealand Medical Association,
08-June-2012, Vol 125 No 1356
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A prospective study of endoscopist-blinded
colonoscopy withdrawal times and polyp detection rates in a tertiary
hospital
Gary Lim, Sharon K Viney, Bruce A Chapman, Frank A Frizelle,
Richard B Gearry
Colonoscopy is widely regarded as the best test for lower
gastrointestinal investigation for colorectal
cancer.1,2 Whilst there is a clear benefit from
colonoscopy in preventing left-sided tumours, colonoscopy has been shown to be
less effective in preventing right-sided
cancers.3–5
Adenoma detection rate (ADR) is an accepted method of
measuring colonoscopy efficacy and as it has shown in the screening situation
that for an individual endoscopist an ADR rate below 20.0% was significantly
associated with an increased risk of interval colorectal
cancer.6 Many factors have been shown to affect
ADR such as quality of bowel preparation, insertion to caecum and
technique7 It is well known that ADR's vary
between endoscopists and there is a significant association between ADR and
colonoscopy withdrawal time.8
A United States Multi-Society Task Force in 2002 recommended
that colonoscopy withdrawal time should average at least 6–10
minutes9. These recommendations were developed
following a tandem colonoscopy study examining adenoma miss rates. The miss
rates were 17 and 48% for the two endoscopists. The endoscopist with the lower
miss rate had a significantly higher score on 4 quality criteria (examining the
proximal sides of flexures, folds and valves; cleaning and suctioning; adequacy
of distension; adequacy of time spent viewing) as well as a significantly longer
withdrawal time (median of 8 minutes 55 seconds versus 6 minutes 41
seconds).7
Subsequent studies have confirmed these findings, with a
significant difference in adenoma detection in screening colonoscopy shown in
gastroenterologists with mean withdrawal times of less than 6 minutes compared
to those with mean withdrawal times of 6 minutes or
more.8,10
Given the above recommendations, we aimed to evaluate the
withdrawal times in our hospital. Christchurch Hospital is a tertiary hospital
located in the South Island of New Zealand. It is the largest tertiary, teaching
hospital in the South Island with 650 beds. The Endoscopy Unit performs
approximately 5000 colonoscopies annually for diagnostic, therapeutic and
surveillance purposes.
MethodsStudy design—All patients
undergoing colonoscopy (regardless of the indication) were included in the
study. Sixteen consultant endoscopists (seven gastroenterologists and nine
surgeons) were included. Procedures where the caecum was not reached were
excluded. Three endoscopists were aware that the study was taking place while
all other endoscopists were unaware that their withdrawal times were being
recorded.
Once the caecum or terminal ileum had been reached, a
nurse used a stop watch to record the withdrawal time which ceased when the
colonoscope was removed from the rectum. The stop watch was not paused at any
stage during the withdrawal phase for any procedures performed, All patients
received conscious sedation with a combination of intravenous midazalom and/or
fentanyl. Patients received oral sodium picosulfate with bisacodyl as bowel
preparation. Procedures took place with or without registrars. The study took
place from 11 April 2007 to 19 May 2007 over 208 consecutive procedures.
Withdrawal time was recorded, as were indication for
the procedure, diagnosis and procedures performed. The withdrawal time included
time taken to perform procedures such as biopsies or polypectomy. Colonoscopy
data was gathered from the Endoscribe v2.25.09 database as entered by the
endoscopist including patient gender, inpatient status, endoscopist, registrar
if present, bowel preparation quality, biopsies, polypectomy, size of polyps,
location and number of polypectomies. Subsequent histology was later reviewed
using a separate electronic database.
Statistical analysis—Statistical
analysis was performed using R. v2.11.2010-07-27 (R Foundation for Statistical
Computing, Vienna, Austria). Chi-squared or Fisher’s exact test were used
for categorical variables and Wilcoxen rank sum test for continuous
variables.
Results208 colonoscopies were performed during the study period.
111 (53%) were for symptom assessment and 97 (47%) were for screening. The mean
age was 53 years and 43% were male (Table 1). Altogether, polyps were found in
66 patients (31%), of which 21 were adenomas (10%).
Table 1. Patient demographics
In the 97 colonoscopies which were performed for screening
purposes, polyps were found in 38 (39.1%), of which 14 were adenomas (14%).
There was one low rectal cancer found which occurred in a 59-year-old male
undergoing colonoscopy for rectal bleeding on a background of longstanding
Crohn’s colitis. Registrars were involved in 17 (8%) of the total
colonoscopies.
There was significant heterogeneity between colonoscopists'
withdrawal times (Figure 1) (p<0.001). The median colonoscopy time was 3
minutes 16 seconds when no polyps were found (range 5 seconds to 11 minutes 50
seconds). The median colonoscopy time when polyps were found was 8 minutes 31
seconds (range 2 minutes 7 seconds to 35 minutes 40 seconds) p<0.001.
Figure 1. Colonoscopy withdrawal
times
 Fourteen out of 16 endoscopists had median withdrawal times
less than 6 minutes. The quickest median withdrawal time was 12 seconds
(Endoscopist 13 over 6 procedures).
Overall, 12 colonoscopies were performed with withdrawal
times less than 1 minute. Another 27 colonoscopies were performed with
withdrawal times of 1-2 minutes. In the screening only group when no polyps were
found, 49 out of 59 colonoscopies (83%) had withdrawal times less than 6 minutes
(Figure 2).
Figure 2. Withdrawal times (surveillance group
without polypectomy)
 Screening-only group—Endoscopists
performed 0-16 screening colonoscopies. Individual ADR was 0-40% (Table 2). 45%
of polyps removed were < 5mm in size. 47% of polyps were 5-10mm in size and
8% greater than 10mm in size.
Two trainees (registrars) performed 7 of the 97 surveillance
colonoscopies with individual ADR of 33% and 50%. Withdrawal times when no
polyps were found were 6 minutes 37 second for one trainee and 2 minutes 35
seconds for the second trainee. The presence of a registrar made no significant
difference to the supervising endoscopist’s withdrawal time or ADR
Gastroenterologists performed 64 (66%) of the surveillance
colonoscopies and the surgeons performed 33 (34%). ADR for the
gastroenterologists was 15.6%, compared to 12% for the surgeons (p=0.65). When
colonoscopies plus procedures were excluded, the gastroenterologists performed
30 colonoscopies with a mean withdrawal time of 190 seconds.
The surgeons performed 17 colonoscopies with a mean
withdrawal time of 127 seconds (p=0.007). 41% of these cases performed by the
surgeons had previous colonic resection compared to 20% for the
gastroenterologists.
Table 2. Polyp detection rate and adenoma detection
rate (surveillance group only)
DiscussionColonoscopy has been shown to decrease the incidence of
colorectal cancer but the effectiveness of colonoscopy depends upon finding and
removing adenomatous polyps. Polyp detection rates, more particularly adenoma
detection rates, are an accepted means of assessing the quality of
colonoscopy.6 In 2006 the ASGE published
several factors shown to affect the quality of a colonoscopy
procedure11. These include preprocedure,
intraprocedure and postprocedure measures.
Intraprocedure measures included caecal intubation rate,
detection of adenomas in asymptomatic individuals, withdrawal times, biopsy
specimens in chronic diarrhoea, biopsy samples in UC/IBD and endoscopic
resection of polyps <2 cm. Other factors include the
proceduralist—non-gastroenterologists are more likely than
gastroenterologists to miss cancer12 although
out local data would suggest otherwise 13.
Other factors suggested to influence the ADR are the role of fatigue and time of
day14, place on the list and timing of the
endoscopy list have also been
implicated15,16.
This study demonstrates that more adenomas were found when
colonoscopy took longer. Also that when proceduralists are not aware that they
are being timed, colonoscopy withdrawal times are significantly faster than
recommended. Furthermore, for colonoscopies where polypectomy was not performed,
only 17% of withdrawal times were greater than 6 minutes. This would imply that
a possible reason why longer withdrawal times (greater than 6 minutes) have been
associated with increased adenoma pick up rate may at least in part, be the self
fulfilling way some studies have been undertaken, namely that the withdrawal
time includes the time to remove polyps 17.
However our study is still consistent with previous data showing increased
adenoma detection with withdrawal times of greater than 6
minutes.8, 10, 18
The adenoma detection rate varied from 0 to 40% between
proceduralists. This may not be a good reflection of individual performance, due
to the low numbers of procedures performed by several endoscopists. However, it
does demonstrate marked heterogeneity and, overall, too rapid a withdrawal time
for most procedures. The overall adenoma detection rate in the surveillance
group of 14% is lower than most studies8,19,.
Reasons for this may include the small number of patients in the study, but may
also be a reflection of the fast withdrawal times.
In the present study there was a slightly higher proportion
of females, who have a lower prevalence of adenomatous polyps. Due to the lack
of a primary screening colonoscopy program in New
Zealand20 and limited resources, our Unit can
only offer surveillance to high risk groups - patients with previous polyps,
strong family of colorectal cancer and possible hereditary non-polyposis
colorectal cancer families. However one would have expected that surveillance of
a group with higher than average risk of colorectal cancer would have even
higher adenoma detection rates than average risk patients.
This was a baseline quality assurance/withdrawal time study
performed in our department prior to any intervention. Most importantly, it was
blinded, giving a true reflection of withdrawal times rather than having
artificially lengthened withdrawal times when colonoscopists are aware they are
being timed. Other studies have shown a non-significant increase in polyp
detection when clinicians are informed that withdrawal time is being
monitored,21 as well as increased inspection
time and improved technique when blinded video assessment becomes
unblinded.22
The weakness of this study includes the small numbers of
colonoscopies, (especially when looked at per endoscopist) and the short time
period over which the study was undertaken . Also the fact that the polyp
removal time was included in the withdrawal time , therefore creating an time
bias in the study i.e. if you had an adenoma then your colonoscopy would take
longer as it had to be removed or biopsied.
Christchurch Hospital has now been chosen as a pilot site in
New Zealand for the Endoscopy Global Rating Scale (GRS). This is a web-based
self assessment tool that provides a standard for accreditation and framework
for service improvement. Factors monitored include clinical quality, patient
experience, workforce and training.23 Hopefully
the introduction of this will lead to improved colonoscopy throughout New
Zealand
In conclusion, our study confirms that colonoscopy
withdrawal times prior to any intervention are much faster than recommended.
Auditing of adenoma detection and colonoscopy withdrawal times should take place
at regular intervals in all Units performing colonoscopy.
Competing interests: None
declared.
Author information: Gary Lim,
Gastroenterologist, Department of Gastroenterology; Sharon K Viney, Registered
Nurse, Department of Gastroenterology; Bruce A Chapman, Gastroenterologist,
Department of Gastroenterology; Frank A Frizelle, Professor and Head of
Department, Department of Surgery; Richard B Gearry, Associate Professor,
Gastroenterologist, Department of Gastroenterology; Christchurch Hospital,
Christchurch
Correspondence: Dr G Lim, Department of
Gastroenterology, Christchurch Hospital, Private Bag 4710, Christchurch, New
Zealand. Fax: +64 (0)3 3640304; email: Gary.Lim@cdhb.govt.nz
References:
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