10.1055/a-0953-1468
In this issue of Endoscopy International Open, the protocol for an ongoing randomized
controlled trial (RCT) is described [1]. The primary objective is to ascertain if procedural pain, assessed post-procedure
and prior to discharge, is reduced in water-assisted sigmoidoscopy (WAS) compared
to carbon dioxide (CO2) insufflation in people undergoing unsedated flexible sigmoidoscopy as part of the
United Kingdom Bowel Scope Screening Program (BSSP). In the BSSP, an enema is given,
colonoscope used, and Entonox (nitrous oxide) readily available as needed. Recognition
that water instead of gas can potentially reduce insertion pain based on published
reports on water-aided colonoscopy represents an important milestone in the history
of water-assisted examination of the colon. This is a well-designed trial which shows
considerable promise in demonstrating a less painful method for people undergoing
screening sigmoidoscopy. This editorial focuses on discussions of the timing of pain
assessment and insertion technique.
Recording of pain data by a blinded research assistant immediately after examination
of the colon is a sound experimental design to minimize observer bias. Pain during
insertion, however, is a clinically relevant parameter as excessive insertion pain
mandates discontinuation, or need to add Entonox. Therefore, real-time maximum insertion
pain more accurately reflects the importance of pain reduction and is a pertinent
measure to track [2]
[3]
[4] in addition to the current primary outcome.
Recognition of the need to reduce pain related to gas insufflation is critical to
development of the protocol. The investigators should be commended for addressing
the issue with this RCT using water-assisted technique. At a risk of stating the obvious,
there are two main approaches to water assistance for examination of the colon, namely,
water immersion (WI) and water exchange (WE) [5]. In the English-language literature, WI dates back to 1984 [6]. Water was administered into the sigmoid colon deformed by diverticulosis to facilitate
passage and the infused water was removed during withdrawal. The practice is simple
and easy to adopt. The approach was extended to the entire colon as WE to facilitate
completion of colonoscopy in unsedated veterans in the United States. WE emphasizes
removal of the infused water (and residual debris) during insertion to minimize distension
and optimize reduction of real-time maximum insertion pain [2]. The serendipitous consequences of salvage cleaning during insertion and reduced
multi-tasking distractions due to cleaning activities during withdrawal [7] are likely instrumental in the increase in adenoma detection when WE is used [8]
[9]
[10]. The key to success of WE appears to be near-complete suction removal of the infused
water (along with residual debris) during insertion [11].
The WAS technique (water infusion based on endoscopist discretion, suction of infused
water as needed or as per usual practice during withdrawal) [1] appears to resemble WI ([Table 1]). Data in the literature would suggest that WAS may need the addition of standardized
water suction during insertion to achieve effectiveness as optimal as WE in minimizing
insertion pain or increasing adenoma detection. To maximize the benefits of water
assistance, it is prudent to consider use of WE for the proposed study, i. e. with
near-complete suction removal of the infused water during insertion, and not just
“as needed.” The history of water-aided colonoscopy showed that the change from WI
to WE [3]
[4] reaped important benefits of significant further reduction of insertion pain.
Table 1
Differences between water exchange and water immersion suggest water-assisted sigmoidoscopy
is similar to water immersion.
|
Characteristics
|
WE (colonoscopy)
|
WI (colonoscopy)
|
WAS (sigmoidoscopy)
|
|
Maneuvers
|
Standardized
|
Based on discretion of endoscopist
|
Based on discretion of endoscopist
|
|
Gas pump turned off
|
Before insertion
|
Before or after
|
After
|
|
Use of blast of gas
|
No
|
Allowed
|
Allowed
|
|
Suction of luminal gas
|
Yes
|
Optional
|
Yes
|
|
Suction of infused water and residual debris
|
Near-complete removal during insertion
|
Removal mainly during withdrawal
|
As needed and as per standard practice during withdrawal
|
|
Salvage cleaning during insertion
|
Integral component
|
Optional
|
As needed
|
|
Cleaning during withdrawal
|
Minimal after insertion cleaning
|
Yes
|
Yes
|
|
Insertion pain reduction
|
Better than WI, AI or CO2 insufflation
|
Better than AI or CO2 insufflation
|
Primary outcome of current RCT, likely comparable to WI
|
AI, air insufflation; CO2, carbon dioxide; RCT, randomized controlled trial; WAS, water-assisted sigmoidoscopy;
WE, water exchange; WI, water immersion.
When WE is indeed adopted for flexible sigmoidoscopy, there is the potential to attempt
extended flexible sigmoidoscopy [12], especially when a colonoscope is already being used in the BSSP. The only significant
change is for the patient to undertake an oral bowel preparation to clean the entire
colon. To the fullest extent of intubation, a WE-assisted extended flexible sigmoidoscopy
is equivalent to an unsedated colonoscopy. The increased coverage of and discovery
of polyps in the proximal colon without the expense and burden of sedation and return
visit to remove polyps beyond the reach of the sigmoidoscope can be substantial. This
would be a reasonable next step for investigators in this RCT to consider.
On a lighter note, the current RCT confirms that the investigators appreciate the
disadvantages of gas insufflation for insertion. On the other hand, WE has distinct
advantages. The investigators could consider trying to avoid using any insufflation
at all and achieve suction salvage cleaning during insertion (should be easy now that
the skills in water-assisted technique have been acquired). The full benefits of further
decrease in pain and increase in adenoma detection, and possibly a greater chance
to complete a higher proportion of unsedated colonoscopies than using the current
technique, could be achieved. It is reasonable to experiment and have fun. Performing
WE is neither boring nor excessively time-consuming in a reasonably well-prepared
colon. In addition to less intense insertion pain for the patient, the annoying task
of cleaning up during withdrawal can be avoided and the hunt for lesions will become
more enjoyable for the colonoscopist.
