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Am J Gastroenterol. 2014 Sep;109(9):1390-400. doi: 10.1038/ajg.2014.126. Epub 2014 Jun 3.

A patient-blinded randomized, controlled trial comparing air insufflation, water immersion, and water exchange during minimally sedated colonoscopy.

Author information

1] Division of Gastroenterology, Department of Medicine, Buddhist Dalin Tzu Chi Hospital, Chiayi, Taiwan [2] Buddhist Tzu Chi University, School of Medicine, Hualien, Taiwan.
1] Department of Medical Research, Buddhist Dalin Tzu Chi Hospital, Chiayi, Taiwan [2] Dalla Lana School of Public Health, University of Toronto, Ontario, Canada.
1] Sepulveda Ambulatory Care Center, Veterans Affairs Greater Los Angeles Healthcare System, North Hill, California, USA [2] David Geffen School of Medicine at UCLA, Los Angeles, California, USA.



Minimal sedation obviates patient recovery burdens, but intolerable pain limits success of cecal intubation. Painless or minimally uncomfortable insertion ensures success of cecal intubation, current patient satisfaction, and willingness to repeat future colonoscopy with minimal sedation. Water immersion (WI) and water exchange (WE), when separately compared with air insufflation (AI), significantly reduced insertion pain. To assess comparative effectiveness, we conducted a randomized controlled trial with head-to-head comparison of these three methods. We hypothesized that WE could produce the highest proportion of patients reporting painless insertion.


This prospective patient-blinded trial (NCT01535326) enrolled minimally sedated (25 mg intramuscular meperidine) patients randomized to AI, WI, or WE (90 patients/group) to aid insertion. The previously validated primary outcome was the proportion of patients reporting painless insertion.


Painless insertion was reported by 30.0% (AI), 43.3% (WI), and 61.1% (WE) of patients (P<0.001). Multivariate logistic regression analysis revealed that, after adjusting for gender, body mass index, abdominal compression, position change, insertion time to cecum, and length of scope at cecum, only WE was significantly associated with painless insertion compared with AI (odds ratio (OR)=0.08, 95% confidence interval (CI)=0.03-0.24, P<0.001) or WI (OR=0.14, 95% CI=0.05-0.40, P<0.001). Adenoma detection rate (ADR) in the right (cecum and ascending) colon was 11.1% (AI), 14.4% (WI), and 26.7% (WE) (P=0.015). The limitations included single site study with unblinded colonoscopist and assistant.


This head-to-head comparison of AI vs. WI vs. WE confirmed that WE was superior to WI and AI, with a significantly greater proportion of patients reporting painless insertion. The significantly higher ADR in the right colon in the WE group warrants further investigations.

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