Magnetic Endoscope Imaging (ScopeGuide®) Elucidates the Mechanism of Action of the Pain-alleviating Impact of Water Exchange Colonoscopy - Attenuation of Loop Formation

Abstract

Purpose: Water exchange colonoscopy produces a significant reduction of pain (scheduled unsedated patients), a lower patient-controlled medication requirement (scheduled sedated patients) and a higher proportion of patients completing unsedated colonoscopy (on-demand sedated patients). The method entails omission of air insufflation and removal of residual air to minimize lumen distension and flexure angulation. Less need for abdominal pressure and position change indirectly suggest less looping may account for pain alleviation. No objective evidence currently exists to substantiate the claim. A recent editorial on magnetic endoscope imaging (MEI) recommended its use in water exchange colonoscopy to elucidate the mechanism of pain alleviation / avoidance of loop formation. Aim: To show that MEI documents less frequent loop formation when water exchange is used. Methods: The MEI equipment (ScopeGuide®, Olympus) with built-in magnetic sensors displays the configuration of the colonoscope inside the patient. Colonoscopy using air or water exchange method was performed as previously described (Endoscopy 2011;43:816-21). During colonoscopy, the endoscopist was blinded to the ScopeGuide images which were recorded. Subsequent review of the recordings was performed. Loop formation was scored based on a visual guide provided by Olympus. Loop formation was defined as full (scope crossing itself); partial (exaggeration of the curvature) and none (a smooth and straight configuration of the scope). Results: Recordings were collected prospectively in routine cases not enrolled in clinical trials (Table). There were 41 and 32 non consecutive cases in the water exchange and air group, respectively. Review of the MEI recording showed that the sigmoid N loop was most common, followed by the sigmoid alpha loop, and exaggeration of scope curvature at the splenic flexure/transverse colon. Of these, 20/32 vs 9/41 patients (p=0.0007) had sigmoid looping, and 17/32 vs 9/41 patients (p=0.0007) had sigmoid/splenic looping when the scope tip was in the transverse colon, in the air and water exchange group, respectively. Limitation: Single center, small number, observational study.Table: Comparison of air vs. water exchange colonoscopyConclusion: For the first time, recorded MEI data objectively demonstrated significantly less loop formation during water exchange colonoscopy, elucidating the mechanism of pain alleviation by water exchange / attenuation of loop formation. Coupled with the emerging RCT data that MEI feedback enhances cecal intubation by trainees, the role of MEI combined water exchange in speeding up trainee learning curves deserves further evaluations. Disclosure: Dr. Joseph Leung: Olympus America. Research and Education support, on loan of MEI for study purposes. Other authors have no conflict of interests to disclose related to this study. This research was supported by an industry grant from Olympus America: on loan of MEI for study purposes.