Magnetic endoscope imaging (ScopeGuide) elucidates the mechanism of action of the pain-alleviating impact of water exchange colonoscopy - attenuation of loop formation.

BACKGROUND: The explanation why water exchange colonoscopy produces a significant reduction of pain during colonoscopy is unknown. A recent editorial recommended use of magnetic endoscope imaging (MEI) to elucidate the explanation.
OBJECTIVE: In unselected patients to show that MEI documents less frequent loop formation when water exchange is used.
DESIGN: Observational, performance improvement.
SETTING: Veterans Affairs outpatient endoscopy. PATIENTS: Routine colonoscopy cases.
INTERVENTIONS: Colonoscopy using air or water exchange method was performed as previously described. The MEI equipment (ScopeGuide, Olympus) with built-in magnetic sensors displays the configuration of the colonoscope inside the patient. During sedated colonoscopy the endoscopist was blinded to the ScopeGuide images which were recorded and subsequently reviewed. MAIN OUTCOME MEASURES: Loop formation based on a visual guide provided by Olympus.
RESULTS: There were 41 and 32 cases in the water exchange and air group, respectively. 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. LIMITATIONS: Colonoscopy method was not blinded and non randomized.
CONCLUSION: MEI data objectively demonstrated significantly fewer loops during water exchange colonoscopy, elucidating its mechanism of pain alleviation - attenuation of loop formation. Since MEI feedback enhances cecal intubation by trainees, the role of MEI combined water exchange in speeding up trainee learning curves deserves further evaluations.