Magnetic imaging of colonoscopy: an audit of looping, accuracy and ancillary maneuvers

Background: Colonoscopy is one of the most frequently performed outpatient examinations. However, the procedure is still technically challenging, largely due to unpredictable looping during insertion. The aims of this study were (1) to assess the frequency of loop formation and types of loop during colonoscopy, (2) to determine the accuracy of the endoscopist's assessment of the anatomic location of the endoscope tip and of the presence and type of endoscope loop formation, and (3) to determine the efficacy of abdominal compression and change in patient position in promoting colonoscope advancement. Methods: Consecutive patients undergoing routine, day-case colonoscopy were studied using real-time, three-dimensional magnetic endoscope imaging. All examinations were performed by expert colonoscopists, blinded to the imager view. The endoscopist estimated the position of the colonoscope tip, assessed when and what type of loop had formed, and the efficacy of ancillary maneuvers such as hand pressure or patient position change. The magnetic imager view of each procedure was recorded and retrospectively analyzed. Results: One hundred complete colonoscopies were performed. Looping occurred in 91% with N-sigmoid (79%) and deep transverse (34%) being most common. Most loops (69%) were incorrectly diagnosed by the endoscopist. Atypical loops were more common in women than men (p = 0.025). The endoscopist's assessment of tip location was correct 85% of the time overall, but 100% in the cecum. Abdominal pressure was less effective (54 of 145 times, 37%) than patient position change (95 of 144 times, 66%) in promoting endoscope tip advancement. Conclusions: Looping occurs frequently during routine colonoscopy. Although the endoscopist's assessment of tip location is fairly accurate, the majority of colonoscope loops are incorrectly appreciated. Although used frequently, ancillary maneuvers (abdominal compression and patient position change) are effective in only 52% of attempts.