Trial Information

Evaluation of the Effect of Position Change During the Withdrawal Phase of Colonoscopy on Adenoma Detection Rate

Colorectal cancer is the second commonest cause of cancer death. In a majority of cases it
is preceded by a precancerous lesion called an adenoma (commonly known as polyp). Detection
and removal of adenomas at colonoscopy has been shown to reduce mortality from colorectal
cancer. The success of the impending colorectal cancer screening programme to reduce cancer
mortality in an average-risk population depends on optimal adenoma detection at colonoscopy.
The detection of adenomas has been shown to vary between different endoscopist. Some of the
factors that have been reported to affect adenoma detection rates included the time spent
viewing, the adequacy of the bowel preparation and the time spent cleaning the colonic
mucosa of excess fluid. Careful examination of proximal side of flexures, folds and valves
by the endoscopist is equally important. However, even with careful examination adenoma
detection rates have been shown to vary between endoscopist from 8.6% to 15.9%. Previous
experience and training may be contributed to this difference. Some endoscopist adopt
regular changes in position during the procedure to maximize distension of the colon. Better
luminal distension enhances mucosal views for detection of the smaller adenomas. The
validity of this approach has never been tested and we propose that this factor may
contribute to the differences in adenoma detection rates.

Patients will be randomised to either position 1 first then position 2 or vice versa and
examined twice. During one withdrawal the colon will be examined with the participant in the
left lateral position only (position 1) or with position changes (position 2)or vice versa.

May 2007: protocol amendment to include additional prospective analysis using High
Definition TV (HDTV). No further patient data collection involved.