Trial Information

Prospective Randomized Controlled Trial Comparing Water Immersion Colonoscopy and Air Colonoscopy in a Community Based Setting

Screening colonoscopy with removal of pre-cancerous adenomas was recently shown to result in
a 53% reduction in mortality from colon cancer. While this clearly validates the practice of
screening colonoscopy, missed adenomas, especially in the proximal colon, defined as
including cecum, ascending colon, and transverse colon, remains a concern. This was
demonstrated in a study of 183 patients who underwent back-to-back colonoscopies. In this
population the overall miss rate for adenomas was 24% with proximal adenomas missed more
often (27%) than left colon adenomas (21%). Another study looked at 4192 patients in the
SEER (Surveillance, Epidemiology, and End Results) Medicare database who developed "interval
cancers", that is colon cancer in a patient who had a colonoscopy done in the previous 6-36
months. These interval cancers were predominantly in the proximal colon (Proximal 68%,
Distal 19.5%, rectum 10.4%, and unspecified 2.1%). This also suggests that pre-cancerous
lesions are being missed in the proximal colon. As such a method that can increase proximal
adenoma detection rate would be a welcome change.

One such emerging technique which shows promise for improving adenoma detection rate is
water colonoscopy. In one of the early studies employing the water method a trend towards a
higher ADR in the water method group was recognized (37% vs. 26%). The observation prompted
a retrospective analysis of 1178 cases of screening and surveillance colonoscopy performed
by a single endoscopist at the Sacramento VAMC, which showed an overall ADR (presence of at
least one adenoma) of 27% with air colonoscopy whereas that for the water method colonoscopy
was 35% (p=0.007). In a subsequent combined analysis of two prospective RCT of air vs. water
colonoscopy for screening and surveillance using scheduled unsedated colonoscopy [5] and
on-demand sedation [6], more patients were found to have at least one diminutive adenoma in
the proximal colon in the water method group than in the air group (28% vs. 14%,
respectively, p=0.0298). Another quasi randomized study of screening patients performed at
Phoenix VAMC using high definition equipment confirmed a significantly higher overall ADR
with the water method (n=177) compared with the air method (n=191) (57% vs. 46%) (p=0.03).
The odds of detecting an adenoma was 81% higher with the water method (OR 1.81; 95% CI:
1.12-2.90) and independent of age, body mass index (BMI), current smoking and alcohol use,
withdrawal time & quality of bowel preparation. In the proximal colon ADR was significantly
higher in patients examined with the water method than with air method (46% vs. 35%)
(p=0.03), particularly for adenomas <10 mm in size (38% vs. 25%) (p=007). These encouraging
preliminary data reflect the potential benefits of water method colonoscopy.

Our current research question is whether this benefit is seen in a community based
population as opposed to the VA population which is mostly male and Caucasian.

The investigators plan to perform a prospective, randomized controlled trial comparing
proximal adenoma detection rate between a water immersion colonoscopy group and an air
colonoscopy group. The investigators intend to employ scheduled sedation, instead of
on-demand sedation, to continue the current protocol in place at our institution.