Suboptimal Bowel Preparation Significantly Impairs Colonoscopic Detection of Non-polypoid Colorectal Neoplasms

It is unclear whether the quality of bowel preparation affects colonoscopic detection of non-polypoid colorectal neoplasms (NP-CRNs).

To evaluate the impact of bowel-cleansing quality on detection of NP-CRNs.

We performed a retrospective analysis of asymptomatic screening colonoscopy cases after standardized bowel preparation at an academic teaching hospital between June 2011 and May 2013. Primary outcome was a comparison of the adenoma detection rate (ADR) of non-polypoid morphology according to quality of bowel preparation. Secondary outcomes included detection prevalence of non-polypoid adenomas.

Of the enrolled 6097 screening examinations, the preparation quality was rated as adequate (excellent or good) in 5224 (85.7 %), fair in 615 (10.1 %), and poor in 258 (4.2 %) patients. The prevalence of NP-CRNs was 40.5 % (1962/4847) of all CRNs. The overall ADR of non-polypoid morphology was 12.3 % (747/6097) of all colonoscopies, but it significantly differed among participating endoscopists (all P < 0.05). The ADR of non-polypoid morphology was significantly lower with fair- or poor-quality preparation, versus adequate-quality preparation (adjusted odds ratio [aOR] 0.55, 95 % confidence interval [CI] 0.41-0.75; aOR 0.49, 95 % CI 0.30-0.79, respectively). Poor-quality preparation was also associated with impaired detection of polypoid, proximal colon, and sub-centimeter adenomas (all P < 0.05).

Suboptimal (fair or poor) bowel preparation significantly impairs colonoscopic detection of NP-CRNs. Given that the prevalence of NP-CRNs is substantial in our average-risk screening cohort, ongoing efforts to improve the preparation quality are practically valuable in increasing the detection of NP-CRNs, thereby improving the efficacy of screening colonoscopies.