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BACKGROUND & AIMS:Efficacy of bowel preparation is an important determinant of outcomes of colonoscopy. It is not clear whether approved low-volume polyethylene glycol (PEG) and non-PEG regimens are as effective as high-volume PEG regimens when taken in a split dose. METHODS:In a systematic review of multiple electronic databases through January 31, 2019 with a registered protocol (PROSPERO: CRD42019128067), we identified randomized controlled trials that compared low- vs high-volume bowel cleansing regimens, administered in a split dose, for colonoscopy. The primary efficacy outcome was rate of adequate bowel cleansing, and the secondary efficacy outcome was adenoma detection rate. Primary tolerability outcomes were compliance, tolerability, and willingness to repeat. We calculated relative risk (RR) and 95% CI values and assessed heterogeneity among studies by using the I2 statistic. The overall quality of evidence was assessed using the GRADE framework. RESULTS:In an analysis of data from 17 randomized controlled trials, comprising 7528 patients, we found no significant differences in adequacy of bowel cleansing between the low- vs high-volume split-dose regimens (86.1% vs 87.4%; RR, 1.00; 95% CI, 0.98-1.02) and there was minimal heterogeneity (I2=17%). There was no significant difference in adenoma detection rate (RR, 0.96; 95% CI, 0.87-1.08) among 4 randomized controlled trials. Compared with high-volume, split-dose regimens, low-volume split-dose regimens had higher odds for compliance or completion (RR, 1.06; 95% CI, 1.02-1.10), tolerability (RR, 1.39; 95% CI, 1.12-1.74), and willingness to repeat bowel preparation (RR, 1.41; 95% CI, 1.20-1.66). The overall quality of evidence was moderate. CONCLUSIONS:Based on a systematic review of 17 randomized controlled trials, low-volume, split-dose regimens appear to be as effective as high-volume, split-dose regimens in bowel cleansing and are better tolerated, with superior compliance.

Original publication




Journal article


Clinical gastroenterology and hepatology : the official clinical practice journal of the American Gastroenterological Association

Publication Date



Endoscopy Department, Humanitas University, Italy. Electronic address: