1 versus 2 L PEG/Asc for bowel preparation in patients with hematochezia: a multicenter, prospective, randomized, non-inferiority study

Background: Patients with hematochezia often present with inadequate bowel preparation, which compromises the accuracy of colonoscopy. Despite this clinical challenge, evidence guiding optimal preparation strategies for this population is limited. Objectives: We directly compared the efficacy and safety of ultra-low-volume (1 L) polyethylene glycol/ascorbic acid (PEG/Asc) versus low-volume (2 L) PEG/Asc in patients undergoing colonoscopy for hematochezia. Design: In a prospective, randomized, multicenter non-inferiority trial, patients received either 1 or 2 L PEG/Asc using standard split-dose regimens. Methods: Bowel preparation quality was assessed using the Boston Bowel Preparation Scale (BBPS). Secondary outcomes included patient satisfaction, adverse events, colonic bleeding source identification rate, and adenoma detection rate (ADR). Results: In total, 184 patients were analyzed. Successful bowel cleansing was achieved in 78.3% of the 1 L PEG/Asc group and 76.1% of the 2 L PEG/Asc group, confirming non-inferiority. The mean BBPS score was higher with 1 L PEG/Asc (6.87 vs 6.30; p = 0.053). Patient satisfaction favored the 1 L PEG/Asc group, although the difference was not statistically significant. Colonic bleeding source identification was slightly higher in the 1 L PEG/Asc group than in the 2 L PEG/Asc group, but the difference did not reach statistical significance (82.4% vs 73.6%; p = 0.165). Completion rates, adverse events, and ADR were similar between groups. Conclusion: Ultra-low-volume (1 L) PEG/Asc is as effective and safe as 2 L PEG/Asc for bowel preparation in patients with hematochezia. Bowel cleansing and satisfaction were higher with the 1 L PEG/Asc regimen without statistically significant differences, supporting its use as a practical alternative. Trial registration: The study was registered with the Clinical Research Information Service, Republic of Korea, a primary registry in the WHO Registry Network (registration number: KCT0006124).