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).
Keywords: bowel preparation; colonoscopy; hematochezia; polyethylene glycol; ultra-low-volume.
Comparing two bowel cleansing volumes for patients with hematochezia who need a colonoscopy Hematochezia, which means passing bright red blood from the bowel, is a common reason for people to seek medical care. When this happens, doctors usually recommend a colonoscopy to find the cause of bleeding and provide treatment. To perform a safe and accurate colonoscopy, the bowel must be properly cleaned. However, drinking large amounts of cleansing solution is often uncomfortable, especially for people who are already unwell. This study examined whether a smaller amount of bowel cleansing solution could work as well as a larger amount in patients with hematochezia. We compared two cleansing regimens: a 1-liter solution and a 2-liter solution. Our main goal was to learn whether the smaller amount would clean the bowel well enough for doctors to clearly see the inside of the colon. We also evaluated how patients felt while taking the solution and whether any side effects occurred. We conducted a randomized clinical study at two hospitals. Adults with hematochezia were assigned to drink either the 1-liter or the 2-liter solution before their colonoscopy. We measured bowel cleanliness, the ability of doctors to identify the bleeding source, patient comfort and willingness to repeat the same preparation, and any safety concerns. The study included 184 patients. Overall, the 1-liter solution cleaned the bowel just as well as the 2-liter solution. In some parts of the colon, especially the transverse and left segments, the 1-liter solution even performed slightly better. Both groups had similar success in identifying the source of bleeding, and no serious side effects were found. Many patients found the smaller-volume preparation easier and more comfortable to take. These results suggest that a 1-liter preparation is an effective and safe option for people with hematochezia who need a colonoscopy. A smaller amount may improve comfort without reducing the quality of the examination.
© The Author(s), 2026.