Background: Colonoscopy reduces colorectal cancer mortality by enabling early detection and removal of adenomas. Its effectiveness, however, depends heavily on bowel preparation quality and mucosal visibility. Simethicone, an anti-foaming agent, decreases intraluminal bubbles and improves visualization; studies in conventional air-insufflation colonoscopy generally show benefits for cleanliness and patient comfort, but evidence in water-exchange (WE) colonoscopy remains limited.Objective: To evaluate whether adding oral simethicone to a split-dose polyethylene glycol (PEG) regimen further improves bowel cleanliness and procedural performance in WE colonoscopy.Methods: Adults undergoing outpatient colonoscopy will be randomly assigned (1:1) to a simethicone group or a control group, with a planned enrollment of 180 participants. All procedures will use the WE insertion technique, and endoscopists will be blinded to group allocation. The primary endpoint is the Boston Bowel Preparation Scale (BBPS); adequate preparation is defined as a total score ≥6 with all segment scores ≥2. Secondary endpoints include bubble score and CEBuS, adenoma detection rate (ADR), polyp detection rate (PDR), cecal intubation rate and time, withdrawal time, volume of water used and flushing/irrigation metrics, and patient-reported tolerability and satisfaction.Expected Results: Compared with PEG alone, adding simethicone is expected to (1) increase the proportion of adequate BBPS preparations, (2) reduce bubble coverage, (3) maintain or potentially improve ADR/PDR, and (4) enhance patient tolerability and satisfaction.Conclusion: If effective, this intervention would provide a simple, low-cost strategy to optimize the quality of WE colonoscopy.
Consecutive patients undergoing screening, surveillance, or diagnostic colonoscopy.
Procedures performed by participating endoscopists.
Ability to provide written informed consent.
Colonoscopy performed using air insufflation or water immersion technique.
History of colorectal surgery (e.g., colectomy or colostomy).
Known or suspected colonic obstruction or severe stricture.
Requirement for inpatient bowel preparation.
Parallel
Simethicone with PEG
DrugAll participants followed a standardized bowel preparation protocol consisting of 10 mg of bisacodyl and 2 liters of PEG solution administered in a split-dose regimen. Participants in the simethicone group additionally received 30 mL of simethicone (600 mg), with 15 mL added to each 1-liter dose of PEG solution.
PEG
DrugAll participants followed a standardized bowel preparation protocol consisting of 10 mg of bisacodyl and 2 liters of PEG solution administered in a split-dose regimen.
Boston bowel preparation scale (BBPS)
Bowel preparation quality assessed using the Boston Bowel Preparation Scale (BBPS). Adequate preparation is defined as a total score ≥6 with all segment scores ≥2.
Bubble score assessed using a 4-point bubble scale
Bubble score assessed during colonoscopy using a 4-point scale (0-3) for each colon segment, where higher scores indicate more bubbles.
Colon Endoscopic Bubble Scale(CEBuS)
Bowel cleanliness assessed using the Colon Endoscopic Bubble Scale (CEBuS), categorized based on the percentage of mucosal surface obscured by bubbles (e.g., \<5%, 5-50%, \>50%).Higher scores indicate poorer visibility due to bubbles.
Adenoma detection rate (ADR)
Polyp detection rate (PDR)
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