Low-volume polyethylene glycol bowel preparation increases high-quality cleansing

1. In this randomized controlled trial, a 1 L polyethylene glycol–ascorbate regimen achieved higher rates of high-quality bowel cleansing compared with both 2 L and 4 L regimens in hospitalized adults undergoing elective colonoscopy.

2. All regimens were well tolerated; however, the 1 L group reported the greatest willingness to repeat the preparation among treatment groups.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Hospitalized patients often experience suboptimal bowel preparation, which can compromise colonoscopy quality and lead to missed lesions, repeat procedures, longer hospital stays, and increased health care costs. Despite its clinical importance, high-quality evidence to guide optimal bowel preparation strategies in inpatient settings remains limited. This study compared polyethylene glycol (PEG)-based bowel preparation regimens of varying volumes in hospitalized adults undergoing elective colonoscopy. Very low-volume (1 L PEG-ascorbate), low-volume (2 L PEG-ascorbate), and high-volume (4 L PEG) regimens achieved similarly high rates of adequate overall bowel cleansing. However, the very low-volume regimen was associated with higher rates of high-quality overall cleansing compared with the higher-volume regimens. Similar patterns were observed in the right colon, where all regimens achieved comparable adequacy, but the 1 L PEG-ascorbate group again demonstrated superior high-quality cleansing. Adherence to bowel preparation was high across all groups. Patient-reported outcomes also favoured lower-volume regimens, with fewer reports of moderate to severe difficulty and greater willingness to repeat the preparation compared with the high-volume regimen. Adverse effects were generally mild across all groups, including nausea and abdominal discomfort, though thirst was more commonly reported with the very low-volume preparation. Serious adverse events were rare. Polyp detection rates were similar across all regimens. The study is limited by slow recruitment and the exclusion of patients requiring urgent colonoscopy or those with severe or unstable comorbidities, which may affect generalizability. Overall, these findings suggest that very low-volume PEG-based regimens may be at least as effective as higher-volume preparations for achieving high-quality bowel cleansing.

Click to read this study in AIM

Relevant Reading: Effect of bowel preparation volume in inpatient colonoscopy. Results of a prospective, randomized, comparative pilot study

In-Depth [randomized controlled trial]: This randomized controlled trial compared the effectiveness and safety of 1 L, 2 L, and 4 L polyethylene glycol (PEG)-based bowel preparation regimens in hospitalized adults undergoing elective colonoscopy. Participants were recruited from seven hospitals in Italy between June 2021 and January 2025. Eligible patients were adults without major gastrointestinal disease, severe systemic illness, pregnancy or lactation, cognitive or functional limitations, or recent participation in another drug trial. The primary outcome was adequate bowel cleansing (Boston Bowel Preparation Scale [BBPS] score of 6). Secondary outcomes included high-quality cleansing (BBPS 8-9), right-colon cleansing quality, adherence, tolerability, willingness to repeat preparation, adverse events, repeat colonoscopy, and polyp detection. A total of 665 patients were randomized to 1 L PEG-ascorbate (n=228), 2 L PEG-ascorbate (n=218), or 4 L PEG (n=219). Baseline characteristics were similar across groups. Adequate bowel cleansing was achieved in 82.0% with 1 L PEG-ascorbate, 78.0% with 2 L PEG-ascorbate, and 78.5% with 4 L PEG. High-quality cleansing was more frequent with 1 L PEG-ascorbate (46.9%) compared with 2 L (35.3%) and 4 L (37.4%). In the right colon, adequate cleansing was similarly high across groups (83.3%, 79.4%, and 82.6%, respectively), while high-quality right-colon cleansing again favored the 1 L regimen (40.6% vs 29.5% and 31.6%). Adherence exceeded 93% in all groups. Moderate to severe difficulty during preparation was reported less often with 1 L and 2 L regimens (29.8% and 29.4%) compared with 4 L PEG (38.4%). Willingness to repeat the preparation was highest with 1 L (84.2%) and lowest with 4 L (68.0%). Nausea (14-17%) and abdominal pain (7-9%) were similar across groups, while thirst was more frequent with 1 L PEG-ascorbate (27.6% vs 14.2% in the other groups). Serious adverse events were rare. Polyp detection rates were 31.1% with 1 L, 22.5% with 2 L, and 31.0% with 4 L. Overall, 1 L PEG-ascorbate achieved similar adequate cleansing and higher rates of high-quality bowel preparation with improved tolerability compared with higher-volume regimens.

Image: PD

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