Low-Volume PEG Wins for Inpatient Bowel Cleansing

In stable hospitalized adults undergoing elective colonoscopy, 1-L polyethylene glycol plus ascorbate (PEG) proved safe and effective for bowel preparation. It yielded comparable overall cleansing and better rates of high-quality bowel cleansing than 2-L and 4-L preparations, the randomized INTERPRET trial found. Moreover, the low-volume preparation was associated with greater patient willingness to repeat than both 2-L and 4-L PEG. “These findings support adopting a low-volume regimen as a practical, patient-centered approach to inpatient bowel preparation,” said Lorenzo Fuccio, MD, gastroenterologist at the Ospedaliero-Universitaria di Bologna and an associate professor of medicine at the University of Bologna, Italy, and colleagues, writing in Annals of Internal Medicine. “Hospitalized patients are among the most difficult to prepare adequately for colonoscopy,” Fuccio told Medscape Medical News. “They are often older, less mobile, affected by comorbidities, and exposed to medications that can impair bowel cleansing.” Yet the evidence guiding bowel preparation choice in this setting has been limited. There’s been a tendency to assume that in difficult-to-prepare patients, more volume means better cleansing, he added. While 4-L PEG has traditionally been viewed as a robust and safe option, it had not been properly tested in a large randomized inpatient trial against lower-volume regimens. “I think the INTERPRET results will change practice, at least for clinically stable hospitalized patients undergoing elective or nonurgent colonoscopy,” he said. “These data support moving away from the reflex use of high-volume preparation in inpatients. The focus should be on evidence-based preparation protocols, not simply on prescribing the largest volume.” A split-dose 1-L PEG regimen can now be considered a practical, evidence-based, and patient-centered option, provided that contraindications are respected and that administration is supported by clear instructions and nursing supervision. Fuccio cautioned, however, that these findings should not be extrapolated to patients undergoing urgent colonoscopy for active bleeding, hemodynamic instability, or severe unstable comorbid conditions, a population excluded from the trial. Updated US guidelines from 2025, however, recommend high-volume PEG for inpatients, but this recommendation is based on low-quality evidence and is extrapolated from outpatient studies, Fuccio said. European guidelines acknowledge the lack of inpatient-specific data and do not endorse a preferred regimen. 1:1:1 Study From 2021 to 2025, the INTERPRET study randomly assigned 665 adult colonoscopy inpatients at seven community and academic Italian hospitals to split doses of three different volumes of PEG: 1 L (n = 228), 2 L (n = 218), and 4 L (n = 219). Efficacy was gauged by a three-segment Boston bowel preparation scale (BBPS) score ≥ 6, with all segments scores ≥ 2. Other endpoints included high-quality cleansing (BBPS score, 8-9; right colon score, 3), as well as patients’ willingness to repeat. Overall cleansing across all three arms occurred in 82%, 78%, and 78.5% of patients, from lowest- to highest-volume regimens, and high-quality overall cleansing occurred in 46.9%, 35.3%, and 37.4%, respectively. The benefit was most evident in the right colon, where inadequate preparation increases the risk for missed proximal lesions. At this site, high-quality cleansing occurred in 40.6%, 29.5%, and 31.6%, respectively. While tolerability was good across all regimens, the highest willingness to repeat was observed in the 1-L group (84.2% vs 82.1% and 68%), despite its more frequent incidence of vomiting and thirst. Adverse events were generally mild, with nausea reported in 17.1%, 14.2%, and 16.4% from lowest to highest PEG. Abdominal pain occurred in 7.5%, 8.3%, and 9.1% across arms, with vomiting reported in 14.9%, 7.3%, and 11.4%, respectively. Across groups from lowest to highest, nausea was reported by 17.1%, 14.2%, and 16.4%, while thirst was reported by 27.6%, 14.2%, and 14.2%. “Inpatient bowel preparation is often treated as a technical detail, but it is actually a quality and safety issue,” Fuccio said, because poor preparation can lead to missed lesions, repeat procedures, delays in diagnosis, longer hospital stays, and increased costs. “Our study suggests that optimizing inpatient preparation does not necessarily mean increasing the burden on patients.” Commenting on the trial but not involved in it, Rajesh N. Keswani, MD, interventional gastroenterologist at the Northwestern Medicine Digestive Health Center in Chicago, called it “a very interesting study that touches on the challenges and importance of high-quality inpatient bowel preparations.” He added that the quality of bowel preparations for inpatients is inferior to those for outpatients. His institute has developed pathways for managing hospitalized patients, including antinausea medications and low-dose regimens. “Some patients simply cannot tolerate the large amount of fluid in a standard preparation, leading to long delays,” Keswani told Medscape Medical News. However, he cautioned, these low-volume options can cause fluid shifts if a patient fails to drink enough accompanying water or has underlying kidney disease. “Patients with severe underlying constipation benefit most from a higher volume, and those who definitely can’t take lower-volume solutions include those with advanced kidney disease.” While the data generally support more liberal use of these lower-volume preparations, Keswani added, “There is still some way to go until they are utilized as standard of care. Again, the reasons include concerns for electrolyte derangements, possibly increased cost, and concern that they may not be as effective for inpatients with underlying constipation.” As to the probable reaction of US gastroenterologists who follow the 2025 guidelines, he said, “I think the data will definitely cause some adjustments to those guidelines, but, as mentioned, many of us continue to default to the higher-volume, universally safe preparation, which also had great effectiveness in this study.” Looking ahead, said Fuccio, it will be important to understand the role of low-volume regimens in more acute scenarios, including unstable inpatients and those requiring urgent colonoscopy for gastrointestinal bleeding. “There is already some lower-quality evidence suggesting that 1-L PEG-based regimens may be an effective alternative in these difficult settings, but dedicated comparative randomized trials are still needed.” This nonprofit investigator-initiated study was partly supported by Norgine Italia SRL, which supplied the bowel preparations. Fuccio had no conflicts of interest. Co-authors Cesare Hassan, Cristiano Spada, and Mauro Manno disclosed consulting work for various private-sector companies. Keswani had no conflicts of interest relevant to his comments.