Low-Volume PEG for Inpatient Colonoscopy: Annals of Internal Medicine | July 2026

Introduction:

Adequate bowel preparation is often difficult to achieve in hospitalized patients because of advanced age, comorbidities, immobility, and concurrent medications. This multicenter randomized INTERPRET trial compared 1-L, 2-L, and 4-L polyethylene glycol (PEG) regimens to determine the optimal bowel preparation for elective inpatient colonoscopy.

Why was this study needed?

• Inpatients frequently have inadequate bowel preparation.
• Current guidelines continue to recommend high-volume PEG despite limited inpatient-specific evidence.
• Poor bowel preparation increases missed lesions, repeat procedures, and healthcare costs.
• Lower-volume preparations may improve patient acceptance and adherence.
• Randomized evidence comparing different PEG volumes in hospitalized patients has been lacking.

Results:

• 1-L PEG plus ascorbate achieved bowel cleansing comparable to 2-L and 4-L PEG while providing significantly better high-quality bowel preparation, particularly in the right colon.
• Patients receiving 1-L PEG were the most willing to repeat the preparation, despite a slightly higher incidence of mild vomiting and thirst.
• Overall safety was similar across all three regimens, with no major differences in serious adverse events.

Clinical Impact:

This landmark randomized trial challenges the routine use of high-volume bowel preparation in stable hospitalized patients. A split-dose 1-L PEG regimen appears to offer an excellent balance between efficacy, patient acceptance, and procedural quality, although caution remains necessary in patients with severe constipation, advanced kidney disease, or those requiring urgent colonoscopy.

Bottom Line:

For stable inpatients undergoing elective colonoscopy, 1-L PEG plus ascorbate provides the best balance of bowel cleansing quality and patient tolerability. These findings are likely to influence future bowel preparation guidelines and support broader adoption of low-volume regimens in hospitalized patients.