# Comparative Effectiveness of Split-dose Colonoscopy Bowel Preparation Regimens

> **NIH VA I01** · PHILADELPHIA VA MEDICAL CENTER · 2020 · —

## Abstract

Anticipated Impacts on Veterans Health Care: by identifying a colonoscopy bowel preparation regimen
which is the most effective in real-world VA practice and can be immediately implemented on a VA-wide scale,
the proposed study will maximize the effectiveness of colonoscopy in reducing colorectal cancer (CRC) risk
among veterans, increase veteran satisfaction, and reduce VA healthcare cost. Background: CRC is a leading
cause of cancer-related death among veterans. Colonoscopy can effectively reduce CRC incidence and
mortality. However, non-adherence to screening colonoscopy substantially undermines this benefit. Existing
evidence indicates that a disagreeable bowel preparation is a leading barrier to completing a colonoscopy from
the patients' perspective. The taste and the volume of the bowel preparation determine patient tolerability and
compliance to the preparation instructions, which in turn affects the incompletion (e.g., cancellation/no-
show/reschedule) rate of scheduled colonoscopies as well as the effectiveness of the completed
colonoscopies and patient satisfaction. The two most commonly used preparations currently in the US are the
split-dose 4L polyethylene glycol (PEG) and the split-dose 2L MiraLAX/Gatorade preparations. While a high-
volume regimen may in theory be more effective than a lower volume one, it may be associated with lower
tolerability and adherence in real-world practice. Three small trials have compared these two preparations.
However, data from these explanatory trials cannot inform policy decisions because they were conducted
under artificial conditions, restricted among narrow patient populations, and most importantly not designed to
capture the full impact of bowel preparation on the completion rate or effectiveness of colonoscopy. To address
this critical knowledge gap, we are proposing a pragmatic trial to determine the optimal split-dose bowel
preparation in the general veteran population. Objectives: to compare the real-world effectiveness of the two
most commonly used split-dose colonoscopy bowel preparation regimens in the US (i.e., 4L PEG and 2L
MiraLAX/Gatorade) with respect to the completion rate of scheduled colonoscopies, adenoma detection rate
and secondarily preparation quality, cancellation/no-show rate and patient-oriented outcomes (e.g., willingness
to repeat the preparation). Methods: the study will be a pragmatic randomized controlled trial comparing the
two existing bowel preparation regimens in a large regional VA healthcare system. All veterans who are > 18
years of age and undergoing an outpatient elective colonoscopy are eligible. This pragmatic trial will be
conducted with a waiver of informed consent. Providers who are ordering a colonoscopy at the point of care
will be asked to choose between allowing the patient to be enrolled in the study or continuing with the current
standard 4L PEG within the context of the VA electronic medical records (EMR) ordering menu. Enrolled
patients will be...

## Key facts

- **NIH application ID:** 9600613
- **Project number:** 5I01HX002133-02
- **Recipient organization:** PHILADELPHIA VA MEDICAL CENTER
- **Principal Investigator:** YU-XIAO YANG
- **Activity code:** I01 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2020
- **Award amount:** —
- **Award type:** 5
- **Project period:** 2017-10-01 → 2021-09-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9600613

## Citation

> US National Institutes of Health, RePORTER application 9600613, Comparative Effectiveness of Split-dose Colonoscopy Bowel Preparation Regimens (5I01HX002133-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9600613. Licensed CC0.

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