During bowel preparation for colonoscopy, stools transition from solid to watery. In Japan, toilets typically offer large and small flush options. This study aimed to evaluate whether encouraging the use of small flushes for watery stools could reduce water consumption.

This single-center prospective observational study included a total of 220 patients undergoing colonoscopy. Over 10 months, 111 patients who received standard instructions during the early period of the study, before the intervention, formed the pre-intervention water-usage (PW) group, while 109 patients in the later period of the study who received the interventional infographic poster promoting small flushes formed the green water-usage (GW) group.

The GW group had significantly lower median (interquartile range) total water usage for bowel preparation (31.5 L [27.9–39.6]) compared with the PW group (35.0 L [30.4–44.6]; P = 0.002), suggesting a reduction of approximately 3.5 L per colonoscopy. No significant differences were observed in fluid intake or bowel cleansing quality.

The educational poster intervention promoting appropriate flush selection during bowel preparation may be a simple option for reducing water consumption, leading to greener endoscopy.

Received: 20 January 2025

Accepted after revision: 21 August 2025

Accepted Manuscript online:
21 August 2025

Article published online:
06 October 2025

© 2025. Thieme. All rights reserved.

Georg Thieme Verlag KG
Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany