Safety and sustainability of potable tap water irrigation in endoscopy in Canada: an interrupted time series study

Background International guidelines recommend sterile water for endoscopic irrigation despite limited evidence. Single-use plastic sterile water bottles generate substantial costs, greenhouse gas emissions, and microplastics. We sought to estimate whether replacing sterile water with potable tap water for endoscopic irrigation affected clinical outcomes. Methods This quasi-experimental study involved an interrupted time series design at a multi-campus tertiary care academic health system (The Ottawa Hospital, Canada). All adults undergoing esophagogastroduodenoscopy, colonoscopy, flexible sigmoidoscopy, enteroscopy, ileoscopy, or pouchoscopy between February 2024 and August 2025 were included. A system-wide switch to tap water took place on February 10, 2025. The primary outcome was a composite of emergency department visits, unplanned admissions, or deaths within 7 days post-procedure. Infectious complications within 30 days constituted secondary endpoints. Data were obtained from validated institutional databases. Segmented regression modeled the weekly outcome proportion to estimate the step change post-implementation, with a non-inferiority margin of <0.5% absolute risk increase. Findings A total of 29,522 procedures were performed on 29,423 patients (18,863 pre-implementation; 10,560 post-implementation). Patient and procedural characteristics were comparable. The weekly proportion experiencing the primary outcome was 1.6% in both phases. The post-implementation step change was −0.40% (95% confidence interval [CI] −1.16 to 0.35), with the upper boundary of the 95% CI below the pre-specified non-inferiority margin of 0.5%. Results were similar for infectious complications (step change −0.23%, 95% CI −0.75 to 0.29). Interpretation Potable tap water was non-inferior to sterile water for endoscopic irrigation with respect to clinical outcomes. These findings provide an evidence base for revising current guideline recommendations that mandate sterile water for endoscopic irrigation. Funding This project was supported by the 2024 Canadian Society of Colorectal Surgeons Research Operating Grant.