Efficacy and safety of remedial hydrotherapy enema for inadequate bowel preparation in colonoscopy: a prospective randomised controlled trial

Inadequate bowel preparation is a common challenge for colonoscopy, compromising mucosal visualization and increasing the risk of missed lesions. The current rescue strategies—repeat oral polyethylene glycol (PEG) administration or procedure cancellation—are often poorly tolerated or resource-intensive. This trial evaluated colon hydrotherapy enemas as an alternative salvage method. In this prospective, single-center randomized trial, 120 patients with inadequate bowel preparation after initial oral PEG were assigned to either hydrotherapy enemas (n = 60) or repeat oral PEG administration (n = 60) before same-day colonoscopy. The primary outcome was bowel cleansing efficacy measured by the Boston Bowel Preparation Scale (BBPS). Secondary outcomes included preparation time, adverse events, patient satisfaction, and safety parameters. The hydrotherapy group achieved higher median (IQR) BBPS scores for overall colon cleansing [7.5 (3) vs. 6.5 (1), P = 0.026] and left hemicolon [3 (1) vs. 2 (1), P < 0.001] compared with the oral PEG group. Preparation time was 40 min shorter (95% CI − 50 to − 39, P < 0.001). Gastrointestinal adverse events occurred in 30.4% of hydrotherapy patients versus 82.8% of oral PEG patients (absolute risk reduction 52.4%, 95% CI 36.9–67.8%; P < 0.001). No severe neurotoxic reactions or clinically significant electrolyte disturbances emerged in either group. Patient satisfaction scores favored hydrotherapy across all domains. In this randomized trial, hydrotherapy enemas provided modestly improved salvage bowel preparation compared with continued oral PEG, with fewer adverse events and higher patient satisfaction. These findings suggest hydrotherapy may serve as a rescue option for selected patients, particularly those intolerant to PEG or requiring same-day salvage. Further multicenter studies assessing adenoma detection rates and post-colonoscopy colorectal cancer incidence are needed to establish its broader clinical role (Chinese Clinical Trial Registry: ChiCTR2400088365, Registered: 2024-08-16).