Background: Adequate bowel preparation is essential for diagnostic accuracy, procedure safety, and overall quality in colonoscopy. Despite standardized split-dose regimens and written instructions, preparation quality remains suboptimal in many settings. Mobile health (mHealth) interventions such as short-message-service (SMS) reminders may improve patient adherence and cleansing quality, but existing evidence is heterogeneous. This randomized controlled trial evaluated the effect of structured SMS reminders on bowel-preparation quality using validated scoring tools.

In this single-center prospective randomized trial, 600 adult outpatients scheduled for colonoscopy were assigned to either an SMS reminder group (n = 300) or a standard education group receiving only a paper pamphlet (n = 300). The SMS group received six automated Persian-language reminders delivered at specific intervals 48 hours before the procedure. Bowel preparation quality was assessed by blinded endoscopists using the Boston Bowel Preparation Scale (BBPS; 0–9) and the Ottawa Bowel Preparation Scale (0–14). Adequate preparation was defined as BBPS ≥ 6 and Ottawa ≤ 5. Data were analyzed using t-tests, χ² tests, and multivariate logistic regression.

The SMS group achieved significantly higher mean total BBPS scores (7.39 ± 0.66 vs. 6.68 ± 0.65; p < 0.0001) and significantly lower Ottawa scores (3.48 ± 0.97 vs. 4.29 ± 1.05; p < 0.0001). Adequate preparation was more frequent in the SMS group based on both BBPS (98.3% vs. 85.7%) and Ottawa criteria (95.7% vs. 74.7%). Improvements were consistent across colon segments and demographic subgroups.

Structured SMS reminders significantly improved bowel-preparation quality compared with standard written instruction alone. SMS-based reinforcement represents a low-cost, scalable strategy to enhance colonoscopy quality and may be incorporated into routine pre-procedure education.