Bowel Preparation in Colonoscopy: Lactulose vs Polyethyleneglycol, Randomized Double-blind Comparative Clinical Trial, Multicenter Study

Background Adequate bowel preparation is essential to ensure optimal visualization during colonoscopy, directly influencing lesion detection rates, procedural success, and overall diagnostic performance. Although Polyethylene Glycol (PEG) is widely used as the standard preparation, Lactulose has emerged as a potential alternative due to its tolerability and availability. Evidence comparing their effectiveness has shown mixed results, and further evaluation is warranted. This multicenter, randomized, double-blind clinical trial aimed to compare Lactulose and Polyethylene Glycol in terms of bowel cleansing quality, endoscopic performance, and diagnostic yield. Methods Of 606 enrolled patients, 449 met inclusion criteria and were randomized to receive either Lactulose (n = 178) or Polyethylene Glycol (n = 271). Colonoscopies were performed at two tertiary hospitals. Demographic variables, comorbidities, and indications for colonoscopy were recorded. Statistical analysis was conducted using IBM SPSS v25. Quantitative variables were compared using the Student’s t test for independent samples, with assumptions of normality (Kolmogorov–Smirnov) and homogeneity of variances (F-test) verified. Categorical variables were analyzed with chi-square testing. The Boston Bowel Preparation Scale (BBPS) was used to assess bowel cleanliness in each colon segment and overall. Endoscopic outcomes (including cecal intubation rate, cecal intubation time, and macroscopic mucosal changes) were compared. Diagnostic yield was evaluated through the Adenoma Detection Rate (ADR). Results Both groups were statistically comparable at baseline in terms of age, sex, and comorbid conditions. Only the indication of lower gastrointestinal bleeding differed significantly, occurring more frequently in the PEG group; however, this imbalance did not influence key outcomes. Macroscopic mucosal changes such as edema, hyperemia, or bleeding were infrequent and showed no significant association with the type of preparation (3.24% vs. 5.13%; p = 0.364). Across colon segments (including ascending, transverse, and descending) the BBPS scores were nearly identical, with no statistical differences observed. The total BBPS score also showed comparable results (Lactulose: 7.21 ± 1.61 vs. PEG: 7.08 ± 1.49; p = 0.37; 95% CI –0.42 to 0.162), demonstrating equivalent cleansing efficacy.Endoscopic performance indicators were similarly consistent between groups. Cecal intubation rates were 94.4% for Lactulose and 94.1% for PEG (p = 0.85), aligning closely with international standards. Cecal intubation time showed no statistical difference. Diagnostic yield, assessed through ADR, revealed a nonsignificant trend toward higher detection in the PEG group (26.4% vs. 32.1%; p = 0.236). Overall, neither preparation demonstrated superiority in adenoma detection. Conclusion This randomized, double-blind, multicenter clinical trial demonstrates that Lactulose and Polyethylene Glycol offer equivalent efficacy as bowel preparations for colonoscopy. Both agents resulted in comparable cleansing quality across all colon segments, similar cecal intubation rates and times, and no significant differences in adenoma detection. These findings support the use of Lactulose as a clinically valid alternative to PEG, allowing for flexibility in preparation choice based on patient tolerance, cost considerations, availability, and institutional preferences—without compromising procedural quality or diagnostic performance.