Abstract:Objective To investigate the efficacy of lactulose combined with magnesium sodium potassium sulfate salts on bowel preparation for colonoscopy in patients with constipation，aiming to improve the quality of bowel cleansing.Methods Prospectively，a total of 220 constipated patients admitted to the Affiliated Jiangning Hospital of Nanjing Medical University from February to December 2024 were enrolled and randomly divided into control（n=110）and experimental（n=110）groups using a random number table. The control group received magnesium sodium potassium sulfate concentrated oral solution，while the experimental group underwent two-day lactulose treatment before taking the same solution. The Boston Bowel Preparation Scale（BBPS）score，time to first defecation，colonoscopy insertion time to the cecum，adenoma detection rate（ADR），and adverse events were compared between the two groups. Results A total of 202 patients were ultimately included in this study，with 102 assigned to the control group and 100 to the experimental group. The rates of inadequate bowel preparation in the experimental and control groups were 2.00% and 11.76% ，respectively. The BBPS scores were（7.34 ± 0.86）and（6.67 ± 1.20）points，respectively，with the experimental group demonstrating superior bowel preparation efficacy compared to the control group（t=4.542，P<0.01）. The time to first defecation was shorter in the experimental group than that in the control group［（109.44 ± 7.68）minutes vs（121.17 ± 11.46）minutes，t=7.565，P<0.01］. There was no statistically significant difference between the two groups in terms of colonoscope insertion time to the cecum and colorectal ADR（P>0.05）. The incidence of adverse reactions was lower in the experimental group compared to the control group（30.00% vs 63.73% ，χ2=23.055，P<0.01），with abdominal distension and nausea being the most common. Conclusion The combination of lactulose and magnesium sodium potassium sulfate salts significantly improves bowel preparation quality in constipated patients undergoing colonoscopy，and reduces adverse events.