Ultra-low Split-dose Oral Lactulose vs High-volume Split-dose Polyethylene Glycol as Bowel Preparation for Outpatient Colonoscopies.

Study Title:Lactulose oral in split‐dose versus high‐volume polyethylene glycol in split‐dose forbowel preparation in outpatient colonoscopies (LACPEG): a randomized, single‐center,single‐blind clinical trial.Background and Rationale Adequate bowel preparation is essential for high‐qualitycolonoscopy. Suboptimal preparation reduces cecal intubation rates, prolongs proceduretime, and decreases adenoma detection. International guidelines (ESGE) currentlyrecommend split‐dose high‐volume polyethylene glycol (PEG) as the gold standard formorning outpatient colonoscopies. However, the large volume required often impairspatient tolerance.Lactulose, a synthetic disaccharide widely used for constipation, has shown promisingresults in recent studies as a bowel preparation agent. It requires significantly lowervolume, has a more acceptable taste, and has demonstrated good cleansing efficacy withfewer adverse effects compared to PEG in some trials. Nevertheless, high‐qualityrandomized controlled trials comparing split‐dose lactulose versus the currentgold‐standard split‐dose 4L PEG are still limited, particularly in Latin Americanpopulations. No such studies have been published in Mexico. This trial was designed toaddress this evidence gap.Study Design This was a prospective, randomized, single‐center, single‐blind,parallel‐group clinical trial conducted at the Department of Gastrointestinal Endoscopy,Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, fromJuly 2024 to December 2025.InterventionsEligible patients were randomized 1:1 to one of two split‐dose bowel preparationregimens:Lactulose arm 125 mL lactulose (10 g/15 mL) diluted in 600 mL water, taken between21:00‐22:00 the evening before the procedure.Second dose: identical regimen (125 mL lactulose in 600 mL water) between 05:00‐06:00 onthe morning of the procedure.Polyethylene glycol arm (control) Macrogol 3350 (Nulitely®) ‐ two sachets (109.6 g each)dissolved in 2 L of water, taken between 20:00‐22:00 the evening before.Second dose: identical regimen (two sachets in 2 L water) between 04:00‐06:00 on themorning of the procedure.Both preparations were completed by 06:00. All participants received a low‐fiber,low‐residue diet the day before colonoscopy. Clear liquids were allowed until 2 hoursbefore the procedure.Blinding Endoscopists and endoscopy staff were blinded to the preparation assignment.Patients were instructed not to reveal their preparation type.Procedures Bowel cleansing quality was assessed using the Boston Bowel Preparation Scale(BBPS) in each colonic segment (right, transverse, left). Adequate preparation wasdefined as total BBPS ≥6. Cecal intubation rate, polyp detection rate, and adenomadetection rate were also recorded. Patient tolerability, taste acceptability (1‐10scale), willingness to repeat the preparation, and adverse effects (nausea, vomiting,abdominal pain, distension) were evaluated using a standardized questionnaire before theprocedure.Statistical Analysis Data were analyzed using SPSS v20.0. Continuous variables arepresented as mean ± SD or median (IQR) according to distribution. Categorical variablesare presented as frequencies and percentages. Between‐group comparisons were performedusing Student's t‐test, Mann‐Whitney U test, or chi‐square test as appropriate. Atwo‐sided p‐value <0.05 was considered statistically significant.This study provides direct comparative data on efficacy, tolerability, and safety ofsplit‐dose lactulose versus split‐dose 4L PEG in a Mexican outpatient populationundergoing elective colonoscopy.