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

Ultra-low Split-dose Oral Lactulose vs High-volume Split-dose Polyethylene Glycol as Bowel Preparation for Outpatient Colonoscopies (LACPEG): Randomized, Single-center, Single-blind Clinical Trial.

This study compared two different ways to clean the bowel before a colonoscopy: lactulose (a sweet syrup mixed with water) versus high-volume polyethylene glycol (PEG, the usual standard treatment). The goal was to find out which one cleans the bowel better, is easier for patients to take, and has fewer side effects.

Researchers wanted to answer these main questions:

Does lactulose clean the bowel as well as PEG according to the Boston Bowel Preparation Scale? Which preparation do patients find more pleasant and are more willing to repeat in the future? Are there differences in side effects such as nausea, vomiting, bloating, or belly pain? Do the two preparations affect how well doctors can see inside the colon, including the chance of finding polyps?

Adults aged 45 to 75 years who were scheduled for a routine outpatient colonoscopy at the Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán in Mexico City were invited to take part. People with certain serious medical conditions (such as advanced liver disease, kidney failure on dialysis, heart failure, pregnancy, or previous colon surgery) could not join.

Participants were randomly assigned to one of two groups:

Lactulose group: 125 ml of lactulose mixed in 600 ml of water the evening before, and again early the next morning.

PEG group: 2 liters of PEG solution the evening before, and another 2 liters early the next morning.

Both preparations were finished by 6:00 a.m. All participants followed a low-fiber diet the day before the procedure. Doctors performing the colonoscopy did not know which preparation each patient had used.

The study included 200 people (100 in each group).

Study Title:

Lactulose oral in split-dose versus high-volume polyethylene glycol in split-dose for bowel preparation in outpatient colonoscopies (LACPEG): a randomized, single-center, single-blind clinical trial.

Background and Rationale Adequate bowel preparation is essential for high-quality colonoscopy. Suboptimal preparation reduces cecal intubation rates, prolongs procedure time, and decreases adenoma detection. International guidelines (ESGE) currently recommend split-dose high-volume polyethylene glycol (PEG) as the gold standard for morning outpatient colonoscopies. However, the large volume required often impairs patient tolerance.

Lactulose, a synthetic disaccharide widely used for constipation, has shown promising results in recent studies as a bowel preparation agent. It requires significantly lower volume, has a more acceptable taste, and has demonstrated good cleansing efficacy with fewer adverse effects compared to PEG in some trials. Nevertheless, high-quality randomized controlled trials comparing split-dose lactulose versus the current gold-standard split-dose 4L PEG are still limited, particularly in Latin American populations. No such studies have been published in Mexico. This trial was designed to address 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, from July 2024 to December 2025.

Interventions

Eligible patients were randomized 1:1 to one of two split-dose bowel preparation regimens:

Lactulose arm 125 mL lactulose (10 g/15 mL) diluted in 600 mL water, taken between 21:00-22:00 the evening before the procedure.

Second dose: identical regimen (125 mL lactulose in 600 mL water) between 05:00-06:00 on the 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 the morning 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 hours before 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 was defined as total BBPS ≥6. Cecal intubation rate, polyp detection rate, and adenoma detection rate were also recorded. Patient tolerability, taste acceptability (1-10 scale), willingness to repeat the preparation, and adverse effects (nausea, vomiting, abdominal pain, distension) were evaluated using a standardized questionnaire before the procedure.

Statistical Analysis Data were analyzed using SPSS v20.0. Continuous variables are presented as mean ± SD or median (IQR) according to distribution. Categorical variables are presented as frequencies and percentages. Between-group comparisons were performed using Student's t-test, Mann-Whitney U test, or chi-square test as appropriate. A two-sided p-value <0.05 was considered statistically significant.

This study provides direct comparative data on efficacy, tolerability, and safety of split-dose lactulose versus split-dose 4L PEG in a Mexican outpatient population undergoing elective colonoscopy.

Inclusion Criteria:

Patients scheduled for outpatient colonoscopies for colorectal cancer screening Ages 45 to 75 Informed consent form required

Exclusion Criteria:

Pregnancy Patients with colon resections and/or ileostomies Allergy to the medications studied Intolerance to the oral route Hepatic cirrhosis Ascites Chronic kidney disease on peritoneal dialysis or hemodialysis, decompensated heart disease (ischemic heart disease, congestive heart failure, unstable angina) Inflammatory bowel disease Inability to understand the instructions for bowel preparation Suspected intestinal obstruction or perforation Patients with lower gastrointestinal bleeding History of colon cancer History of inadequate bowel preparation History of polyps in previous colonoscopies Bow preparation intake <50%