Colonoscopy is a common screening method to detect polyps and CRC. With the early detection of CRC through screening colonoscopy, patients could have better therapeutic effects and outcomes. In population screening programs, an increase in completed colonoscopies is related to a decrease in mortality from CRC. However, the miss rate for detecting colorectal neoplastic polyps of colonoscopy is 5-28%. The reluctance of participants to undergo bowel preparation results in the relatively low rate of detection of polyps and CRC, because poor preparation interferes with successful colon mucosa examination during a colonoscopy.

Low-volume bowel preparations provide equivalent cleansing effect compared with standard 4 liter polyethylene glycol. However, studies comparing the superiority between low-volume bowel preparations are rare, and results are controversial. This study aimed to compare the bowel cleansing quality and tolerability between split-dose sodium picosulfate/magnesium citrate and polyethylene glycol with ascorbic acid.

1. Study design: endoscopist-blinded, prospective, randomized controlled trial

2. Subjects

   1. Entry criteria: Male or female patients, aged between18 and 80 years undergoing elective outpatient colonoscopy were eligible for the study.
   2. Exclusion criteria:

   patients who had chronic kidney disease, severe heart failure(New York Heart Association [NYHA] class III or IV), uncontrolled hypertension (systolic pressure ≥170 mm Hg, diastolic pressure ≥100 mm Hg), severe constipation, any bowel resection, significant gastroparesis, or suspected bowel obstruction or perforation.

3. Sampling design: Consecutive recruitment of consenting patients

4. Variables Predictor

   1. group 1 (SPMC 2) received one sachet of SPMC at 7 p.m the evening before colonoscopy and another sachet of SPMC at 5 hours before procedure
   2. group 2 (PEG-Asc) received 1 L solution of PEG-Asc at 7 p.m the evening before colonoscopy and another 1 L solution of PEG-Asc at 5 hours before procedure;

5. Primary Outcome: Quality of bowel preparation (Boston Bowel Preparation Scale, Aronchick scale, bubble score)

6. Secondary Outcome: Tolerability, palatability

Inclusion Criteria:

• Male or female patients, aged between18 and 80 years undergoing elective outpatient colonoscopy were eligible for the study

Exclusion Criteria:

• patients who had chronic kidney disease, severe heart failure(New York Heart Association [NYHA] class III or IV), uncontrolled hypertension (systolic pressure ≥170 mm Hg, diastolic pressure ≥100 mm Hg), severe constipation, any bowel resection, significant gastroparesis, or suspected bowel obstruction or perforation.