4L split dose PEG is the gold standard for bowel preparation, however it comes with poor tolerability and poor compliance. Combination of PEG with different agent is useful in reducing total volume, improving compliance and tolerance of patient.

The objective of this study is to demonstrate that combination bowel preparation, PEG plus SPMC solution, has similar efficacy and safety profile whereas with a better tolerance when compared to large volume PEG.

This is a prospective, randomized, single-center, single-blinded, non-inferiority trial.

Participants with out patient colonoscopy arranged will be included and randomized in a 1:1 ratio to receive either a split dose of 4L PEG + Electrolyte (Klean-prep® ) or 1L Klean-prep® plus 2 sachets SPMC (Picoprep®).

Trained endoscopists will be using the Boston Bowel Preparation Scale (BBPS) to assess the quality of bowel preparation. Patient would also rate the tolerance, compliance and adverse effect by filling the questionnaire before the colonoscopy.

Inclusion Criteria:

1. Patient who mentally capable to consent for participating the trial
2. 18 - 65 years old
3. Scheduled for 1st colonoscopy
4. Elective outpatient colonoscopy

Exclusion Criteria:

1. Prior colorectal or abdominal-pelvic surgery
2. Inflammatory bowel disease
3. Active bowel condition eg intestinal obstruction
4. Gastrointestinal disorders eg active ulcer, gastric outlet obstruction, gastroparesis and hypomotility syndrome
5. Recent myocardial infarction, congestive heart failure, uncontrolled hypertension
6. Renal dysfunction, hepatic disease
7. Patient on long term tranquilizer, anti-spasmodic, prokinetic, laxative or antidiarrhoeal agents
8. Hypersensitivity to PEG or SPMC solution
9. Pregnant or breastfeeding women
10. Inability to give informed consent