Comparison of Methods to Distend the Colon During Insertion: CO2, Air Insufflation, Water-aided Colonoscopy

Design: Prospective double blinded two-center randomized controlled trial. Methods: Colonoscopy with air insufflation, CO2, Water Immersion/CO2, Water Exchange/CO2, Water Immersion/AI and Water Exchange/AI to aid insertion of colonoscope; split dose bowel preparation; on demand-sedation. Control method: Air insufflation colonoscopy. Study methods: CO2 colonoscopy, Water Immersion/CO2 colonoscopy, Water Exchange/CO2 colonoscopy, Water Immersion/AI colonoscopy, Water Exchange/AI colonoscopy. Population: Consecutive 18 to 85 year-old diagnostic in-patients and outpatients. After informed consent, assignment to control or study arms based on computer generated randomization list with block allocation and stratification. Primary outcome: Maximum pain score recorded during colonoscopy. Secondary outcomes: Cecal intubation rate and time, total procedure time (including biopsy and/or polypectomy), need for sedation and its dosage, overall pain score at discharge. In addition, Adenoma Detection Rate, Mean Adenomas per Procedure, position changes, amount of infused and suctioned water during insertion and withdrawal will be recorded. Bloating after examination and at discharge and patient willingness to repeat the examination will be evaluated.