Our aim is to perform a randomized-controlled trial comparing air insufflation sedated colonoscopy (conventional method) vs. water infusion sedated colonoscopy (study method) by supervised trainees. Randomized trials demonstrating reduced need for sedation medications without compromising patients' comfort, cecal intubation rates or polyps detection may cause a paradigm shift and positively alter the way traditional colonoscopy is performed and future endoscopists are trained.

Background: A novel water method permitted 52% of patients accepting on-demand sedation to complete colonoscopy without medications and significantly increased successful cecal intubation from 76% to 97% in patients accepting scheduled unsedated colonoscopy.

Aim: To perform a randomized controlled trial comparing air insufflation (conventional method) vs. water infusion in lieu of air (study method) colonoscopy in minimally sedated patients by supervised trainees.

Hypothesis: Compared with the conventional method, patients examined by the study method have lower pain scores and require less medication but have similar cecal intubation rate and willingness to repeat future colonoscopy.

Setting: Outpatient colonoscopy in a single VA hospital Methods: After informed consent and standard bowel preparation, patients received pre-medications administered as 0.5 increment of Fentanyl (25 μg) and 0.5 increment of Versed (1 mg) plus 50 mg Diphenhydramine. The conventional and the study method for colonoscopy were implemented as previously described. Additional pain medications were administered at the patients' request.

Outcome measures: Increments of medications, pain scores, cecal intubation and willingness to repeat colonoscopy.

Limitations: Single VA site, older male population

Inclusion criteria:

• Adult (> 50 years old) male and female patients who are scheduled and consented for screening or surveillance colonoscopy,
• Accept randomization to the study or the conventional method, and agree to complete study questionnaires
• The adults will be normal healthy patients or patients with mild systemic disease, ASA 1 or ASA 2

Exclusion criteria:

• Patients who have contraindications for sedation, decline to participate, unable to give informed consent or complete the questionnaires due to language or other difficulties will be excluded
• Excluded patients will be managed by usual procedures