Colonoscopy can be performed by a one-operator technique with endoscopist personally advancing and withdrawing the scope or by a two-operators technique, with the GI-assistant doing the physical insertion and withdrawal of the scope directed by the endoscopist. Uncontrolled data report that 1 operator technique is associated with a higher adenoma detection rate, although it is also characterized by a lowwer cecal intubation rate and longer intubation time. The aim of present randomized controlled study was to assess whether one technique is better than the other one in terms of colonoscopy quality performances.

Inclusion Criteria:

• adult outpatients colonoscopy for screening or surveillance indications

Exclusion Criteria:

• previous colonic surgery
• poor bowel prep
• inability to provide consent

colon cancer screening population