Current recommendations for colonoscopy screening programs usually involve patients older than 50 years of age. However, little is known about polyp or adenoma detection rates under 50. We compared these detection rates according to age in a large series of patients in common practice.

Methods: All colonoscopies performed in 2016 in our unit were prospectively recorded. We determined adenoma detection rate (ADR), polyp detection rate (PDR), mean number of polyps (MNP), and advanced neoplasia detection rate (ANDR).

Patients All consecutive patients who were scheduled for colonoscopy were included. Exclusion criteria were: patients scheduled for partial colonoscopy, interventional colonoscopy (for stent insertion, stenosis dilation).

Data collection The following data have been prospectively collected: age, gender, indication for colonoscopy, preparation procedure and quality of the preparation (assessed by the Boston Bowel Preparation Scale; BBPS) [19-20], caecal intubation (yes/no), withdrawal time, number and size of polyps and polyp histopathology.

All clinical data were collected during the procedure by a nurse and an endoscopist on a dedicated software. The database was then supplemented by the Clinical Research Associate for histopathological data.

We determined adenoma detection rate (ADR; percentage of colonoscopies with at least one adenoma), polyp detection rate (PDR: percentage of colonoscopies with at least one polyp), mean number of polyps per colonoscopy (MNP), large polyp detection rate (LPDR; percentage of colonoscopies with at least one polyp of 1 cm or more) and advanced neoplasia detection rate (ANDR: percentage of colonoscopies with at least one advanced neoplastic lesion as defined below).

Inclusion Criteria:

• All consecutive patients who were scheduled for colonoscopy were included.

Exclusion Criteria:

• patients scheduled for partial colonoscopy, interventional colonoscopy (for stent insertion, stenosis dilation).

During the study period, 6335 colorectal endoscopic procedures were realized in the endoscopy unit. We excluded 278 sigmoidoscopies and 30 interventional procedures for stent insertion or stenosis dilation. Only diagnostic colonoscopies were recorded, performed in 3308 women (54.9%) and 2719 men (45.1%) with a median age of 57 (range, 15-96: IQR 18).