Screening colonoscopy has been established as the most effective means of colorectal cancer prevention. This is based on the fact that colonoscopy detects and removes colonic polyps (adenomas) which are known to progress to cancer if left untreated. The present study examines the question whether case volume (i.e., the number of colonoscopies performed per year) correlates with colonoscopy quality, i.e., adenoma detection rate.

21 private practice gastroenterologist endoscopists from Berlin performed a prospective quality assessment study including at least 10.000 screening colonoscopies. After informed consent, patients data are included (age, sex, family history, colonoscopy performance parameters and findings, therapy performed, histology of biopsies and/or polypectomies, complications (immediate and late) and patient acceptance. The latter was retrieved by patient questionnaires returned after a minimum of 2 weeks. Data were centrally collected in an anonymized way

Primary outcome parameter:

• Correlation of adenoma detection rate with case volume and other confounding factors (e.g., withdrawal time)

Secondary outcome parameters:

• Complications and method of assessment (immediate recording versus later questionnaire enquiry)
• Quality of bowel preparation in relation to outcome Patient acceptance in relation to procedural factors (e.g., sedation)
• Quality of pathology reports and histologic outcome of polypectomy

Later follow-up (after 5-10 years) of the preventive effect of colonoscopy is planned and has been part of the protocol and patient consent form.

Inclusion Criteria:

• all persons willing and able to undergo screening colonoscopy over the age of 55 years

Exclusion Criteria:

• any condition not compatible with the definition of screening colonoscopy

In Germany screening colonoscopy is reimbursed over the age of 55 years. All persons willing to undergo screening colonsocopy without contraindications are asked for consent to be included