| Screening is a systematic intervention that uses clinical, strumental, laboratory means in order to detect a disease in a preclinical phase or its precursors in general population or one of its subgroups. A screening program is a complex process that acts on an asintomatic population invited to undergo a test. In order to carry out a screening program it is necessary that its efficacy in terms of reduction of incidence and mortality has been demonstrated. The aim of the screening is to reduce the specific mortality in the population that regularly undergoes exams for the early diagnosis of tumors or precancerous lesions. As an organized intervention of public health it is a process controlled in its quality and it involves many disciplines and professions. It mu7st also guarantee the maximum equity and foresee a balance between positive and negative effects and a cost estimate. Its realization requires also an adequate information of the heath service but also about the participation and the impact on incidence and mortality. People with a higher risk of colorectal cancer compared to general population (personal or familiar history for cancer and/or adenoma, hereditary forms with high penetrance, inflammatory bowel diseases) are not included in these recommendations. In these last groups the surveillance is based on clinical pathways of high complexity that often need to be adapted to the clinical history of the single patient.
Some screening programs suggest to perform a sigmoidoscopy if the patient has a positive fecal occult blood test. In our experience a complete colonoscopy should always be performed because it has been demonstrated that in these last decades a left-right shift occurred and because sessile serrated polyps are mostly right sided.