[Colonoscopies for colorectal cancer screening].

Colonoscopies play a vital role in population screening programs, either for initial examinations or as a test carried out after a positive result from a fecal occult blood test or sigmoidoscopy. Colonoscopies, and ancillary techniques such as polipectomies, must comply with basic quality criteria that must be reflected in the quality standards of screening programs. A quality colonoscopy is absolutely vital to avoid the occurrence of interval cancers. It is extremely important to detect any proximal lesions during a colonoscopy, especially those which are serrated, because they are difficult to identify and due to the increased risk of colorectal cancer. Regarding follow-up programs for resected colorectal polyps, current evidence of the relationship between the risk of neoplasia and certain variables (age, sex, smoker, BMI, diabetes, etc.) must allow for individualized risk and algorithms for screening and follow-up frequency to be developed for these patients. However, initial endoscopic exploration in a screening colonoscopy is essential to establishing the optimum interval and ensuring follow-up. Despite poor adherence to follow-up programs, mostly due to their overuse, follow-up colonoscopies 3 years after resection of all polypoid lesions detect clinically significant lesions as effectively as colonoscopies at one year.