These guidelines are developed under the auspices of the American College of Gastroenterology (ACG) and its Practice Parameters Committee and approved by the Board of Trustees. They have been intensely reviewed and revised by the Committee, other experts in the field, physicians who will use them, and specialists in the science of decision analysis. When approved by the ACG, they are submitted to the other major gastrointestinal societies (American Gastroenterological Association and the American Society for Gastrointestinal Endoscopy) for their approval. To develop the guidelines, the world literature is searched, then all appropriate studies are reviewed and evaluated by the authors. In the literature review, evidence is evaluated along a hierarchy, with randomized, controlled trials given the greatest weight. Abstracts presented at national and international meetings are only used in special circumstances in which unique data from ongoing trials were presented. When scientific data is lacking, recommendations are based on expert consensus. These guidelines are intended to be applicable to all physicians who address the subject without regard to specialty training or interests, and are intended to indicate the preferable, but not the only acceptable, approach to this problem. Given the wide range of specifics in any health care problem, the physician must always choose the course best suited to the individual patient and the variables in existence at the moment of decision.