When compared to colonoscopy, FS has the advantages of being an unsedated procedure, requiring less stringent bowel prep, and being less technically demanding. While flexible sigmoidoscopy have traditionally been performed by gastroenterologists or surgeons, studies have demonstrated that adequately trained primary care doctors and nurse endoscopists can perform screening flexible sigmoidoscopy as safely and effectively as gastroenterologists or surgeons. The American Society for Gastrointestinal Endoscopy (ASGE), the Society of American Gastrointestinal Endoscopic Surgeons (SAGES), and the The Society of Gastrointestinal Nurses and Associates (SGNA) recommend 25 supervised procedures for training in FS. Hawes R et al reported that at least 30 supervised procedures were needed before 85% - 90% of the procedures were graded as competent in doctors without prior experience on rigid sigmoidoscopy. In another report, at least 50 supervised procedures have been suggested for FS training of clinicians without prior endoscopic skills.