Grading the Quality of Bowel Preparation **

In colonoscopy, even a complete examination has little diagnostic accuracy when the endoscopic view of the mucosa was impaired by residual stool. Therefore, an assessment of the visibility of the mucosa is important, in order to be able to judge the reliability of positive, but even more importantly, negative findings during colonoscopy.Insufficient visualization can result in lesions, especially small or flat ones, being missed. Poor bowel preparation may also result in difficult progression, an increased risk of complications, prolonged procedure duration and an increase in the amount of sedatives and analgetics required. Poor bowel preparation is also a frequent cause for incomplete procedures.The optimal grading scale uses objective terminology, is validated, and informs both on segmental as overall bowel preparation quality. The Boston bowel preparation scale fulfils all these criteria, making it the most uses bowel preparation scale in colorectal cancer screening programs.