Optimal bowel preparation is essential for a more accurate, comfortable, and safe colonoscopy. The majority of postcolonoscopy colorectal cancers can be explained by procedural factors, mainly missed polyps or inadequate examination. Therefore the most important goal of optimal bowel preparation is to reduce the incidence of colorectal cancer. Although adequate preparation should be achieved in 85-90% or more of all colonoscopy as a quality indicator, unfortunately 20-30% shows inadequate preparation. Laxatives for oral colonoscopy bowel preparation can be classified into polyethylene glycol (PEG)-electrolyte lavage solution, osmotic laxatives, stimulant laxatives, and divided into high-volume solution (≥3 L) and low-volume solution (<3 L). The updated 2019 European Society of Gastrointestinal Endoscopy (ESGE) guideline is broadly similar to the 2014 American Society for Gastrointestinal Endoscopy (ASGE) recommendations and reaffirms the importance of split-dosing. However, new ESGE guideline, unlike the 2014 ASGE recommendation, suggests the use of high volume or low volume PEG-based regimens as well as that of non-PEG based agents that have been clinically validated for most outpatient scenarios. For effective, safe, and highly adherent bowel preparation, physicians who prescribe and implement colonoscopy should properly know the advantages and limitations, the dosing, and the timing of regimens. Recently many studies have attempted to find the most ideal regimens, and more convenient, effective, and safe regimens have been developed by reducing the dosing volume and improving the taste. The high tolerability and acceptability of the new low-volume regimens suggest us how we should use it to increase the participation of the national colorectal cancer screening program. (Korean J Gastroenterol 2020;75:65-73)
