Colonoscopy is a basic but important tool to diagnose and treat lesions of the colon. Proper
colon cleansing is essential for colonoscopy to be performed with a good quality. Inadequate
bowel preparation leads to longer colonoscopic insertion time and patient discomfort, as well
as inadequate diagnostic yield of colonic lesions. Frequency of colonoscopy failure due to
bad bowel preparation is reported to be 0.3% to 6.5 percent, and the rate increases with
liver cirrhosis, constipation, dementia, stroke, or administration of tricyclic
antidepressants. In case of colonoscopy failure due to bad bowel preparation, the second
colonoscopy can be performed with either adding a colon cleansing solution immediately, or it
can be performed after a few days with colon cleansing agent together with prokinetics. These
different kinds of bowel preparations after first colonoscopy failure have not been compared.