Morning-Only 4 L PEG vs Split Dose Prep for Afternoon Colonoscopies, Endoscopist-Blinded Prospective Study

The aim of colorectal cancer screening is to reduce mortality. This can be effectively achieved by colonoscopy with direct visualization of the entire colon to detect preneoplastic lesions such as adenomatous polyps. Bowel preparation quality is critical for the accuracy of colonoscopy, time required to complete the procedure and its success. On the other hand, poor quality of bowel preparation was shown to be associated with a lower adenoma detection rate. Prior studies have shown that time of colonoscopy is one of the major factors influencing bowel preparation quality with the afternoon colonoscopies being notable for a high failure rate. This failure rate is related to poor bowel preparation quality. Given that, the number of afternoon colonoscopies performed is still high due to the increased need for colonoscopies. Therefore, it is suggested that improving the bowel preparation quality can reduce failure rate of afternoon colonoscopies. Several studies on split-dose bowel preparation have shown that it is superior to the conventional day-before regimen, in terms of preparation quality and patient's tolerability. Another study on split-dose bowel preparation also showed that it is associated with a better adenoma detection rate, better polyp detection rate and colonoscopy completion rate. There also have been few studies comparing same day dose vs. day-before for afternoon colonoscopies and showed that same day was superior to day before.There is no data comparing quality of preparation of colonoscopy in patients taking same day 4L preparation vs. 4 L split-dose preparation for an afternoon colonoscopy. Using a 4L PEG-ELS solution, the investigators aim to evaluate the efficacy and patient's tolerability for the same day versus split-dose regimen.