Dose the Saline Reduce the Mucus Production When Water Exchange Colonoscopy is Used?

This is a study to compare the left colon mucus production between carbon dioxide (CO2) insufflation and water exchange (WE) colonoscopy in patients that require a routine or repeat colonoscopy. There will be four arms in this study: CO2 insufflation (control group 1), WE with water infusion (control group 2), WE with 50% saline infusion (study group 1), and WE with 25% saline infusion (study group 2). The patient will prepare himself/herself for the colonoscopy as per normal instructions and he/she will be given the information for the study at that time so that he/she can make a decision to participate in the study. The WE control group will use sterile water filling during colonoscope insertion. The study method will use saline filling during colonoscopy insertion. This study will confirm if using the saline infusion is a better method in reducing mucus production when WE colonoscopy is used.