Studies that have investigated different bowel preparations in patients with history of colorectal surgery are surprisingly lacking.Therefore, which is the best colon preparation in this subgroup of patients is still unknown. Polyethylene glycol (PEG)-based solutions are the most popular and safest bowel preparation regimens, however the 4-Liter volume is often poorly tolerated. More recently, it has been shown that the use of a low volume preparation (2-Liter PEG solution with the adjunct of a laxative, bisacodyl) achieves comparable bowel cleanliness rates to 4-Liter PEG in general population.The primary aim will be to compare the efficacy of 2-L mixed preparation (bisacodyl plus PEG) to 4-L PEG preparation.