Comparision of Air Versus CO2 for Distention During Sigmoidoscopy

Intra-operative colonoscopy (inserting a flexible endoscope with a camera at its tip through the anus and up into the rectum and colon) is most often indicated to locate or verify the location of small cancer, polyp, bleeding site, or simply to inspect the bowel after the two ends have been rejoined together. Usually colonoscopy utilizes ambient air to expand and inflate the colon and, as a result, leaves the colon bloated or distended until the gas is either expelled or absorbed. This endoscopy related bowel distension is problematic in the setting of both traditional open (big incision) colorectal surgery and after minimally invasive (laparoscopic assisted) procedures. In the case of the former, it may prove difficult to close a traditional laparotomy incision if the bowel is distended and may hinder respiration with the abdomen closed. In the setting of a laparoscopic procedure, the bowel distension limits the working space available to the surgeon. Since the laparoscopic domain is limited, a distended colon following intra-operative colonoscopy can prevent the minimally invasive completion of a case (meaning that a conversion to traditional "open" methods would be necessary) that otherwise was going well with good prospects of laparoscopic completion. Colonic distension also causes abdominal pain and lengthens the recovery time from the procedure. The investigators believe that the use of CO2 during intra-operative colonoscopy or sigmoidoscopy (exam of only the last 2 to 2 ½ feet of the colon) will not cause long lasting bloating or distension of the colon as opposed to air. Carbon dioxide is absorbed 250 times faster than ambient air and may decrease after procedure colonic distension. This prospective, randomized study will compare the two gases in terms of colonic distension. Patients undergoing open or minimally invasive colorectal resection will be randomized to undergo intra-operative colonoscopy using one of the two gases. Direct measurements of colon diameter will be taken at specific time intervals after the colonoscopy.