The ability of a colonic cleansing preparation to clean the colon effectively also must be balanced by its ability to not induce changes in the lining of the bowel itself. Ulceration and inflammation of the colon has been shown to occur in 3-24% of patients using NaP compared with 1-2% in those receiving PEG. Such findings can be mistaken for inflammatory bowel disease such as Crohns or put down to drug induced changes such as non steroidal anti inflammatory agents (NSAIDs). However, these studies have been either non randomised5 or underpowered to detect real differences.