SUBJECTS AND METHODS ; Two hundred twenty-four participants were randomly allocated to one of four groups : control ( no bowel relaxant and IV saline placebo before CT colonography with manual carbon dioxide insufflation ) , hyoscine butylbromide ( IV hyoscine butylbromide before examination with manual carbon dioxide insufflation ) , automated ( no bowel relaxant before examination with automated carbon dioxide insufflation ) , and combined ( hyoscine butylbromide before examination with automated carbon dioxide insufflation ) .