Colonoscopy and flexible sigmoidoscopy are techniques for visualizing the lumen of the large bowel. In expert hands, after appropriate explanation to the patient (which increases the chances of the procedure being well tolerated), bowel preparation, and (usually) some form of ‘conscious sedation’, then total colonoscopy is possible in 98 to 99% of cases in the absence of obstruction, a severely ulcerated colon, or other contraindication....

Colonoscopy and flexible sigmoidoscopy are techniques for visualizing the lumen of the large bowel. In expert hands, after appropriate explanation to the patient (which increases the chances of the procedure being well tolerated), bowel preparation, and (usually) some form of ‘conscious sedation’, then total colonoscopy is possible in 98 to 99% of cases in the absence of obstruction, a severely ulcerated colon, or other contraindication....