Kristen Miller, a colonoscopy patient, sits with Dr. Stephen Hanauer at the University of Chicago Medical Center in Chicago in 2010. They're looking at an interactive computer program describing benefits and risks of the procedure. Brian Kersey/AP hide caption

itoggle caption Brian Kersey/AP

Before the colonoscopy begins, it pays to ask your doctor some pointed questions. Sebastian Schroeder/iStockphoto.com hide caption

itoggle caption Sebastian Schroeder/iStockphoto.com

No anesthesia here: A patient watches his colonoscopy as it happens at Memorial Sloan-Kettering Hospital in New York. Ted Thai/Time & Life Pictures/Getty Image hide caption

itoggle caption Ted Thai/Time & Life Pictures/Getty Image