Screening for rectal prolapse is usually done with a complete anorectal exam. If necessary, to demonstrate the prolapse patients may be asked to sit on a commode and strain as if having a bowel movement. If the rectal prolapse is internal or “hidden,” diagnosing it is more difficult. In this case, the doctor may take what’s called a videodefecogram, wherein x-rays are taken during a bowel movement. Another test called an anorectal manometry may be used to evaluate the function of the muscles around the rectum.