Anal and distal rectal dilation is the act of opening, widening, or stretching the anus with tools called anal dilators. It is often done after surgical procedures on the anus to restore the area to its normal state. Understanding anal anatomy and muscular contractility is a must in sexual education, all in the hopes of long lasting and powerful experiences. As it pertains to anything in anal play, one must think of the sphincter as having two major functions:. Most people have a difficult time with complete relaxation, during both defecation and intercourse.
Reflex anal dilation RAD is the reflexive dilation of the human anus to a diameter greater than two centimeters in response to the parting of the buttocks or anal stimulation, such as brushing with a medical instrument. RAD was theorized to be a clinical marker associated with anal sexual assault in children,  and has been associated with other signs of sexual assault  but also appears in children with severe chronic constipation and those subject to invasive medical treatments of the anus. From Wikipedia, the free encyclopedia. Forensic Sci. Arch Dis Child. Understanding the medical diagnosis of child maltreatment: a guide for nonmedical professionals. Oxford [Oxfordshire]: Oxford University Press.