Reflex anal dilatation (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,[1] and has been associated with other signs of sexual assault[2] but also appears in children with severe chronic constipation and those subject to invasive medical treatments of the anus.[3] The finding of RAD alone is not considered indicative of sexual abuse,[4] and a normative sample of children not suspected of having been sexually abused found that a significant number of children showed anal dilatation either continuously or intermittently.[5]
Used extensively in the Cleveland child abuse scandal, it was discredited during the trial as the sole indication of sexual abuse, determined to be considered a sign of sexual assault by a tiny minority of British physicians.[6] RAD is now considered discredited.[7]