Fisting
Anal fisting carries risks of colorectal tearing; people doing it should use latex gloves and lubricant, and have a safeword, which they can say when they want it to stop immediately. The practice, along with the insertion of hard objects into the anus or the vagina has been significantly related to the traumatization of the vaginal or rectal mucosa in increasing the likelihood of infection, including Hepatitis B virus.