You may well be right, Richard Bridge, I may have misinterpreted the comment 'It's about gay anal sex, doh' to refer to more than just the song 'Relax', in the midst of all the commentary on terms that have in various times and places referred to the backside or the feminine front side.
Actually (mild thread drift) in the office it is important to make sure the patient does understand; I know too many doctors do not make a point of this, and some are notorious for using medical jargon leaving patients confused at best. I once had a memorable conversation in a pediatrics clinic with the mother of an infant who seemed dehydrated, as follows:
"Does your baby have diarrhea?"
   "Huh?"
"Watery bowel movements?"
   "Huh?"
"Are his stools loose?"
   "Huh?"
"Does he have the runs?"
   "Uhhh..."
"Your baby got the shits?"
   "Oh, yeah, doc, my baby got the shits real bad!"