You said, "I am not aware of any legitimate reason why someone would put gold in their anus"
A book (not the movie) called Papillion is an amazing book on the survival of prisoners on a the prison island called Devil's Island. It was a French Penal Colony. They stored their valuables in a tube that screwed shut and was called "their plan" and it was inserted up their rectum and into their intestine. This was to protect their valuables from the guards and other inmates.