The patient only revealed his painful predicament after suffering with the blockage for two days, doctors in China said.
And even then he would not confess as to how or why the glass came to be lodged in his back passage.
The Shanghaiist in China reports doctors were able to finally remove the glass cup stuck up without it shattering.
The recent case in Guangzhou apparently involved a married man who came in complaining of unbearable pain.
The patient was screaming for help when he was brought in at 2am.
He was sent for X-ray and the cause of his discomfort immediately became apparent.
Medics feared the glass cup was under so much pressure from the man's rectum muscles that there was a real danger it would break causing a serious and potentially deadly injury.
It was said to be eight centimetres tall and seven centimetres in diameter.
According