Terry Brazier was meant to be having botox injected in his bladder when he went in for treatment at the Leicester Royal Infirmary last summer.
However, there was a mix-up and afterwards Mr Brazier said he was told "sorry, but we've circumcised you". The hospital said it was "deeply and genuinely sorry".
The 70-year-old said after the procedure he was left waiting for two hours until they broke the news and he just replied "Oh, have you?" "What else could I say? I was stunned, I couldn't believe what they were telling me," he said.