At a medical convention, a male doc, and a female doc start eyeing each
other. The male doc asks her to dinner and she accepts. As they sit down
at the restaurant, she excuses herself to go and wash her hands.
After dinner, one thing leads to another and they end up in her hotel
bedroom. Just as things get hot, the female doc interrupts and says she
has to go and wash her hands. Once she comes back they go for it. After the
sexual interlude, she gets up and says she is going to wash her hands.
As she comes back the male doc says "I bet you are a surgeon". She
confirms and asks how he knew.

"Easy, you're always washing your hands".
She then says "I bet you're an anaesthesiologist".
Male doc: "Wow, how did you guess?"
Female doc: "I didn't feel a thing"