How would you respond?

Most of the time, people ask "How are you?" and expect a brief, affirmative reply that they're not really listening to. It's the sort of interaction not meant to slow you down. Sometimes, though, someone makes you stop with an answer.

LOCATION: Coffeeshop, Saturday morning.
I see a friend.
ME: Hi. How are you?
SHE: I'm having a colonoscopy on Monday.