Oh I know exactly when I was closest: my appendix burst at 14 and pus was leaking when they opened me up. They had no clue it had burst because it was reversed and the pus had mostly been contained by its positioning. If they'd waited much longer I might have died.

I have really good pain tolerance too so I wasn't in much pain nor puking or whatnot for the half day they kept me in the ER running tests and all. It literally just felt like mild period cramps or being unable to pass gas... after I'd just finished having my period a few days before.