Ear Infection !
This joke is a little bit rude but not crude.
An old man walks into a doctor's surgery and is asked by the receptionist what he's there for. " I've come about my dick" he says. " You shouldn't say things like that you'll embarrass the other patients ". "But you asked me and I answered honestly" ." Use a bit of tact" said the receptionist, "You can always pretend that you've come about your ear, for example, and tell the doctor the truth when you see him"
The man turned around and walked out. A few seconds later he came back to the receptionist who again asked him why he was there. "I've come about my ear". "That's better, what's wrong with your ear?" " I can't pee out of it". The waiting room was engulfed with laughter.