I am 59 and have a 15mm calcified splenic anerusym. found on x-ray for other reason. see vs next week should i prepare myself for surgery or watching?

Depends: Most probably your vascular surgeon would observe and ask for more imaging studies before deciding surgery, depending on size and site of the aneurysm, also other health factors , what kind of procedure to chose if surgery decided, like embolization or laparoscopic vs open surgery, just relax, you had it for sometime, and it is asymptomatic, wait and see your doctor, goodluck