Large kidney stones can be removed by a surgical procedure where a small puncture is made through the back into the kidney (percutaneous nephrolithotomy or PNL) but the stones usually need to be broken into smaller pieces before they can be removed through the small surgical incision. There are a number of FDA approved devices commercially available used to break up the stones including pneumatic, ultrasonic, and a combination of the two. Each technology has advantages and disadvantages.