Extracorporeal shock wave lithotripsy is a special technique of removing kidney stones without involving any kind of surgery on the ureter. It is performed on patients suffering from kidney stones. In this method, high energy shock waves, generated by a machine known as a lithotripter are passed on the body. The shock waves are focused by X-ray, onto the kidney stones so that the stones in the kidney get crushed into very small pieces, as fine as grains of sand. As the stones have now crushed into finer form, they will be excreted out of the body while urinating. In cases where the stone is large, the surgeon may use a stent. A stent is a small tube made of flexible plastic mesh that holds the ureter open. This helps pass out the small stone pieces without blocking the ureter.