Kidney stones, which are also known as renal calculi, are formed from certain types of salts in the urine. When these stones pass into the ureters, the thin tubes that carry urine from the kidneys to the bladder, they can block the flow of urine causing intense pain. In addition, infections that may become life threatening can develop due to kidney stones. Approximately 12% of men and 7% of women will develop a kidney stone at some point in their lives. Although small stones often pass spontaneously in the urine, larger stones that become lodged in the lower ureters may require intracorporeal (inside the body) lithotripsy (ICL). For this procedure, a small endoscope (ureteroscope) is passed through the urethra and bladder and into the ureter so that the stone can be seen. Lasers or other instruments are then used to shatter the stone into fragments that can be extracted manually using specially designed expandable wire baskets. In many cases, the stone or large fragments are pushed backwards towards or into the kidney during ICL, requiring additional
procedures for extraction.