Lithotomy from Greek for "lithos" (stone) and "tomos" (cut), is a surgical method for removal of calculi, stones formed inside certain organs, such as the urinary tract (kidney stones), bladder (bladder stones), and gallbladder (gallstones), that cannot exit naturally through the urinary system or biliary tract. The procedure is usually performed by means of a surgical incision (therefore invasive). Lithotomy differs from lithotripsy, where the stones are crushed either by a minimally invasive probe inserted through the exit canal, or by an acoustic pulse (extracorporeal shock wave lithotripsy), which is a non-invasive procedure. Because of these less invasive procedures, the use of lithotomy has decreased significantly in the modern era.