Lithotripsy

Lithotripsy, extracorporeal shock wave (ESWL), is the first non-invasive (not requiring surgical opening of the body) treatment for eliminating kidney stones by breaking them into sand-like particles, usually by means of high pressure waves generated in water. The particles are then eliminated from the body during urination.

The ESWL machine, called a lithotripter, generates shock waves in a reservoir of water outside the body, then focuses them with a reflecting device so they pass through the water and into the body, striking individual stones. Waves are disturbances that travel from one point to another without transporting the material of the medium itself. Rather, there is successive compression and expansion of adjacent areas of the fluid. This can be visualized by imagining a cork bobbing up and down in water as a wave passes by. There is no net movement of water that can carry the cork along, only the passage of the disturbance itself. A shock wave is a compression wave (wave formed by compression of a fluid) that is fully developed, of very large amplitude, and travels through the medium at the speed of sound.