SWL is done with a machine that can break stones from outside the body. To break the stone, focused shock waves (short pulses of high energy sound waves) are transmitted to the stone through the skin. The stone absorbs the energy of the shock waves and this breaks it into smaller pieces. The stone fragments then pass with urine.

SWL is suitable for over 90% of all patients. However, its success depends on several factors like stone characteristics and your physical condition.