Extracorporeal Shock Wave Lithotripsy
Extracorporeal Shock Wave Lithotripsy (ESWL) is the noninvasive treatment of kidney stones, stones in the gallbladder as well as calcium build ups in the liver using acoustic pulses.
A lithotriptor breaks up the calcium stones without damage being done to the patient through the use of high-intensity, externally-applied, focused acoustic pulses. By laying the patient down on their back and placing a water-filled coupling device under the back at the level of the kidneys, the doctor is able to use an imaging system to locate the stones and aim the treatment in the right location. The pulses are then produced and are sent to the targeted area. The pulses start at a very low rate and leave a long gap between the pulses in order for a more effective commination of the stones. The intensity of the pulses’ power level is then gradually increased. The ending level of the power is reliant on the patient’s threshold for pain. The feeling of this treatment is compared to a rubber band vibrating off of the skin. It is an option to be sedated during the lithotripsy which can allow for a faster increase of the power, a higher frequency and it is common to have up to 120 shocks per minute. The process takes about an hour.
Cavitation bubbles, result of the ESWL treatment, surround the stone to break it into smaller pieces that can then be passed as if nonexistent. A stent can also be placed in the ureter to expand the passage but only under the discretion of the urologist. For stones between 4 mm and 20 mm (0.4 cm and 2.0 cm) in diameter, an extracorporeal lithotripsy allows for the best results.
Risk Factors of ESWL: (Complication Rate: 5-20%)
• Capillary Damage
• Renal Parenchymal
• Subcapsular Hemorrhage
• Renal Failure
Image Caption: The Dornier Human Model 1 (HM1) prototype lithotripter (Deutsche Museum at Bonn). Credit: Wikipedia