Extracorporeal shock wave lithotripsy ESWL uses special energy waves to break a kidney stone into small pieces that can more easily pass into the bladder.
ESWL is a non-invasive option for kidney and ureteral stones that will not pass through the urinary system by themselves. Depending on the size, location, and composition of the stone, this treatment has a success rate of approximately 80 percent.
During ESWL, stones are pulverized inside the body and the fragments are allowed to pass spontaneously through the urinary tract. First performed in 1980, ESWL is now the most commonly used treatment for stones found in the kidneys. ESWL is not the ideal treatment to remove:
- Very hard stones such as cystine stones or calcium oxalate monohydrate stones;
- Stones larger than 1 inch (2.54 centimeters) in diameter; the fragments produced by larger stones may be too large and may become lodged elsewhere in the urinary tract; or
- Stones in certain locations within the urinary tract that have a decreased chance of spontaneous passage
ESWL is performed as an outpatient or day-surgery basis under intravenous (IV) sedation. During ESWL the patient may be placed in a water bath that helps transmit the energy waves. Tubless machines may be utilized, where the patient is positioned lying on a soft cushion or membrane without the need for a water bath. With the lithotripsy device pressed against the patient’s skin, the physician uses ultrasound (high-frequency sound waves that echo off internal structures and appear as an image on a computer screen) or x ray imaging to locate the stone. When the stone is located the lithotripsy device sends shock waves (pressure waves similar to a sonic boom) into the body. Each shock wave makes a popping noise, and the patient may feel something similar to a gentle tap on his or her side or slight sting as the shock wave travels through the body to fragment the stone. The stone is struck repeatedly by the sound waves until it is broken into particles the size of grains of sand. The fragments exit the body naturally through the urinary tract. If the stones are not completely broken up, additional treatments may be necessary. In some cases the physician may insert a tiny flexible tube called a ureteral stent into the ureter to prevent obstruction from the fragments. Multiple stones can be treated during one session that usually lasts from 40 to 60 minutes.