An overview of shock wave therapy for kidney stones

This study reviewed recent evidence on shock wave lithotripsy (SWL) in the treatment of kidney stones.

Kidney stones are small mineral deposits that can form in or near the kidneys. They can be very painful and need to be passed or removed to avoid complications. Shock wave lithotripsy (SWL) is a common, non-surgical treatment for kidney stones. It involves targeting shock waves from outside the body at a kidney stone in order to break it into fragments that are small enough to pass in urine. After over 30 years in clinical practice, SWL has undergone a variety of advances.

The aim of this review was to summarize recent findings and trends on the use of SWL for kidney stones.

Studies have failed to show better treatment outcomes for newer generation SWL devices compared to older generation SWL devices. Stone fragmentation was generally comparable across different models.

SWL can be combined with imaging techniques such as fluoroscopy, which uses radiation to show a continuous X-ray image. Since a kidney stone is a moving target, SWL can be more precise when guided with an imaging technique. In a study of 1,332 patients, SWL plus fluoroscopy was associated with a stone-free rate of 80% at 3 months. Visio-Track is another imaging technique that uses infrared technology to guide SWL. Stone-free rates were significantly higher when Visio-Track was used for SWL (79.5%) compared to conventional ultrasound (54.5%).

The shock wave delivery rate typically varies between 60 and 120 pulses per minute with most studies finding improved success at a rate of 60. Previous findings have also suggested that gradually increasing shock wave intensity significantly reduces the risk of kidney damage (5.6%) compared to patients received a fixed voltage (13%).

Ureteroscopy is another treatment for kidney stones, especially for stones closest to the bladder in the lower half of the ureter (urine tract between the kidney and the bladder). Studies have shown comparable stone-free rates between SWL and ureteroscopy for lower ureteral stones. However, for stones between 10 and 20 mm in size, ureteroscopy was generally associated with higher stone-free rates at 3 months (86.5%) compared to SWL (67.7%).

Factors such as age, gender, body weight as well as stone location, quantity, and diameter have all been identified as predictors of stone-free rates. In a study of 235 patients, those with a stone volume less than 150 microliters, a skin to stone distance of less than 12 cm, and a stone density of less than 600 HU achieved a stone-free rate of 96.1% after SWL. Patients who did not meet these 3 criteria had a stone-free rate of only 21.4%.

Some side effects associated with SWL include bruising on the kidney, small ureteral stones, blood in the urine, and infection. These are typically mild and are considered short-term. While SWL has been found to have a short-term effect on semen counts, all semen parameters appear to return to normal by 3 months. SWL has been previously found to increase the risk of high blood pressure by 42%. However, evidence to this effect is mixed with other studies finding no association between SWL and high blood pressure. There has also been no evidence to suggest that SWL leads to long-term kidney damage.

Authors concluded that SWL remains a first-line treatment for kidney stones. Any recent advances have led to the continued recommendation of SWL for kidney stones.