Introduction
Kidney stones are a common and painful problem, and often, surgery is needed if the stones do not pass on their own. Shock wave lithotripsy (SWL) is a common method for treating kidney stones. Over time, the technology behind SWL has improved to get better results and lower the chances of it not working. However, there are still some key limitations that can make it less suitable for certain cases. New technology now allows doctors to move the stones around, which can help relieve pain or make it easier to treat them. One advanced method called burst wave lithotripsy (BWL) can break up stones noninvasively, meaning it does not require surgery and can be done on awake patients with minimal pain and no major harm to the kidneys.
What Is Lithotripsy Technology?
Kidney stone disease or nephrolithiasis is a common and painful issue affecting individuals. Most small stones can pass through the urinary tract on their own. However, some people need surgery because of severe pain, infection, or blockages. These surgeries usually involve breaking up and removing the stones, but sometimes, they can create more fragments that need further treatment. Because of these challenges, there has been a long-standing interest in finding noninvasive ways to help pass kidney stones.
Lithotripsy is a non-invasive procedure used to treat large kidney stones. Instead of making cuts or using instruments inside the body, doctors use shock waves or ultrasound to break the stones into smaller pieces. These smaller pieces then pass out the body through urine. Lithotripsy is often used when stones are too large to pass on their own and can help avoid more invasive surgeries. The procedure is effective for certain types of stones and locations, and doctors have developed techniques to improve its safety and success.
How Was Lithotripsy Technology Used Earlier?
In the past, methods to clear stones included physical techniques like tapping or moving around after shock wave treatments. There was also some promise in using external vibrations and even riding roller coasters, though these methods are not widely used. Now, ultrasound is becoming an important noninvasive tool. It can help move stones around to make them easier to pass or prepare them for surgery. Additionally, burst wave lithotripsy, a form of therapeutic ultrasound, offers a new way to break up stones without surgery.
The Dornier HM3 was the first machine used for breaking up kidney stones. It was a big water bath to help transmit shock waves, uses X-ray imaging, and has an ellipsoid reflector with a small opening. It works with an electrohydraulic shock wave generator.
Overtime, different types of shock wave generators have been developed:
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Electrohydraulic Generators: These use a spark to create a bubble of vapor that collapses quickly, producing a powerful shock wave. This wave is then focused by the ellipsoid reflector.
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Electromagnetic Generators: These create shock waves using magnetic fields. The field pushes against a membrane, generating the shock wave, which is then focused by a parabolic reflector or acoustic lens. These generators last much longer than electrohydraulic ones.
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Piezoelectric Generators: These use piezoelectric materials to create shock waves. A large number of piezoelectric elements are fired at the same spot to generate the shock wave.
What Are the Recent Advancements in Lithotripsy Technology?
Shock Wave Lithotripsy: In the 1980s, shock wave lithotripsy was a major advancement because it used high-intensity sound waves to break up stones without surgery, making it seem like a perfect solution. Initially, SWL was praised and used for even tough cases, like multiple stones or stones in challenging locations. However, as doctors got more experience, they noticed some problems. Certain types of stones were hard to break with SWL, and sometimes, stones that were broken still left fragments that needed more treatment. Also, SWL could be less effective due to kidney anatomy and could only handle stones up to about 9.8 inches in size. There were also side effects like bleeding and damage to the kidneys or other organs. Research found that SWL could cause injuries to the kidneys, including bleeding and inflammation, though often the kidney healed well over time.
Recent Advancements Are:
1. Ultrasound Propulsion: In 2010, ultrasonic propulsion was introduced as a new way to move kidney stones within the urinary tract. This method uses ultrasound waves to push stones around in small, controlled movements. The technology involves using a handheld ultrasound device to direct these waves, which can move stones effectively when the ultrasound is strong enough and the duration is long enough.
The initial device combined an imaging probe with a focused ultrasound probe to move and monitor stones. Stones were seen moving at a rate of about one centimeters (0.4 inches) per second in a test setup, showing that ultrasonic propulsion could potentially help remove stones without surgery.
Later, a clinical device was developed that used updated technology to enhance the ultrasound’s effectiveness. This device includes a special transducer for both imaging and propulsion, which allows precise targeting and movement of stones. Newer research has also explored advanced techniques, like “acoustic forceps,” to move stones in a more controlled manner, demonstrating that this approach can be safe and effective without damaging surrounding tissues.
2. Burst Wave Lithotripsy (BWL): In 2015, researchers tested BWL to break up kidney stones in both artificial and natural samples. They found that using different ultrasound frequencies affected the size of the fragments produced: higher frequencies created smaller fragments. BWL proved effective, with further improvements allowing it to break up larger stones using a broad beam transducer.
Animal studies showed that BWL is both safe and effective. Combining BWL with ultrasonic propulsion also helps clear small fragments. Another study showed that BWL could reduce 7 mm stones to very small fragments with no signs of kidney damage.
3. Wide Focal Zone Shock Wave Generators: Modern lithotripters have improved designs that create a larger focal zone for breaking up stones. This makes them more effective in breaking multiple stones compared to older models. New designs, like those in electromagnetic lithotripters, have made the focal zone bigger and reduced tissue damage, leading to better stone fragmentation.
4. Dual Pulse Lithotripters: Some newer devices use two shockwave sources instead of one. This setup can deliver shock waves in two different ways: either at the same time or in sequence. This could potentially reduce treatment time and improve stone breaking. However, the clinical benefits of this method are unclear, and it can be challenging to ensure shock waves properly reach the stones.
Conclusion
Recent advancements in lithotripsy technology have significantly improved the effectiveness and safety of kidney stone treatment. Innovations such as ultrasonic propulsion, BWL, and other lithotripters have enhanced the ability to break stones more effectively and with reduced tissue damage. As these technologies continue to evolve, they hold the potential to further optimize stone removal processes, minimize patient discomfort, and reduce overall treatment time.
