Extracorporeal shock wave lithotripsy is a common procedure used today to break up urinary, biliary, renal, and salivary stones. The high-energy shock waves (sound waves) used to break up the stones are generated outside the body (extracorporeally) and focused on the stone. If successful, the remnants of the “shattered” stones can be excreted naturally, saving the patient a surgical procedure with hospitalization and the associated risks.
What is extracorporeal shock wave lithotripsy?
Extracorporeal shock wave lithotripsy is a common procedure used today to break up urinary, biliary, renal, and salivary stones. The figure shows an illustration of the gallbladder with gallstones. A special feature of extracorporeal shock wave lithotripsy (ESWL) is the generation of the pressure waves outside the body. In contrast, intracorporeal lithotripsy also exists, in which the shock waves are generated through an endoscopically inserted probe. By far the most common application of ESWL involves the disintegration of urinary and renal stones. However, the procedure is also suitable for the treatment of gallstones and salivary stones if the consistency of the stones meets certain conditions. ESWL was developed by Dornier System GmbH, Friedrichshafen, and first brought to clinical application maturity in 1980 in collaboration with Klinikum Großhadern, Munich. The devices used to generate extracorporeal shock waves have since changed significantly toward efficiency and lower operating costs. Overall, ESWL has become the standard procedure for the noninvasive removal of urinary and renal stones. The high-energy short-pulsed shock waves are directed to use a relatively large entry site at the skin and only converge concentrically in the body in the stone to be destroyed to exert their effect. The skin entry site and the tissue immediately below it survive the passage of the shock waves largely unharmed.
Function, effect and objectives
The main areas of application are in the disintegration of kidney stones and urinary stones. In far fewer cases, gallstones and salivary stones are also treated. Modern devices can also be used to treat calcium deposits in joints such as the so-called calcific shoulder (tendinosis calcarea). For several years, ESWL has also been used to treat poorly healing bone fractures or osteotomies (pseudarthroses). For precise localization of the stones, the lithotriptors are equipped with a special X-ray and an ultrasound device, which allow the patient or the shock wave generator to be positioned so that the stone is exactly (to the millimeter) in the focus of the shock wave. Shock wave generation is performed according to different physical-technical principles, depending on the type of device. A distinction is made between electromagnetic, electrohydraulic and piezoelectric generation of shock waves. During treatment, it is important that the transfer of the shock waves from the shock wave generator to the body is as trouble-free as possible. This is achieved by a good body contact of the water bubble of the shock wave generator wrapped in silicone at the point of entry of the pressure waves. The treatment is usually performed under mild analgesia with no general anesthesia and lasts about 20 to 30 minutes. Approximately 2,000 to 3,000 shock waves are generated during the treatment, and the frequency can be adjusted to the individual heart rate to avoid possible cardiac arrhythmias. The shock waves are therefore usually delivered at a frequency of 60 to 80 pulses per minute. Experience has shown that a low frequency of the above order is more effective than a higher frequency of 120 shock waves per minute, because microscopic cavitation bubbles form after each shock wave, which should first decay before the next shock wave, otherwise a large part of the energy of the shock wave is absorbed by the bubbles and fizzles out ineffectively. The focused shock waves generate small-scale pressure, traction and shear effects in the stones, which leads to disintegration of the stones into small fragments. About 90% of diagnosed kidney and urinary stones are treatable by lithotripsy, of which about 80% are successfully disintegrated.If a treatment does not bring the desired success, another attempt can be made after waiting several days. During the treatment, the position of the stone to be treated is automatically checked by X-ray and ultrasound to ensure the exact focusing of the shock waves on the stone at all times. A hospital stay of one to two days is usually necessary. However, there are also specialized practices that offer outpatient ESWL.
Risks, side effects and dangers
Contraindications to the use of extracorporeal shock wave therapy include patients who are suffering from any form of anticoagulation or who are taking anticoagulation medications to prevent thrombosis and stroke, as internal tissue injury may occur during treatment, which could then lead to complications. Especially large stones with a length of more than 2.5 cm and stones that cannot be localized exactly are not suitable for treatment by ESWL. Since ESWL is a non-invasive procedure, all risks associated with surgery are eliminated, including minimally invasive procedures. Overall, ESWL represents the lowest-risk procedure for the treatment of urinary, renal, biliary and salivary stones. Chronic long-term damage is not known to date. The risks of ESWL are mainly that, for example, during kidney stone disintegration, some kidney tissue is usually also damaged, so that the urine may temporarily contain blood. The damaged kidney tissue regenerates within a few weeks and heals completely. Other risks are that the discharge of the stone fragments may temporarily cause painful colic, or that it may cause urinary retention that requires drainage treatment. Renal colic occurs in approximately 30% of successfully treated patients.
