At the International Kidney Stone Institute, our goal is nothing less than the cure.

Extracorporeal Shock Wave Lithotripsy

Extracorporeal Shock Wave Lithotripsy (ESWL) is perhaps the most common treatment for kidney stones. It involves the administration of shock waves to the kidney stone. The shock waves are generated by a machine called a lithotriptor and travel from outside the body, through the skin and tissue until they reach the stone inside the kidney or ureter. X-rays are used during the ESWL treatment to target the kidney stone. Repeated shock waves will cause the stone to break into smaller fragments that can be passed out in the urine. The first ESWL treatment in the United States was performed in 1984 at Methodist Hospital in Indianapolis by urologist James Lingeman, M.D. The original lithotriptor, known as the HM3, is still in use today. It is operated with the patient sitting in a water bath while the machine generates shock waves that travel through the water and into the kidney to break up the targeted stone.

Most ESWL treatments can be performed on an outpatient basis. The use of anesthesia will depend on the lithotripsy machine used and the preference of the physician. However, recent data suggests that the results of ESWL may be improved by administration of a general anesthetic. (see Eichel et al, JEndo 2002 and Sorensen et al, JUrol 2002).

Following the lithotripsy treatment, it is normal to experience some soreness and bruising over the treatment site. Some blood may also be present in the urine for a few days. Medications for pain may be prescribed following the treatment. Antibiotics are not usually necessary if there is no history of previous urinary tract infection.

ESWL should not be used in the case of: pregnancy, bleeding disorder, untreated kidney infection, and abdominal aortic aneurysm near the stone to be treated.

Stone size and composition will affect the results of ESWL. Stones composed of cystine and certain types of calcium are resistant to fragmentation by ESWL. Large stones may not fragment adequately, and patients are therefore more likely to require additional treatment.

The most common adverse effect after ESWL is incomplete or inadequate stone fragmentation or passage. This is particularly true with newer lithotriptors that are less efficient than the original HM3 lithotriptor, still in use at Methodist Hospital. Although multiple ESWL treatments are often necessary with newer lithotriptors, the need for retreatment with the HM3 lithotriptor is less than 10 percent of cases.

Another potential problem with ESWL is difficulty in passing the stone fragments after treatment. Although ESWL is a non-invasive technology, the reality is that the kidney must discharge the fragments produced to achieve a successful result. If there are many fragments or if some stone fragments are too large, they can get caught in the ureter, necessitating further treatments with either another ESWL session, ureteral stenting and/or ureteroscopy.

(At Methodist Hospital, where the HM3 lithotriper is used, the need for secondary treatments for fragments caught in the ureter following ESWL is rare, less than five percent of cases. This is because the HM3 lithotriptor continues to be very efficient at stone fragmentation. Likewise, research conducted at Methodist has enabled urologists to identify which stones are likely to respond well to ESWL and which ones are better treated by some other technique, such as ureteroscopy or percutaneous stone removal.)

Occasionally, a stone will be broken up into pieces that are still too large to pass down the ureter. If this occurs, the fragments may block the flow of urine out of the kidney, causing severe pain. This happens more frequently when stones are large in size. Sometimes it is necessary to temporarily insert a small tube called a stent to relieve the obstruction and aid passage of the stone fragments. Many practicing urologists routinely place a stent in the ureter prior to performing ESWL.

(The clinical arm of the International Kidney Stone Institute a Methodist Hospital does not routinely employ the use of ureteral stents for ESWL, because studies published in the urologic literature have failed to demonstrate an improvement in the passage of stone fragments with routine ureteral stenting. In addition, ureteral stents can often be uncomfortable for patients due to symptoms of back and/or bladder pain, burning with urination and urinary frequency.)

ESWL is one of the International Kidney Stone Institute's primary research interests. IKSI believes that understanding how shock waves affect the kidney is important in improving the safety and efficiency of ESWL. IKSI researchers' experiments to date have shown that ESWL affects the kidney by causing a direct injury to small blood vessels within the kidney, which can be seen as blood in the urine following ESWL treatment. In addition, EWSL temporarily reduces the amount of blood that is supplied to the kidney. With this knowledge, researchers have concentrated on answering the question, What can we do with ESWL to maximize breakage of a kidney stone while minimizing injury to the kidney?

Lithotripsy machine design has changed considerably since the introduction of the first lithotripsy machine in the 1980s. Newer lithotriptors were designed to be more portable and powerful, while eliminating the need for anesthesia. Unfortunately, the results of ESWL using some of these new machines have not been encouraging. Overall, fewer patients remain stone free following ESWL with these newer lithotriptors, and the risk of bleeding around the kidney following treatment has increased. (see Dhar et al, JUrol 2004)

However, the type of lithotriptor that is used may not be as important as the technique used to administer the shock waves. IKSI's clinical research group in Indianapolis has identified four factors that can improve the safety of ESWL while still maximizing breakage of a kidney stone:

  • Starting at low energy shock wave levels and only increasing the power if the stone is not breaking
  • Reducing the number of shock waves delivered
  • Slowing the rate at which the shock waves hit the stone improves fragmentation (see Pace et al JUrol 2003 and Paterson et al JUrol 2002)
  • Providing adequate anesthesia during treatment.

Unlike many other ESWL machines, the HM3 has been extensively studied such that the expected results of ESWL can be predicted with a high degree of certainty, given the stone size and location (refer to Tables I and II):

  • Table I. Stone free rates based on stone size and location for ESWL of solitary kidney stones, using Methodist Hospital's Dornier HM3 Lithotriptor
    Stone location and size 0-10 mm 11-20 mm 21-30 mm
    Pelvis 316/351 (90%) 225/272 (83%) 48/59 (81%)
    Upper Calyx 53/69 (77%) 21/28 (75%) 8/12 (67%)
    Middle Calyx 61/76 (80%) 12/17 (71%) 1/2 (50%)
    Lower Calyx 253/317 (80%) 60/103 (58%) 6/19 (32%)
  • Table II. Retreatment rates based on stone size and location for ESWL of solitary kidney stones using the Dornier HM3 Lithotriptor

    Stone location and size 0-10 mm 11-20 mm 21-30 mm
    Pelvis 17/493 (3.4%) 29/426 (6.8%) 11/81 (14%)
    Upper Calyx 3/95 (3.2%) 3/48 (6.3%) 4/15 (27%)
    Middle Calyx 5/126 (3.9%) 3/34 (8.8%) 1/2 (50%)
    Lower Calyx 4/428 (0.93%) 47/123 (38%) 5/23 (22%)