AUTHOR AND EDITOR INFORMATION

Section 1 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Further Reading
• References

INTRODUCTION

Section 2 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Further Reading
• References

Prior to the introduction of extracorporeal shockwave lithotripsy (ESWL) in 1980, the only treatment available for calculi that could not pass through the urinary tract was open surgery. Since then, ESWL has become the preferred tool in the urologist’s armamentarium for the treatment of renal stones, proximal stones, and midureteral stones. Compared with open and endoscopic procedures, ESWL is minimally invasive, exposes patients to less anesthesia, and yields equivalent stone-free rates in appropriately selected patients.

The efficacy of ESWL lies in its ability to pulverize calculi in vivo into smaller fragments, which the body can then expulse spontaneously. Shockwaves are generated and then focused onto a point within the body. The shockwaves propagate through the body with negligible dissipation of energy (and therefore damage) owing to the minimal difference in density of the soft tissues. At the stone-fluid interface, the relatively large difference in density, coupled with the concentration of multiple shockwaves in a small area, produces a large dissipation of energy. Via various mechanisms, this energy is then able to overcome the tensile strength of the calculi, leading to fragmentation. Repetition of this process eventually leads to pulverization of the calculi into small fragments (ideally <1 mm) that the body can pass spontaneously and painlessly.

Technical Aspects

All lithotripsy machines share 4 basic components: (1) a shockwave generator, (2) a focusing system, (3) a coupling mechanism, and (4) an imaging/localization unit.

Shockwave generator

Shockwaves can be generated in 1 of 3 ways, as follows:

• Electrohydraulic: The original method of shockwave generation (used in the Dornier HM3) was electrohydraulic, meaning that the shockwave is produced via spark-gap technology. In an electrohydraulic generator, a high-voltage electrical current passes across a spark-gap electrode located within a water-filled container. The discharge of energy produces a vaporization bubble, which expands and immediately collapses, thus generating a high-energy pressure wave.
• Piezoelectric: The piezoelectric effect produces electricity via application of mechanical stress. The Curie brothers first demonstrated this in 1880. The following year, Gabriel Lippman theorized the reversibility of this effect, which was later confirmed by the Curie brothers. The piezoelectric generator takes advantage of this effect. Piezoelectric ceramics or crystals, set in a water-filled container, are stimulated via high-frequency electrical pulses. The alternating stress/strain changes in the material create ultrasonic vibrations, resulting in the production of a shockwave.
• Electromagnetic: In an electromagnetic generator, a high voltage is applied to an electromagnetic coil, similar to the effect in a stereo loudspeaker. This coil, either directly or via a secondary coil, induces high-frequency vibration in an adjacent metallic membrane. This vibration is then transferred to a wave-propagating medium (ie, water) to produce shockwaves.

Focusing systems

The focusing system is used to direct the generator-produced shockwaves at a focal volume in a synchronous fashion. The basic geometric principle used in most lithotriptors is that of an ellipse. Shockwaves are created at one focal point (F1) and converge at the second focal point (F2). The target zone, or blast path, is the 3-dimensional area at F2, where the shockwaves are concentrated and fragmentation occurs.

Focusing systems differ, depending on the shockwave generator used. Electrohydraulic systems used the principle of the ellipse; a metal ellipsoid directs the energy created from the spark-gap electrode. In piezoelectric systems, ceramic crystals arranged within a hemispherical dish direct the produced energy toward a focal point. In electromagnetic systems, the shockwaves are focused with either an acoustic lens (Siemens system) or a cylindrical reflector (Storz system).

Coupling mechanisms

In the propagation and transmission of a wave, energy is lost at interfaces with differing densities. As such, a coupling system is needed to minimize the dissipation of energy of a shockwave as it traverses the skin surface. The usual medium used is water, as this has a density similar to that of soft tissue and is readily available. In first-generation lithotriptors (Dornier HM3), the patient was placed in a water bath. However, with second- and third-generation lithotriptors, small water-filled drums or cushions with a silicone membrane are used instead of large water baths to provide air-free contact with the patient's skin. This innovation facilitates the treatment of calculi in the kidney or the ureter, often with less anesthesia than that required with the first-generation devices.

Localization systems

Imaging systems are used to localize the stone and to direct the shockwaves onto the calculus, as well as to track the progress of treatment and to make alterations as the stone fragments. The 2 methods commonly used to localize stones include fluoroscopy and ultrasonography.

Fluoroscopy, which is familiar to most urologists, involves ionizing radiation to visualize calculi. As such, fluoroscopy is excellent for detecting and tracking calcified and otherwise radio-opaque stones, both in the kidney and the ureter. Conversely, it is usually poor for localizing radiolucent stones (eg, uric acid stones). To compensate for this shortcoming, intravenous contrast can be introduced or (more commonly) cannulation of the ureter with a catheter and retrograde instillation of contrast (ie retrograde pyelography) can be performed.

Ultrasonographic localization allows for visualization of both radiopaque and radiolucent renal stones and the real-time monitoring of lithotripsy. Most second-generation lithotriptors can use this imaging modality, which is much less expensive to use than radiographic systems. Although ultrasonography has the advantage of preventing exposure to ionizing radiation, it is technically limited by its ability to visualize ureteral calculi, typically due to interposed air-filled intestinal loops. In particular, smaller stones may be difficult to localize accurately.

History of the Procedure

Evolution of shockwave lithotriptors

The Dornier HM3, originally designed to test supersonic aircraft parts, was the first shockwave lithotriptor introduced in the United States. Despite being somewhat dated, it is still one of the most effective lithotriptors and has become the standard to which other devices are compared. The design of the HM3 is based on an electrohydraulic shockwave generator; the shockwaves are focused via an ellipsoid metal water-filled tub in which both the patient and the generator are submerged. Biplanar fluoroscopy is used for localization, allowing placement of the calculi to be fragmented in the target zone.

Second-generation lithotriptors typically use piezoelectric or electromagnetic generators as the energy source. When coupled with the appropriate focusing device, these shockwave generators commonly have a smaller focal zone. Although a smaller focal zone may minimize damage to the surrounding tissue, this comes at a price. During respiratory excursion, the stone may move in and out of the focal zone; this may compromise fragmentation rates. The coupling device in a second-generation lithotriptor is a silicone-encased water cushion that coapts to the patient, a design that greatly simplifies the positioning of patients.

The newest-generation lithotriptors have been designed to offer greater portability and adaptability. These systems often provide imaging with both fluoroscopy and ultrasonography. The ability to alternate between imaging modalities allows the urologist to compensate for the deficiencies of either system.

Most current lithotriptors are powered by an electromagnetic generator. Electromagnetic generators and their focusing units are capable of delivering shockwaves that are similar in intensity to those of the HM3, but usually to a smaller focal zone. As mentioned above, this has the theoretical advantage of minimizing damage to surrounding soft tissue. However, because of the smaller focal zone, respiration may cause the stone to move out of the target zone for portions of the treatment. Although improved localization techniques and anesthetic manipulation can be used to account for this, the shockwaves applied while the stones are out of the target zone do not cause fragmentation. Thus, certain second- and third-generation machines are associated with higher failure rates, incomplete treatment, and the need for retreatment.

Pathophysiology

A stone is fragmented when the force of the shockwaves overcomes the tensile strength of the stone. Although incompletely understood, fragmentation is thought to occur through a combination of methods, including compressive and tensile forces, erosion, shearing, spalling, and cavitation. Of these various forces, the generation of compressive and tensile forces and cavitation are thought to be the most important.

When a shockwave is propagated through a medium (water), it loses very little energy until it crosses into a medium with a different density. If the medium is denser, compressive forces are produced on the new medium. Similarly, if the new medium is less dense, tensile stress is produced on the first medium. Upon hitting the anterior surface of a stone, the change in density creates compressive forces, causing fragmentation. As the wave proceeds through the stone to the posterior surface, the change from high to low density reflects part of the shockwave’s energy, producing tensile forces, which again disrupt and fragment the stone.

INDICATIONS

Section 3 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Further Reading
• References

The current options available for the treatment of renal and ureteral calculi include conservative management (watchful waiting for spontaneous passage), extracorporeal shockwave lithotripsy (ESWL), endoscopic techniques (rigid or flexible ureteroscopic lithotripsy), and percutaneous treatments.

The American Urological Association Stone Guidelines Panel has classified ESWL as a potential first-line treatment for ureteral and renal stones smaller than 2 cm.

Indications for ESWL include the following:

• Individuals who work in professions in which unexpected symptoms of stone passage may prompt dangerous situations (eg, pilots, military personnel, physicians) (In such individuals, definitive management is preferred to prevent adverse outcomes.)
• Individuals with solitary kidneys in whom attempted conservative management and spontaneous passage of the stone may lead to an anuric state
• Patients with hypertension, diabetes, or other medical conditions that predispose to renal insufficiency

RELEVANT ANATOMY

Section 4 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Further Reading
• References

See Preoperative details.

CONTRAINDICATIONS

Section 5 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Further Reading
• References

Absolute contraindications to extracorporeal shockwave lithotripsy (ESWL) include the following:

• Acute urinary tract infection or urosepsis
• Uncorrected bleeding disorders or coagulopathies
• Pregnancy
• Uncorrected obstruction distal to the stone

Relative contraindications include the following:

• Body habitus: Morbid obesity and orthopedic or spinal deformities may complicate or prevent proper positioning. In these situations, attempting to position the patient prior to anesthetic induction is useful to ensure the practicality of the approach.
• Renal ectopy or malformations (eg, horseshoe kidneys and pelvic kidneys)
• Complex intrarenal drainage (eg, infundibular stenosis)
• Poorly controlled hypertension (due to increased bleeding risk)
• Gastrointestinal disorders: In rare cases, these may be exacerbated after ESWL treatment.
• Renal insufficiency: Stone-free rates in patients with renal insufficiency (57%) (serum creatinine level of 2–2.9 mg/dL) were significantly lower than in patients with better renal function (66%) (serum creatinine level <2 mg/dL).

Preexisting pulmonary and cardiac problems are not contraindications, provided they are appropriately addressed both preoperatively and intraoperatively. In patients with a history of cardiac arrhythmias, the shockwave can be linked to electrocardiography (ECG), thus firing only on the R wave in the cardiac cycle (ie, gated lithotripsy). 

Cardiac pacemakers are also not contraindicated, although seeking assistance from a cardiologist for possible changes to pacemaker settings would be prudent. 

Oral anticoagulants (eg, clopidogrel [Plavix] and warfarin [Coumadin]) should be discontinued to allow normalization of clotting parameters. Platelet function is normalized by discontinuing aspirin-containing products and nonsteroidal anti-inflammatory drugs (NSAIDs) 7 days before treatment.

WORKUP

Section 6 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Further Reading
• References

Lab Studies

• CBC count
• Anticoagulation profile (PT/aPTT)
• Urinalysis, with or without urine culture

Imaging Studies

• Renal ultrasonography
• Noncontrast CT scanning
• Intravenous pyelography

Other Tests

• Electrocardiography in patients older than 50 years and in patients with a history of cardiac disease

TREATMENT

Section 7 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Further Reading
• References

Preoperative details

Several factors related to the stone, including stone burden (size and number), composition, and location, affect the outcome of extracorporeal shockwave lithotripsy (ESWL).

Stone size

As stone size approaches 2 cm, the likelihood of success with ESWL decreases, and the need for retreatment and adjunctive therapy increases. ESWL has also been found to be most efficacious in treating nonobstructing renal calculi. In patients with a large stone burden, pre-ESWL stenting may secure drainage and prevent obstructive urosepsis.

Stone composition

The density and ability of a stone to resist ESWL is based in part on the composition of the stone. Stones composed of calcium oxalate dihydrate, magnesium ammonium phosphate, or uric acid tend to be softer and to fragment more easily with ESWL. Stones composed of calcium oxalate monohydrate or cystine, on the other hand, are less susceptible to ESWL. To a degree, this can be predicted with CT scanning by measuring the radio-opacity of stones. A recent retrospective study showed that ESWL monotherapy is more likely to be effective against stones with a lower radio-opacity (551 Hounsfield units [HU]) than those with a higher radio-opacity (926 HU).

In addition, certain radiolucent stones (uric acid, indinavir [Crixivan]) are difficult to visualize on fluoroscopy and therefore require either ultrasonography-guided localization or the addition of retrograde or intravenous contrast to localize a calculus.

Stone location

• Lower-pole calculi: Although ESWL can fragment stones in the lower pole of the kidney, the resulting stone-free rate is decreased because of the difficulty in passing stones from this location. Recent studies have delineated renal morphology associated with improved stone-free rates (eg, lower infundibular length–to–diameter ratio of <7, lower-pole infundibular diameter of >4 mm, single minor calyx), as well as factors associated with decreased stone-free rates (infundibulopelvic angle of <70°, an infundibular length of >3 cm, an infundibular width of <5 mm). Regardless of anatomy, ESWL tends to yield better results in patients with smaller stone burdens.
• Calyceal diverticula with infundibular stenosis: In patients with diverticula caused by or related to infundibular stenosis, fragmented stones cannot easily bypass the obstruction, with resultant retained stone fragments. These patients are best served by more invasive techniques that allow the surgeon to address the obstruction and the stones simultaneously, either with retrograde ureteroscopy or in an antegrade percutaneous fashion.
• Ureteral calculi: Fragmentation of proximal stones is more effective than mid or distal stones. In addition, when associated with hydronephrosis, ureteroscopy yields better stone-free rates for stones larger than 15 mm.

Preoperative and intraoperative stenting

In the modern setting, where access to ESWL and ureteroscopy is readily available, the indications for stenting prior to definitive treatment are much fewer. These indications include (1) obstructed pyelonephritis or pyelitis and (2) newly onset renal insufficiency or renal failure. In these situations, the stent helps to ensure internal drainage and allows passive dilatation of the ureter, facilitating future endoscopic evaluation and treatment. With the advent of newer and smaller ureteroscopic equipment, the rates of endoscopic complications (ie, strictures) have subsequently declined. When preoperative stenting is required, the authors believe that ureteroscopy, especially for ureteral stones, may yield higher stone-free rates without a significant increase in morbidity, time, or cost.

Intraoperative details

The optimal shockwave lithotripsy treatment is thought to be about 80-90 shocks per minute. Faster rates have been shown to be associated with decreased stone-free rates, especially for larger stones (11-20 mm). The difference in stone-free rates is less significant for smaller stones. Conversely, slower rates obviously increase the total operative time.

During shockwave lithotripsy, tracking the stone burden becomes an important issue, in part because of the natural movement of the kidney during respiration, with subsequent movement of the stone burden in and out of the focal zone. The smaller focal zone of the newest devices necessitates less anesthesia, but the patient’s increased ability and susceptibility to cough, shift, or otherwise move requires vigilance to ensure the appropriate targeting accuracy in the application of energy to the stone. This means that the targeting of the machine needs to be adjusted more often.

Postoperative details

Common adverse effects associated with ESWL include flank petechiae, hematuria, and passage of stone fragments with associated renal colic. Many patients are issued a urine strainer to help collect stone fragments, which can later be chemically analyzed to assist with prevention of future stones. Hydration and analgesia alleviate most flank discomfort and symptoms caused by the passage of fragments. Some groups have initiated trials of pharmacologic aids similar to those involved in medical stone-passage protocols to facilitate stone passage. In the treatment arm, pharmacologic aids (stone-free rate of 86% with nifedipine and 82% with tamsulosin) were superior to placebo (stone-free rate of 52-57%).

Quantification of residual stone burden and resolution of hydronephrosis was defined with postoperative radiography or ultrasonography. Postoperative imaging is usually obtained within 6 weeks following the procedure or sooner if the patient is symptomatic.

Follow-up

Stone-prevention strategies

All patients who undergo surgery for stones should be given information about kidney-stone prevention. General measures include increased fluid intake and restriction of dietary sodium and purine. In patients with calcium oxalate stones, intake of foods high in oxalate (eg, spinach, nuts, beer, chocolate, rhubarb, green leafy vegetables) should be discouraged. Calcium intake should be moderated; extremely high or low levels of calcium can increase stone production.

Blood work and 24-hour urine collections measuring for pH, urinary volume, citrate, calcium, oxalate, uric acid, sodium, magnesium, phosphates, and electrolytes can assist in identifying and alleviating risk factors for future stone production. Following treatment of the initial stone event, testing should be performed in all children and in patients with solitary kidneys, chronic diarrhea, a history of bariatric surgery, renal failure, and nephrocalcinosis, as well as in any patient with kidney stones who has sufficient motivation to follow long-term treatment recommendations to prevent future stones. Twenty-four–hour urine-testing protocols are available from a number of sources, including Mission, Dianon, UroCor, Quest, LabCorp, and Litholink.

The National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC), which is part of the National Institutes of Health (NIH), is a good general patient information Web site.

The NIH has also recommended The Kidney Stones Handbook (Savitz and Leslie, 2000). This award-winning patient guide to kidney stones can be ordered directly from the publisher (Grant Gibbs) by email (gsavitz@earthlink.net) or by telephone (530-889-1727).

COMPLICATIONS

Section 8 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Further Reading
• References

Renal complications

Bacteriuria develops in 7.7-23.5% of patients undergoing extracorporeal shockwave lithotripsy (ESWL) and is more likely to develop in patients with infection-related stones. Bacteremia is less common, developing in up to 14% of patients, with fewer than 1% developing clinical sepsis (although this number increases to 2.7% in patients with staghorn calculi). Although preoperative antibiotic coverage remains controversial, antibiotics may be recommended in patients with infection-related stones, positive urine cultures results, or recurrent urinary tract infections. 

Post-ESWL hematuria is usually mild and transient. In the event of significant hematuria with clots or frank clot retention, imaging the kidneys should be considered to identify a perinephric hematoma. Perinephric, subcapsular, or intranephric hematomas may be associated with severe pain, ileus, and, infrequently, shock or hypotension. Unexplained or unusually severe pain or any unusual drop in blood pressure may suggest a hematoma. Subcapsular hematoma following ESWL usually responds to bedrest, transfusions, and supportive care. If the patient requires multiple transfusions, arteriography and selective embolization should be considered. 

Stone fragments may pass with a minimal amount of discomfort. In some patients, the comminuted stone fragments pile up in the ureter, creating a virtual column of stone called steinstrasse. The overall rate of steinstrasse is 1-4%, with the rate progressively increasing for greater stone burdens (10% for stone burdens >2 cm²) and approximately 40% for complete staghorn calculi. Patients with asymptomatic nonobstructing steinstrasse can be monitored closely with serial imaging.

Asymptomatic or mildly symptomatic steinstrasse with mild dilatation of the upper urinary tract can be managed conservatively. If fragments fail to progress within 3-4 weeks or if patients develop significant symptoms or obstruction, endoscopic lithotripsy or percutaneous drainage should be performed. Patients with high-grade obstruction and concomitant pyelonephritis require prompt percutaneous nephrostomy drainage with appropriate antibiotic coverage, followed by staged endoscopic removal of stone fragments. 

Renal atrophy, although uncommon, can result from renal vascular or severe atherosclerotic disease. Patients with underlying renal parenchymal disease are at a higher risk of renal atrophy. However, studies of ESWL in patients with a solitary kidney have shown no statistical evidence of renal function deterioration secondary to shockwave lithotripsy.

Hypertension is an unusual complication of ESWL but may occur as a sequela of a large perinephric hematoma (ie, page kidney). Older patients with abnormal renal perfusion may develop hypertension within 26 months after the ESWL session.

Patients who undergo ESWL may have a slightly higher likelihood of eventually developing hypertension and diabetes than patients who undergo other therapies for stone removal. The evidence, however, may be biased because of the high usage of first-generation ESWL machines in the study group and other problems, but it still suggests a possible connection. In addition, alternative therapies may not be as effective or may carry higher initial morbidity and complication rates. For now, the authors continue to use ESWL, when appropriate. Hopefully, further studies will better delineate the actual risks involved and provide solutions to eliminate or minimize them.

Other possible complications

Less-common complications may include (1) pulmonary contusion, (2) pancreatitis, (3) splenic hematoma, (4) elevated liver functions (transient), and (5) biliary colic with inadvertent fragmentation of adjacent biliary stones.

OUTCOME AND PROGNOSIS

Section 9 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Further Reading
• References

In appropriately selected patients, the overall success rate of extracorporeal shockwave lithotripsy (ESWL) is higher than 90% for stone clearance, with patients remaining stone-free for up to 2 years. ESWL is safe and effective. Although small series have shown successful treatment of stones in young children, long-term follow-up of the potential complications, including hypertension and decreased renal function, are not yet mature.

As the degree of stone burden increases and exceeds 2 cm, the stone-free rate drops significantly. In patients with stones sized 2-3 cm, the stone-free rate with ESWL monotherapy is typically 50%. Stone-free rates in patients with larger stones (complete and incomplete staghorn calculi) are correspondingly lower.

The location of the stone also affects the efficacy of ESWL. In a meta-analysis of 2927 patients from 14 centers, Lingeman et al (1996) found that the overall stone-free rate for all lower-pole stones treated with ESWL (59.2%) was lower than the stone-free rate associated with percutaneous nephrolithotomy (90%).¹ Some studies have suggested that select patients with appropriate renal collecting system anatomy may see good results with ESWL despite lower-pole stone location. In these studies, the overall stone-free rate was approximately 50%, with a stone-free rate of 85% in patients with favorable anatomy versus 7% in those with unfavorable anatomy.

In a prospective, randomized, multicenter clinical trial performed by the Lower Pole Study Group, patients with lower-pole stones treated with ESWL or percutaneous nephrolithotomy had overall stone-free rates of 37% and 95%, respectively. In contrast, this prospective study did not show any difference in stone-free rates based on renal anatomy, but an inverse relationship was found between stone size and stone-free rate. In patients with stones or stone aggregates measuring larger than 1 cm, percutaneous nephrolithotomy was the most efficacious modality to render patients stone-free.

Sheir et al (2003) evaluated the safety and efficacy of ESWL in patients with an anomalous kidney, including 49 patients with a horseshoe kidney, 120 patients with a malrotated kidney, and 29 patients with a duplex kidney.² Two second-generation lithotriptors were used. Although the type of renal anomaly and the type of lithotriptor did not affect the stone-free rate, stone length and number (stone burden) significantly influenced the stone-free rate. The prone position facilitated treatment in 38% of the patients with a horseshoe kidney and in 31% of patients with a duplex kidney. The overall retreatment success rate was 64.1%. However, with an overall stone-free rate of 72.2%, Sheir et al deemed ESWL to be safe and reliable in patients with an anomalous kidney and to be considered the primary treatment option for stones smaller than 20 mm.

FUTURE AND CONTROVERSIES

Section 10 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Further Reading
• References

Technical improvements, such as synchronous twin-pulse technique with variable angles between the shockwave reflectors, have been attempted to increase the quality and rate of stone disintegration. In a study of 50 patients with renal or ureteral stones (mean size, 12.3 mm; range, 9-18 mm) undergoing the synchronous twin-pulse technique , 17 patients (34%) were stone-free, 20 patients (40%) had less than 5 mm of residual stone, and 13 (26%) patients had 6-9 mm of residual stone 14 days following extracorporeal shockwave lithotripsy (ESWL).³ Thirteen (26%) patients with more than 5 mm of residual stone underwent repeat ESWL. Following treatment, gross hematuria developed in 50% of the patients on the day of treatment and resolved the next day.

Shockwave therapy is efficacious in treating urinary calculi. The mechanism of action is based on pressure waves that, when focused onto a stone, fragment the stone into more easily passable pieces. Success rates, defined as becoming stone-free or having residual fragments less than 4 mm in diameter, are acceptable. However, future improvement of lithotriptor design may increase success rates, decrease renal trauma, and increase patient comfort.

Other groups have attempted to improve the fragmenting capability of the cavitation bubbles created during lithotripsy by forcing their collapse with a second weaker pulse timed immediately after the initial pulse. Using a porcine model with BegoStone phantoms, Young et al (2003) used a 22-kV shock from an HM3 followed with a 4-kV shockwave 500-600 ms later from a separate piezoelectric source. Their initial results showed increased stone comminution rates with reduced renal injury.

Controversy exists with some of the newer shockwave generators. The smaller focal zone and newer tabletop designs increase the indications for treatment and lower the anesthetic requirements, but they may decrease overall efficacy of the treatment. Many newer generators require precise localization, with little margin for error in light of the greatly reduced focal zones. The focal zone of the original Dornier HM3 exceeded 2 cm, but most new electromagnetic generators have focal zones averaging only 6 mm. As a result, the operator must be more attentive and must actively compensate for respiratory movements during treatment. On a positive note, however, less renal parenchyma is affected or damaged during treatment.

FURTHER READING

Section 11 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Further Reading
• References

For additional information, see Medscape’s Stone Disease Resource Center.

REFERENCES

Section 12 of 12

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Further Reading
• References

1. Lingeman JE, Zafar FS. Lithotripsy systems. In: Smith AD, Badlani GH, Bagley DH, et al. Smith's Textbook of Endourology. St Louis, Mo: Quality Medical Publishing; 1996:553-89.
2. Sheir KZ, Madbouly K, Elsobky E, Abdelkhalek M. Extracorporeal shock wave lithotripsy in anomalous kidneys: 11-year experience with two second-generation lithotripters. Urology. Jul 2003;62(1):10-5; discussion 15-6. [Medline].
3. Sheir KZ, El-Diasty TA, Ismail AM. Evaluation of a synchronous twin-pulse technique for shock wave lithotripsy: the first prospective clinical study. BJU Int. Feb 2005;95(3):389-93. [Medline].
4. Abe T, Akakura K, Kawaguchi M, Ueda T, Ichikawa T, Ito H, et al. Outcomes of shockwave lithotripsy for upper urinary-tract stones: a large-scale study at a single institution. J Endourol. Sep 2005;19(7):768-73. [Medline].
5. Albala DM, Assimos DG, Clayman RV, Denstedt JD, Grasso M, Gutierrez-Aceves J, et al. Lower pole I: a prospective randomized trial of extracorporeal shock wave lithotripsy and percutaneous nephrostolithotomy for lower pole nephrolithiasis-initial results. J Urol. Dec 2001;166(6):2072-80. [Medline].
6. Anagnostou T, Tolley D. Management of ureteric stones. Eur Urol. Jun 2004;45(6):714-21. [Medline].
7. Auge BK, Preminger GM. Update on shock wave lithotripsy technology. Curr Opin Urol. Jul 2002;12(4):287-90. [Medline].
8. Chacko J, Moore M, Sankey N, Chandhoke PS. Does a slower treatment rate impact the efficacy of extracorporeal shock wave lithotripsy for solitary kidney or ureteral stones?. J Urol. Apr 2006;175(4):1370-3; discussion 1373-4. [Medline].
9. Chaussy CG, Fuchs GJ. Current state and future developments of noninvasive treatment of human urinary stones with extracorporeal shock wave lithotripsy. J Urol. Mar 1989;141(3 Pt 2):782-9. [Medline].
10. Collins JW, Keeley FX. Is there a role for prophylactic shock wave lithotripsy for asymptomatic calyceal stones?. Curr Opin Urol. Jul 2002;12(4):281-6. [Medline].
11. Delius M. This month in Investigative Urology: effect of extracorporeal shock waves on the kidney. J Urol. Aug 1988;140(2):390. [Medline].
12. Joshi HB, Obadeyi OO, Rao PN. A comparative analysis of nephrostomy, JJ stent and urgent in situ extracorporeal shock wave lithotripsy for obstructing ureteric stones. BJU Int. Aug 1999;84(3):264-9. [Medline].
13. Kim FJ, Rice KR. Prediction of shockwave failure in patients with urinary tract stones. Curr Opin Urol. Mar 2006;16(2):88-92. [Medline].
14. Krambeck AE, Gettman MT, Rohlinger AL, Lohse CM, Patterson DE, Segura JW. Diabetes mellitus and hypertension associated with shock wave lithotripsy of renal and proximal ureteral stones at 19 years of followup. J Urol. May 2006;175(5):1742-7. [Medline].
15. Lee C, Ugarte R, Best S, Monga M. Impact of renal function on efficacy of extracorporeal shockwave lithotripsy. J Endourol. May 2007;21(5):490-3. [Medline].
16. Lee YH, Tsai JY, Jiaan BP, Wu T, Yu CC. Prospective randomized trial comparing shock wave lithotripsy and ureteroscopic lithotripsy for management of large upper third ureteral stones. Urology. Mar 2006;67(3):480-4; discussion 484. [Medline].
17. Lindqvist K, Holmberg G, Peeker R, Grenabo L. Extracorporeal shock-wave lithotripsy or ureteroscopy as primary treatment for ureteric stones: a retrospective study comparing two different treatment strategies. Scand J Urol Nephrol. 2006;40(2):113-8. [Medline].
18. Lingeman JE, Kim SC, Kuo RL, McAteer JA, Evan AP. Shockwave lithotripsy: anecdotes and insights. J Endourol. Nov 2003;17(9):687-93. [Medline].
19. Liou LS, Streem SB. Long-term renal functional effects of shock wave lithotripsy, percutaneous nephrolithotomy and combination therapy: a comparative study of patients with solitary kidney. J Urol. Jul 2001;166(1):36; discussion 36-7. [Medline].
20. Madaan S, Joyce AD. Limitations of extracorporeal shock wave lithotripsy. Curr Opin Urol. Mar 2007;17(2):109-13. [Medline].
21. Martin TV, Sosa RE. Shock-wave lithotripsy. In: Walsh PC, Retik AB, Vaughan ED, Wein AJ. Campbell's Urology. Vol 3. 7^th ed. Philadelphia, Pa: WB Saunders; 1998:2735-52.
22. Micali S, Grande M, Sighinolfi MC, De Stefani S, Bianchi G. Efficacy of expulsive therapy using nifedipine or tamsulosin, both associated with ketoprofene, after shock wave lithotripsy of ureteral stones. Urol Res. Jun 2007;35(3):133-7. [Medline].
23. Moody JA, Evans AP, Lingeman JE. Extracorporeal shockwave lithotripsy. In: Weiss RM, George NJR, O'Reilly PH, eds. Comprehensive Urology. Mosby International Limited; 2001:623-36.
24. Pareek G, Armenakas NA, Fracchia JA. Hounsfield units on computerized tomography predict stone-free rates after extracorporeal shock wave lithotripsy. J Urol. May 2003;169(5):1679-81. [Medline].
25. Putman SS, Hamilton BD, Johnson DB. The use of shock wave lithotripsy for renal calculi. Curr Opin Urol. Mar 2004;14(2):117-21. [Medline].
26. Sayed MA, el-Taher AM, Aboul-Ella HA, Shaker SE. Steinstrasse after extracorporeal shockwave lithotripsy: aetiology, prevention and management. BJU Int. Nov 2001;88(7):675-8. [Medline].
27. Segura JW, Preminger GM, Assimos DG, Dretler SP, Kahn RI, Lingeman JE, et al. Nephrolithiasis Clinical Guidelines Panel summary report on the management of staghorn calculi. The American Urological Association Nephrolithiasis Clinical Guidelines Panel. J Urol. Jun 1994;151(6):1648-51. [Medline].
28. Skolarikos A, Alivizatos G, de la Rosette J. Extracorporeal shock wave lithotripsy 25 years later: complications and their prevention. Eur Urol. Nov 2006;50(5):981-90; discussion 990. [Medline].
29. Tan EC, Tung KH, Foo KT. Comparative studies of extracorporeal shock wave lithotripsy by Dornier HM3, EDAP LT 01 and Sonolith 2000 devices. J Urol. Aug 1991;146(2):294-7. [Medline].
30. Unal B, Kara S, Bilgili Y, Basar H, Yilmaz E, Batislam E. Giant abdominal wall abscess dissecting into thorax as a complication of ESWL. Urology. Feb 2005;65(2):389. [Medline].
31. Weiland D, Lee C, Ugarte R, Monga M. Impact of shockwave coupling on efficacy of extracorporeal shockwave lithotripsy. J Endourol. Feb 2007;21(2):137-40. [Medline].

Article Last Updated: Feb 14, 2008