Marshall L. Stoller, Maxwell V. Meng-Urinary Stone Disease

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Chapter 28 / Extracorporeal Shockwave Lithotripsy 557

IMPLANTED CARDIAC DEVICES

The presence of implanted pacemakers or cardioverter defibrillators is no longer a

contraindication to SWL, given that certain precautions are taken. An experienced car-

diologist familiar with the device and a backup external device or corrective equipment

should be readily available during the procedure. Devices must be thoroughly tested

before and immediately after the procedure. Dual-chamber pacers should be set to a

ventricular pacing mode only. Lastly, as mentioned above, patients with abdominally

located devices containing piezoelectric crystals should not be treated with SWL owing

to the risk of physical damage to the device (12–14).

OAGULOPATHY

Shockwave lithotripsy has been performed successfully in patients with significant

reversiblebleeding diatheses, such as hemophilia, hepatitis and cirrhosis, hypersplenism,

and von Willebrand disease (15,16). The caveats in these or any such patient include the

proper identification of the reversible coagulopathy and the appropriate normalization

of bleeding and clotting studies before, during, and 24–48 h after SWL. Patients with

irreversible coagulopathy should not be treated with SWL.

Technical Limitations

Based on the physics and the technical aspects of SWL, certain situations will limit

the utility of SWL, including morbid obesity, unfavorable stone composition, and distal

urinary tract obstruction. Although not contraindications per se, these limitations may

reduce the overall efficacy of intervention, and reasonable expectations should be

relayed to patients during counseling. With the incorporation of second and third gen-

eration lithotriptors, treating children is no longer a technical limitation, and in fact is

associated with excellent results.

ORBID OBESITY

Several factors limit the utility of SWL in obese (greater than 300 pounds) patients.

First, patients that exceed the weight limit of the machine, which currently can be as high

as 400 lb, cannot be positioned at the focal point. Second, the focal length (maximum

distance from stone to skin) of current machines ranges from 11 to 17 cm, which may

still be too short for some obese patients (17). Third, the increased amount of intervening

adipose and muscular tissue both dampen the peak shockwave focal pressure and hinder

stone localization.

Various techniques have been used to overcome these limitations. Compression belts,

similar to those used during intravenous pyelography, may decrease the focal length

enough to reach the target stone. In addition, retrograde stone manipulation into the most

posterior calyx may further decrease the focal length. Thomas and Cass described a

technique of positioning the stone to within 4 cm beyond the focal point in the z (up and

down) axis, along the so-called “extended shockwave pathway” (18). Their overall

stone-free rate for SWL in obese patients was 68%, although these data were not strati-

fied for the use of the extended shockwave pathway.

TONE IMPACTION AND COMPOSITION

Effective fragmentation of a given calculus by SWL requires a strong acoustic inter-

face through a fluid medium. Impacted ureteral calculi lack such an interface between

558 Ng, Fuchs, and Streem

the surrounding ureteral walls and therefore respond poorly to SWL. In addition, certain

stone compositions, particularly matrix and cystine, provide poor interfaces for frag-

mentation by SWL. Urinary matrix is composed primarily of proteins, water and sugars;

most calcium stones are comprised of about 2–3% urinary matrix. However, matrix

calculi contain about 65% urinary matrix, resulting in a gelatinous amorphous structure

(19). As such, there is no role for SWL in the management of matrix calculi (20).

In contrast, pure cystine stones have a unique amino-acid crystalline structure con-

taining repeated disulfide bonds, creating “hard” stones that are relatively resistant to

SWL (21). Because cystine calculi require larger numbers of shockwaves at higher

energy levels to induce fragmentation, treatment with SWL should be limited to stones

1.5 cm or less in greatest diameter. Interestingly, cystine calculi with a calcium compo-

nent, which are believed to be caused by the incorporation of calcium salts after partial

chemical dissolution, tend to respond better to SWL than pure cystine calculi (22). With

careful patient selection, efficiency quotients (see “Comparing Apples to Apples” fol-

lowing) as high as 0.90 can be achieved with SWL monotherapy for small cystine stones

that have failed medical therapy (23).

ISTAL OBSTRUCTION

Stone-free results after SWL require adequate fragmentation and spontaneous pas-

sage through the urinary tract. Generally, SWL monotherapy in the setting of distal

urinary tract obstruction is not recommended unless a simultaneous procedure to cor-

rect the obstruction is planned. This includes patients with obstruction caused by con-

genital renal anomalies, such as ureteropelvic junction obstruction. Of note, however,

initial success rates for SWL in small series of horseshoe kidneys are unexpectedly

high, ranging from 50 to 85%, although recurrence rates and auxiliary procedure rates

approach 30% (24).

Calyceal diverticular calculi have also been managed with success by SWL. In care-

fully selected patients with calculi measuring less than 1.5 cm associated with a radio-

graphically patent calyceal diverticular neck, stone-free rates of 58% with symptomatic

relief in 86% of patients can be achieved (25).

OUTCOMES

Evaluating the Literature

DEFINITIONS OF SUCCESS AFTER SHOCKWAVE LITHOTRIPSY

As with any therapy for stone disease, the ultimate definition of success is “radio-

graphically stone-free without symptoms.” However, what is unique to SWL is that

complete stone clearance relies on both adequate fragmentation and spontaneous pas-

sage. Therefore, the time to stone-free and symptom-free status may be prolonged after

SWL compared to other urologic interventions. In turn, with the rapid increase in the

world-wide experience with SWL, there exists a commensurate increase in the number

of patients with small residual fragments after treatment. Such a finding is indeed inher-

ent to the technique of SWL itself and has come to carry a much less ominous “prognosis”

than it did before the advent of SWL. In fact, the presence of small asymptomatic residual

fragments after SWL has been equated to successful treatment in some series, and as

such, has been referred to as “clinically insignificant residual fragments.” However,

long-term follow-up studies evaluating the fate of these residual fragments after SWL

suggest otherwise.

Chapter 28 / Extracorporeal Shockwave Lithotripsy 559

In a review of the long-term follow up of a very carefully selected group of 160

patients with anatomically normal upper tracts and 4 mm or less asymptomatic residual

calcium oxalate or calcium phosphate calculi after SWL monotherapy for renal calculi,

18% of patients demonstrated growth of residual fragments (26). Furthermore, 43%

developed a symptomatic episode, and 59% of these required intervention. By Kaplan-

Meier estimations, the probability of developing a symptomatic episode within 5 yr after

treatment was 71%. Fortunately, of patients that require urologic intervention for a

symptomatic episode, the majority (79%) can be managed with repeat SWL alone, and

98% will require SWL and/or retrograde endoscopic procedures alone (26,27).

Candau and colleagues retrospectively reviewed 83 patients with residual fragments

4 mm or less at 3 mo after SWL. During a median of 40 mo follow up, 31 (37%) patients

demonstrated an increase in stone burden, and 58% of these underwent a secondary

procedure (28). Therefore, patients with residual stone fragments after SWL require

continued surveillance and should be informed of the potential for recurrent symptom-

atic episodes and the possibility of secondary interventions. Furthermore, application

of the term “clinically insignificant” to any residual stone after SWL may not be appro-

priate.

OMPARING APPLES TO APPLES

Owing to the wide variety of makes and models of lithotriptors, with different

generators and energies, and subtle variations in overall patient care among investiga-

tors, it becomes difficult to make comparisons between series of reported data. For

example, for a given stone-free rate, one machine may require multiple re-treatments

or subsequent stent placements. Denstedt and colleagues (29) described the use of an

“efficiency quotient” to take such factors into account as follows: efficiency quotient

(EQ) = % stone-free divided by (100 + % re-treated + % auxiliary procedures). There-

fore, a lithotriptor with an 85% stone-free rate, 10% re-treatment rate, and 15% rate of

additional procedures would have an efficiency quotient of 0.68, whereas another

machine which also has an 85% stone-free rate but with no re-treatments or ancillary

procedures would have an EQ of 0.85. It is evident that despite the same stone-free

rates, the two machines are not equally “efficient.” This methodology is also useful in

comparing results of SWL to other modalities, such as ureteroscopy or percutaneous

nephrolithotomy. Unfortunately, only a small fraction of the current peer-reviewed

literature reported EQs, and stone-free rates were the primary measure of success.

Renal Calculi

Overall results of SWL for solitary nonstaghorn renal calculi in any location vary from

EQs of 0.45 to 0.82 for electrohydraulic lithotriptors and 0.42–0.67 for electromagnetic

lithotriptors (24,30,31). However, two fundamental truths are well documented in the

literature. First, stone-free rates are inversely proportional to the total stone burden.

Second, stone-free rates are worse for calculi located in the lower pole of the kidney.

TONE BURDEN

Although there is no data defining the number of shockwaves that can safely be

administered per kidney per session for any given lithotriptor and energy level, it is

generally recommended that the safe maximum is approx 3000 to 3500 shockwaves.

Therefore, one is inherently limited in the stone burden that can be treated per session.

560 Ng, Fuchs, and Streem

Stone composition plays a key role in this determination. For example, it is generally

recommended that calcium oxalate/phosphate stones larger than 2 cm and struvite stones

larger than 3 cm be excluded from primary SWL monotherapy.

In contemporary series, overall stone-free rates for renal calculi measuring 10 mm or

less range from 53.7 to 81%, regardless of location within the kidney. For 11–20 mm

calculi, overall stone-free rates decrease to 38.4–66%. The widest range of success rates

exist for calculi greater than 20 mm, from 28.1 to 83%, where stone location plays a

greater role in the clearance of fragments. Lower pole stones >20 mm are associated with

stone-free rates of 25–42% (30,32,33). Interestingly, these contemporary data do not

differ greatly from the first report by the US Cooperative Group in 1986, where 3-mo

stone-free rates for stones <10 mm, 10–20 mm, and >20 mm were 81.9%, 78%, and

52.5%, respectively (34).

TAGHORN CALCULI

The American Urological Association Nephrolithiasis Clinical Guidelines Panel

evaluated the available literature before 1994 regarding the management of staghorn

calculi (35). The recommended guideline for a newly diagnosed staghorn calculus was

primary percutaneous nephrolithotomy followed by SWL and/or repeat percutaneous

procedures as needed. Furthermore, SWL monotherapy should not be used as first-line

treatment.

Subsequent studies corroborated these recommendations. In a prospective random-

ized trial of percutaneous nephrolithotomy with or without SWL vs SWL monotherapy,

the stone-free rates were 74% and 22%, respectively, and septic episodes occurred in 9%

and 37% of patients, respectively (36). Furthermore, we reviewed our experience with

combination “sandwich” therapy, defined as primary percutaneous debulking followed

by SWL and secondary percutaneous procedures, in 100 consecutive patients with stag-

horn calculi. Our stone-free rate was 63%, with 20% of patients developing fever or

sepsis episodes during the course of treatment (37). Interestingly, stone-free rates im-

proved from 52% to 70% from the first 25 patients treated compared to the most recent

25 patients, implying a learning curve.

In summary, the current role for SWL in the management of staghorn calculi is merely

as an adjunctive procedure to primary percutaneous intervention.

Lower Pole Renal Calculi

The optimal management of lower pole renal calculi continues to be an area of con-

troversy and has recently received heightened attention within the endo-urologic com-

munity (38). The anatomic disadvantage faced by lower pole calyceal stones becomes

particularly important when considering SWL for definitive treatment, where spontane-

ous stone passage is just as crucial as adequate fragmentation. It was evident early in the

world’s experience with SWL that when stone-free rates were stratified by stone loca-

tion, lower pole stones faired less well. In fact, in a large meta-analysis of the available

data from 1986–1994, Lingeman and associates reported an overall stone-free rate of

62.2% for lower pole stones in 1931 patients. Interestingly, for stones less than 10 mm,

stone-free rate was 74% compared to 33% for stones greater than 20 mm. Approximately

half of all patients with stones 10–20 mm were stone free. In this retrospective compari-

son, the results of percutaneous nephrolithotomy (PCNL) were better than SWL for each

size group, with an increasing advantage to PCNL as stone size increased.

Chapter 28 / Extracorporeal Shockwave Lithotripsy 561

Multiple retrospective studies have since reported similar findings. However, suffi-

cient debate remained such that the Lower Pole Study Group was established to com-

pare the efficacy of SWL and PCNL for the treatment of symptomatic lower pole renal

calculi. In their initial report of a prospective, multicenter clinical trial of 128 patients

with lower pole renal calculi less than 3 cm who were randomized to PCNL or SWL,

overall stone-free rates at 3 mo were 95% and 37% respectively (38). When stratified

by size, stone-free rates for SWL for stones <10 mm, 11–20 mm, and 21–30 mm were

63%, 23%, and 14%, respectively. EQ for SWL and PCNL for stones <10 mm were 0.51

and 0.91, respectively. For stones >10 mm, EQs were 0.16 and 0.82, respectively.

However, SWL was associated with only an 11% rate of mostly minor complications.

The conclusions from the Lower Pole Study Group were that SWL is recommended for

lower pole stones 10 mm or less, whereas PCNL is recommended for lower pole stones

>10 mm.

However, our own experience suggests that selected patients with stones 10–20 mm

in size can be managed successfully with SWL. Such factors that must be considered in

this regard are the same as those described above, and include but are not limited to

presumed stone composition, concomitant medical problems, body habitus, and perhaps

pyelocalyceal anatomy. The Lower Pole Study Group data, at the very least, provide the

most objective information to date with which to counsel patients regarding the manage-

ment of lower pole renal calculi.

DJUNCTIVE PROCEDURES FOR LOWER POLE RENAL CALCULI

In attempts to improve on the stone-free rates of SWL for lower pole stones, a variety

of adjunctive procedures have been used with varying results. Despite some encouraging

reports, none have yet become routine to our clinical practice, but are nevertheless

worthy of discussion. Brownlee and colleagues were first to report the use of “controlled

inversion therapy,” which involved placing the patient in a head-down position at a

defined interval and duration after SWL (39,40). The goal of this procedure was to use

gravity to their advantage to reposition stone fragments into more favorable calyces.

Although this method indeed made theoretical sense, its practical utility was limited.

This idea was revisited with the addition of manual percussion (41,42). In a prospec-

tive randomized trial of inversion greater than 60°, forced diuresis and manual percus-

sion for patients with lower pole residual fragments after SWL, an additional 37% were

stone-free compared to 3% of those observed (41).

Other adjunctive procedures include lower pole irrigation using either antegrade or

retrograde catheters (43,44), and repeat office treatment with a piezoelectric lithotriptor

to merely “stir up” fragments (45). Again, despite isolated reports of favorable results

with these measures, none have been employed with any regularity in our current prac-

tice.

HE ROLE OF LOWER POLE ANATOMY

In recognizing the marked variability of the anatomy of the renal collecting system,

Sampaio and colleagues sought to categorize patients based of the anatomy of the lower

pole calyx to predict who may have better outcomes after SWL (46,47). Others have

subsequently contributed further to these analyses (48,49). In brief, from a representa-

tive pyelogram, measurements were obtained of the lower pole infundibular length and

width as well as the angle of the infundibulum in relation to the renal pelvis and proximal

ureter—the so-called “infundibulopelvic angle.” Based on the retrospective review of

562 Ng, Fuchs, and Streem

stone-free status, cut-off values were determined to divide patients into “favorable” or

“unfavorable” categories of lower pole renal anatomy.

However, using these methods, the Lower Pole Study Group found no significant

correlation between lower pole anatomy and stone-free status (38). It is conceivable that

the measurements of static images do not fully depict the dynamic system of lower pole

drainage. In addition, there have been no reports on using these methods prospectively

in clinical decision-making. Nevertheless, the role of evaluating lower pole anatomy is

still being determined.

Ureteral Calculi

The indications for urologic intervention for ureteral calculi depend on many factors,

including but not limited to stone size and location, stone shape and orientation, indi-

vidual anatomy, and history of prior stone passage. Generally, stones 5 mm or less will

pass spontaneously in up to 98% of cases, regardless of location within the ureter,

whereas stones 5–10 mm have, at best, a 50% chance of passage (50). These probabilities

are used to counsel patients regarding the options of watchful waiting vs intervention for

ureteral calculi.

However, one cannot accurately predict how long it will take to spontaneously pass

a given ureteral calculus. Thus, the duration and degree of renal colic as well as the

development of other symptoms associated with stone passage may persuade the patient

and surgeon to proceed with intervention, despite a high probability of passage. Cer-

tainly, any indication of infection or renal functional compromise associated with obstruc-

tion requires immediate temporary urinary diversion via ureteral stent or percutaneous

nephrostomy tube and subsequent staged stone treatment.

In 1997, the Ureteral Stones Clinical Guidelines Panel reviewed the existing literature

up through 1996 regarding the management of ureteral calculi (50).Owing to the marked

inconsistency in the reporting of results, only broad categorizations could be made.

Median stone-free rates after SWL for proximal ureteral calculi (above the iliac vessels)

10 mm or less vs greater than 10 mm were 84% and 72%, respectively, whereas those

for distal stones (below the iliac vessels) were 85% and 74%, respectively. From the

available data, there appeared to be no benefit to ureteral stenting or stone manipulation

into the kidney (50,51).

However, more recent reports suggest less favorable results of SWL for larger ureteral

calculi (>10 mm), with reported stone-free rates of 32–51% (33,52,53). In nonrandom-

ized retrospective comparisons, ureteroscopic lithotripsy for ureteral calculi >10 mm

was associated with 88–93% stone-free rates (52,53). From these data, primary SWL

therapy for proximal or distal ureteral calculi should be limited to solitary stones 10 mm

or less in size.

ISTAL URETERAL CALCULI

In recent series, stone-free rates after SWL for distal ureteral stones <20 mm were 73–

100% (54–58). Although not stratified by size, the mean or median stone size was <10

mm in each series. The unmodified HM3 (Dornier Medical Systems, Inc., Marietta,

Georgia) was associated with lower re-treatment and ancillary procedure rates compared

to other lithotriptors. However, in select patients with small distal ureteral calculi, ex-

cellent results can be obtained using office-based electromagnetic or piezoelectric SWL

under ultrasound guidance without anesthesia or heavy analgesia. In one study of 165

Chapter 28 / Extracorporeal Shockwave Lithotripsy 563

patients, 97% had stones <10 mm, and none were >15 mm. Stone-free rate at 3 mo was

99% with re-treatment in only 7% (57).

HOCKWAVE LITHOTRIPSY VERSUS URETEROSCOPY

With improved technology and expertise with ureteroscopy, the optimal management

of distal, and even proximal, ureteral calculi less than 10 mm has come into debate.

Peshcel and colleagues reported a randomized, prospective comparison between SWL

and ureteroscopy for distal ureteral calculi of <10 mm (55). Interestingly, repeat SWL

was not part of the study, and all patients were to be “salvaged” on or before postopera-

tive-day 43 by ureteroscopy only. There were no re-treatments in any patient in the

ureteroscopy arm, and all patients were stone-free by 8 d. The re-treatment rates after

SWL for stones <5 mm vs >5 mm were 15% and 5%, respectively. Although the results

of both modalities in this series were excellent, it appears that ureteroscopy may have the

greatest advantage over SWL in the setting of distal ureteral stones <5 mm. However,

their level of expertise with ureteroscopy was indeed high given that their procedure

times were much shorter for ureteroscopy than for SWL.

In a multicenter randomized prospective comparison of SWL and ureteroscopy for

distal ureteral stones <15 mm, Pearle and associates emphasized the importance of

secondary outcome parameters because stone-free rates were 100% in each group (56).

They favored SWL with the Dornier HM3 over ureteroscopy because of its higher

efficiency, fewer complications, fewer postoperative symptoms and flank pain, and

higher patient satisfaction.

It is evident that SWL and ureteroscopy are both excellent approaches for solitary

distal ureteral calculi <10 mm in size, and the decision to proceed with either procedure

still depends on the surgeon’s expertise and informed patient preference.

Pediatric Urolithiasis

SWL has become an established and accepted treatment modality for urinary tract

calculi in children. Long-term follow-up studies have found no adverse effects on renal

function or morphology, blood pressure, or overall growth and development (59–62).

Furthermore, at 6 mo after SWL, no renal parenchymal scars were noted by di-mercapto-

succinic acid (DMSA) renal scan, even after four sessions for staghorn calculi (61,

63,64). Stone-free rates for solitary nonstaghorn renal calculi range from 80 to 100%

(61,62,65). In addition, a limited experience with SWL for renal calculi in premature

infants has demonstrated excellent results, with all 8 patients stone-free by 8 wk after

one session using a modified Dornier HM3 (66).

SWL monotherapy is the treatment of choice for partial and complete staghorn calculi

in children, affording far better results than those seen in the adult population. Stone-free

rates of 73–83% have been reported (63,64,67). Up to 5 SWL sessions per kidney have

been administered, although most patients required one or two sessions. Despite mul-

tiple treatments with SWL, no renal parenchymal scars were noted by DMSA scan at

6 mo, and no changes in blood pressure were noted out to 9 yr (63,64).

Excellent results from SWL for ureteral calculi in children have also been achieved.

Initial stone free rates of 82% increase to 97% overall with additional SWL monotherapy

for ureteral stones of any location. For calculi <10 mm, stone-free rates up to 100% have

been reported (68).

Pre-SWL ureteral stent placement in children, particularly for staghorn calculi, was

shown to reduce the rate of obstructive complications and shorten hospital stay (67).

564 Ng, Fuchs, and Streem

Other technical considerations for children include lead shielding of the gonads, lungs,

and thyroid when using fluoroscopy, and minimizing number of shockwaves and energy

level. For infants, Styrofoam shielding of organs has also been used.

COMPLICATIONS

Steinstrasse

Post-SWL urinary obstruction owing to ureteral impaction of fragments is referred to

as steinstrasse, or “street of stone,” which connotes the classic radiographic findings.

Steinstrasse occurs in up to 15% of radiography obtained within 48 h of SWL, and is

found most commonly in the distal one-third of the ureter. Up to 50% of patients found

to have steinstrasse require intervention, which most often involves either placement of

a percutaneous nephrostomy tube or repeat SWL (69,70).

Coptcoat and associates classified steinstrasse into three subtypes (69). Type I con-

sists of a column of dust or gravel, and is the most common type. Type II is caused by

an impacted large “lead fragment” with dust or gravel stacked behind it. Type III refers

to a column of large fragments.

The initial management of symptomatic steinstrasse consists of fluid hydration and

analgesia. Persistent obstruction requires the placement of a percutaneous nephrostomy

tube. Middle or upper pole access is preferred in case an antegrade approach is needed.

Ureteral stent placement can be difficult and dangerous because the ureter is acutely

inflamed and often tightly impacted with fragments. Subsequent intervention for failed

conservative management is tailored to the type of steinstrasse. Most type I steinstrasse

will pass with nephrostomy placement alone, which relieves the acute obstruction and,

in turn, restores ureteral peristalsis. Type II steinstrasse may need repeat SWL or

ureteroscopic lithotripsy to the lead fragment. Type III steinstrasse will need definitive

management with SWL, ureteroscopy, or a percutaneous approach, depending on the

location and stone burden. Open surgery has been required in 2–4% of patients with

symptomatic steinstrasse (69,70).

Preoperative placement of a ureteral stent may reduce the incidence of steinstrasse.

In 400 patients randomized to stent or none before SWL for 1.5–3.5-cm renal calculi, the

incidence of steinstrasse was 6% and 12%, respectively (71). However, according to the

authors, stenting did not seem to alter the presentation, treatment, or outcome of

steinstrasse.

As an adjunct to endoscopic management of severe steinstrasse, ureteral meatotomy

has been employed by the authors. Using a wide “cutting” incision of the ureteral orifice

and judicious “spot” fulguration as needed, this technique provides improved ureteral

drainage and easier ureteral access, and is particularly useful when multiple procedures

for steinstrasse are anticipated. Resultant vesicoureteral reflux has not been found to be

an issue in our experience.

Perirenal Hematoma

Perirenal hematomas, including intrarenal, subcapsular, and perinephric locations,

can be detected in up to 30% by CT scan, however are clinically significant in less than

1% of patients. Risk factors for the development of post-SWL hematomas include

hypertension (2.5% in controlled vs 3.8% in uncontrolled hypertension), coagulopathy,

and acute urinary tract infection (72,73).

Chapter 28 / Extracorporeal Shockwave Lithotripsy 565

Patients that present with severe ipsilateral flank pain despite oral analgesics within

48 h after SWL should be suspected to have a clinically significant perirenal hematoma.

The initial evaluation should include a hematocrit level, abdominal X-ray, and renal

ultrasound. If a hematoma is detected, the patient should be admitted to the hospital for

intravenous hydration and analgesia and serial blood counts. Blood transfusions are

given as warranted. Angiographic selective embolization or surgical intervention is

rarely necessary.

In a recent yet unpublished review of 400 consecutive patients treated with SWL for

renal calculi using the Storz Modulith SLX electromagnetic lithotriptor (Storz Medical,

Kreuzlinsen, Switzerland) at our institution, fourteen (3.5%) developed perirenal he-

matomas. Thirteen were detected incidentally on routine follow-up ultrasound or CT

scan. Only one patient (0.25%) developed symptoms and required hospitalization and

blood transfusion. The development of a perirenal hematoma was not associated with

higher energy levels or increased number of shockwaves administered.

The long-term outcome after development of a post-SWL hematoma is excellent. Up

to 86% resolve in 2 yr. At 5 yr, there was no evidence of new onset hypertension or renal

deterioration (73).

New-Onset Hypertension

Despite some debate regarding the development of new-onset hypertension after

SWL, several long-term follow-up studies suggest that there is no significant increase

in the incidence of new hypertension after SWL (74–76). Furthermore, a recent prospec-

tive randomized, albeit poorly powered, trial comparing SWL vs observation revealed

no difference in the incidence of new-onset hypertension between groups at 12-mo

follow-up (77). In addition, as mentioned above, even in a subset of patients who devel-

oped post-SWL hematoma in whom one might expect a Page kidney phenomenon, there

was no evidence of new-onset hypertension or renal deterioration at 5 yr (73). Lastly, in

a recent review of 228 patients with small asymptomatic calyceal calculi randomized to

SWL or observation, 11% and 7% of patients, respectively, developed new-onset hyper-

tension after a mean 2-yr follow-up, which was not statistically significant (78).

Renal Functional Effects

The risk of long-term renal deterioration after SWL is a legitimate concern, and has

been yet another topic of debate. Several studies have suggested a decrease in glomerular

filtration rate after SWL, particularly in those patients with pre-existing renal insuffi-

ciency, defined as serum creatinine >2 mg/dL or with solitary kidney (79,80).

However, more contemporary series demonstrated no deleterious effect of SWL on

renal function. Pienkny and Streem compared 319 patients who underwent simultaneous

bilateral SWL to 41 patients who underwent staged bilateral SWL (81). There was no

clinically or statistically significant decrease in renal function in either group as mea-

sured by serum creatinine at a mean follow-up of 3.2 yr. Furthermore, there was no

difference between groups. Perry and colleagues corroborated these findings in 120

patients who underwent simultaneous bilateral SWL, with a mean follow-up of 21 mo

(82).

Further evidence toward the long-term safety of SWL regarding renal function was

demonstrated by Liou and Streem in a recent series of 83 patients with a solitary kidney,

who were treated with SWL, PCNL, or both and followed a mean of 4.4 yr with a

566 Ng, Fuchs, and Streem

maximum follow-up of 14 yr (83). Renal function remained stable within treatment

groups. As importantly, there was no difference in the effect on function among treat-

ment groups. This finding implies that SWL, PCNL, and the two therapies combined are

equally efficacious for preserving renal function in patients with a solitary kidney. Thus,

the choice of therapeutic modality may be confidently based on stone size, configuration

and presumed composition rather than on concerns regarding the long-term effects on

renal function.

CONCLUSIONS

There is no doubt that SWL has revolutionized the urologic management of stone

disease and remains the sole noninvasive surgical modality. However, there have been no

significant advancements in its technology in the past decade. Conversely, ureteroscopic

and percutaneous approaches have improved remarkably and continue to improve rap-

idly.

Therefore the relative role of SWL will indeed continue to evolve, perhaps into a more

well-defined and limited capacity. It is interesting that current ureteroscopic procedures

in skilled hands may be superior to SWL for small distal ureteral calculi. Thus it is not

inconceivable that ureteroscopy may someday become superior to SWL for all upper

tract calculi. So long as it proves to be better, we may be steering in the direction of more

invasive rather than noninvasive interventions for stone disease. But for now, SWL

continues to be the mainstay of endo-urologic management for most patients with uri-

nary tract calculi.

REFERENCES

1. Eisenberger F, Chaussy C. Contact-free renal stone fragmentation with shock waves. Urol Res

1978; 6: 111.

2. Chaussy C, Brende, W, Schmiedt E. Extracorporeally induced destruction of kidney stones by

shock waves. Lancet 1980; 2: 1265.

3. Chaussy C, Schmiedt E, Jocham D, et al. First clinical experience with extracorporeally induced

destruction of kidney stones by shock waves. J Urol 1982; 127: 417.

4. Streem SB. Contemporary clinical practice of shock wave lithotripsy: a reevaluation of

contraindications. J Urol 1997; 157: 1197.

5. Asgari MA, Safarinejad MR, Hosseini SY, et al. Extracorporeal shock wave lithotripsy of renal

calculi during early pregnancy. BJU Int 1999; 84: 615.

6. Vieweg J, Weber HM, Miller K, et al. Female fertility following extracorporeal shock wave

lithotripsy of distal ureteral calculi. J Urol 1992; 148: 1007.

7. Erturk E, Ptak AM, Monaghan J. Fertility measures in women after extracorporeal shockwave

lithotripsy of distal ureteral stones. J Endourol 1997; 11: 315.

8. Vasavada SP, Streem SB, Kottke-Marchant K, et al. Pathological effects of extracorporeally

generated shock waves on calcified aortic aneurysm tissue. J Urol 1994; 152: 45.

9. Abber JC, Langberg J, Mueller SC, et al. Cardiovascular pathology and extracorporeal shock wave

lithotripsy. J Urol 1988; 140: 408.

10. Hunter PT, Finlayson B, Hirko RJ, et al. Measurement of shock wave pressures used for lithotripsy.

J Urol 1986; 136: 733.

11. Carey SW, Streem SB. Extracorporeal shock wave lithotripsy for patients with calcified ipsilateral

renal arterial or abdominal aortic aneurysms. J Urol 1992; 148: 18.

12. Cooper D, Wilkoff B, Masterson M, et al. Effects of extracorporeal shock wave lithotripsy on

cardiac pacemakers and its safety in patients with implanted cardiac pacemakers. Pacing Clin

Electrophysiol 1988; 11: 1607.

13. Drach GW, Weber C, Donovan JM. Treatment of pacemaker patients with extracorporeal shock

wave lithotripsy: experience from 2 continents. J Urol 1990; 143: 895.