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STONE
DISEASE
Shock
wave lithotripsy at 60 or 120 shocks per minute: a randomized, double-blind
trial
Pace KT, Ghiculete D, Harju M, Honey RJ; University of Toronto Lithotripsy
Associates
Division of Urology, Department of Surgery, St. Michael’s Hospital,
University of Toronto, Toronto, Ontario, Canada
J Urol. 2005; 174: 595-9
-
Purpose:
The rate of shock wave administration is a factor in the per shock efficiency
of shock wave lithotripsy (SWL). Experimental evidence suggests that
decreasing shock wave frequency from 120 shocks per minute results in
improved stone fragmentation. To our knowledge this study is the first
to examine the effect of decreased shock wave frequency in patients
with renal stones.
- Materials
and Methods: Patients with previously untreated radiopaque
stones in the renal collecting system were randomized to SWL at 60 or
120 shocks per minute. They were followed at 2 weeks and 3 months. The
primary outcome was the success rate, defined as stone-free status or
asymptomatic fragments less than 5 mm 3 months after treatment.
-
Results: A
total of 220 patients were randomized, including 111 to 60 shocks per
minute and 109 to 120 shocks per minute. The 2 groups were comparable
in regard to age, sex, body mass index, stent status and initial stone
area. The success rate was higher for 60 shocks per minute (75% vs 61%,
p = 0.027). Patients with larger stones (stone area 100 mm or greater)
experienced a greater benefit with treatment at 60 shocks per minute.
The success rate was 71% for 60 shocks per minute vs 32% (p = 0.002)
and the stone-free rate was 60% vs 28% (p = 0.015). Repeat SWL was required
in 32% of patients treated with 120 shocks per minute vs 18% (p = 0.018).
Fewer shocks were required with 60 shocks per minute (2,423 vs 2,906,
p < 0.001) but treatment time was longer (40.6 vs 24.2 minutes, p
< 0.001). There was a trend toward fewer complications with 60 shocks
per minute (p = 0.079).
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Conclusions: SWL
treatment at 60 shocks per minute yields better outcomes than at 120
shocks per minute, particularly for stones 100 mm or greater, without
any increase in morbidity and with an acceptable increase in treatment
time.
- Editorial
Comment
Over the last decade, lithotripter technology has been disappointingly
stagnant. Indeed, current lithotripters are less effective at stone
fragmentation than the original Dornier HM3 lithotripter. As a result,
endoscopic stone management, which has advanced substantially during
this same time frame, has become an increasingly attractive option for
the treatment of renal calculi. Recent efforts, however, have been underway
to improve SWL efficacy and efficiency through optimization of treatment
parameters.
Paterson and colleagues first demonstrated in a novel porcine model
that slowing the rate of shock wave delivery improved stone fragmentation
(1). In the current study, Pace and co-workers report the first prospective,
randomized clinical trial comparing slow with fast shock wave delivery
on SWL outcomes. Among 220 patients with > 5 mm renal calculi randomized
to slow (60 shocks/minute) versus fast (120 shocks/minute) shock wave
delivery, “success rates” (defined at stone free or asymptomatic
fragments less than 5 mm) were superior in the slow shock wave group.
When stratified by stone size into smaller and larger stones (< 100
mm2 or ≥ 100 mm2), the difference in success
rates and stone free rates between the 2 treatment groups was more pronounced
in the larger stone group.
While small stones are generally successfully fragmented under most
conditions, larger stones have been less successfully treated, particularly
with newer generation lithotripters. Therefore, slowing the rate of
shock wave delivery may provide a means of achieving acceptable outcomes
with SWL for stones which are increasing being treated by endoscopic
means. The small increase in treatment time associated with slower shock
wave delivery should be more than compensated for by the less frequent
need for retreatment and the fewer complications associated with poorer
fragmentation. Perhaps with optimization of SWL treatment parameters,
non-invasive management will once again become the preferred treatment
option for renal calculi.
Reference
1. Paterson RF, Lifshitz DA, Lingeman JE, Evan AP, Connors BA, Fineberg
NS, Williams JC Jr, McAteer JA: Stone fragmentation during shock wave
lithotripsy is improved by slowing the shock wave rate: studies with a
new animal model. J Urol. 2002; 168: 2211-5.
Dr.
Margaret S. Pearle
Associate Professor of Urology
University of Texas Southwestern Med Ctr
Dallas, Texas, USA |