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Extracorporeal Shock-wave Lithotripsy
Why large stones, even following repeated treatment of residuals, stone disintegration and subjects the tissues to less trauma.
63
are associated with lower stone-free rates than small stones is an Stepwise increments of the shock-wave power, termed ramping, has
unresolved issue. This outcome cannot easily be understood unless also been reported to be better than a rapid increase to high energy
larger stones in some way disturb the physiology of the calyx. levels,
54,64,65
and in this regard it is important to know that low energy
results in small fragments and high energy in large fragments.
An issue of great concern is the residuals left in the kidney, and Nevertheless, the energy has to be increased to a level where the
many urologists suggest various alternative invasive methods to binding forces between the stone crystals are exceeded.
completely clear the collecting system. Undoubtedly, the risk of
forming new stones in a stone-free kidney is lower than that in a Whenever treating stones in the kidney, it is the author’s routine to
kidney with residuals. In a four-year follow-up of patients with start each treatment session with 100–200 shock waves at a low
residual calcium stone fragments (≤4mm), 12% formed new stones energy level. The reason for this is to obtain an arterial
in another part of the kidney as an expression of the recurrent vasoconstriction
66
and in that way reduce the risk of bleeding that
character of the stone disease. In as many as 52% there was no or otherwise might occur as a result of tissue contusion. The
clinically discrete and insignificant growth of the residuals. Another advantage of such a procedure is based on findings in experimental
38% had obvious growth or consolidation of the fragments but studies. In addition, other experiments have shown the advantage of
remained without symptoms, and in only 14% of all patients with a pause of three to four minutes after the initial shock waves before
residual fragments was there an increased stone size associated the ramping is begun.
54,65
Other precautions that are essential for
with symptoms that made treatment necessary. Therefore, at least minimising the risk of the feared complication of subcapsular
concerning calcium stones, adding invasive procedures in an haematoma is to stop intake of salicylates 10 days before the
attempt to remove all residual fragments in every patient appears to treatment and also to replace warfarin treatment by low-dose low-
be overtreatment. The drawback of leaving residuals is the need for molecular-weight heparin.
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No treatment of stones in the kidney
follow-up in the future, but increased intervals can be used for those should be undertaken in patients with untreated hypertension.
patients in whom the fragments remain stable. Moreover, the When high blood pressure is noted, conservative treatment should
recurrent character of stone disease in a substantial fraction of be given until the the blood pressure has been adequately
patients requires some kind of follow-up anyway. controlled. In addition, it is recommended to be careful in terms of
shock-wave power and number of shock waves in patients with a
Inversion therapy is a seldom used though promising alternative for history of hypertension or in elderly patients.
elimination of lower calyx residuals. Such a method has proved
successful in some centres.
48,49
Combined treatment using ESWL and For patients with a history of urinary tract infection with a positive
percutaneous chemolysis for removal of large infected or cystine bacterial test or positive urine culture, an appropriate antibiotic
stones is another useful treatment.
50
For infected staghorn stones in should be administered intravenously approximately one hour
seriously ill patients with neurological or other diseases, such an before the treatment. If the resistance pattern is unknown, a single
approach might be the only possible treatment alternative.
51,52
dose of gentamicin 120–150mg has proved successful. Antibiotics
should always be given to patients with nephrostomy catheters.
Important Considerations
A successful outcome of ESWL without complications cannot be When large stones in the kidney (diameter >20mm; surface area
expected unless attention is paid to a number of factors.
48,53,54
First of >300mm
2
) are treated, the obstructing accumulation of fragments in
all, it is fundamental to place the stone correctly in focus and to check the ureter, termed steinstrasse, should be avoided by insertion of an
repeatedly that the stone or stone fragments are kept in that position internal stent.
68–71
On the other hand, it is not recommended to insert
during the whole treatment. The patient can move and the stone stents or ureteral catheters at the first treatment session of ureteral
material can change position. Respiratory movements of the kidney stones.
5,72
Also, an internal stent can be avoided when treating even
and the proximal ureter can be restricted using a supportive belt. large stones in children, because the peristaltic power of their
ureters is much better than that of adults.
Great care must be taken to avoid any significant interference
between the shock-wave path and skeletal structures, and the Although general or regional anaesthesia is unnecessary (except in
patient’s position has to be adjusted accordingly. In order to avoid children), administration of analgesics is nevertheless required. In
attenuation of the shock wave, it is important to use transmission this regard, small intermittent doses of alfentanyl and propofol
media such as ultrasound jelly, silicon oil or water without air have proved to be an excellent method. These agents have a very
bubbles;
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the presence of air leads to a reflection surface that will short duration of action and the patients are in good shape shortly
seriously reduce or even extinguish the shock wave’s power. after the treatment. In the author’s department, all patients are
given 2l of oxygen/minute during the procedure, and the oxygen
In several experimental studies, the importance of an adequate saturation and electrocardiogram (ECG) are continuously monitored
shock-wave frequency has been emphasised. With high-frequency during the procedure.
shock-wave administration, cavitation bubbles at the surface of the
stone or stone remnants are not given sufficient time to disappear, Pharmacological Treatment
which also leads to undesirable reflection surfaces.
56,57
From the For patients in whom a series of ESWL sessions is anticipated in order
literature it can be deduced that a frequency of 60–90 (1–1.5Hz) is to obtain sufficient stone disintegration, it is recommended to protect
adequate, whereas a frequency of 120 (2Hz) is associated with less the kidney by administration of calcium-blocking or anti-oxidative
efficient disintegration.
56,58–62
Recent experimental studies have agents such as verapamil or allopurinol. Experimental studies have
suggested that a frequency of 1Hz or even lower provides better shown that such treatment strategies might be useful.
73,74
EUROPEAN UROLOGICAL REVIEW 71