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Stone Management
Figure 1: StoneBreaker™
and collapse of which lead to shock-wave generation. Developed in
the 1950s at the University of Kiev as a 9Fr probe, it was initially used
to fragment bladder stones. Electrohydraulic lithotripsy (EHL) was then
applied in the kidney by Raney
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in the 1970s, but it was not until the
late 1980s that 3Fr EHL probes were developed that could be passed
through 9Fr and 11Fr flexible ureterorenoscopes; subsequently,
smaller-calibre 1.9Fr probes have been described.
12
Although EHL can technically be used during either PCNL or
ureteroscopy, the technique is associated with more tissue trauma and
bleeding than newer energy sources such as lasers. The quoted stone
clearance rates are 83% for the distal ureter, 90% for the mid-ureter
and 70% for the proximal ureter, all of which are marginally inferior
to the newer modalities.
13
The key advantage over pneumatic
lithotripsy is the malleability of the EHL probe (much like a laser fibre),
which allows retrograde upper tract work.
Laser Lithotripsy
Laser technology has established itself as the most popular energy
modality for ureteroscopy due to its versatility, the flexibility of the
The underlying principle of this
Figure 2: Cyberwand™
spark-gap generator is that ignition
creates a spark that vaporises water
into a gaseous bubble, expansion
and collapse of which lead to
shock-wave generation.
fibres and its ability to treat all types of stone. Stone fragmentation
is effected by a photothermal effect at the stone surface. As the
thermal effects of the laser are restricted to 0.5–1.0mm from the fibre
tip, the risk of urothelial injury is minimised. The limitations are that
the treatment takes a long time if there is significant stone burden.
The most commonly used laser is the holmium: yttrium–aluminium–
called the Cyberwand
®
(see Figure 2) has been developed. This has a garnet (Ho:YAG) instrument, which operates at a wavelength of
dual-probe design with the two probes vibrating at different 2,150nm: stone-free rates are quoted at 98–100% in the distal ureter,
frequencies, and has been shown to have a significantly faster stone 100% in the mid-ureter and 89–100% in the proximal ureter.
13
The
penetration time than the LithoClast Ultra (4.6 versus 8.1 seconds).
10
Ho:YAG laser can also be used for transurethral enucleation or
ablation in benign prostatic hyperplasia, contributing to its popularity
within urology departments as a versatile investment. The
complication rates are low, and the different fibre sizes (550, 365 and
Laser technology has established itself
200µm) allow treatment of both ureteric and renal stones.
as the most popular energy modality
Generally, most published guidelines (for example those of the
for ureteroscopy due to its versatility,
European Association of Urology) advocate the use of retrograde
treatment of stones up to 2cm in size, beyond which PCNL may be
the flexibility of the fibres and its
more suitable. However, a recent study comments on renal stones
ability to treat all types of stone. larger than 2cm being cleared by flexible ureterorenoscopy with a
200µm laser fibre with a 93% clearance rate, although it should be
remembered that the operative time ranged from 45 to 140 minutes
in this study.
14
Electrohydraulic Lithotripsy
The underlying principle of this spark-gap generator is that ignition The first laser to be used was the pulsed-dye laser, which was
creates a spark that vaporises water into a gaseous bubble, expansion introduced in the 1980s;
15
however, the high cost of coumarin dye and
82 EUROPEAN UROLOGICAL REVIEW