When it comes to getting rid of
kidney stones that won't budge on their own, urologists
have two choices: minor surgery or shock wave treatment.
The decision on which to use is based on clinical judgement
and experience — not least because we have no clear
guidelines on which technique is preferable in what
circumstances.
Head-to-head trials have been few
and far between, and those few are often limited by
faulty methodology or sketchy data. Now, the folks at
the Cochrane Collaboration have attempted to clear things
up. Though they were unable to pick a clear winner,
they did note that patients who undergo lithotripsy
— shock wave treatment — are less likely to
suffer complications or hospitalizations, but are also
less likely to be stone-free after treatment.
LIMITED
DATA
The team led by Ghulam Nabi of the University of Aberdeen
considered six of the best available trials, comprising
833 cases in all. The raw material was admittedly not
of the highest quality. "The most important finding
from our review is that current practice of managing
kidney stones is based on poor-quality evidence, mostly
from small trials with a lot of heterogeneity," Dr Nabi
said in a press release.
For one thing, the two biggest
trials looked at patients with lower kidney stones —
those below the lower edge of the pelvis. In real practice,
there would be three treatment choices here, not two,
because conservative treatment often sees these stones
flushed out spontaneously.
Many urologists believe stone location
is a key factor in deciding which treatment to use.
Ureteroscopy, the gold standard surgical technique,
can seem more attractive when the stone is lower, because
the ureteroscope need not be inserted so far, and the
risk of damage is correspondingly less. But the available
data didn't permit the Cochrane researchers to pronounce
on this question.
Nor could they address differences
in patient characteristics. For example, two previous
studies have suggested that lithotripsy has a higher
failure rate in obese patients.
In fact, many questions remain
unanswered because the data is so sparse and contradictory.
Four studies in the analysis compared the time taken
to remove stones. Two found ureteroscopy a swifter procedure,
while two declared lithotripsy faster.
TECH
CHALLENGE
Much of the confusion is really due to changing technology.
Ureteroscopy was always acknowledged to have a high
complication rate. As the surgeon pulls out the stone
with a basket or forceps attachment, the potential for
tissue damage or even perforation is clear.
The lithotripter offered a welcome
alternative to ureteroscopy. But since then, it's the
older technique that has come on by leaps and bounds,
while new improvements in lithotripters remain very
much at the prototype stage.
The introduction of the Holmium:
YAG laser allows the surgeon performing a ureteroscopy
the option of ablating the stone before dragging it
out. And the miniaturization of components has permitted
narrower, more flexible ureteroscopes, reducing the
threat of scarring and bleeding.
Even the six trials in the Cochrane
analysis, all less than eight years old, are now somewhat
obsolete because they took place when ureteroscopy was
commonly followed by stenting of the ureter. That practise
is increasingly being abandoned due to pain complications.
KNOW
WHAT'S BEST
Ultimately, the group concludes, physicians should consider
what equipment is available, and what is usable in the
particular. If a small-calibre ureteroscope is feasible
and the stone is readily accessible, that might be the
best option.
Not all lithotriptor machines are
equal, and the newest may not be the best. The original
machine, the HM3 made by Dornier, is a large, clunky
thing with a rather crude focus. That broader focal
zone can increase discomfort, but it also minimizes
the chance of missing part of the stone. Dornier's newer
offering, the portable HM4, is more refined but has
been linked to lower stone-free rates.
The Cochrane researchers argue
that if any research should take priority, it would
be studies that seek to establish best practices in
both lithotripsy and ureteroscopy. Only once we know
that can we usefully compare the two against each other.
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