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Current Management of Ureteral Calculi
an absolute decrease in the stone-free results for SWL management of and fertility. To date, no study has documented a negative effect on
ureteral calculi compared with the analysis of the 1997 guidelines (82 and female fertility with such treatment methods.
74% versus 83 and 85% for SWL-treated proximal and distal ureteral
stones, respectively). However, this difference is statistically significant Currently, SWL is an acceptable first-line treatment for ureteral stones
only for stones located in the distal ureter. As anticipated, stones >10mm >10mm along the course of the ureter. Smaller stones may also be
required a greater number of additional SWL procedures and had lower treated with SWL when intervention other than MET is required, i.e.
stone-clearance rates. failure of stone passage/progression, patient choice. Care should be
taken to assure adequate patient–lithotripter coupling. Although still
A number of proposed mechanisms attempt to explain this reduction in debatable, there is enough evidence to support the use of a slower
clinical efficacy despite improvements in lithotripter outputs. Beam size is (60Hz) shock-wave delivery rate.
considered by many experts to play a significant role in the
currently observed decrease in the effectiveness of SWL. Newer- Ureteroscopy
generation lithotripters have narrower beam foci in an attempt to For many years, URS has been the treatment of choice for distal and
improve patient discomfort and minimise tissue damage. Studies have middle ureteral calculi. Treatment of distal ureteral calculi is associated
demonstrated that a narrower beam size reduces the amount of time a with success rates (stone-free status) as high as 97% for stones <10mm
stone is exposed to the shock wave focus, due to respiratory excursion and 94% for stones >10mm, with an overall stone-free rate of 94%.
1
and dispersion of stone particles during fragmentation. Additionally,
investigators have found that higher internal tensile stresses (>60mPa) are
reached as a shock wave passes along the stone periphery. This evidence
Along with the improved outcomes of
supports the idea that the beam focal width needs to be larger than the
ureteroscopy, it is encouraging to note
stone being treated in order to optimise fragmentation stresses.
19
that complication rates remain
The shock-wave rate has also been purported to effect fragmentation
considerably lower, with minor
efficacy. One investigation reported a higher success rate when shock
complications such as ureteral
waves were administered at 60Hz (75 versus 61%; p=0.027) compared
with 120Hz.
20
In this study, patients with larger stones (>100mm
2
) perforation occurring in <5% of cases
experienced an even greater benefit. The success rate was 71% for 60Hz
and a stricture rate of 2%.
versus 32% (p=0.002) with a stone-free rate of 60 versus 28%
(p=0.015). Furthermore, a decreased number of secondary procedures
were required (18 versus 32%; p=0.018). This work has been verified by The limitations of URS for proximal and middle ureteral calculi have largely
additional investigators.
21–23
been obviated by significant technological advances. Diminution in the size
of flexible and semi-rigid scopes, improved optics including digital imaging,
Another barrier to effective stone comminution is the coupling of the advances in wire technology (i.e. combination wires), creation of backstop
shock wave head. Air pockets located within the applied gel–patient devices (i.e. Stone Cone
™
, Boston Scientific, Natick, Massachusetts;
interface can result in a 57% decrease in acoustic pressure transmission.
24
NTrap
®
, Cook Urological, Spencer, Indiana; and Accordian
®
, PercSys, Palo
Careful attention to the method of gel application can minimise the Alto, California), access sheaths, smaller, more flexible baskets and
defects and thereby optimise stone comminution.
25
widespread use of the holmium laser have all greatly added to the ability of
urologists to approach and treat stones in all locations of the ureter both
Stone characteristics such as size, location and hardness also affect the safely and effectively. With these improvements, success rates have
success of SWL. When tabulated by size, the 2007 EAU-AUA guidelines approached or surpassed SWL for middle and proximal ureteral stones. The
panel identified a stone-free rate following primary- or first-treatment meta-analysis performed and reported in the EAU-AUA 2007 guidelines
SWL for proximal ureteral stones of 90 and 68% for stones <10 or documented overall success rates of 94, 86 and 81% for distal, middle
>10mm, respectively.
1
Distal ureteral stones, when treated with SWL, had and proximal stones, respectively. Significant differences were not noted
an 86 and 74% stone-free rate for stones <10 and >10mm, respectively. for proximal ureteral stones treated with URS regardless of size; however,
Despite the high success rate for small distal ureteral calculi, this optimal middle ureteral calculi were found to have significantly worse stone-free
management is controversial because of the improved stone passage rate rates if the stone size was >10mm (78% for >10mm versus 91% for
of MET and the high success rate of URS. Regardless of the slightly lower <10mm). Significant improvements in stone-free rates are documented
success rate, the non-invasive outpatient nature of the procedure remains when using flexible URS for proximal stones (87%) compared with semi-
appealing to physician and patient alike. rigid ureteroscopes (77%). Along with the improved outcomes of URS, it is
encouraging to note that complication rates remain considerably lower,
Two special considerations for SWL are its use in the paediatric with minor complications such as ureteral perforation occurring in <5% of
population and in women of child-bearing age. Initial concerns regarding cases and a stricture rate of 2%.
1
decreased size of paediatric ureters and increased risk of ureteral trauma
are not found in clinical studies. In fact, paediatric patients have higher One particular scenario where URS may be particularly useful is during
rates of stone passage than adults.
26–30
The 2007 EAU-AUA guidelines pregnancy. Historically, stones have been difficult to identify due to fear of
documented an overall stone passage rate of 80 and 81% regardless of ionising radiation exposure to the foetus and the limitation of sonographic
the size of distal and ureteral stones, respectively. Questions remain imaging for ureteral calculi. Patients have often been temporised until post-
regarding the effect of distal ureteral SWL on female reproductive organs partum with ureteral stents and/or percutaneous nephrostomy tube
EUROPEAN UROLOGICAL REVIEW 85