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Endourology and Stones
Effect of Supine vs Prone Position onOutcomes of Percutaneous Nephrolithotomy
in Staghorn Calculi: Results From the ClinicalResearch Ofce of the Endourology SocietyStudyGaston Astroza, Michael Lipkin, Andreas Neisius, Glenn Preminger, Marco De Sio,
Hiren Sodha, Christian Saussine, and Jean de la Rosette, on behalf of the CROES PNL
study group
OBJECTIVE To analyze the effect of patient positioning on outcomes of percutaneous nephrolithotomy (PNL)among patients with staghorn stones. The choice of optimal position for these patients under-
going PNL remains challenging. No previous studies exclusively addressing this point have beenperformed.
METHODS From November 2007 to December 2009, prospective data were collected by the Clinical
Research Ofce of the Endourological Society. We included all patients with staghorn stones.
Patients were divided on the basis of the position used during PNL (prone/supine). Patientcharacteristics, stone burden, operative details, and outcomes were compared. Multivariate
analysis was performed to evaluate the relationship between patient position and stone-free rateand complication rate adjusting for number of access puncture sites.
RESULTS A total of 1079 PNLs were performed in prone and 232 in supine positions. There were no
differences in comorbidities or preoperative stone burden. A higher percentage of patients in theprone position had access through the upper pole (P
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and complications. (CROES; Global PNL Observational
Study;http://www.croesofce.org/OngoingProjects/PCNLStudy.aspx).
No study has previously analyzed the role of posi-
tioning using the CROES PNL database focusing exclu-sively on patients with staghorn calculi.
PATIENTS AND METHODS
Data SourceFrom November 2007 to December 2009, prospective data were
collected by CROES for consecutive patients who underwent
PNL over a 1-year period in 96 centers globally.4
This study included all adult patients who were enrolled in
the Global PNL study who were classied as having staghorn
calculi. A stone was classied as staghorn when located in the
renal pelvis and was in at least 2 of the calices. Patients with
renal congenital anomalies were excluded from the analysis.
Patients were divided into 2 groups on the basis of the position
used at operation (prone or supine). Patient demographics
characteristics (age, body mass index [BMI], gender, comorbid-
ities, and American Society of Anesthesiologist classication
(ASA)), operative details (renal puncture site and numbers,surgical time), and outcomes (stone-free rate, retreatment rate,
length of hospital stay, complications, and decrease in hemo-
globin level) were compared between both groups. The distri-
bution of imaging modality for determining stone-free status and
the distribution of caseload were calculated. Caseload was
dened as the median estimated caseload per year. Multivariate
analysis was performed to evaluate the relation between patient
position and stone-free rate and complication rate adjusting for
number of access puncture sites.
All statistical analysis was performed using R-statistical
programming software version 2.12.2, and the level of statistical
signicance was set at .05.
RESULTS
A total of 1311 patients with complete or incomplete
staghorn stones were included in the analysis. A total of
1079 (82.3%) PNLs were performed in prone positionand 232 (17.7%) in supine.
The mean age was higher in the supine group, and
there was a higher number of male patients in the pronegroup. No differences in BMI, diabetes mellitus, and
cardiovascular disease were found between both groups.However, the prone group had a higher percentage of
patients with lower ASA classication.
Patients demographic characteristics and comorbid-ities are summarized inTable 1.
The mean stone burden was similar in both groups with
446.4 mm2 in the supine and 402.2 mm2 in the proneposition (P .997).
In the group of patients treated in the prone position,
a higher percentage of multiple nephrostomy tracts was
used (19.1% vs 9.6%). There was a higher percentage of
upper pole access in the prone group compared with thesupine group (12.6% vs 3.6%; P
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and the number of renal access puncture sites. Patients
who needed multiple renal access did not achievea statistically signicant difference in the stone-free rate
(P .12) compared with patients with a single access
tract.If we compare the different imaging modalities used to
assess the stone-free rate, the patients who were assessedusing uoroscopy and patients using ultrasound were
judged to have higher stone-free rates compared with
those evaluated using computed tomography (CT) image(P
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completely removed, it is important to evaluate various
factors that might yield thehighest stone-free rate.5
Recently, Valdivia et al6 have published the results of
CROES series comparing prone vs supine positioning in
all the patients enrolled in the Global PNL study, butstaghorn stones were not independently analyzed.
Prone PNL remained the only position used until
Valdivia Uria rst described the supine technique in1998.2 This modication in patients positioning has been
associated with a decrease in the operative time because itavoids repositioning the patient to the prone position.7
Different results were found in our series in which oper-
ative time was longer in the supine than in prone positionsimilar to the ndings previously described by de la
Rosette et al.8 The supine position could also potentially
decrease some of the complications associated with theprone position, such as respiratory restriction andcardiovascular problems in obese patients.9 No difference
between the complication rates in both groups was found
in our study after adjusting for the number of tracts,although the supine group had a signicantly higher
percentage of patients with higher ASA score. Multipleaccess punctures were associated with higher rate ofcomplications independent of patient position.
Another advantage listed for the supine position isa longer distance between percutaneous tract and the
colon when it has been compared with the prone posi-
tion.10 This would be the result of the movement of theintra-abdominal organs when the abdominal wall is
compressed during the prone position. In this series, there
were no colon injuries reported in either position.The supine position might keep the intrarenal pressure
at a lower level because of the descending position of the
percutaneous tract. This factor could be associated withthe collapse of the collective system andthe consequent
decrease of vision during the procedure.11 There is also
a narrower area for trocar insertion and instrument
movements compared with the prone position.11 Some ofthese factors might account for the lower stone-free rates
associated with patients treated in the supine position inthe present study.
The stone-free rate was higher for the group of patients
treated in the prone position after adjusting for thenumber of access sites and the type of imaging method
used to determine the stone-free status. Therefore,
varying imaging modalities was not responsible for thedifferences reported.
The difference in stone-free rate for staghorn stones inour series is larger than the difference reported by Val-
divia et al6 when they analyzed all the patients from theCROES database. This nding could be associated with
the limitations to perform an upper pole access in patients
with staghorn stones in supine position; something that
has been previouslyreported and that is rarely needed innonstaghorn calculi.7,12 In the present study, a higher
percentage of patients in prone position had an upperpole access. Upper pole access might be associated with
a higher stone-free rate, and thus serves as a confounder
for this relationship. Unfortunately, we have limited data
on patients with upper pole access, which prevents usfrom performing regression analysis. We would have
needed a larger sample to establish whether this rela-
tionship truly exists, so this remains speculative.
There are a number of limitations to this study. Thedenition of staghorn stone was not standardized on the
data entry form and therefore was subject to the bias ofthe surgeon. Although the data were collected prospec-
tively, no randomization was used. This issue can beassociated with a selection bias. However, with respect to
factors that could inuence the choice of position, espe-
cially BMI, no signicant differences were found between
the groups. In addition, it is important to note that theinternational CROES database is an observational data-
base and some differences in the follow-up protocol canbe found. At the same time, some of ourndings could be
related to the fact that the centers performing the highestnumber of supine PNL arenot the highest volume centers
taking part in this study.3,6,13 Although we found anassociation between caseload and position in this study, it
probably reects a coincidental relationship, not a causalone. Because we found no difference in key patientcharacteristics, choice of position is not related to prog-
nostic factors.Different imaging modalities are associated with
differing stone-free rates.14 Because the imaging modali-
ties differ between the groups in this study, this could bea severe limitation. Nevertheless, CT is used equally in
both groups. Given that CT is the most detailed diag-
nostic tool, and thus the most likely to detect anydifferences in stone-free rate, this distribution is not
considered to be problematic.
Another limitation is the lack of standardization forhow PNL was performed in terms of access (balloon vs
serial dilators) and lithotrites (ultrasound vs pneumatic vslaser), althoughwe do not believe this affected the results
considerably.15 Yet, to our knowledge, this is the rststudy specically analyzing the role of the positioning
during PNL management of staghorn stones. The largenumber of patients included in this study is a signicant
strength.
CONCLUSION
Higher stone-free rates are achieved with patients in theprone position during PNL management of staghorn
calculi. Complication rates are not different between the
2 positions. Further prospective randomized trials mightbe necessary to ultimately determine the optimal patient
position during PNL management of staghorn calculi.
References
1. Preminger GM, Assimos DG, Lingeman JE, et al. Chapter 1: AUA
guideline on management of staghorn calculi: diagnosis and treat-
ment recommendations. J Urol. 2005;173:1991-2000.
2. Valdivia Uria JG, Valle Gerhold J, Lopez JA, et al. Technique and
complications of percutaneous nephroscopy: experience with 557
patients in the supine position. J Urol. 1998;160(6 Pt 1):1975-1978.
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3. Desai M, De Lisa A, Turna B, et al. The clinical research ofce of
the endourological society percutaneous nephrolithotomy global
study: staghorn versus nonstaghorn stones. J Endourol. 2011;25:
1263-1268.
4. de la Rosette J, Assimos D, Desai M, et al. The Clinical Research
Ofce of the Endourological Society Percutaneous Nephrolithotomy
Global Study: indications, complications, and outcomes in 5803
patients.J Endourol. 2011;25:11-17.
5. Beck EM, Riehle RA Jr. The fate of residual fragments after
extracorporeal shock wave lithotripsy monotherapy of infection
stones. J Urol. 1991;145:6-9; discussion 9-10.
6. Valdivia JG, Scarpa RM, Duvdevani M, et al. Supine versus proneposition during percutaneous nephrolithotomy: a report from the
clinical research ofce of the endourological society percutaneous
nephrolithotomy global study.J Endourol. 2011;25:1619-1625.
7. Liu L, Zheng S, Xu Y, et al. Systematic review and meta-analysis
of percutaneous nephrolithotomy for patients in the supine versus
prone position.J Endourol. 2010;24:1941-1946.
8. de la Rosette JJ, Tsakiris P, Ferrandino MN, et al. Beyond prone
position in percutaneous nephrolithotomy: a comprehensive review.
Eur Urol. 2008;54:1262-1269.
9. Pearle MS, Nakada SY, Womack JS, et al. Outcomes of contem-
porary percutaneous nephrostolithotomy in morbidly obese patients.
J Urol. 1998;160(3 Pt 1):669-673.
10. Tuttle DN, Yeh BM, Meng MV, et al. Risk of injury to adjacent
organs with lower-pole uoroscopically guided percutaneous neph-rostomy: evaluation with prone, supine, and multiplanar reformat-
ted CT. J Vasc Interv Radiol. 2005;16:1489-1492.
11. De Sio M, Autorino R, Quarto G, et al. Modied supine versus
prone position in percutaneous nephrolithotomy for renal stones
treatable with a single percutaneous access: a prospective random-
ized trial. Eur Urol. 2008;54:196-202.
12. Rodrigues N, Ikonomidis J, Ikari O, et al. Comparative study of
percutaneous access for staghorn calculi. Urology. 2005;65:659-663.
13. Opondo D, Tefekli A, Esen T, et al. Impact of case volumes on the
outcomes of percutaneous nephrolithotomy. Eur Urol. 2012;62:
1181-1187.
14. Skolarikos A, Papatsoris AG. Diagnosis and management of
percutaneous nephrolithotomy residual stone fragments.J Endourol.
2009;23:1751-1755.
15. Pietrow PK, Auge BK, Zhong P, Preminger GM. Clinical efcacy of
a combination pneumatic and ultrasonic lithotrite. J Urol. 2003;
169:1247-1249.
APPENDIX
SUPPLEMENTARYDATASupplementary data associated with this article can be found,
in the online version, at http://dx.doi.org/10.1016/j.urology.2013.06.068.
EDITORIAL COMMENT
Percutaneous nephrolithotomy (PCNL) is the treatment ofchoice for large, complex, and staghorn kidney stones. The
effect of patient positioning during any type of surgery and
specically PCNL can be profound. Proper patient positioning is
a critical part of the surgery and has a major inuence on success
rates and complication rates.1 Since PCNL was rst introduced,
the prone position has been the preferred approach, which
enables good access to all renal calyces. During the last several
years, other approaches have been suggested for this surgery,
with supine PCNL becoming an attractive option especially for
patients with medical comorbidities such as morbid obesity,
skeletal deformities, and signicant heart or lung disease.2 In
this article, the Clinical Research Ofce of the Endourology
Society study group authors investigated a large cohort of
patients who underwent PCNL for staghorn stones. They
analyzed for the rst time the effect of patient positioning
(prone vs supine) on outcomes in patients undergoing PCNL for
staghorn stone. The study included 1311 patients, of whom
82.3% underwent surgery in prone position and the reminder in
supine position. They found that surgical time was signicantly
shorter in the prone group and that the stone-free rate was
higher with a lower retreatment rate for this group of patients
comparing with patients who underwent the surgery in the
supine position. Surprisingly, in contrast to the common
assumption that the supine position could also potentiallydecrease some of the complications associated with the prone
position such as respiratory restriction and cardiovascular
problems, no difference between the complication rates of both
groups was found. They also found that the supine position was
rarely performed in high-volume centers. This can partially
explain the poorer results in stone-free rates and surgical time in
the supine group of patients compared with the group of patients
who underwent surgery in prone position.
The authors recommended that further prospective random-
ized trials might be necessary to ultimately determine the
optimal patient position during PCNL management of staghorn
calculi.
Their impressive results might suggest that until proven other-wise and if there are no contraindications for prone position, this
should be the preferred option to achieve better stone-free rates
in patients undergoing PCNL for staghorn calculi. The supine
position or other modications should be reserved for specic
patient groups with comorbidities that make the prone position
impossible and be reserved for selected experienced centers.
Mordechai Duvdevani, M.D., Department of Urology,
Hadassah Hebrew University Hospital, Jerusalem, Israel
References
1. Akhavan A, Gainsburg DM, Stock JA. Complications associatedwith patient positioning in urologic surgery.Urology. 2010;76:1309-
1316.
2. DasGupta R, Patel A. Percutaneous nephrolithotomy: does position
matter? e prone, supine and variations. Curr Opin Urol. 2013;23:
164-168.
http://dx.doi.org/10.1016/j.urology.2013.06.072
UROLOGY 82: 1244, 2013. 2013 Elsevier Inc.
REPLY
We are rapidly moving from a time of urinary stone treatment
when only limited options were available: semirigid uretero-
scopy, prone percutaneous nephrolithotomy (PCNL), and shockwave lithotripsy, to a more exciting present. Currently, the
window of opportunities is rapidly increasing for a multitude of
approaches facilitated by the availability of sophisticated
endoscopic equipment enabling us to customize the treatment to
each patients situation.
Historically, PCNL has been performed in the prone position,
and there is nothing wrong with that. It therefore comes to no
surprise that this is the dominating method taught to many and
consequently reected in the data from the global PCNL study
by the Clinical Research Ofce of the Endourology Society.1
Because endourologists are innovators, during the past years,
the need to improve results to treat patients with increasing
comorbidity and surgical innovation has revolutionized the
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approach to PCNL. Besides the increased use of exible ure-
teroscopes for the treatment of larger renal stones,2 we do
witness a signicant downsizing on the instruments for PCNL.3
Within that perspective, the endourological community has also
assessed whether other approach positions might be more
favorable for patients. In this line, an increasing number of
communications has been published to date.4
Nevertheless, we should not forget to look at a larger picture.
It is not only the position of the patient or the instruments used
that drive improvements in outcomes but most likely their
combination. Renal stone treatment has changed dramaticallyover the past years, and increasingly larger renal stones (in
increasingly complicated patients) are being treated in
a combined approach: transureterally by exible ureteroscopes
with a size barely larger than a ureter stent and simultaneously
percutaneous with semirigid nefroscopes in combination withexible nefroscopes.5
Overall, operative time and stone-free rates favor prone
PCNL, but on the issue of patient safety, supine PNCL seems to
overweight its prone counterpart. Indeed, a thorough evaluation
of these new approaches is a must, and we should neither reject
the old ones nor straightforward embrace the new comers.4 I
therefore sympathize with my colleges concluding that at present,
the prone approach for staghorn stones seems to be more favor-able. But I am condent that they will also agree that the nal
choice on patients position should be tailored to individual
patient characteristics and to surgeons preferences. Finally, I
want to encourage centers of excellence to bring together data
that support the use of the supine approach within the perspec-
tive of Combined Endoscopic Intra Renal Surgery. In such
a work, not only safety should be studied but also other outcomes,
including stone-free rate, avoidance of multiple percutaneous
tracts, need for auxiliary treatments, and in-hospital stay.
The future for advancements in endourology is in our hands,
and by now we are aware that collaborative work such as from
the Clinical Research Ofce of the Endourology Society has the
capability to meaningfully contribute to that. Through such
work we will eventually reach the ultimate goal of our profes-
sional work: to provide the absolute best, least invasive, quality
of care for all patients.
Jean de la Rosette, M.D., Ph.D., Department of Urology,
AMC University Hospital, Amsterdam, The Netherlands
References
1. de la Rosette J, Assimos D, Desai M, et al. The Clinical Research
Ofce of the Endourological Society Percutaneous Nephrolithotomy
Global Study: indications, complications, and outcomes in 5803
patients. J Endourol. 2011;25:11-17.
2. Hyams ES, Munver R, Bird VG, et al. Flexible ureterorenoscopy and
holmium laser lithotripsy for the management of renal stone burdens
that measure 2 to 3 cm: a multi-institutional experience. J Endourol.
2010;24:1583-1588.
3. Bader MJ, Gratzke C, Seitz M, et al. The "all-seeing needle": initial
results of an optical puncture system conrming access in percuta-
neous nephrolithotomy. Eur Urol. 2011;59:1054-1059.
4. Valdivia JG, Scarpa RM, Duvdevani M, et al. Supine versus proneposition during percutaneous nephrolithotomy: a report from the
clinical research ofce of the endourological society percutaneous
nephrolithotomy global study. J Endourol. 2011;25:1619-1625.
5. Scoffone CM, Cracco CM, Cossu M, et al. Endoscopic combined
intrarenal surgery in Galdakao-modied supine Valdivia position:
a new standard for percutaneous nephrolithotomy? Eur Urol. 2008;
54:1393-1403.
http://dx.doi.org/10.1016/j.urology.2013.06.073
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