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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.

UROLOGY 82 (6), 2013 1243

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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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