REVIEW URRENT C OPINION
How well tolerated is supine percutaneous nephrolithotomy? Joyce Baard, Guido M. Kamphuis, Matias Westendarp, and Jean J.M.C.H. de la Rosette
Purpose of review Supine percutaneous nephrolithotomy (PCNL) has been described in 1988 and several modifications followed since. Despite claimed benefits, supine PCNL is still neglected by the majority of urologists. Lack of experience and the fear of complications are possible explanations for the resistance to supine positioning. This review evaluates recent literature on the use of supine PCNL, focussing on benefits and safety. Recent finding The Clinical Research Office of the Endourological Society Global Study and several (retrospective) reports comment on efficacy and safety of PCNL, differences in techniques, or identify conditions and patient factors for best practice. Anesthesiologic benefits (especially in the high risk, cardiopulmonary compromised, patient) and anatomical advantages are described in supine position theoretically favoring safety of supine PCNL. However, there are no prospective randomized studies conducted to support this assumption. Overall, benefits in efficacy or safety, of one position over the other, are not yet proven. Summary Supine PCNL has advantages in selected patients. Ultimately, the decision on position should be made on patient’s characteristics and surgeon’s preference and experience. Keywords percutaneous nephrolithotomy, renal stones, safety, supine
INTRODUCTION Percutaneous nephrolithotomy (PCNL) is first described in 1976 as a novel technique for the treatment of renal stones. The technique has been adopted for everyday practice and methods for approach are continuing to evolve [1–3]. Traditionally, PCNL is performed in prone position, providing a well tolerated approach to the kidney with good access to the collecting system. A disadvantage of a procedure in the prone position is the need for repositioning after inserting a ureteral stent in supine position. Repositioning is time-consuming and accompanied by possible risks, namely, ocular, neck, limb, or nerve injury. Furthermore, prone-positioned PCNL is impaired in patients with skeletal deformities and in the morbidly obese. From an anaesthesiological point of view, negative cardiovascular and respiratory implications exist in prone position especially in high-risk patients [4]. Improvements in the PCNL procedure, available equipment, and imaging modalities resulted in reduced morbidity and stone-free rates of greater www.co-urology.com
&
than 90% [5 ,6]. To improve the success rate and overcome existing limitations, urologists have attempted to modify the traditional pronepositioned technique. In 1988, Valdivia Urı´a et al. [7] described a supine PCNL approach in 557 consecutive patients. This study prompted several modifications on supine position [8]. Apart from shorter operation times, supine PCNL benefits from the possibility of endoscopic combined intrarenal surgery and less radiation exposure for the surgeon. In supine position, the downward angle of the Amplatz sheath results in better drainage, and subsequently Department of Urology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands Correspondence to Jean J.J.M.C.H. de la Rosette, Department of Urology G4-172, Academic Medical Center, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands. Tel: +31 20 5666377; e-mail: j.j.delarosette@ amc.uva.nl Curr Opin Urol 2014, 24:184–188 DOI:10.1097/MOU.0000000000000023 Volume 24 Number 2 March 2014
Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
How well tolerated is supine percutaneous nephrolithotomy? Baard et al.
KEY POINTS Supine position can overcome difficulties of anatomical nature that can occur in prone position and offer a possibility to perform a PCNL. PCNL has the same complication rate and stone-free rate in supine and prone position. PCNL in supine position has the same success rate as PCNL in prone position.
spontaneous evacuation, of stone fragments. This is believed to cause a lower pressure in the collecting system resulting in less fluid uptake, lowering the risks of possible cardiac decompensation in the compromised patient [9]. Over time several investigators published their experience with (modified) supine techniques. However, just two randomized controlled trials (RCTs) have compared different PCNL positions [6,10]. Despite claimed benefits, supine positioning in PCNL is still neglected by the majority of urologists. The Clinical Research Office of the Endourological Society (CROES) PCNL Global Study found that only 20% of patients were operated on in the supine position [11]. A lack of experience and the fear of complications are possible explanations for the resistance to supine positioning. This review evaluates recent literature on the use of supine PCNL, focussing on benefits and safety compared with traditional prone PCNL.
GENERAL ASPECTS OF SUPINE POSITION The traditional Valdivia supine position is a complete supine position with a 3-l serum bag supporting the ipsilateral flank and extended legs. After this landmark article, several modified supine positions were described, addressing technical difficulties related to the complete supine position [12]. Main disadvantages are the relatively small space for renal puncture and difficult nephroscope manipulation. Vicentini et al. [13] described a modified technique placing the patients in a supine decubitus position with the posterior axillary line located just outside the border of the surgical table and the flank extended. Aimed at increasing the space between the last rib and the iliac crest. No ipsilateral flank elevation was used during the procedure. In theory, this modified technique provides a better area for renal puncture and instrumentation. In order to improve lateral access to the kidney and instrument manipulation, multiple variations in ipsilateral flank elevation have been described
[6,10,14]. Furthermore by elevating the flank, the posterior calix projects more laterally; this is usually the preferred calix due to a lower chance of bleeding. However, a tendency of medialization was observed with flank elevation in supine-positioned PCNL [10,15]. Furthermore, variations in supine position concern positioning of the legs, in order to enable endoscopic combined intrarenal surgery for large and complex urolithiasis [16]. In the Galdakaomodified Valdivia position, the contralateral leg is in an abducted lithotomy position, with the ipsilateral leg extended, providing combined access [17]. The Barts-modified Valdivia position offers both simultaneous retrograde access and a large surface area for access. Furthermore, placing the trunk at a 908 angle to the operating table provides easy manipulation of the nephroscope [18]. However, an increased rotation of the kidney makes it more difficult to perform the access puncture in this position. Kumar et al. [12] described the Barts flank-free modified supine position involving a 158 tilt using a 3-l saline bag under the ipsilateral rib cage, and a small gel pad under the ipsilateral pelvis. Legs are in lithotomy position with the ipsilateral leg extended and the contralateral leg abducted. The ipsilateral arm is positioned across the chest. Observed benefits were good exposure, access for combined intrarenal surgery, and less mobility of the kidney compared with the Valdivia–Barts-modified position. An RCT comparing the different methods of positioning during supine PCNL has yet to be performed. Therefore, there is no consensus on which position is ideal.
POSITIONING AND ANATOMICAL CHANGES Positioning is of great influence on anatomical proportions during PCNL. Duty et al. [19 ] examined the anatomical variations between prone, supine, and supine oblique positioning, evaluating the potential impact on access and the risk of visceral injury. They concluded that a prone position provided more potential access sites. Furthermore, the mean nephrostomy tract was significantly shorter compared with the supine position. The longer the nephrostomy tract the less manoeuvrable the distal end of the access sheath will be, requiring more torque to be applied to the access sheath. The latter can result in increased parenchymal bleeding. Diminished freedom of movement causes increased difficulty for nephroscopy that could result in decreased stone-free rates. Longer nephrostomy tracts could also result in practical problems because
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longer instruments are needed especially in morbidly obese patients. The CROES PCNL Global Study showed that in the supine-positioned patients infracostal access with lower pole kidney puncture is more frequent [20]. Conversely, prone-positioned patients were more likely to receive an upper pole puncture of the kidney as well as punctures at multiple sites. However, it was less likely for a prone-positioned patient to receive a lower pole kidney puncture than vice versa. This is further studied by Duty et al. [19 ] who compared tract length between the upper pole in prone position and lower pole in the supine position. Lower pole tract length in the supine position was found to be significantly longer than upper pole tract in prone position. Overall, access to the kidney was mainly obtained below the 12th rib in the CROES PCNL Global Study. Supracostal access was more common in prone-positioned patients and infracostal access was significantly more common in the supine group. In supine position, the upper pole is more medial and posterior located making the access puncture more challenging. Higher incidences of intrathoracic complications and splanchnic or hepatic injury were described for supracostal access [21]. A well tolerated entry point for PCNL is located between the paraspinous muscles and the posterior border of the liver, spleen, and colon. The angle of access was evaluated between different PCNL positions [19 ]. The prone position had a significant larger maximum access angle compared with the supine and oblique supine position. Despite these findings visceral injury incidence is low in prone as in supine PCNL [7,22–24]. Azhar et al. [25] compared the percutaneous access tract in supine and prone position in 16 patients, using CT imaging. Visceral organ to tract distance was significantly longer in the supine position, which in theory should lower the risk of visceral organ injury. A study by Falahatkar et al. [26] showed more kidney displacement when access is gained in prone position compared with supine position. Gaining access proved to be more difficult with greater kidney displacement. However, the increased difficulty did not impair overall success in gaining access. &
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HEMODYNAMIC, ELECTROLYTE, AND METABOLIC CHANGES IN SUPINE POSITION During PCNL irrigation, fluids are used for optimizing the endoscopic vision. Continuous irrigation can lead to complications, namely, retroperitoneal extravasation. Few studies have been conducted 186
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into possible metabolic, electrolyte, and hemodynamic changes during PCNL. Khoshrang et al. [27 ] conducted a comparative study, including 40 patients (ASA 1 and 2) comparing these changes, during supine and prone PCNL. No significant differences in electrolyte and metabolic changes were observed between the supine or prone group. Though fluid absorption was significantly higher in the prone group, whereas mean irrigation fluid volume was equal. In the prone group, systolic and diastolic blood pressure decreased considerably compared with the supine group, both during operation and in the recovery room. Abdominal compression, more specifically abdominal vein compression, might be an explanation for the observed hypotension during prone-positioned PCNL [4]. In preliminary study by Kukreja et al. [28] fluid absorption was confirmed in 148 patients treated with prone PCNL. However, no patient showed clinical or biochemical signs of intraoperative or postoperative electrolyte imbalance. It could be argued that fluid absorption may only be clinically significant in high-risk patients with a compromised cardiorespiratory status. The use of an Amplatz sheath could create a low-pressure system. &
OUTCOME Falahatkar et al. and De Sio et al. [6,10] performed the only two RCTs comparing the traditional prone PCNL with supine PCNL, focussing on effectiveness, operation time, and safety. Both effectiveness, expressed in stone-free rate, and safety showed no significant differences between prone and supine positioning. Operation time was found to be significantly shorter for supine-positioned PCNL procedures. Valdivia et al. [20] determined differences in patient characteristics, operation time and procedures, and perioperative outcomes between prone and supine positioning using the CROES PCNL database. Prone-positioned PCNL was performed in 80.3% of the cases. In contrary to the RCTs, a significant higher operation time was observed for the supine position. Another contradictory outcome was a significantly higher stone-free rate in the prone position PCNL group. These contradictory outcomes might be explained by differences in definition of operation time and different methods and protocols for assessing a stone-free status. The ability to shorten operation times is of importance as it is known to be of influence on blood loss during PCNL and is described as a prognostic factor on PCNL morbidity [28,29]. Smith et al. [30] assessed factors of influence on treatment outcome using patient data collected from the CROES Global Study database. A prediction Volume 24 Number 2 March 2014
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How well tolerated is supine percutaneous nephrolithotomy? Baard et al.
analysis of stone-free rates was conducted using patient factors and preoperative radiological findings. Stone burden was found to be the best predictor of stone-free rate. Other factors of influence were stone location, stone count, staghorn stones, prior stone treatment, and case volume. These efforts resulted in a highly reliable nephrolithometric nomogram.
HIGH-RISK PATIENTS Obesity is an increasing burden associated with stone formation. Obese patients tend to have more comorbidity, resulting in a surgical risk. Morbidly obese patients with compromised cardiovascular status are not always suitable for prone positioning, for which supine positioning offers an alternative. Mazzucchi et al. [31] compared the prone and complete supine techniques in obese patients (BMI > 30), finding similar outcomes in treatment effect and complications. Furthermore, supine positioning showed significantly shorter operation times and hospital stays. Manohar et al. [32] presented their experience with supine PCNL in 62 patients with obesitas or ASA classification of at least 3. They report a stonefree rate of 95% with no increase in surgical complications. Fuller et al. [33] presented a series of 3709 patients from the CROES database, grouped in four BMI categories (normal weight BMI 18.5–25, overweight 25–30, obese 30–40, and super obese >40). A significantly longer operation time was observed in obese patients. Stone-free rates decreased with obesity corresponding to a significantly higher retreatment rate. However, it has to be noted that a significantly higher rate of staghorn stones was seen in the super obese patient group. No significant difference was seen in the overall complication rate among the four groups. The negative effect of BMI on operative time was also found by Falahatkar et al. [34]. The influence of high volume centres was analyzed on stone-free rate and patient weight. Super obese patients had a worse outcome independent of case volume. Okeke et al. [35], using the CROES database, found no differences in position between elderly and young patients treated with PCNL. A retrospective study on PCNL for lower pole stones found that patients with a higher ASA score of at least 2 had a bigger chance of supine position than ASA 1 patients [36].
COMPLICATIONS Complication rates following PCNL vary widely and are reported up to 83% [22,24]. These are mostly
minor complications, namely, extravasation 7.2%, transfusion rate 11.2–17.5%, and fever 21.0–32.1%. Frequency rates of major complications are 0.9– 4.7% for septicaemia, 0.6–1.4% for severe renal haemorrhage needing intervention, 2.3–3.1% for pleural injury, and 0.2–0.8% for colonic injury. The multicentre CROES PCNL Global Study described an overall complication rate of 15% and low-modified Clavien morbidity scores. This Illustrates PCNL to be a well tolerated procedure in general [11]. Meta-analysis of Wu et al. and Liu et al. [37,38] showed no statistical differences in complication rates between prone and supine-positioned PCNL procedures. Both groups showed similar rates of (postoperative) transfusion and fever. Out of the four included studies only one of 389 supinepositioned patients suffered a colon injury (0.5%); no pleural injuries were reported. This is the only colonic injury case reported in the literature in supine PCNL. The incidence of retrorenal colon is 10% in prone position compared with 2% in supine position, theoretically diminishing the chance for colonic injury [39–41]. Finally, pelvic perforation and failed access were comparable between the prone and supine group as well. Concluding from these meta-analyses, with limited included studies, similar numbers were found in terms of complication rate.
CONCLUSION PCNL has been established as a standard treatment for kidney stones. Traditionally, it is performed in the prone position that can have its limitations, especially in obese patients or patients with skeletal deformities. Several lateral and supine positions have been described to overcome these limitations. However, the prone position is still favoured by many urologists and about 80% of PCNL worldwide are performed in this position. Two RCTs show equal overall results in terms of efficacy and safety. The assumed differences in complications because of anatomical differences, between PCNL in prone or supine position, are not demonstrated. This might partly be explained by patient selection, as supine PCNL has advantages in selected highrisk patients. In theory, supine PCNL has advantages over prone PCNL, in terms of reduced risk and potential trauma related with anaesthesia and repositioning, resulting in shorter operative time. Supine PCNL also allows easier combined retrograde access, easier access to lower calyx, with consequent lower risk of pleural injury. Furthermore, supine positioning implies a better management of fluid balance.
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All these issues suggest benefits in terms of safety and efficacy in supine PCNL. However, no prospective randomized studies are conducted to support this assumption. PCNL seems to be as well tolerated in supine as in the prone position, with comparable complication rates. Because of advantages of supine position in the morbidly obese, patients with skeletal deformities and patients with severe cardiorespiratory morbidity, it is important to have experience with several positions. Ultimately, the decision on position should be made on patient’s characteristics and surgeon’s preference and experience. Acknowledgements None. Conflicts of interest There are no conflicts of interest.
REFERENCES AND RECOMMENDED READING Papers of particular interest, published within the annual period of review, have been highlighted as: & of special interest && of outstanding interest 1. Fernstro¨m I, Johansson B. Percutaneous pyelolithotomy. A new extraction technique. Scand J Urol Nephrol 1976; 10:257–259. 2. Tiselius HG, Ackermann D, Alken P, et al. Guidelines on urolithiasis. Eur Urol 2001; 40:362–371. 3. Skolarikos A, Alivizatos G, de la Rosette JJMCH. Percutaneous nephrolithotomy and its legacy. Eur Urol 2005; 47:22–28. 4. Atkinson CJ, Turney BW, Noble JG, Reynard JMSM. Supine vs prone percutaneous nephrolithotomy: an anaesthetist’s view. BJU Int 2011; 108:306–308. 5. Karami H, Mohammadi R, Lotfi B. A study on comparative outcomes of & percutaneous nephrolithotomy in prone, supine, and flank positions. World J Urol 2012; 31:1225–1230. A randomly assigned study comparing outcome of prone, supine, and flank position PCNL. 6. Falahatkar S, Moghaddam AA, Salehi M, et al. Complete supine percutaneous nephrolithotripsy comparison with the prone standard technique. J Endourol 2008; 22:2513–2517. 7. Valdivia Urı´a JG, Valle Gerhold J, Lo´pez Lo´pez 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. 8. DasGupta R, Patel A. Percutaneous nephrolithotomy: does position matter? Prone, supine and variations. Curr Opinion Urol 2013; 23:164–168. 9. Kukreja RA, Desai MR, Lon F, et al. Fluid absorption during percutaneous nephrolithotomy: does it matter? J Endourol 2002; 16:221–224. 10. De Sio M, Autorino R, Quarto G, et al. Modified supine versus prone position in percutaneous nephrolithotomy for renal stones treatable with a single percutaneous access: a prospective randomized trial. Eur Urol 2008; 54:196–202. 11. Rosette J, De, Assimos D, Desai M, et al. The Clinical Research Office of the Endourological Society Percutaneous Nephrolithotomy Global Study: indications, complications, and outcomes in 5803 patients. J Endourol 2011; 25:11–17. 12. Kumar P, Bach C, Kachrilas S, et al. Supine percutaneous nephrolithotomy (PCNL): ‘in vogue’ but in which position? BJU Int 2012; 110:1018–1021. 13. Vicentini FC, Torricelli FCM, Mazzucchi E, et al. Modified complete supine percutaneous nephrolithotomy: solving some problems. J Endourol 2013; 27:845–849. 14. Ng M-T, Sun W-H, Cheng C-W, Chan E-S. Supine position is safe and effective for percutaneous nephrolithotomy. J Endurol 2004; 18:470–474. 15. Shoma AM, Eraky I, El-Kenawy MR, El-Kappany HA. Percutaneous nephrolithotomy in the supine position: technical aspects and functional outcome compared with the prone technique. Urology 2002; 60:388–392.
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16. Scoffone CM, Cracco CM, Cossu M, et al. Endoscopic combined intrarenal surgery in Galdakao-modified supine Valdivia position: a new standard for percutaneous nephrolithotomy? Eur Urol 2008; 54:1393–1403. 17. Ibarluzea G, Scoffone CM, Cracco CM, et al. Supine Valdivia and modified lithotomy position for simultaneous anterograde and retrograde endourological access. BJU Int 2007; 100:233–236. 18. Papatsoris AG, Zaman F, Panah A, et al. Simultaneous anterograde and retrograde endourologic access: ‘the Barts technique’. J Endourol 2008; 22:2665–2666. 19. Duty B, Waingankar N, Okhunov Z, et al. Anatomical variation between the & prone, supine, and supine oblique positions on computed tomography: implications for percutaneous nephrolithotomy access. Urology 2012; 79:67–71. An interesting insight into anatomical variations between the prone, supine, and supine oblique position PCNL. 20. Valdivia JG, Scarpa RM, Duvdevani M, et al. Supine versus prone position during percutaneous nephrolithotomy: a report from the clinical research office of the endourological society percutaneous nephrolithotomy global study. J Endourol 2011; 25:1619–1625. 21. Munver R, Delvecchio FC, Newman GE, Preminger GM. Critical analysis of supracostal access for percutaneous renal surgery. J Urol 2001; 166:1242– 1246. 22. Skolarikos A, de la Rosette J. Prevention and treatment of complications following percutaneous nephrolithotomy. Curr Opin Urol 2008; 18:229–234. 23. El-Nahas AR, Shokeir AA, El-Assmy AM, et al. Colonic perforation during percutaneous nephrolithotomy: study of risk factors. Urology 2006; 67:937– 941. 24. Michel MS, Trojan L, Rassweiler JJ. Complications in percutaneous nephrolithotomy. Eur Urol 2007; 51:899–906. 25. Azhar RA, Szymanski KM, Lemercier E, et al. Visceral organ-to-percutaneous tract distance is shorter when patients are placed in the prone position on bolsters compared with the supine position. J Endourol 2011; 25:687–690. 26. Falahatkar S, Asgari SA, Nasseh H, et al. Kidney displacement in complete supine PCNL is lower than prone PCNL. Urol Res 2011; 39:159–164. 27. Khoshrang H, Falahatkar S, Ilat S, et al. Comparative study of hemodynamics & electrolyte and metabolic changes during prone and complete supine percutaneous nephrolithotomy. Nephrourol Mon 2012; 4:622–628. A comparative study on the electrolyte and metabolic changes of prone and complete supine PCNL showing no significant differences. Though significant differences were seen in hemodynamics favoring supine PCNL. 28. Kukreja R, Desai M, Patel S, et al. Factors affecting blood loss during percutaneous nephrolithotomy: prospective study. J Endourol 2004; 18:715–722. 29. De la Rosette JJMCH, Zuazu JR, Tsakiris P, et al. Prognostic factors and percutaneous nephrolithotomy morbidity: a multivariate analysis of a contemporary series using the Clavien classification. J Urol 2008; 180:2489– 2493. 30. Smith A, Averch TD, Shahrour K, et al. A nephrolithometric nomogram to predict treatment success of percutaneous nephrolithotomy. J Urol 2013; 190:149–156. 31. Mazzucchi E, Vicentini FC, Marchini GS, et al. Percutaneous nephrolithotomy in obese patients: comparison between the prone and total supine position. J Endourol 2012; 26:1437–1442. 32. Manohar T, Jain P, Desai M. Supine percutaneous nephrolithotomy: effective approach to high-risk and morbidly obese patients. J Endourol 2007; 21:44– 49. 33. Fuller A, Razvi H, Denstedt JD, et al. The CROES percutaneous nephrolithotomy global study: the influence of body mass index on outcome. J Urol 2012; 188:138–144. 34. Falahatkar S, Moghaddam KG, Kazemnezhad E, et al. Factors affecting operative time during percutaneous nephrolithotomy: our experience with the complete supine position. J Endourol 2011; 25:1831–1836. 35. Okeke Z, Smith AD, Labate G, et al. Prospective comparison of outcomes of percutaneous nephrolithotomy in elderly patients versus younger patients. J Endourol 2012; 26:996–1001. 36. Sanguedolce F, Breda A, Millan F, et al. Lower pole stones: prone PCNL versus supine PCNL in the International Cooperation in Endourology (ICE) group experience. World J Urol 2012; 4–9. 37. Wu P, Wang L, Wang K. Supine versus prone position in percutaneous nephrolithotomy for kidney calculi: a meta-analysis. Int Urol Nephrol 2011; 43:67–77. 38. Liu L, Zheng S, Xu Y, Wei Q. Systematic review and meta-analysis of percutaneous nephrolithotomy for patients in the supine versus prone position. J Endourol 2010; 24:1941–1946. 39. Tuttle DN, Yeh BM, Meng MV, et al. Risk of injury to adjacent organs with lower-pole fluoroscopically guided percutaneous nephrostomy: evaluation with prone, supine, and multiplanar reformatted CT. J Vasc Interv Radiol 2005; 16:1489–1492. 40. Chalasani V, Bissoon D, Bhuvanagir AK, et al. Should PCNL patients have a CT in the prone position preoperatively? Can J Urol 2010; 17:5082–5086. 41. Boon JM, Shinners B, Meiring JH. Variations of the position of the colon as applied to percutaneous nephrostomy. Surg Radiol Anat 2001; 23:421–425.
Volume 24 Number 2 March 2014
Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
How well tolerated is supine percutaneous nephrolithotomy? Joyce Baard, Guido M. Kamphuis, Matias Westendarp, and Jean J.M.C.H. de la Rosette
Purpose of review Supine percutaneous nephrolithotomy (PCNL) has been described in 1988 and several modifications followed since. Despite claimed benefits, supine PCNL is still neglected by the majority of urologists. Lack of experience and the fear of complications are possible explanations for the resistance to supine positioning. This review evaluates recent literature on the use of supine PCNL, focussing on benefits and safety. Recent finding The Clinical Research Office of the Endourological Society Global Study and several (retrospective) reports comment on efficacy and safety of PCNL, differences in techniques, or identify conditions and patient factors for best practice. Anesthesiologic benefits (especially in the high risk, cardiopulmonary compromised, patient) and anatomical advantages are described in supine position theoretically favoring safety of supine PCNL. However, there are no prospective randomized studies conducted to support this assumption. Overall, benefits in efficacy or safety, of one position over the other, are not yet proven. Summary Supine PCNL has advantages in selected patients. Ultimately, the decision on position should be made on patient’s characteristics and surgeon’s preference and experience. Keywords percutaneous nephrolithotomy, renal stones, safety, supine
INTRODUCTION Percutaneous nephrolithotomy (PCNL) is first described in 1976 as a novel technique for the treatment of renal stones. The technique has been adopted for everyday practice and methods for approach are continuing to evolve [1–3]. Traditionally, PCNL is performed in prone position, providing a well tolerated approach to the kidney with good access to the collecting system. A disadvantage of a procedure in the prone position is the need for repositioning after inserting a ureteral stent in supine position. Repositioning is time-consuming and accompanied by possible risks, namely, ocular, neck, limb, or nerve injury. Furthermore, prone-positioned PCNL is impaired in patients with skeletal deformities and in the morbidly obese. From an anaesthesiological point of view, negative cardiovascular and respiratory implications exist in prone position especially in high-risk patients [4]. Improvements in the PCNL procedure, available equipment, and imaging modalities resulted in reduced morbidity and stone-free rates of greater www.co-urology.com
&
than 90% [5 ,6]. To improve the success rate and overcome existing limitations, urologists have attempted to modify the traditional pronepositioned technique. In 1988, Valdivia Urı´a et al. [7] described a supine PCNL approach in 557 consecutive patients. This study prompted several modifications on supine position [8]. Apart from shorter operation times, supine PCNL benefits from the possibility of endoscopic combined intrarenal surgery and less radiation exposure for the surgeon. In supine position, the downward angle of the Amplatz sheath results in better drainage, and subsequently Department of Urology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands Correspondence to Jean J.J.M.C.H. de la Rosette, Department of Urology G4-172, Academic Medical Center, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands. Tel: +31 20 5666377; e-mail: j.j.delarosette@ amc.uva.nl Curr Opin Urol 2014, 24:184–188 DOI:10.1097/MOU.0000000000000023 Volume 24 Number 2 March 2014
Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
How well tolerated is supine percutaneous nephrolithotomy? Baard et al.
KEY POINTS Supine position can overcome difficulties of anatomical nature that can occur in prone position and offer a possibility to perform a PCNL. PCNL has the same complication rate and stone-free rate in supine and prone position. PCNL in supine position has the same success rate as PCNL in prone position.
spontaneous evacuation, of stone fragments. This is believed to cause a lower pressure in the collecting system resulting in less fluid uptake, lowering the risks of possible cardiac decompensation in the compromised patient [9]. Over time several investigators published their experience with (modified) supine techniques. However, just two randomized controlled trials (RCTs) have compared different PCNL positions [6,10]. Despite claimed benefits, supine positioning in PCNL is still neglected by the majority of urologists. The Clinical Research Office of the Endourological Society (CROES) PCNL Global Study found that only 20% of patients were operated on in the supine position [11]. A lack of experience and the fear of complications are possible explanations for the resistance to supine positioning. This review evaluates recent literature on the use of supine PCNL, focussing on benefits and safety compared with traditional prone PCNL.
GENERAL ASPECTS OF SUPINE POSITION The traditional Valdivia supine position is a complete supine position with a 3-l serum bag supporting the ipsilateral flank and extended legs. After this landmark article, several modified supine positions were described, addressing technical difficulties related to the complete supine position [12]. Main disadvantages are the relatively small space for renal puncture and difficult nephroscope manipulation. Vicentini et al. [13] described a modified technique placing the patients in a supine decubitus position with the posterior axillary line located just outside the border of the surgical table and the flank extended. Aimed at increasing the space between the last rib and the iliac crest. No ipsilateral flank elevation was used during the procedure. In theory, this modified technique provides a better area for renal puncture and instrumentation. In order to improve lateral access to the kidney and instrument manipulation, multiple variations in ipsilateral flank elevation have been described
[6,10,14]. Furthermore by elevating the flank, the posterior calix projects more laterally; this is usually the preferred calix due to a lower chance of bleeding. However, a tendency of medialization was observed with flank elevation in supine-positioned PCNL [10,15]. Furthermore, variations in supine position concern positioning of the legs, in order to enable endoscopic combined intrarenal surgery for large and complex urolithiasis [16]. In the Galdakaomodified Valdivia position, the contralateral leg is in an abducted lithotomy position, with the ipsilateral leg extended, providing combined access [17]. The Barts-modified Valdivia position offers both simultaneous retrograde access and a large surface area for access. Furthermore, placing the trunk at a 908 angle to the operating table provides easy manipulation of the nephroscope [18]. However, an increased rotation of the kidney makes it more difficult to perform the access puncture in this position. Kumar et al. [12] described the Barts flank-free modified supine position involving a 158 tilt using a 3-l saline bag under the ipsilateral rib cage, and a small gel pad under the ipsilateral pelvis. Legs are in lithotomy position with the ipsilateral leg extended and the contralateral leg abducted. The ipsilateral arm is positioned across the chest. Observed benefits were good exposure, access for combined intrarenal surgery, and less mobility of the kidney compared with the Valdivia–Barts-modified position. An RCT comparing the different methods of positioning during supine PCNL has yet to be performed. Therefore, there is no consensus on which position is ideal.
POSITIONING AND ANATOMICAL CHANGES Positioning is of great influence on anatomical proportions during PCNL. Duty et al. [19 ] examined the anatomical variations between prone, supine, and supine oblique positioning, evaluating the potential impact on access and the risk of visceral injury. They concluded that a prone position provided more potential access sites. Furthermore, the mean nephrostomy tract was significantly shorter compared with the supine position. The longer the nephrostomy tract the less manoeuvrable the distal end of the access sheath will be, requiring more torque to be applied to the access sheath. The latter can result in increased parenchymal bleeding. Diminished freedom of movement causes increased difficulty for nephroscopy that could result in decreased stone-free rates. Longer nephrostomy tracts could also result in practical problems because
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longer instruments are needed especially in morbidly obese patients. The CROES PCNL Global Study showed that in the supine-positioned patients infracostal access with lower pole kidney puncture is more frequent [20]. Conversely, prone-positioned patients were more likely to receive an upper pole puncture of the kidney as well as punctures at multiple sites. However, it was less likely for a prone-positioned patient to receive a lower pole kidney puncture than vice versa. This is further studied by Duty et al. [19 ] who compared tract length between the upper pole in prone position and lower pole in the supine position. Lower pole tract length in the supine position was found to be significantly longer than upper pole tract in prone position. Overall, access to the kidney was mainly obtained below the 12th rib in the CROES PCNL Global Study. Supracostal access was more common in prone-positioned patients and infracostal access was significantly more common in the supine group. In supine position, the upper pole is more medial and posterior located making the access puncture more challenging. Higher incidences of intrathoracic complications and splanchnic or hepatic injury were described for supracostal access [21]. A well tolerated entry point for PCNL is located between the paraspinous muscles and the posterior border of the liver, spleen, and colon. The angle of access was evaluated between different PCNL positions [19 ]. The prone position had a significant larger maximum access angle compared with the supine and oblique supine position. Despite these findings visceral injury incidence is low in prone as in supine PCNL [7,22–24]. Azhar et al. [25] compared the percutaneous access tract in supine and prone position in 16 patients, using CT imaging. Visceral organ to tract distance was significantly longer in the supine position, which in theory should lower the risk of visceral organ injury. A study by Falahatkar et al. [26] showed more kidney displacement when access is gained in prone position compared with supine position. Gaining access proved to be more difficult with greater kidney displacement. However, the increased difficulty did not impair overall success in gaining access. &
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HEMODYNAMIC, ELECTROLYTE, AND METABOLIC CHANGES IN SUPINE POSITION During PCNL irrigation, fluids are used for optimizing the endoscopic vision. Continuous irrigation can lead to complications, namely, retroperitoneal extravasation. Few studies have been conducted 186
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into possible metabolic, electrolyte, and hemodynamic changes during PCNL. Khoshrang et al. [27 ] conducted a comparative study, including 40 patients (ASA 1 and 2) comparing these changes, during supine and prone PCNL. No significant differences in electrolyte and metabolic changes were observed between the supine or prone group. Though fluid absorption was significantly higher in the prone group, whereas mean irrigation fluid volume was equal. In the prone group, systolic and diastolic blood pressure decreased considerably compared with the supine group, both during operation and in the recovery room. Abdominal compression, more specifically abdominal vein compression, might be an explanation for the observed hypotension during prone-positioned PCNL [4]. In preliminary study by Kukreja et al. [28] fluid absorption was confirmed in 148 patients treated with prone PCNL. However, no patient showed clinical or biochemical signs of intraoperative or postoperative electrolyte imbalance. It could be argued that fluid absorption may only be clinically significant in high-risk patients with a compromised cardiorespiratory status. The use of an Amplatz sheath could create a low-pressure system. &
OUTCOME Falahatkar et al. and De Sio et al. [6,10] performed the only two RCTs comparing the traditional prone PCNL with supine PCNL, focussing on effectiveness, operation time, and safety. Both effectiveness, expressed in stone-free rate, and safety showed no significant differences between prone and supine positioning. Operation time was found to be significantly shorter for supine-positioned PCNL procedures. Valdivia et al. [20] determined differences in patient characteristics, operation time and procedures, and perioperative outcomes between prone and supine positioning using the CROES PCNL database. Prone-positioned PCNL was performed in 80.3% of the cases. In contrary to the RCTs, a significant higher operation time was observed for the supine position. Another contradictory outcome was a significantly higher stone-free rate in the prone position PCNL group. These contradictory outcomes might be explained by differences in definition of operation time and different methods and protocols for assessing a stone-free status. The ability to shorten operation times is of importance as it is known to be of influence on blood loss during PCNL and is described as a prognostic factor on PCNL morbidity [28,29]. Smith et al. [30] assessed factors of influence on treatment outcome using patient data collected from the CROES Global Study database. A prediction Volume 24 Number 2 March 2014
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How well tolerated is supine percutaneous nephrolithotomy? Baard et al.
analysis of stone-free rates was conducted using patient factors and preoperative radiological findings. Stone burden was found to be the best predictor of stone-free rate. Other factors of influence were stone location, stone count, staghorn stones, prior stone treatment, and case volume. These efforts resulted in a highly reliable nephrolithometric nomogram.
HIGH-RISK PATIENTS Obesity is an increasing burden associated with stone formation. Obese patients tend to have more comorbidity, resulting in a surgical risk. Morbidly obese patients with compromised cardiovascular status are not always suitable for prone positioning, for which supine positioning offers an alternative. Mazzucchi et al. [31] compared the prone and complete supine techniques in obese patients (BMI > 30), finding similar outcomes in treatment effect and complications. Furthermore, supine positioning showed significantly shorter operation times and hospital stays. Manohar et al. [32] presented their experience with supine PCNL in 62 patients with obesitas or ASA classification of at least 3. They report a stonefree rate of 95% with no increase in surgical complications. Fuller et al. [33] presented a series of 3709 patients from the CROES database, grouped in four BMI categories (normal weight BMI 18.5–25, overweight 25–30, obese 30–40, and super obese >40). A significantly longer operation time was observed in obese patients. Stone-free rates decreased with obesity corresponding to a significantly higher retreatment rate. However, it has to be noted that a significantly higher rate of staghorn stones was seen in the super obese patient group. No significant difference was seen in the overall complication rate among the four groups. The negative effect of BMI on operative time was also found by Falahatkar et al. [34]. The influence of high volume centres was analyzed on stone-free rate and patient weight. Super obese patients had a worse outcome independent of case volume. Okeke et al. [35], using the CROES database, found no differences in position between elderly and young patients treated with PCNL. A retrospective study on PCNL for lower pole stones found that patients with a higher ASA score of at least 2 had a bigger chance of supine position than ASA 1 patients [36].
COMPLICATIONS Complication rates following PCNL vary widely and are reported up to 83% [22,24]. These are mostly
minor complications, namely, extravasation 7.2%, transfusion rate 11.2–17.5%, and fever 21.0–32.1%. Frequency rates of major complications are 0.9– 4.7% for septicaemia, 0.6–1.4% for severe renal haemorrhage needing intervention, 2.3–3.1% for pleural injury, and 0.2–0.8% for colonic injury. The multicentre CROES PCNL Global Study described an overall complication rate of 15% and low-modified Clavien morbidity scores. This Illustrates PCNL to be a well tolerated procedure in general [11]. Meta-analysis of Wu et al. and Liu et al. [37,38] showed no statistical differences in complication rates between prone and supine-positioned PCNL procedures. Both groups showed similar rates of (postoperative) transfusion and fever. Out of the four included studies only one of 389 supinepositioned patients suffered a colon injury (0.5%); no pleural injuries were reported. This is the only colonic injury case reported in the literature in supine PCNL. The incidence of retrorenal colon is 10% in prone position compared with 2% in supine position, theoretically diminishing the chance for colonic injury [39–41]. Finally, pelvic perforation and failed access were comparable between the prone and supine group as well. Concluding from these meta-analyses, with limited included studies, similar numbers were found in terms of complication rate.
CONCLUSION PCNL has been established as a standard treatment for kidney stones. Traditionally, it is performed in the prone position that can have its limitations, especially in obese patients or patients with skeletal deformities. Several lateral and supine positions have been described to overcome these limitations. However, the prone position is still favoured by many urologists and about 80% of PCNL worldwide are performed in this position. Two RCTs show equal overall results in terms of efficacy and safety. The assumed differences in complications because of anatomical differences, between PCNL in prone or supine position, are not demonstrated. This might partly be explained by patient selection, as supine PCNL has advantages in selected highrisk patients. In theory, supine PCNL has advantages over prone PCNL, in terms of reduced risk and potential trauma related with anaesthesia and repositioning, resulting in shorter operative time. Supine PCNL also allows easier combined retrograde access, easier access to lower calyx, with consequent lower risk of pleural injury. Furthermore, supine positioning implies a better management of fluid balance.
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All these issues suggest benefits in terms of safety and efficacy in supine PCNL. However, no prospective randomized studies are conducted to support this assumption. PCNL seems to be as well tolerated in supine as in the prone position, with comparable complication rates. Because of advantages of supine position in the morbidly obese, patients with skeletal deformities and patients with severe cardiorespiratory morbidity, it is important to have experience with several positions. Ultimately, the decision on position should be made on patient’s characteristics and surgeon’s preference and experience. Acknowledgements None. Conflicts of interest There are no conflicts of interest.
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16. Scoffone CM, Cracco CM, Cossu M, et al. Endoscopic combined intrarenal surgery in Galdakao-modified supine Valdivia position: a new standard for percutaneous nephrolithotomy? Eur Urol 2008; 54:1393–1403. 17. Ibarluzea G, Scoffone CM, Cracco CM, et al. Supine Valdivia and modified lithotomy position for simultaneous anterograde and retrograde endourological access. BJU Int 2007; 100:233–236. 18. Papatsoris AG, Zaman F, Panah A, et al. Simultaneous anterograde and retrograde endourologic access: ‘the Barts technique’. J Endourol 2008; 22:2665–2666. 19. Duty B, Waingankar N, Okhunov Z, et al. Anatomical variation between the & prone, supine, and supine oblique positions on computed tomography: implications for percutaneous nephrolithotomy access. Urology 2012; 79:67–71. An interesting insight into anatomical variations between the prone, supine, and supine oblique position PCNL. 20. Valdivia JG, Scarpa RM, Duvdevani M, et al. 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Prospective comparison of outcomes of percutaneous nephrolithotomy in elderly patients versus younger patients. J Endourol 2012; 26:996–1001. 36. Sanguedolce F, Breda A, Millan F, et al. Lower pole stones: prone PCNL versus supine PCNL in the International Cooperation in Endourology (ICE) group experience. World J Urol 2012; 4–9. 37. Wu P, Wang L, Wang K. Supine versus prone position in percutaneous nephrolithotomy for kidney calculi: a meta-analysis. Int Urol Nephrol 2011; 43:67–77. 38. Liu L, Zheng S, Xu Y, Wei Q. Systematic review and meta-analysis of percutaneous nephrolithotomy for patients in the supine versus prone position. J Endourol 2010; 24:1941–1946. 39. Tuttle DN, Yeh BM, Meng MV, et al. Risk of injury to adjacent organs with lower-pole fluoroscopically guided percutaneous nephrostomy: evaluation with prone, supine, and multiplanar reformatted CT. J Vasc Interv Radiol 2005; 16:1489–1492. 40. Chalasani V, Bissoon D, Bhuvanagir AK, et al. Should PCNL patients have a CT in the prone position preoperatively? Can J Urol 2010; 17:5082–5086. 41. Boon JM, Shinners B, Meiring JH. Variations of the position of the colon as applied to percutaneous nephrostomy. Surg Radiol Anat 2001; 23:421–425.
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