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Fluoroscopy-guided Renal Access in Supine Percutaneous Nephrolithotomy
Surgeon’s Workshop Fluoroscopy-guided Renal Access in Supine Percutaneous Nephrolithotomy András Hoznek, Idir Ouzaid, Matthew Gettman, Julie Rode, Alexandre De La Taille, Laurent Salomon, and Clément-Claude Abbou OBJECTIVE PATIENTS AND METHODS:
RESULTS
CONCLUSIONS
To describe a standardized and easily reproducible method for fluoroscopy-guided renal access during supine percutaneous nephrolithotomy (sPCNL). From January 2009 to January 2010, 35 patients underwent sPCNL. In 10 patients, ultrasoundguided puncture was unsuccessful. In these patients, we completed percutaneous access with a method based on fluoroscopy. We used a simple technique, adapted to sPCNL, consisting of cephalad tilting of the C-arm during puncture of the targeted calyx. We prospectively recorded the time necessary for the puncture, the success, and the complication rate of the puncture. Among the 10 study patients, the mean operative time for the puncture was 50 seconds (range 35–180). The puncture was successful after 1 attempt in 7 patients and in the remaining patients after a second or a third attempt. There were no complications related to the puncture technique. This technique is easy and reproducible for creating a fluoroscopy-guided renal access adjunctive to ultrasound during sPCNL. It may also be useful for urologists not familiar with ultrasoundguided access. UROLOGY 78: 221–224, 2011. © 2011 Elsevier Inc.
G
aldakao-modified Valdivia position for percutaneous nephrolithotomy is becoming increasingly popular worldwide.1-3 Similar to the prone position, access creation to the collecting system is a decisive step during supine percutaneous nephrolithotomy (sPCNL). Two primary methods are used for fluoroscopyguided renal access in the classic prone position: triangulation and the bull’s-eye technique.4 However, these methods are not readily adaptable to sPCNL. We describe a simple and easily reproducible method for fluoroscopy-guided renal access customized to sPCNL. This is an adaptation of a principle already reported but seldom used with the patient in the prone position.5
PATIENTS AND METHODS From January 2009 to January 2010 we performed sPCNL in 35 patients. In 10 patients, ultrasound-guided puncture was unsuccessful. In these patients, we performed percutaneous access with a method using a modified and standardized technique based on cephalad tilting of the C-arm during fluoroscopy. Inclusion criteria for sPCNL were single or multiple renal stones ⬎2 cm and any body mass index (BMI). Exclusion criteria were uncontrolled coagulopathy and pregnancy. All sPCNL were performed by one surgeon.
From the Service d’Urologie, Centre Hospitalier Universitaire Henri Mondor, Assistance Publique des Hôpitaux de Paris, Créteil, France; and Mayo Clinic Department of Urology, Rochester, MN Reprint requests: Idir Ouzaid, M.D., 51 Av. du Ml. De Lattre de Tassigny, 94010 Créteil, Cedex, France. E-mail: [email protected] Submitted: December 22, 2010, accepted (with revisions): February 25, 2011
© 2011 Elsevier Inc. All Rights Reserved
Preoperative radiologic evaluation included kidney-ureter-bladder and computed tomography. Before PCNL, urine cultures were obtained, and if positive, appropriate antibiotics were prescribed for 1 week. Urine cultures were repeated to document sterile urine. All procedures were carried out under general anesthesia. A 7-F ureteral catheter was introduced, and a retrograde ureteropyelography was done. The site of the puncture was chosen according to the location of the largest bulk of the stone. After creating the renal access, dilatation was performed and a 24 or 30-F Amplatz sheath was positioned, allowing the introduction of the nephroscope (Olympus OES 4000 reference A3336A, Olympus Europa, Hamburg, Germany, or Storz 27 295 AA, Karl Storz, Tuttlingen, Germany). Small stones were directly extracted with a grasper, and large stones were treated by Lithoclast Master (Electro Medical Systems SA, Nyon, Switzerland). An 8-F nephrostomy was left in for the first night after surgery, and the ureter was drained with a ureteral catheter or a double-J stent. The success rate and the operative time of the puncture (defined from the beginning of surgery until urine was obtained percutaneously) were recorded. Complications were graded according to modified Clavien classification.6
Puncture Technique This technique is performed with the patient placed in the Galdakao-modified2 Valdivia position (Fig. 1A). Because the flank is elevated 20°, the plane of the puncture needle is roughly horizontal; the entry point on the skin is situated on the posterior axillary line. Consequently, the needle is perpendicular to the axis of the X-ray beam, when the C-arm is in the vertical position. To facilitate spatial orientation further on, a small metallic clamp is attached to the drape overlying the anterior abdominal wall with the tip of the clamp in the vertical projection of the lower calyx (Fig. 1B). The axis of the needle 0090-4295/11/$36.00 doi:10.1016/j.urology.2011.02.058
221
Figure 1. (A) The patient is placed in the Galdakao-modified Valdivia position. (B) The entry point of the puncture needle is situated on the posterior axillary line perpendicular to the axis of the X-ray beam. The C-arm is in vertical position. (C, D) A metallic clamp is attached to the drape overlying the anterior abdominal wall with the tip of the clamp in the vertical projection of the lower calyx. The axis of the needle matches the axis of the infundibulum of the lower calyx.
should match the axis of the infundibulum of the targeted lower calyx. The needle is advanced toward the lower calyx. If no urine appears when the tip of the needle is in the projection of the calyx, this means that the puncture is either posterior or anterior to the calyx (Fig. 1C, 1D). To determine the position of the tip of the needle relative to the calyx, the C-arm is tilted 30° cephalad (Fig. 2A). Displacement of the needle on the fluoroscopy screen in the same direction as the tip of the clamp means that the needle is anterior to the calyx. If the needle moves in the opposite direction than the clamp, the tip of the needle is posterior to the calyx (Fig. 2B, 2C). On the basis of this information, the needle is slightly withdrawn; its inclination is modified as necessary upward or downward, but always remaining in the plane that passes through the axis of the caliceal infundibulum (Fig. 2D). The accompanying detailed video highlights each step of the puncture procedure (Video 1).
RESULTS Thirty-five patients had a unilateral sPCNL. In 10 patients, ultrasound-guided renal puncture was unsuccessful because of patient obesity or poor ultrasound penetrability of the tissues. In these patients, we used the technique based on cephalad tilting of the C-arm. In this subgroup of patients (6 male and 4 female), the mean age was 56 years (range 17–72). The mean BMI was 26.8 kg/m2 (range 21.8 – 40.5). The stones were solitary and multiple in 6 and 4 patients, respectively. The mean size of the stones was 28 ⫾ 7 mm. The lower posterior calyx was punctured in 8 cases and the middle posterior in the 222
remaining 2. The mean operative time for the renal puncture was 50 ⫾ 20 seconds (range 35–180). The urine was obtained after 1 attempt in 7 patients. A second or a third attempt was needed for the 3 remaining patients. We observed no complication related to the puncture, no patient was transfused, and injury to adjacent organs was not observed.
COMMENT The supine position is attractive for many reasons during PCNL: less patient handling, the need for draping only once, the ability to perform simultaneous PCNL and ureteroscopic procedures, better intraoperative drainage because of dependent Amplatz sheath, and easier management of the airway during procedures. Finally, the ability to avoid colonic injury is at least equivalent if not superior with the patient in supine position.7,8 However, the efficiency of this novel installation remains controversial and many urologists remain faithful to classic prone position. Two review articles identified a “trend in favor of better outcomes in the prone position over the supine position”9 and recommend supine position only in “carefully selected patients”.10 However, these studies included mostly case series and only a few comparative studies. Furthermore, it is rather hazardous to come to a conclusion on the basis of noncomparative studies because of the extensive heterogeneity of reporting the results.11 More recently, a meta-analysis based UROLOGY 78 (1), 2011
Figure 2. (A) 30° cephalad tilting of the C-arm. (B, C) The position of the needle relative to the calyx is determined. (D) The axis of the needle is adjusted and the targeted lower calyx is successfully punctured.
exclusively on higher-evidence-level, randomized, comparative studies confirmed that the simplification of the procedure in supine position invariably leads to a significant and clinically relevant reduction in operative time while maintaining equivalent stone-free rates and similarly low complications.8 Possibly, the main obstacle for the wider diffusion of supine position is related to less opportunity for specific training and the less abundant description of technical details, especially the method of puncturing the kidney. The success of PCNL is critically dependent on achieving a suitable percutaneous access to the collecting system. This is more commonly gained by the urologist in Europe than in the UK or the United States, where it is generally established by radiologists.12 In a study assessing the learning curve during PCNL, the most time-consuming part of the procedure is the puncture and dilatation of the tract required to obtain proper renal access.13 This may be caused by the lack of methodology during the teaching of the procedure. In addition, many urologists are less familiar with the use of ultrasound; in some cases, the device is not available in the operating room. Furthermore, the ultrasound visibility of the renal cavities depends on many factors, including the size of the target calyx, the existence of a dilatation, the presence or absence of stone material, the skin-kidney distance, and the individual acoustic characteristics of the tissues. The latter is quite variable and unpredictable among patients. In most patients, ultrasound is sufficient to gain renal access, and fluoroscopy plays only an accessory role. However, in a few patients, the combination of several of the UROLOGY 78 (1), 2011
aforementioned factors sometimes renders ultrasoundguided puncture difficult to perform. To overcome these difficulties and improve this cornerstone step of the procedure, we standardized a simple, reproducible fluoroscopy-based technique to create a renal access during sPCNL. Because this technique needs a minimal manipulation (30° cephalad tilting) of the Carm, most punctures are successful in ⬍1 minute. In most of the cases, we puncture the lower posterior calyx, because large renal vessels are usually not present in this area and the risk of thoracic injury is absent. This route permits a good access to the renal pelvis and a good stone removal. However, the method that we described is also suitable for the puncture of the middle or upper pole calyces. Another important issue related to the puncture technique is the risk of injury to adjacent organs. In our routine, in addition to systematic preoperative computed tomography scan, we systematically use ultrasound during access creation to ensure that no bowel or pleura is in the pathway of the puncture. Colon injury is a rare complication. In the meta-analysis of Liu et al,8 only 1 of 389 patients in the supine position had a colon lesion. The fear of increased risk of colonic or splanchnic injury in the supine position is unfounded. On the contrary, several computed tomography– based studies show that in prone position, because of the abdominal compression, the colon tends to move laterally and posteriorly to the kidney.14,15 These data suggest that independently from the calyx and depending on how lateral the puncture is, the PCNL tract in the supine position is safe. However, given 223
the small sample size, the estimation of access-related complications is potentially limited and a study with a larger sample size is needed to adequately answer this.
CONCLUSIONS sPCNL is more frequently emerging as an alternative mini-invasive technique in the treatment of large and complex kidney stones. Our standardized fluoroscopybased technique for renal access is simple, reproducible, and safe. However, it should be validated by other teams to permit its widespread use. References 1. Valdivia Uría JG, Valle Gerhold J, López López JA, et al. Technique and complications of percutaneous nephroscopy: experience with 557 patients in the supine position. J Urol. 1998;160:19751978. 2. 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. 3. 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. 4. Steinberg PL, Semins MJ, Wason SE, Matlaga BR, Pais VM. Fluoroscopy-guided percutaneous renal access. J Endourol. 2009;23: 1627-1631. 5. Makhoul B, Yatim M, Guinard J, et al. Comment ponctionner un rein pour réaliser une néphrolithotomie percutanée? Ann Urol. [Paris] 2006;40:139-148. 6. Tefekli A, Ali Karadag M, Tepeler K, et al. Classification of percutaneous nephrolithotomy complications using the modified clavien grading system: looking for a standard. Eur Urol. 2008;53: 184-190.
224
7. 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. 8. Liu L, Zheng S, Xu Y, Wei Q. Systematic Review and MetaAnalysis of Percutaneous Nephrolithotomy for Patients in the Supine versus Prone Position. J Endourol. 2010;24(12):1941. 9. 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. 10. Basiri A, Mohammadi Sichani M. Supine percutaneous nephrolithotomy, is it really effective? A systematic review of literature. Urol J. 2009;6:73-77. 11. Hyams ES, Bruhn A, Lipkin M, Shah O. Heterogeneity in the reporting of disease characteristics and treatment outcomes in studies evaluating treatments for nephrolithiasis. J Endourol. 2010; 24:1411-1414. 12. Watterson JD, Soon S, Jana K. Access related complications during percutaneous nephrolithotomy: urology versus radiology at a single academic institution. J Urol. 2006;176:142-145. 13. Tanriverdi O, Boylu U, Kendirci M, et al. The learning curve in the training of percutaneous nephrolithotomy. Eur Urol. 2007;52: 206-211. 14. Hopper KD, Sherman JL, Luethke JM, Ghaed N. The retrorenal colon in the supine and prone patient. Radiology. 1987;162:443446. 15. 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.
Supplementary data associated with this article can be found, in the online version, at doi: 10.1016/j.urology.2011.02.058.
UROLOGY 78 (1), 2011
RESULTS
CONCLUSIONS
To describe a standardized and easily reproducible method for fluoroscopy-guided renal access during supine percutaneous nephrolithotomy (sPCNL). From January 2009 to January 2010, 35 patients underwent sPCNL. In 10 patients, ultrasoundguided puncture was unsuccessful. In these patients, we completed percutaneous access with a method based on fluoroscopy. We used a simple technique, adapted to sPCNL, consisting of cephalad tilting of the C-arm during puncture of the targeted calyx. We prospectively recorded the time necessary for the puncture, the success, and the complication rate of the puncture. Among the 10 study patients, the mean operative time for the puncture was 50 seconds (range 35–180). The puncture was successful after 1 attempt in 7 patients and in the remaining patients after a second or a third attempt. There were no complications related to the puncture technique. This technique is easy and reproducible for creating a fluoroscopy-guided renal access adjunctive to ultrasound during sPCNL. It may also be useful for urologists not familiar with ultrasoundguided access. UROLOGY 78: 221–224, 2011. © 2011 Elsevier Inc.
G
aldakao-modified Valdivia position for percutaneous nephrolithotomy is becoming increasingly popular worldwide.1-3 Similar to the prone position, access creation to the collecting system is a decisive step during supine percutaneous nephrolithotomy (sPCNL). Two primary methods are used for fluoroscopyguided renal access in the classic prone position: triangulation and the bull’s-eye technique.4 However, these methods are not readily adaptable to sPCNL. We describe a simple and easily reproducible method for fluoroscopy-guided renal access customized to sPCNL. This is an adaptation of a principle already reported but seldom used with the patient in the prone position.5
PATIENTS AND METHODS From January 2009 to January 2010 we performed sPCNL in 35 patients. In 10 patients, ultrasound-guided puncture was unsuccessful. In these patients, we performed percutaneous access with a method using a modified and standardized technique based on cephalad tilting of the C-arm during fluoroscopy. Inclusion criteria for sPCNL were single or multiple renal stones ⬎2 cm and any body mass index (BMI). Exclusion criteria were uncontrolled coagulopathy and pregnancy. All sPCNL were performed by one surgeon.
From the Service d’Urologie, Centre Hospitalier Universitaire Henri Mondor, Assistance Publique des Hôpitaux de Paris, Créteil, France; and Mayo Clinic Department of Urology, Rochester, MN Reprint requests: Idir Ouzaid, M.D., 51 Av. du Ml. De Lattre de Tassigny, 94010 Créteil, Cedex, France. E-mail: [email protected] Submitted: December 22, 2010, accepted (with revisions): February 25, 2011
© 2011 Elsevier Inc. All Rights Reserved
Preoperative radiologic evaluation included kidney-ureter-bladder and computed tomography. Before PCNL, urine cultures were obtained, and if positive, appropriate antibiotics were prescribed for 1 week. Urine cultures were repeated to document sterile urine. All procedures were carried out under general anesthesia. A 7-F ureteral catheter was introduced, and a retrograde ureteropyelography was done. The site of the puncture was chosen according to the location of the largest bulk of the stone. After creating the renal access, dilatation was performed and a 24 or 30-F Amplatz sheath was positioned, allowing the introduction of the nephroscope (Olympus OES 4000 reference A3336A, Olympus Europa, Hamburg, Germany, or Storz 27 295 AA, Karl Storz, Tuttlingen, Germany). Small stones were directly extracted with a grasper, and large stones were treated by Lithoclast Master (Electro Medical Systems SA, Nyon, Switzerland). An 8-F nephrostomy was left in for the first night after surgery, and the ureter was drained with a ureteral catheter or a double-J stent. The success rate and the operative time of the puncture (defined from the beginning of surgery until urine was obtained percutaneously) were recorded. Complications were graded according to modified Clavien classification.6
Puncture Technique This technique is performed with the patient placed in the Galdakao-modified2 Valdivia position (Fig. 1A). Because the flank is elevated 20°, the plane of the puncture needle is roughly horizontal; the entry point on the skin is situated on the posterior axillary line. Consequently, the needle is perpendicular to the axis of the X-ray beam, when the C-arm is in the vertical position. To facilitate spatial orientation further on, a small metallic clamp is attached to the drape overlying the anterior abdominal wall with the tip of the clamp in the vertical projection of the lower calyx (Fig. 1B). The axis of the needle 0090-4295/11/$36.00 doi:10.1016/j.urology.2011.02.058
221
Figure 1. (A) The patient is placed in the Galdakao-modified Valdivia position. (B) The entry point of the puncture needle is situated on the posterior axillary line perpendicular to the axis of the X-ray beam. The C-arm is in vertical position. (C, D) A metallic clamp is attached to the drape overlying the anterior abdominal wall with the tip of the clamp in the vertical projection of the lower calyx. The axis of the needle matches the axis of the infundibulum of the lower calyx.
should match the axis of the infundibulum of the targeted lower calyx. The needle is advanced toward the lower calyx. If no urine appears when the tip of the needle is in the projection of the calyx, this means that the puncture is either posterior or anterior to the calyx (Fig. 1C, 1D). To determine the position of the tip of the needle relative to the calyx, the C-arm is tilted 30° cephalad (Fig. 2A). Displacement of the needle on the fluoroscopy screen in the same direction as the tip of the clamp means that the needle is anterior to the calyx. If the needle moves in the opposite direction than the clamp, the tip of the needle is posterior to the calyx (Fig. 2B, 2C). On the basis of this information, the needle is slightly withdrawn; its inclination is modified as necessary upward or downward, but always remaining in the plane that passes through the axis of the caliceal infundibulum (Fig. 2D). The accompanying detailed video highlights each step of the puncture procedure (Video 1).
RESULTS Thirty-five patients had a unilateral sPCNL. In 10 patients, ultrasound-guided renal puncture was unsuccessful because of patient obesity or poor ultrasound penetrability of the tissues. In these patients, we used the technique based on cephalad tilting of the C-arm. In this subgroup of patients (6 male and 4 female), the mean age was 56 years (range 17–72). The mean BMI was 26.8 kg/m2 (range 21.8 – 40.5). The stones were solitary and multiple in 6 and 4 patients, respectively. The mean size of the stones was 28 ⫾ 7 mm. The lower posterior calyx was punctured in 8 cases and the middle posterior in the 222
remaining 2. The mean operative time for the renal puncture was 50 ⫾ 20 seconds (range 35–180). The urine was obtained after 1 attempt in 7 patients. A second or a third attempt was needed for the 3 remaining patients. We observed no complication related to the puncture, no patient was transfused, and injury to adjacent organs was not observed.
COMMENT The supine position is attractive for many reasons during PCNL: less patient handling, the need for draping only once, the ability to perform simultaneous PCNL and ureteroscopic procedures, better intraoperative drainage because of dependent Amplatz sheath, and easier management of the airway during procedures. Finally, the ability to avoid colonic injury is at least equivalent if not superior with the patient in supine position.7,8 However, the efficiency of this novel installation remains controversial and many urologists remain faithful to classic prone position. Two review articles identified a “trend in favor of better outcomes in the prone position over the supine position”9 and recommend supine position only in “carefully selected patients”.10 However, these studies included mostly case series and only a few comparative studies. Furthermore, it is rather hazardous to come to a conclusion on the basis of noncomparative studies because of the extensive heterogeneity of reporting the results.11 More recently, a meta-analysis based UROLOGY 78 (1), 2011
Figure 2. (A) 30° cephalad tilting of the C-arm. (B, C) The position of the needle relative to the calyx is determined. (D) The axis of the needle is adjusted and the targeted lower calyx is successfully punctured.
exclusively on higher-evidence-level, randomized, comparative studies confirmed that the simplification of the procedure in supine position invariably leads to a significant and clinically relevant reduction in operative time while maintaining equivalent stone-free rates and similarly low complications.8 Possibly, the main obstacle for the wider diffusion of supine position is related to less opportunity for specific training and the less abundant description of technical details, especially the method of puncturing the kidney. The success of PCNL is critically dependent on achieving a suitable percutaneous access to the collecting system. This is more commonly gained by the urologist in Europe than in the UK or the United States, where it is generally established by radiologists.12 In a study assessing the learning curve during PCNL, the most time-consuming part of the procedure is the puncture and dilatation of the tract required to obtain proper renal access.13 This may be caused by the lack of methodology during the teaching of the procedure. In addition, many urologists are less familiar with the use of ultrasound; in some cases, the device is not available in the operating room. Furthermore, the ultrasound visibility of the renal cavities depends on many factors, including the size of the target calyx, the existence of a dilatation, the presence or absence of stone material, the skin-kidney distance, and the individual acoustic characteristics of the tissues. The latter is quite variable and unpredictable among patients. In most patients, ultrasound is sufficient to gain renal access, and fluoroscopy plays only an accessory role. However, in a few patients, the combination of several of the UROLOGY 78 (1), 2011
aforementioned factors sometimes renders ultrasoundguided puncture difficult to perform. To overcome these difficulties and improve this cornerstone step of the procedure, we standardized a simple, reproducible fluoroscopy-based technique to create a renal access during sPCNL. Because this technique needs a minimal manipulation (30° cephalad tilting) of the Carm, most punctures are successful in ⬍1 minute. In most of the cases, we puncture the lower posterior calyx, because large renal vessels are usually not present in this area and the risk of thoracic injury is absent. This route permits a good access to the renal pelvis and a good stone removal. However, the method that we described is also suitable for the puncture of the middle or upper pole calyces. Another important issue related to the puncture technique is the risk of injury to adjacent organs. In our routine, in addition to systematic preoperative computed tomography scan, we systematically use ultrasound during access creation to ensure that no bowel or pleura is in the pathway of the puncture. Colon injury is a rare complication. In the meta-analysis of Liu et al,8 only 1 of 389 patients in the supine position had a colon lesion. The fear of increased risk of colonic or splanchnic injury in the supine position is unfounded. On the contrary, several computed tomography– based studies show that in prone position, because of the abdominal compression, the colon tends to move laterally and posteriorly to the kidney.14,15 These data suggest that independently from the calyx and depending on how lateral the puncture is, the PCNL tract in the supine position is safe. However, given 223
the small sample size, the estimation of access-related complications is potentially limited and a study with a larger sample size is needed to adequately answer this.
CONCLUSIONS sPCNL is more frequently emerging as an alternative mini-invasive technique in the treatment of large and complex kidney stones. Our standardized fluoroscopybased technique for renal access is simple, reproducible, and safe. However, it should be validated by other teams to permit its widespread use. References 1. Valdivia Uría JG, Valle Gerhold J, López López JA, et al. Technique and complications of percutaneous nephroscopy: experience with 557 patients in the supine position. J Urol. 1998;160:19751978. 2. 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. 3. 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. 4. Steinberg PL, Semins MJ, Wason SE, Matlaga BR, Pais VM. Fluoroscopy-guided percutaneous renal access. J Endourol. 2009;23: 1627-1631. 5. Makhoul B, Yatim M, Guinard J, et al. Comment ponctionner un rein pour réaliser une néphrolithotomie percutanée? Ann Urol. [Paris] 2006;40:139-148. 6. Tefekli A, Ali Karadag M, Tepeler K, et al. Classification of percutaneous nephrolithotomy complications using the modified clavien grading system: looking for a standard. Eur Urol. 2008;53: 184-190.
224
7. 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. 8. Liu L, Zheng S, Xu Y, Wei Q. Systematic Review and MetaAnalysis of Percutaneous Nephrolithotomy for Patients in the Supine versus Prone Position. J Endourol. 2010;24(12):1941. 9. 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. 10. Basiri A, Mohammadi Sichani M. Supine percutaneous nephrolithotomy, is it really effective? A systematic review of literature. Urol J. 2009;6:73-77. 11. Hyams ES, Bruhn A, Lipkin M, Shah O. Heterogeneity in the reporting of disease characteristics and treatment outcomes in studies evaluating treatments for nephrolithiasis. J Endourol. 2010; 24:1411-1414. 12. Watterson JD, Soon S, Jana K. Access related complications during percutaneous nephrolithotomy: urology versus radiology at a single academic institution. J Urol. 2006;176:142-145. 13. Tanriverdi O, Boylu U, Kendirci M, et al. The learning curve in the training of percutaneous nephrolithotomy. Eur Urol. 2007;52: 206-211. 14. Hopper KD, Sherman JL, Luethke JM, Ghaed N. The retrorenal colon in the supine and prone patient. Radiology. 1987;162:443446. 15. 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.
Supplementary data associated with this article can be found, in the online version, at doi: 10.1016/j.urology.2011.02.058.
UROLOGY 78 (1), 2011