Endoscopic Combined Intrarenal Surgery for Large Calculi: Simultaneous Use of Flexible Ureteroscopy and Mini-Percutaneous Nephrolithotomy Overcomes the Disadvantageous of Percutaneous Nephrolithotomy Monotherapy

Abstract

Background and Purpose:

Percutaneous nephrolithotomy (PCNL) is considered the standard procedure for the removal of large renal calculi. The development of the “minimally invasive PCNL” (mini-PCNL) has reduced the complications of the surgery; it also appears to be associated with less morbidity than the conventional PCNL (con-PCNL). This study aimed at evaluating the efficacy of endoscopic intrarenal surgery, using the prone-split leg position, using flexible ureteroscopy and mini-PCNL (mini- endoscopic combined intrarenal surgery [ECIRS]) by retrospectively comparing this technique with mini-PCNL and con-PCNL.

Patients and Methods:

In total, 161 consecutive patients who were observed for the follow-up of large renal calculi between February 2004 and January 2013 were selected for mini-ECIRS (60), mini-PCNL (19), or con-PCNL (82). Mini-ECIRS was performed with patients in the prone split-leg position via 18F minipercutaneous tract and 14F ureteral access sheath. The mini-PCNL was performed via 18F percutaneous tract and con-PCNL performed via the 30F tract. Mean size of the renal calculi removed via mini-ECIRS, mini-PCNL, and con-PCNL were 39.2, 38.4, and 34.6 mm, respectively.

Results:

Average surgical time for mini-ECIRS was shorter than that for mini-PCNL and con-PCNL (120.5 vs 181.9 vs 134.1 min, respectively; P<0.001). The stone-free rate for mini-ECIRS was significantly higher than that of the other procedures (initial rates 81.7% vs 38.9% vs 45.1%, respectively; P<0.001; rates after further treatment 86.7% vs 61.1% vs 61.0%, respectively; P=0.002). Only one patient in the mini-ECIRS group needed blood transfusions. The decrease in hemoglobin during mini-ECIRS and mini-PCNL was significantly lower than that during con-PCNL (P=0.011).

Conclusion:

Mini-ECIRS is better than monotherapy with mini-PCNL or con-PCNL. The study results show that mini-ECIRS is a safe, efficient, and versatile procedure that can be effective for the management of renal calculi.

Introduction

The currently available modalities for the removal of renal calculi include extracorporeal shockwave lithotripsy (SWL), flexible ureteroscopy (fURS), and percutaneous nephrolithotomy (PCNL). According to the European Association of Urology (EAU) guidelines, SWL remains the method of choice for the removal of stones within the renal pelvis and upper or middle calices measuring <20 mm, while larger stones should be managed using PCNL.¹ PCNL has a higher stone-free rate (SFR), shorter treatment time, and a reduced risk of febrile urinary tract infection compared with SWL.^2,3 Conventional PCNL (con-PCNL) requires a 30F nephrostomy sheath. Because it may be difficult to access all the calices through a single percutaneous tract, multiple access tracts are needed in as many as 20% to 58% of percutaneous procedures; these multiple PCNL access tracts are known to increase the risk of renal parenchymal injury.^4

–7 Complications associated with PCNL, including extravasation (7.2%), need for transfusion (11.2%–17.5%), and fever (21.0%–32.1%), may also occur at higher rates when multiple tracts are needed.^7
–9

The minimally invasive PCNL (mini-PCNL) procedure was introduced in an attempt to avoid the complications associated with con-PCNL.¹⁰ Mini-PCNL can be performed with a tract size of 16F to 20F, which can reduce procedure-related morbidity.^11

–15 This procedure has disadvantages, however, including diminished therapeutic efficacy in the removal of large stone burdens because of diminished intraoperative field visibility and increased surgical time.¹⁶

This study aimed at introducing a new technique of endoscopic intrarenal surgery using fURS and mini-PCNL (mini-endoscopic combined intrarenal surgery [ECIRS]) performed with patients in the prone split-leg position. The efficacy of this procedure was also retrospectively evaluated and compared with that of the mini-PCNL and con-PCNL.

Patients and Methods

The records of 161 patients who underwent mini-ECIRS (60 patients), mini-PCNL (19 patients), or con-PCNL (82 patients) for the removal of large renal calculi between February 2004 and January 2013 were retrospectively reviewed and analyzed. All patients underwent PCNL at Nagoya City University or Toyota Kosei Hospital. Written informed consent was obtained from all patients. This study was approved by the Institutional Review Board of Toyota Kosei Hospital.

All patients completed a minimum follow-up of 3 months. All those who were candidates for PCNL surgery as the primary indication based on the EAU and American Urological Association (AUA) guidelines were eligible for the study. Inclusion criteria were single or multiple renal stones including staghorn stones, stone diameter >2 cm, and no contraindications to perform PCNL surgery in the prone position. There were no specific exclusion criteria. Treatment of patients with PCNL was based on the presence of symptoms of pain in the flank, hematuria, fever, and/or sepsis.

Preoperative evaluation

Our usual preprocedural evaluation included measurement of hemoglobin (Hb), hematocrit (Hct), and estimated glomerular filtration rate (eGFR). The location, size, and density of the stones were evaluated by preoperative imaging studies, including plain abdominal radiography, ultrasonography, excretory urography, and CT. The maximum size was determined by the long axis of the largest stone. We usually performed preprocedural urine cultures, and we changed the antibiotics based on the results of the urine cultures. If the urine culture result was negative, we administered cefotiam before and after the procedure for 3 days.

Surgical techniques

Con-PCNL. With the patient maintained in a lithotomy position, a 6F occlusion ureteral catheter (Boston Scientific Japan K.K. Tokyo, Japan) was placed at the ureteropelvic junction of the target ureter. The patient was then turned to a prone position, and percutaneous access was achieved under ultrasonographic and fluoroscopic guidance. The tract was dilated using balloon dilators of up to 30F. Lithoclast lithotripsy (Boston Scientific Japan K.K. Tokyo, Japan) was then performed, using a 26F nephroscope (Karl Storz GmbH & Co. KG. Tuttlingen, Germany) for stone fragmentation. All procedures were performed completely with a single tract. A 26F nephrostomy tube (CLINY^® Create Medic Co., Ltd., Yokohama, Japan) was inserted at the conclusion of the procedure. The nephrostomy was removed 1 week later, unless ancillary PCNL was necessary.

Mini-PCNL. The procedures leading up to tract insertion were performed similar to that in con-PCNL. The mini-PCNL tract (Karl Storz) was smaller (18F) than that used for con-PCNL (30F). Stone disintegration was performed using a lithoclast or holmium- yttrium-aluminum-garnet (YAG) laser (Boston Scientific Japan K.K. Tokyo, Japan) through a 12F miniscope (Karl Storz) instead of a 26F nephroscope. An 18F nephrostomy tube (CLINY) was inserted at the conclusion of the procedure. The nephrostomy was removed 3 days later, unless ancillary PCNL was necessary.

Mini-ECIRS. The patient was maintained in the prone split-leg position throughout the operation, thus allowing both retrograde and antegrade access. Two urologists worked simultaneously to fragment the renal stones. One urologist performed retrograde intrarenal surgery (RIRS) and the other performed PCNL. A 12/14F ureteral access sheath was inserted under fluoroscopic guidance, to allow frequent passage of the ureteroscope (Flex X-2,^® Karl Storz, Tuttlingen, Germany) to the site of the renal calculi. A 200- or 365-μm YAG laser fiber was used in conjunction with fURS to fragment the renal calculi. Renal puncture and antegrade IRS were performed similar to that in mini-PCNL. Stones were broken into fragments using a lithoclast, and smaller fragmented stones were washed through the sheath by retrograde irrigation. A 4.7F Double-J ureteral stent was inserted in the urinary tract (INLAY OPTIMA^® C.R. Bard Inc., New Jersey), and an 18F nephrostomy tube (CLINY) was inserted. The nephrostomy was removed 3 days after surgery, and the ureteral stent was removed 1 month later.

Postoperative evaluation

Laboratory tests, including those for Hb, Hct, and e-GFR, were also conducted on the first postoperative day. The SFR was determined 4 weeks after surgery by plain abdominal radiography of the kidneys, ureters, and bladder and renal sonography. “Stone free” was defined as presence of no stones or only residual stone fragments of <4 mm in diameter.

Complications

Perioperative complications were graded according to the modified Clavien classification system as applied to PCNL.^9,17 We defined fever as a body temperature >38.5°C.

Statistical analysis

Continuous data comparing the three different types of procedures were analyzed using one-way analysis of variance and expressed as mean±standard deviation (SD). Categorical data were compared using the chi-square test. Statistical significance was defined as P<0.05.

Results

Patient characteristics

The characteristics of the patients in each group are summarized in Table 1. The preoperative demographic parameters of the three groups did not differ significantly.

Table 1.

Patient Characteristics and Preoperative Parameters

	Mini-ECIRS	Mini-PCNL	Con-PCNL	P value
No. of patients	60	19	82
Age (years)	54.5±1.5	48.9±3.3	53.2±1.5	n.s.
Sex				n.s.
Male (%)	44 (73.3)	12 (63.1)	66 (80.4)
Female (%)	16 (26.7)	7 (36.8)	16 (19.5)
BMI (kg/m²)	24.6±0.6	24.8±1.3	24.6±0.5	n.s.
Hb (g/dL)	14.4±0.2	13.6±0.4	14.0±0.2	n.s.
Hct (%)	40.7±1.3	40.5±1.5	42.2±0.5	n.s.
eGFR	75.5±3.0	67.7±6.3	71.6±4.5	n.s.
(mL/min/1.73m²)

Data are reported as numbers and percentages or as mean±SD, as appropriate.

ECIRS=endoscopic combined intrarenal surgery; PCNL=percutaneous nephrolithotomy; BMI=body mass index; Hb=hemoglobin; Hct=hematocrit; eGFR=estimated glomerular filtration rate.

Sex, age, body mass index, Hb, Hct, and eGFR in the three groups were comparable.

Stone data

Stone characteristics are summarized in Table 2. There were no significant differences among the three surgical groups in the mean size or density of the removed stones. Compared with mini-PCNL and con-PCNL, staghorn calculi comprised a greater proportion of stones removed by mini-ECIRS (P<0.001).

Table 2.

Stone Features

	Mini-ECIRS	Mini-PCNL	Con-PCNL	P value
Side				n.s.
Right (%)	21 (33)	5 (26)	22 (37)
Left (%)	39 (67)	14 (74)	60 (63)
Maximum size (mm)	39.2±2.6	38.4±5.8	34.6±2.3	n.s.
Mean CT density (HU)	1043.7±36.2	1121.1±94.6	903.8±50.2	n.s.
No. of staghorn calculi (%)	33 (55)	6 (32)	18 (22)	<0.001
Complete	12	4	12
Partial	21	2	6

Data are reported as numbers and percentages or as mean±SD, as appropriate.

ECIRS=endoscopic combined intrarenal surgery; PCNL=percutaneous nephrolithotomy; CT=computed tomography; HU=Hounsfield units.

Surgery data

Surgery parameters are summarized in Table 3. The mean±SD surgery time, including time for patient positioning, for mini-ECIRS, mini-PCNL, and con-PCNL, was 120.5±6.7, 181.9±15.5, and 134.1±7.8 minutes, respectively. The surgery time for mini-PCNL was significantly longer than that for mini-ECIRS (P<0.001). The mean±SD decrease in Hb level for mini-ECIRS, mini-PCNL, and con-PCNL was 1.06±0.15, 1.10±0.13, and 1.64±0.19 g/dL, respectively. The amount of bleeding during the mini-ECIRS and mini-PCNL surgeries was significantly lower than that during con-PCNL. Kidney function, as determined by the eGFR, remained unchanged for each modality. Hospital stays were significantly shorter for patients who underwent mini-ECIRS and mini-PCNL (P<0.05).

Table 3.

Surgery Parameters

	Mini-ECIRS	Mini-PCNL	Con-PCNL	P value
Total length operation (min)	120.5±6.7	181.9±15.5	134.1±7.8	<0.001
Hb drop (g/dL)	1.06±0.15	1.10±0.13	1.64±0.19	0.011
Hct drop (%)	2.33±0.41	2.31±0.53	4.22±0.94	0.005
eGFR drop (ml/min./1.73m²)	2.50±2.39	1.19±1.34	3.09±0.98	n.s.
Hospital stay	7.0±0.6	8.3±0.6	12.9±1.4	0.033
Initial stone free (%)	49 (81.7)	7 (38.9)	37 (45.1)	<0.001
No. of ancillary treatment	7	9	42	<0.001
Second PCNL	2	0	4
SWL	4	5	21
URS	1	0	3
Mixed	0	4	7
Final stone free (%)	52 (86.7)	11 (61.1)	50 (61.0)	0.002

Data are reported as numbers and percentages or as mean±SD, as appropriate.

ECIRS=endoscopic combined intrarenal surgery; PCNL=percutaneous nephrolithotomy; Hb=hemoglobin; Hct=henatocrit; eGFR=estimated glomerular filtration rate; SWL=shockwave lithotripsy; URS=ureteroscopy.

SFR

SFRs are summarized in Table 3. Complete stone clearance after a single session of treatment was achieved in 49 (81.7%) mini-ECIRS patients, 7 (38.9%) mini-PCNL patients, and 37 (45.1%) con-PCNL patients. The SFR was significantly higher in mini-ECIRS patients (P<0.001). Ancillary treatment was needed more frequently in patients who underwent mini-PCNL and con-PCNL than in those who underwent mini-ECIRS. Seven mini-ECIRS patients needed ancillary treatments, specifically four SWL, one URS, and two PCNL. Five mini-PCNL patients needed SWL and four needed combination therapy involving secondary PCNL and SWL. Of the patients who underwent con-PCNL, 42 needed additional therapy including secondary PCNL, SWL, and URS. The final SFR was significantly higher (P=0.002) in the mini-ECIRS patients (86.7%) than in the mini-PCNL patients (61.1%) and con-PCNL (61.0%) patients.

Complications

The postoperative complications included a transient high-grade fever of >38.5°C in 4 mini-ECIRS patients (6.7%), 1 mini-PCNL patient (5.6%) and 12 con-PCNL patients (14.6%). One patient who underwent mini-ECIRS needed blood transfusion. One mini-PCNL patient had urosepsis that promptly resolved with specific antibiotic therapy. Ten patients in the con-PCNL group had Clavien grading scores of II from urosepsis and renal parenchymal bleeding necessitating blood transfusions. No patients had a Clavien grading score of ≥III. The Clavien grading scores indicated that significantly fewer postoperative complications occurred in the mini-ECIRS and mini PCNL groups than in the con-PCNL group (Table 4).

Table 4.

Intraoperative and Postoperative Complications

	Mini-ECIRS	Mini-PCNL	Con-PCNL	P value
Required blood transfusion	1 (1.7)	0 (0)	6 (7.3)	n.s.
Fever up (>38.5)	3 (6.7)	1 (5.6)	12 (14.6)	n.s.
Clavien grade
0	54 (90.0)	16 (84.2)	57 (69.5)	0.042
I	5 (8.3)	2 (10.5)	15 (18.3)
II	1 (1.7)	1 (5.3)	10(12.2)
≥III	0	0	0

Data are reported as numbers and percentages or as mean±SD, as appropriate.

ECIRS=endoscopic combined intrarenal surgery; PCNL=percutaneous nephroliothotomy.

Discussion

This nonrandomized study demonstrates that mini-ECIRS has a higher SFR than either mini-PCNL or con-PCNL alone, and that it is associated with fewer complications than con-PCNL. PCNL was a well-established option for treating patients with large stones.^18,19 Con-PCNL traditionally necessitates a large nephrostomy sheath, and multiple access tracts are frequently needed to achieve complete stone clearance. These multiple access tracts may be associated with greater renal parenchymal injury.⁶

We used an 18F tract for mini-PCNL, instead of the 30F tract used for con-PCNL. Jackman and associates²⁰ described the mini-PCNL procedure as “mini-perc,” a PCNL achieved through a small sheath. This procedure was developed to reduce the risk of complications encountered with con-PCNL. In our study, the mini-PCNL had a low SFR, needed many rounds of ancillary treatment, and increased surgical time, despite the reduction in complications related to severe bleeding compared with con-PCNL. Mini-PCNL also had low therapeutic efficacy for the removal of large stones.¹⁶

Our newly developed hybrid technique, i.e., ECIRS using mini-PCNL in combination with retrograde fURS, however, resulted in few percutaneous tracts and a higher single-step SFR than that in other procedures. With this combination procedure, small stone fragments were easily washed out through the mini-PCNL tract with the help of retrograde irrigation. After most of the stone burden had been removed, we used fURS to search for residual stone fragments in locations that were inaccessible by the nephroscope, such as beside the PCNL tract insertion and in the calices. This increased the SFR. Simultaneous use of anterograde-retrograde devices increased the efficiency of fluid irrigation during stone removal and reduced the number of residual stones, compensating for the limitations of mini-PCNL.

Six (7.3%) patients in the con-PCNL group and one (1.7%) patient in the mini-ECIRS group needed blood transfusion; no patients in the mini-PCNL group needed blood transfusion. While this difference in need for transfusion among groups was not significant, patients in the con-PCNL group had a greater mean decrease in Hb level than those in the mini-ECIRS and mini-PCNL groups (P=0.011). This finding reflects severe bleeding during surgery caused by the large working sheath. It has been noted that “torquing” a rigid nephroscope against the pelvicaliceal system to reach an inaccessible calix is the most important cause of bleeding during PCNL.^21,22 The simultaneous use of the mini-tract and URS helped to reduce excessive movement of the PCNL tract, thereby reducing bleeding. Clavien grading scores showed significantly fewer postoperative complications in mini-ECIRS and mini-PCNL than in con-PCNL. We believe that the shorter duration of surgery, improved visibility during surgery because of irrigation via the ureteroscope and nephroscope, and less renal parenchymal bleeding were responsible for the lower complication rate. According to the PCNL Global Study conducted by the Clinical Research Office of the Endourological Society (CROES), the Clavien grading score was Grade I in 11.1%, Grade II in 5.3%, and Grade III in 2.3% of cases.²³ Our results for mini-ECIRS were also superior to those obtained in the CROES study (8.3% in Grade I, 1.7% in Grade II, and 0% in Grade III).

We performed mini-ECIRS with the patients maintained in the prone split-leg position. The Galdakao-modified supine Valdivia position may be a more familiar approach for simultaneous use of fURS and PCNL.^24

–28 The supine position has anesthesiologic advantages, including elimination of cardiovascular and respiratory problems.²⁶ Renal pelvis pressure is also lower when the patient is in the supine position, reducing the risk of fluid absorption.²⁷ Disadvantages of the supine position include constant collapse of the pyelocaliceal system and difficulties while performing upper-pole caliceal puncture. These problems necessitate longer tracts and reduce nephroscope mobility, particularly in obese patients. As a result, greater torque is needed to manipulate the nephroscope, increasing the risk of damage to the renal parenchyma and bleeding from the tract.²⁹

Urologists find the prone position the most convenient for performing a renal puncture in PCNL. The prone position provides a larger area for percutaneous renal access, allowing a wider space for instrument manipulation.^21,26 It is also associated with significantly shorter nephrostomy tract length and more numerous potential access sites, both of which may improve the ease and safety of PCNL.³⁰ In this study, all mini-ECIRS procedures were easily achieved with the patient in the prone split-leg position, without any anesthesiologic complications.

This study has certain limitations because of its retrospective design. First, the number of cases included was relatively small. Second, the three treatment methods were asynchronously adopted at different time intervals. Therefore, although we recommended that patients undergo the procedures based on the EAU or AUA guidelines (more than 2 cm stones), patient selection bias may still be present. Prospective studies are therefore needed to confirm the effectiveness of mini-ECIRS.

Conclusions

Mini-ECIRS performed with patients in the prone split-leg position is a safe, efficient, and versatile procedure for one-step complete resolution of large stone burdens. The simultaneous anteroretrograde approach allowed effective extraction of small stone fragments with bilateral irrigation. We believe that mini-ECRIS performed with patients in the prone split-leg position is an effective option for the management of renal stones, including staghorn calculi.

Footnotes

Acknowledgment

We would like to thank Ms. K. Ichikawa for her secretarial assistance, including data input and data analysis.

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

References

Preminger

, Tiselius

, Assimos

, et al. 2007 Guidelines for the management of ureteral calculi. Eur Urol, 2007; 52:1610–1631.

Netto

, Claro

, Lemos

, et al. Renal calculi in lower pole calices: What is the best method of treatment?. J Urol, 1991; 146:721–723.

Fuchs

, Miller

, Rassweiler

, Eisenberger

. Extracorporeal shockwave lithotripsy: One-year experience with the Dornier lithotripter. Eur Urol, 1985; 11:145–149.

Desai

, Ganpule

. Management of the staghorn calculus: Multiple-tract versus single-tract percutaneous nephrolithotomy. Curr Opin Urol, 2008; 18:220–223.

Desai

, Jain

, Ganpule

, et al. Developments in technique and technology: The effect on the results of percutaneous nephrolithotomy for staghorn calculi. BJU Int, 2009; 104:542–548.

El-Nahas

, Shokeir

, El-Assmy

, et al. Post-percutaneous nephrolithotomy extensive hemorrhage: A study of risk factors. J Urol, 2007; 177:576–579.

Mousavi-Bahar

, Mehrabi

, Moslemi

. Percutaneous nephrolithotomy complications in 671 consecutive patients: A single-center experience. Urol J, 2011; 8:271–276.

Michel

, Trojan

, Rassweiler

. Complications in percutaneous nephrolithotomy. Eur Urol, 2007; 51:899–906.

Tefekli

, Ali Karadag

, Tepeler

, et al. Classification of percutaneous nephrolithotomy complications using the modified Clavien grading system: Looking for a standard. Eur Urol, 2008; 53:184–190.

10.

Jackman

, Hedican

, Peters

, Docimo

. Percutaneous nephrolithotomy in infants and preschool age children: Experience with a new technique. Urology, 1998; 52:697–701.

11.

Lahme

, Bichler

, Strohmaier

, Götz

. Minimally invasive PCNL in patients with renal pelvic and calyceal stones. Eur Urol, 2001; 40:619–624.

12.

Mishra

, Sharma

, Garg

, et al. Prospective comparative study of miniperc and standard PNL for treatment of 1 to 2 cm size renal stone. BJU Int, 2011; 108:896–899.

13.

Knoll

, Wezel

, Michel

, et al. Do patients benefit from miniaturized tubeless percutaneous nephrolithotomy? A comparative prospective study. J Endourol, 2010; 24:1075–1079.

14.

, Gao

, Yang

, et al. Does a smaller tract in percutaneous nephrolithotomy contribute to less invasiveness? A prospective comparative study. Urology, 2010; 75:56–61.

15.

Zhong

, Zeng

, Wu

, et al. Minimally invasive percutaneous nephrolithotomy with multiple mini tracts in a single session in treating staghorn calculi. Urol Res, 2011; 39:117–122.

16.

Giusti

, Piccinelli

, Taverna

, et al. Miniperc?. No, thank you! Eur Urol, 2007; 51:810–815.

17.

Labate

, Modi

, Timoney

, et al. The percutaneous nephrolithotomy global study: Classification of complications. J Endourol, 2011; 25:1275–1280.

18.

Fernström

, Johansson

. Percutaneous pyelolithotomy. A new extraction technique. Scand J Urol Nephrol, 1976; 10:257–259.

19.

Skolarikos

, Alivizatos

, de la Rosette

. Percutaneous nephrolithotomy and its legacy. Eur Urol, 2005; 47:22–28.

20.

Jackman

, Docimo

, Cadeddu

, et al. The “mini-perc” technique: A less invasive alternative to percutaneous nephrolithotomy. World J Urol, 1998; 16:371–374.

21.

de la Rosette

, Tsakiris

, Ferrandino

, et al. Beyond prone position in percutaneous nephrolithotomy: A comprehensive review. Eur Urol, 2008; 54:1262–1269.

22.

Aron

, Yadav

, Goel

, et al. Multi-tract percutaneous nephrolithotomy for large complete staghorn calculi. Urol Int, 2005; 75:327–332.

23.

de la Rosette

, Assimos

, Desai

, 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.

24.

Scoffone

, Cracco

, Cossu

, et al. Endoscopic combined intrarenal surgery in Galdakao-modified supine Valdivia position: A new standard for percutaneous nephrolithotomy?. Eur Urol, 2008; 54:1393–1403.

25.

Valdivia Uría

, Valle Gerhold

, López López

, et al. Technique and complications of percutaneous nephroscopy: Experience with 557 patients in the supine position. J Urol, 1998; 160:1975–1978.

26.

Ibarluzea

, Scoffone

, Cracco

, et al. Supine Valdivia and modified lithotomy position for simultaneous antegrade and retrograde endourological access. BJU Int, 2007; 100:233–236.

27.

Daels

, González

, Freire

, et al. Percutaneous lithotripsy in Valdivia-Galdakao decubitus position: Our experience. J Endourol, 2009; 23:1615–1620.

28.

Kawahara

, Ito

, Yerao

, et al. Effectiveness of ureteroscopy-assisted retrograde nephrostomy (UARN) for percutaneous nephrolithotomy (PCNL). PLoS One., 2012; 7:e52149.

29.

Kumar

, Bach

, Kacchrilas

, et al. Supine percutaneous nephrolithotomy (PCNL): ‘In vogue’ but in which position?. BJU Int, 2012; 110:E1018–E1021.

30.

Duty

, Waingankar

, Okhunov

, 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.

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.26 MB