Miniperc and retrograde intrarenal surgery: When and how?

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Actas Urol Esp. 2015;xxx(xx):xxx---xxx

Actas Urológicas Españolas www.elsevier.es/actasuro

REVIEW ARTICLE

Miniperc and retrograde intrarenal surgery: When and how?夽 F. Ramón de Fata a , K. Hauner b , G. Andrés a , J.C. Angulo a,∗ , M. Straub b a b

Servicio de Urología, Hospital Universitario de Getafe, Universidad Europea de Madrid, Madrid, Spain Urologische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, Múnich, Alemania, Germany

Received 14 September 2014; accepted 17 September 2014

KEYWORDS Kidney stone; Retrograde intrarenal surgery; Minipercutaneous nephrolithotomy; Indications; Technique

Abstract Context: Extracorporeal shock wave lithotripsy (ESWL) and percutaneous nephrolithotomy (PCNL) are consolidated procedures for the treatment of kidney stones; however, their primary weak points are the lower efficacy of ESWL, especially for lower calyx stones, and the morbidity of PCNL resulting from the creation and dilation of the percutaneous trajectory. The increasing miniaturization of percutaneous surgery instrumentation and the development of retrograde intrarenal surgery (RIRS) are recent innovations. Acquisition of evidence: A structured nonsystematic review was conducted through a literature search of articles published between 1997 and 2013, using the terms kidney stones, miniperc, mini-PCNL, RIRS and flexible ureteroscopy in the PubMed, Google Scholar and Scopus databases. Summary of the evidence: RIRS requires greater surgical time, several procedures for voluminous stones and higher hospital costs, due in part to the relative fragility of the instruments. On the other hand, miniperc requires a longer hospital stay, an increased need for postoperative analgesia and a greater reduction in hemoglobin levels, although these do not translate into an increased rate of transfusions. Conclusions: The current treatment of kidney stones uses minimally invasive procedures such as miniperc and RIRS. The two procedures are equivalent in terms of efficacy (stone clearance) and are associated with minimal complications. Comparative prospective studies are necessary to determine the position of each of these techniques in the treatment of kidney stones. In our experience, the two techniques are complementary and should be part of the current urological therapeutic arsenal. © 2014 AEU. Published by Elsevier España, S.L.U. All rights reserved.

夽 Please cite this article as: Ramón de Fata F, Hauner K, Andrés G, Angulo JC, Straub M. Miniperc y Cirugía Retrógrada Intrarrenal: ¿cuándo y cómo? Actas Urol Esp. 2015. http://dx.doi.org/10.1016/j.acuro.2014.09.003 ∗ Corresponding author. E-mail address: [email protected] (J.C. Angulo).

2173-5786/© 2014 AEU. Published by Elsevier España, S.L.U. All rights reserved.

ACUROE-704; No. of Pages 9

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Litiasis renal; Cirugía retrógrada intrarrenal; Mini-nefrolitotomía percutánea; Indicaciones; Técnica

Miniperc y Cirugía Retrógrada Intrarrenal: ¿cuándo y cómo? Resumen Contexto: La Litotricia Extracorpórea por Ondas de Choque (LEOCH) y la Nefrolitotomía Percutánea (NLP) son procedimientos consolidados en el tratamiento de la litiasis renal, pero sus principales puntos débiles son la menor eficacia de la LEOCH, especialmente en litiasis de cáliz inferior, y la morbilidad de la NLP, derivada de la creación-dilatación del trayecto percutáneo. La creciente miniaturización del instrumental de cirugía percutánea, y el desarrollo de la cirugía retrógrada intrarrenal (CRIR) son innovaciones recientes. Adquisición de evidencia: Se ha llevado a cabo una revisión estructurada no sistemática, a través de una búsqueda bibliográfica de los artículos publicados entre 1997 y 2013, utilizando los términos litiasis renal, miniperc, mini-NLP, CRIR y ureteroscopia flexible en las bases de datos PubMed, Google Scholar y Scopus. Síntesis de evidencia: La CRIR consume mayor tiempo operatorio, precisa varios procedimientos en litiasis voluminosas e implica mayor coste hospitalario, derivado en parte de la relativa fragilidad del instrumental. Por otro lado, miniperc, precisa una estancia hospitalaria más prolongada, mayor necesidad de analgesia postoperatoria y mayor descenso de hemoglobina, aunque sin traducirse en una mayor tasa de transfusión. Conclusiones: El tratamiento contemporáneo de la litiasis renal emplea procedimientos mínimamente invasivos como miniperc y CRIR. Ambos son equivalentes en términos de eficacia (aclaramiento litiásico) y se asocian con mínimas complicaciones. Son necesarios estudios comparativos prospectivos que determinen la posición de cada una de estas técnicas en el tratamiento de la litiasis renal. En nuestra experiencia ambas resultan complementarias y deben formar parte del arsenal terapéutico actual urológico. © 2014 AEU. Publicado por Elsevier España, S.L.U. Todos los derechos reservados.

Minimally invasive treatment of kidney stones Goodwin et al.1 described in 1955 the percutaneous nephrostomy technique in patients with hydronephrosis and 21 years later Fernström and Johansson2 used this same approach to treat a kidney stone, after dilation guided by radioscopy of a previously established percutaneous route. Thus, percutaneous nephrolithotomy (PNL) was born. Alken et al.3 developed a system of dilation of the route by means of coaxial telescopic metal dilators and presented their findings in 1981, a year after Chaussy et al.4 , which revolutionized the treatment of kidney stones with extracorporeal shock wave lithotripsy (ESWL). Apparently, it was thought that a procedure as minimally invasive of extracorporeal fragmentation would replace PNL. However, the lower rate of removal of stones with ESWL, especially in lower calyx stones, the high rate of retreatment for stones over 1.5 cm, and the non-exemption of complications have led to the fact that both techniques coexist and complement each other in the treatment of kidney stones. In 1997 Helal et al.5 designed an alternative to PNL in pediatric patients using a 15Ch sheath and a 10Ch pediatric cystoscope. One year later, the implementation of this new form of PNL in children and adults6,7 was described, and the term ‘miniperc’ was established.7 Lower surgical trauma and lower bleeding due to miniaturization of the access involved reduction in the morbidity of the procedure.7 In 2001, the first specific 12Ch mini-nephroscope was presented to perform this minimally invasive PNL technique

(mini-PNL or miniperc)8 (Fig. 1). The instrument consisted of two metal sheaths (15 and 18Ch), a system of continuous low pressure irrigation, and a working channel (6Ch) for gallstone removal and fragmentation. Initially, it was indicated in kidney stones smaller than 2 cm, pediatric population, and as an auxiliary procedure to PNL in large and complex stones.8 Currently, thanks to the acquired experience and its lower morbidity, some groups have adopted this approach sistematically regardless of the size of the stone, managing to completely replace standard PNL. For decades, there have been significant improvements in endourological instruments, both in the design of flexible ureteroscopes and in laser technology and the accessory instruments to perform retrograde intrarenal surgery (RIRS). Thanks to these advances, the totally endoscopic MiniPCNL

PCNL

1 cm

PALABRAS CLAVE

Figure 1 Comparative diagram between the diameter of percutaneous mini-nephrolithotomy (miniperc or mini-PCNL) and conventional percutaneous nephrolithotomy (PCNL). This miniaturization leads to reduced morbidity.

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Mini-PCNL vs. RIRS Table 1

Indications of retrograde intrarenal surgery (RIRS).

1. 1---3 cm pielo-calyceal stones 2. Stones >3 cm (need for 2 or more procedures) 3. Failure os ESWL (especially in lower calyceal group) 4. Failure of PNL 5. Radiolucent stones (failure of chemolysis) 6. Bleeding diathesis 7. Morbid obesity 8. Musculoskeletal deformities 9. Severe associated comorbidity 10. Reno-ureteral abnormalities (horseshoe kidney, pelvic kidney,. . .) 11. Endoscopic Combined Intrarenal Surgery (ECIRS) 12. Bilateral stones

management of kidney stones has also consolidated gaining ground to ESWL and competing with PNL as well. Finally, in an effort to miniaturize the PNL instruments intended to further reduce its morbidity and compare in terms of security to RIRS, PNL systems of even smaller caliber have been developed without dilation; although its role in the therapeutic arsenal of kidney stones is yet to be defined.9---11

RIRS: indications, instruments, and surgical technique Initially, RIRS indications were limited to the failure of ESWL, especially in lower stones of the lower calyceal group and size ≤1.5 cm. Currently, the indications are less restrictive, being considered first-line treatment along with ESWL in kidney stones smaller than 2 cm, especially in lower calyx, and an alternative to PNL in stones ≥2 cm (European Association of Urology Clinical Guidelines).12 Due to the limited morbidity of RIRS, the current trend is to expand the range of possibilities of this surgery to multiple, complex stones and even over 3 cm, sometimes using more than one procedure if necessary13---16 (Table 1). The basic equipment necessary to carry out the procedure includes optical or digital fiber flexible ureterorenoscope, Ho: YAG laser with a wavelength of 2100 nm, diverse power (20---30---60---100 W), laser fibers of different diameters (200---273---365 ␮m), endoscopic camera, source and endourology power line (2.3 mm), monitor, fluoroscopy generator, irrigation pump and accessory fungibile instruments (Fig. 2). Regarding the irrigation pump, gravity-fed irrigation and complementary irrigation manual systems can also be used in cases of poor visibility. With regard to the accessory instruments, we require: guidewires, ureteral access sheath, nitinol baskets, and devices that seal the working channel for introducing instruments without loss of flow (port seal) and maintaining visibility fixing also the laser fiber to avoid damage to the endoscope. Some models of these devices have double lumen which allows for the simultaneous use of basket and laser. The optimum guidewire has a hydrophilic tip, with hard polytetrafluoroethylene (PTFE) shell (0.035---0.038 ;

3 145---180 cm). It is used as a safety guidewire in case of complications, it makes it possible to straighten the ureter and thus exceed stenoses and tortuous areas, and it is also used as a working guide to enter the ureteral access sheath. The ureteral access sheath is used to decrease intrarenal pressure, especially when irrigation pump is used. It also allows for the input and output of the endoscope repeatedly in patients with large stone burden, thus decreasing the surgical time, it protects the ureter from injuries, increases the durability of the flexible ureteroscope, and prevents bladder distention. Its size is variable (primarily 11/13Ch or 12/14Ch) and the length 35---36 cm for women and 45---46 cm for men. They must always be entered under radiological control. However, not everything is advantageous. Among the problems that can be associated with its use, we can point out the fact that sometimes the ureteral blood flow decreases and may cause ischemia, the radiation exposure time also increases and it sometimes requires previous placement of double-J catheter. This fact occurs in approximately 3.8---14% of cases.15,16 This maneuver decreases the incidence of ureteral injuries and facilitates insertion of the sheath. But it should not be performed routinely, as it increases the morbidity inherent to the double-J and is not cost-effective, due to the need to perform two procedures. Blunt nitinol baskets allow for intrarenal mobilization of the lithiasis without traumatizing the mucosa and extraction of significant fragments through the sheath. Any basket ≤3Ch and 120 cm of length can be used. It is advisable to carry out sterile urine culture prior to surgery. In patients with persistent bacteriuria, specific antibiotic therapy should be given. Under general anesthesia, the patient is placed in lithotomy position and the process begins by performing a rigid ureteroscopy (6.5/8.5Ch mini-ureteroscope, Richard Wolf Gmbh, Knittlingen, Germany), after passage of a 0.035’’ hydrophilic guidewire to the renal cavities (Sensor, Boston Scientific, Natick. MA, USA) in order to dilate the orifice and the intramural ureter under vision, to facilitate the insertion of the ureteral access sheath. In this way, we can also rule out the presence of associated ureteral stones. The tutor of the ureteral access sheath is an excellent tool for dilation, in cases where the ureter provides reasonable resistance to the passage of the sheath. Generally, two hydrophilic guidewires are used, a working one and a security one, with the exception of the Re-Trace sheath (Coloplast, Humlebaek, Denmark), which makes it possible to use the same guidewire with both purposes, because when removing the tutor of the access sheath, it is housed in parallel. With flexible ureterorenoscope (6/9.9Ch Cobra with 3.3Ch dual-channel or 6/8.8Ch Viper with 3.6Ch unique working channel and 270◦ active deflection, Richard Wolf GmbH, Knittlingen, Germany), the pelvis and renal cavities are orderly inspected to identify the stones. Single-channel flexible ureterorenoscope provides better visibility thanks to its greater flow, but by introducing through its working channel a 200 ␮m laser fiber its flow is drastically reduced (from 57 to 22 ml/min). By contrast, in the same situation the flexible dual channel instruments remain unchanged flow around 47 ml/min.

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Figure 2 Retrograde intrarenal surgery: (A) Surgical field; (B) Port Seal device (Boston Scientific, USA) that seals the working channel of the Cobra ureteroscope (Richard Wolf GmbH, Germany) to be able to insert material without loss of flow; (C) Escape basket (Boston Scientific, USA) that allows for capture of the stone and fragmentation with Flexiva TracTip atraumatic laser fiber (Boston Scientific, USA), which allows for use with active deflection.

The fragmentation of the stones is carried out with laser Ho: YAG (Megapulse Desktop 30 W, 2100 nm, Richard Wolf GmbH, Knittlingen, Germany) with 200---272 ␮m fibers. 365 ␮m fibers may also be used, but they limit the deflection of the ureterorenoscope. With low energy (0.6 J) and high frequency (15---20 Hz), the stone is sprayed, for in a second time fragmenting with high energy (1---2 J) and low frequency (4---5 Hz); until a size that allows for its extraction through the sheath with a nitinol basket is achieved. The mobilization of the stone located in the calyceal group lower to a more comfortable location, usually the upper calyx, using a nitinol basket makes it possible to work without forced deflection, which increases the durability of the instruments. One of the most common causes of disablement of the ureterorenoscope is the injury of the working channel by introducing any tool. Therefore, facing impacted lower calyx or large stones preventing mobilization to a safe working area, it must be fragmented in situ using the smaller diameter laser fiber (200 ␮m). The atraumatic laser fiber of 200 ␮m (Flexiva TracTip, Boston Scientific, Natick. MA, USA) allows for maximum active deflection. Although there is no unanimous consensus on the exact definition of the lithiasic clearance rate, it is considered that those fragments below 2---4 mm can be eliminated spontaneously.15---18 When the procedure finishes, the absence of fragments is checked under direct and radiological vision and the sheath is removed inspecting the ureteral mucosa to rule out the presence of undetected lesions.19 It ends by placing double-J, which is removed 7 days later on an outpatient basis. In the event of ureteral injury, depending on the length and severity, the catheter should remain 3---6 weeks. It is recommended that urinary tract radiography is performed in the early 24 h to assess the immediate result of the surgery.

Miniperc: indications, preparation and surgical technique PNL is the treatment of choice for renal stones over 2 cm in diameter; while ESWL and RIRS are the recommended procedures in renal stones of smaller size, unless it is located in the lower calyceal group.12 In this topography, the percutaneous approach and RIRS show improved removal rate

because the ESWL efficiency is limited. Actually, the clearance rate with ESWL depends on the lithiasic characteristics (size, location, and nature of the stone) and the anatomical configuration of the excretory system. Several sessions are often needed, prolonging the therapeutic process. All these variables make ESWL a procedure with unpredictable results, so in the last decade endourological procedures have been developed competing in morbidity and improving the rate of re-treatment. PNL is a consolidated procedure with better success rate and shorter treatment time, although sometimes it causes bleeding secondary to the creation of the access.20 Mini-PNL was developed in the treatment of the renal stones in adults to decrease the therapeutic step between ESWL and PNL. Its effectiveness is equivalent to conventional percutaneous surgery but it is safer, thanks mainly to the miniaturization of the instruments.21 However, there are differing views as to the actual advantages of miniperc versus conventional PNL, this point being object of debate.22 There is no unanimous agreement as to the exact size that is used for the miniperc procedure, but generally the 11---20 Fr material is accepted, although 15 and 18Fr are the most used gauges.8,23---25 Currently, miniperc coexists with RIRS and ESWL in the treatment of stones smaller than 2 cm, but it has advantages over them in difficult anatomical variants and locations of difficult retrograde access (calyceal diverticulum, excluding hydrocalyx, long and narrow infundibulum). On the other hand, its main indication is the treatment of calyceal and pyelic stones greater than 2 cm, although we tend to reserve classical PNL (24---30 F) in large and complex stones (Table 2). Preoperative requirements include the study of the location, size, and relation of the stone with pyelocalyceal anatomy to plan the access pathway. Traditionally, intravenous urography has been the imaging method of choice, but in recent years it has been replaced by CT with reconstruction of the urinary tract. Conducting intraoperative ultrasound allows for puncture of the chosen calyx, reducing the rate of radiation to the patient and the surgical team and identifies anatomical abnormalities, such as colon interposition in the puncture pathway. Sterile urine culture is also required. Bacteriuria must be treated with specific antibiotics 5---7 days before the procedure. In patients with low stone burden, sterile preoperative

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Table 2 Indications for minimally invasive percutaneous nephrolithotomy (Mini-PNL).

Table 3 Indications of percutaneous approach without nephrostomy (Tubeless).

1. 1---3 cm diameter pyelic stones • Primary treatment • Alternative to RIRS 2. Lower calyceal group stones • Primary treatment • Unfavorable anatomy for ESWL • RIRS failure 3. Stones in calyceal diverticulum or excluded hydrocalyx 4. Pediatric population 5. Ancillary procedure to conventional PNL in complex stones

• Surgical time ≤2 h • Absence of significant stone fragments, requiring a second procedure • Single percutaneous access • Healthy contralateral kidney • Absence of significant intraoperative bleeding • No perforation of the excretory pathway • Absence of other intraoperative complications (injury to adjacent organs)

urine culture, and without dilation of the excretory tract, intravenous antibiotic prophylaxis is sufficient. By contrast, patients with large stones and/or pyelocalyceal dilation receive preoperative antibiotic treatment one week before the procedure despite having negative urine culture.12,26 Uncorrected alterations in coagulation and anticoagulant drugs intake are contraindications for percutaneous surgery. The procedure is usually performed under general anesthesia. The patient’s position is debated, although the supine position27 has clear advantages such as reduced surgical time not having to change the patient’s position, benefits from the anesthetic point of view with better access to the air pathway without detriment to ventilation capacity, possibility of practising combined anterograde and retrograde simultaneous access (combined endoscopic intrarenal surgery or CEIRC),28 visual control of the puncture, spontaneous drainage of stone fragments by gravity due to the decline disposal of the Amplatz sheath, and less risk of colon puncture. Despite all these advantages, and the fact that the supine position entails a similar rate of efficacy and complications,20,27,28 the prone position is more widespread in the endourologic community.29 Possibly, this is due to the fact that historically the prone position has been more used, technically easier, and it also allows for easier access to upper calyxes (Fig. 3). A straight ureteral or mono-J (7---8Ch) catheter is inserted in the collecting system for filling the tract with contrast or methylene blue, reducing intrarenal pressure during the procedure, and preventing stone fragments from migrating to the ureter. Under radiological and/or ultrasound control, puncture of the renal papilla of the desired calyx with 18G Chiba needle was performed to introduce Lünderquist guidewire that prevents kinking during dilation. Then, a minimal skin incision is performed with a n◦ 11 scalpel, to proceed to the simplified dilation of the percutaneous tract with no coaxial 12 and 15CH metal dilators (Fig. 4). The sheath of the mini-nephroscope (15 or 18Ch) is coaxially inserted on the appropriate dilator. The 12Ch mininephroscope has a length of 205 mm, a viewing angle of 12◦ , 50,000 pixels of optical resolution, 6Ch working channel and it makes it possible to work with low intrarenal pressure due to its continuous irrigation system (Richard Wolf Gmbh, Knittlingen, Germany). Lithiasic fragmentation is usually performed with 60---100 W Ho: YAG laser and 550 ␮m laser

fibers for working with speed, efficiency and safety. Other authors use pneumatic ballistic lithotripsy with a similar result8 ; however, the ultrasonic lithotriptor, widely used in conventional PNL, is used less, since the larger gauge of its probe reduces visibility. The hydrodynamic characteristics of the continuous irrigation system allow for extraction by turbulent flow that absorbs the fragments. The miniperc instruments also allow for the use of reusable metallic clamps and disposable nitinol baskets for the removal of impacted fragments, adhered to the mucosa or out of reach of the hydrosuction mechanism. When the fragments cannot be reached with the nephroscope, the 18Ch metal sheath makes it possible to insert a flexible ureteroscope or create a new percutaneous access using the 15Ch sheath. After the procedure, if there are no significant fragments (<2---4 mm), and in the absence of complications, nephrostomy placement (tubeless technique) can be avoided (Table 3). In these cases, if there is no significant hematuria, ureteral catheter is used, which is removed together with the Foley probe in 48 h or anterograde double-J catheter if the chosen position is prone. In supine position, the double-J can be introduced both in an anterograde and retrograde way, being removed on an outpatient basis in a week. Postoperative evaluation should include monitoring of vital signs, blood test, and plain urinary tract radiography in the first 24 h. In very selected cases with radiotranslucent stones, postoperative evaluation will be performed with abdominal ultrasound or CT scan.

CRIR y miniperc: convivencia y complementariedad The morbidity associated with standard PNL has favored the miniaturization of the percutaneous instruments to treat intermediate-sized pyelocalyceal stones with similar efficacy and improved safety. Obviously, a smaller section of the instrument may involve less invasiveness and renal parenchymal damage, less blood loss and less need for transfusion of blood products.20,24,29,30 Also it entails shorter hospital stay, lower rate of radiation to the patient and the surgical team, less postoperative pain, and less need for painkillers by avoiding the routine use of nephrostomy catheter.21,24,29 However, not everything is advantageous. The lower section of the instruments involves some limitation to treat

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Figure 3

Different positions to carry out percutaneous mini-nephrolithotomy (miniperc): (A) Prone; (B) Supine.

patients with large stone burden, requiring longer operating time to perform a finer fragmentation and the subsequent removal of the fragments.21 This concern made that initially miniperc indication was limited to stones <2 cm.8,21,31 Even for this same reason, some authors advised against its use in favor of the classical technique.22 But actually the groups that routinely use it describe that the hydrodynamic characteristics of the continuous irrigation system at low pressure favor extraction of the fragments by means of a washing effect and suction in the nephroscope sheath. Thus, the use of clamps and baskets, which consume operation time, is reduced. Furthermore, this low pressure system reduces the possibility of infectious complications by pyelo-venous reflux.24 The development of powerful laser fragmentation instruments of last generation, the refinement of the technique, and the experience gained by some groups has expanded the range of indications, completely replacing conventional PNL and competing with other emerging minimally invasive endourological procedures such as RIRS or CEIRC.24,28,32 Miniperc really not only can replace PNL, but it can also even expand its indications. In fact, the indications of miniperc and RIRS partly overlap and it is difficult to draw a clear separation. A prospective comparative study in stones of 1---2 cm in diameter concluded that both procedures are effective and safe.23 The rate of immediate elimination was higher with miniperc, but very similar with both procedures

after a month of follow-up. RIRS was associated with lower hemoglobin decrease, but without transfusion in any group. Postoperative pain and analgesic requirement was significantly lower in RIRS, but in this group the surgical time used was slightly higher.23 Another retrospective study compares both approaches in renal lithiasis ≤2 cm with similar results, but miniperc has slightly higher efficiency without reaching statistical significance, reduced operating time, and longer hospital stay.31 Using a single procedure, the success rate is higher for mini-PNL.33 In general, most of the series have an average hospital stay of 1---2 days for flexible ureteroscopy and 2---4 days, with some exceptions, for miniperc.16,23,24 But not only the characteristics of the stone matter, but the characteristics of the patient must also be taken into account. It is more appropriate to raise RIRS than percutaneous surgery in patients with bleeding diathesis, morbid obesity, musculoskeletal deformities, and impaired renal anatomy such as horseshoe kidney or renal ectopia. By contrast, anatomical variations of the excretory system such as long, narrow infundibula and with closed uretero-pielocalyceal angle make use of percutaneous surgery as first choice preferable. Tables 4 and 5 show the major series published with Miniperc and RIRS and describe the efficacy and safety of both techniques. There is no doubt that one of the main limitations of RIRS is the cost, resulting from the use of accessory equipment (guides, sheaths, and baskets) and the

Figure 4 Percutaneus mini-nephrolithotomy (miniperc): (A) Surgical field; (B) mini-nephroscope with dilators (Richard Wolf GmbH, Germany).

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Main series published with minimally invasive percutaneous nephrolithotomy (Mini-PNL).

Author 5

Helal et al. Jackman et al.6 Jackman et al.7 Monga et al.35 Lahme et al.8 Sung et al.36 Giusti et al.22 Liao-Yuan Li et al.30 Knoll et al.33 Abdelhafez et al.24

Year

Fr

N◦ cases

Size (mm)

SFR (%)

Complications (%)

1997 1998 1998 2000 2001 2006 2007 2010 2011 2013

15 11 13 20 15 14 13 14---18 18 18

1 (child) 7 (children) 9 21 19 72 40 98 25 172

17 12 15 28 24 34.2 28 28.6 19 25.2

100 85 89 90 100 (1.7)a 80.6 77.5 83.9 96 83.8

0 0 0 4.7 5.3 18.1 --14.1 16 23

Fr, French; mm, millimeters; SFR, stone-free rate. a Average treatments.

Table 5

Principales series publicadas de Cirugía Retrógrada Intrarrenal (CRIR).

Author 37

Grasso et al. Breda et al.14 Hyams et al.38 Al-Qahtani et al.17 Cohen et al.39 Takazawa et al.40 Resorlu et al.41 Miernik et al.42 Bagley et al.43 Palmero et al.15 Caskurlu et al.44 Cepeda et al.16

Year

N◦

Size (mm)

SFR (%)

Procedures (%)

Complications (%)

1998 2009 2010 2012 2012 2012 2012 2012 2012 2013 2013 2014

51 51 120 120 145 65 207 153 417 106 207 150

24.9 6.6 24 26 29 21 16 10.5 >20 24.6 18 19

93 64.7 83 58.5 87 80 86 96.7 68.2 73.6 77.5 91.6

1.3 1.4 1.2 1.6 1.6 1.3 1.1 --1.2---2.3 1.7 1.1 1.06

3 13.6 6 12.5 2 4.6 7.7 9.1 10.3 6.7 15.3 14.6

Fr, French; mm, millimeters; SFR, stone-free rate; *average tratments: syst rev: systematic review.

durability of the flexible endoscope. This factor depends on the number of procedures and a half-life of the flexible ureteroscope has been calculated in approximately 50---60 cases; although this number can be higher avoiding working in circumstances that decrease the durability, such as the in situ treatment of lower calyceal stones.34 Fortunately, the new generation ureterorenoscopes offer improved deflection mechanism and the working channel is more resistant than its predecessors. On the other hand, miniperc involves lower cost due to the greater strength and durability of endoscopic instruments and the reduced need for consumables.

analgesia, and greater decrease in hemoglobin, but it does not translate into a higher rate of transfusion. Prospective comparative studies must be carried out with large series and in stones of different degree of complexity to accurately determine the position of each of these techniques in minimally invasive treatment of kidney stones.

Conclusions

The authors thank Mr. Stefan Gillé and Mr. Juergen Steinbeck (Richard Wolf GmbH, Knittlingen, Germany) for their continued support and the provision of instruments.

Miniperc and RIRS represent two treatment modalities equally effective and safe for pyelocalyceal stones of intermediate size. The growing effort to reduce the morbidity of standard PNL has increased indications of both procedures. RIRS consumes more operating time, requires several procedures in bulky stones and implies higher hospital cost, due to increased fragility of the instruments and the need for accessory equipment. On the other hand, miniperc involves slightly longer hospital stay, greater need for postoperative

Conflict of interest The authors declare that they have no conflict of interest.

Acknowledgements

References 1. Goodwin WE, Casey WC, Woolf W. Percutaneous trocar (needle) nephrostomy in hydronephrosis. J Am Med Assoc. 1955;157:891---4. 2. Fernström I, Johansson B. Percutaneous pyelolithotomy: a new extraction technique. Scand J Urol Nephrol. 1976;10:257.

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