|Year : 2020 | Volume
| Issue : 3 | Page : 301-305
Microperc versus miniperc for the management of medium-sized renal stones: a comparative two-center clinical study
Amr A Gaber1, Medhat Abdallah1, Hassan Abolella1, Esam Othman1, Bianchi Giampaolo2, Michael Truss3
1 Department of Urology, Assiut University Hospital, Assiut, Egypt
2 Department of Urology, University of Modena and Reggio Emilia, Modena, Italy
3 Department of Urology, Dortmund Teaching Hospital, Dortmund, Germany
|Date of Submission||09-Jan-2020|
|Date of Decision||21-Jan-2020|
|Date of Acceptance||24-Jan-2020|
|Date of Web Publication||10-Aug-2020|
Amr A Gaber
Department of Urology, Urology and Nephrology Hospital, Assiut University, Assiut 71515
Source of Support: None, Conflict of Interest: None
To date, there is very little evidence directly comparing the outcomes between Mini-percutaneous nephrolithotomy and Micro-percutaneous nephrolithotomy. Because of this evidence gap, we wanted to compare miniperc and microperc with an ultimate purpose to determine which modality is preferred for different stone characteristics. Our hope is that these findings may help guide which technique is most suitable for a given renal stone burden.
Patients and methods
This is a retrospective collaborative multi-institutional study between Dortmund Teaching Hospital (Germany) and Modena University Hospital (Italy) in which we compared two matched groups of patients. The first group (32 patients) underwent miniperc for medium-sized renal stones in Dortmund, and the second group (19 patients) underwent microperc in Modena. Both groups were matched according to age, sex, BMI, and maximum stone diameter according to preoperative plain KUB films.
The primary stone-free rates in the miniperc and microperc groups were similar (93.8 vs. 84.2%, P = 0.262). Mean operative time for miniperc was significantly shorter than that of microperc (45.6 ± 18.9 vs. 68.7 ± 35.2 min, P = 0.004). The overall complication rate was 11.7%, with no significant difference between the two groups (12.5% for miniperc vs. 10.5% for microperc, P = 0.604). Mean hospital stay in miniperc was significantly longer than that of microperc (4.7 ± 1.6 vs. 3 ± 1.5 days,P < 0.001).
Our current data show that microperc is emerging as an effective and safe treatment option for intermediate-sized kidney stones, with outcomes comparable even to miniperc, which is already a well-established treatment with high safety profile in experienced hands.
Keywords: Micro-percutaneous nephrolithotomy, Mini-percutaneous nephrolithotomy, nephrolithiasis, percutaneous nephrolithotomy, renal stones
|How to cite this article:|
Gaber AA, Abdallah M, Abolella H, Othman E, Giampaolo B, Truss M. Microperc versus miniperc for the management of medium-sized renal stones: a comparative two-center clinical study. J Curr Med Res Pract 2020;5:301-5
|How to cite this URL:|
Gaber AA, Abdallah M, Abolella H, Othman E, Giampaolo B, Truss M. Microperc versus miniperc for the management of medium-sized renal stones: a comparative two-center clinical study. J Curr Med Res Pract [serial online] 2020 [cited 2020 Sep 25];5:301-5. Available from: http://www.jcmrp.eg.net/text.asp?2020/5/3/301/291776
| Introduction|| |
Extracorporeal shockwave lithotripsy (ESWL), ureteroscopic retrograde intrarenal surgery (RIRS), and percutaneous nephrolithotomy (PCNL) may all be used to treat small kidney stones . The urological community has attempted to define the specific indications for these different minimally invasive and endourological techniques, but with stones between 10 and 20 mm in size, the preferred approach remains controversial, with all techniques demonstrating reasonable success ,. It has been suggested that tract size reduction in PCNL procedures could decrease bleeding risk and other complications .
With this aim, advances in PCNL technology have led to miniaturization of the instruments. To date, many reports exist describing PCNL through tracts smaller than 30 Fr ,. Micro-PCNL or microperc (5–8 Fr) and Mini-PCNL or miniperc (12–18 Fr) are two minimally invasive percutaneous techniques that have demonstrated feasibility and efficacy with small renal stones [6–9]. As reported by Ganpule et al. , Micro-PCNL and Ultramini-PCNL may be suitable for stones less than 1.5 cm, but they have never been directly compared. Recently, Micro-PCNL has demonstrated acceptable stone clearance and complication rates in small-sized and intermediate-sized stones when compared with RIRS ,.
To date, there is very little evidence directly comparing the outcomes between Mini-PCNL and Micro-PCNL. Because of this evidence gap, we wanted to compare microperc and miniperc with an ultimate purpose to determine which modality is preferred for different stone characteristics. Our hope is that these findings may help guide which technique is most suitable for a given renal stone burden.
| Patients and Methods|| |
Upon approval of the Institutional Ethics and Research Committee, this study was conducted as a retrospective collaborative multi-institutional study between Dortmund Teaching Hospital (Germany) and Modena University Hospital (Italy). The investigators explained the steps and value of the research to all eligible participants and obtained an informed consent from all patients. We compared two matched groups of patients: the first group (32 patients) underwent miniperc for renal stones in Dortmund Teaching Hospital, and the second group (19 patients) underwent microperc in Modena University Hospital. Both groups were matched according to age, sex, BMI, and maximum stone diameter according to preoperative plain KUB films. Patients' demographics and preoperative variables are detailed in [Table 1]. Our inclusion criteria were (a) stone size between 1.5 and 3 cm, (b) stone size less than 1.5 cm if ESWL failed to clear the stone as a primary treatment, and (c) pelvicalyceal system not favorable for stone clearance after ESWL as in case of lower calyceal stones. Exclusion criteria of the study were (a) pregnancy, (b) uncorrected coagulopathy, and (c) an active untreated urinary tract infection.
|Table 1: Stone criteria and patients demographics of Mini-percutaneous nephrolithotomy and micro-percutaneous nephrolithotomy groups|
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All miniperc cases took place under general intubational anesthesia using a 12-Fr nephroscope (Karl Storz Miniatur Nephroskop, Tuttlingen, Germany). In this procedure, the patient was placed in the lithotomy position, and a 5-Fr open-tip ureteral catheter was placed on the side ipsilateral to the stone, and a retrograde pyelogram was obtained. The patient was then placed prone with all pressure points padded.
The initial percutaneous puncture performed by the urologist was done into the stone carrying calyx or the most appropriate posterior calyx leading to the stone under both sonographic and fluoroscopic guidance. Single-step dilatation was done over a stiff guide wire using a 16-Fr telescopic metal dilator. Then a 16.5-Fr Amplatz sheath was introduced into the pelvicalyeal system over the metal dilator. Stone disintegration took place using the pneumatic LithoClast. Retrieval of stone fragments occurred mainly via suction and to a lesser extent by stone graspers. Intraoperative stone clearance was endoscopically and fluoroscopically assessed. A 16-Fr nephrostomy tube was placed in all cases at the end of the procedure.
The procedure was performed under general anesthesia. A ureteral occlusion balloon catheter was placed with the patient in the lithotomy position. Puncture of the renal calyx was carried out in the prone position. In all procedures, the three-part 4.8-Fr diameter 'all-seeing' needle (Polydiagnost, Pfaffenhofen, Germany) was used, and 8- and 10-Fr sheaths were used as necessary to facilitate navigation within the collecting system, as movement through the 4.8-Fr sheath is limited because of its poor resistance to bending. This was most problematic, and hence access tract sheaths were more commonly employed when the angle of the puncture, and so the axis of the needle, was not directly aligned with the long axis of the calyx–stone tract, which depended on the position of the stone in relation to the anatomy of the renal collecting system. Ultrasound and fluoroscopic guidance were used during calyceal puncture. In addition, puncture precision was enhanced with the use of a high-resolution, 0.9-mm diameter micro-optical probe specifically designed for insertion into the access needle during percutaneous tract creation. Lithotripsy of the stone was performed with a 200-μm fiber and Holmium: YAG laser Versapulse P20 (Lumenis, Santa Clara, California, USA). A three-way adapter was fitted onto the back end of the puncture needle to which irrigation was connected and the laser fiber was introduced. Lithotripsy was started with high-frequency (20 Hz) and low-energy (0.4 J) settings to maximize stone dusting and minimize stone movements, whereas the irrigation pump was used to flush out the stone dust and aid with clear visualization.
All patients were examined with plain radiograph and abdominal ultrasound on the first postoperative day. Non-contrast computed tomography was used in only a few doubtful cases where radiograph and ultrasound imaging were inconclusive. Hemoglobin level and serum creatinine were monitored preoperatively and postoperatively. The data were recorded for the following clinical parameters: operative time (the time from puncture to closure of the tract), length of hospital stay, stone-free rate (absence of any detectable stone upon nephroscopy at the end of the procedure and on postoperative radiograph and ultrasound control), and complications (any adverse event within 30 days of the procedure). Postoperative complications were assessed using the modified Clavien–Dindo classification .
Asymptomatic fragments less than 4 mm were considered clinically insignificant residual fragments. Follow-up of patients from both groups consists of renal ultrasound and plain KUB film at one month postoperatively.
Clinical data and outcome measures of the two groups were compared using SPSS, version 19 (SPSS Inc., Chicago, IL, USA). Student's t-test was applied for continuous variables, and χ2 test or Fisher exact test for nominal variables. A P value less than 0.05 was considered statistically significant.
| Results|| |
In total, we identified 51 cases fulfilling the inclusion criteria who underwent percutaneous stone extraction procedures for renal stones. A total of 32 cases (group 1) were treated with miniperc and 19 cases (group 2) with microperc. [Table 1] shows the demographic and preoperative characteristics for both groups, confirming matching according to age, sex, laterality, BMI, and stone size.
Mean operative time for group 1 was significantly shorter than that of group 2 (45.6 ± 18.9 vs. 68.7 ± 35.2 min, P = 0.004).
In group 1, 30 (93.8%) patients were rendered stone free from a single session, whereas 16 (84.2%) patients became stone free in group 2. There was no significant difference between the two groups in terms of stone-free rate [Table 2].
|Table 2: Comparison of operative and postoperative outcomes between mini-percutaneous nephrolithotomy and micro-percutaneous nephrolithotomy|
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The mean hemoglobin drop was 0.7 ± 0.6 g/dl, with no significant difference between both groups [Table 2]. No single case required blood transfusion or angioembolization.
We experienced only six (11.7%) complications overall. There was no significant difference between group 1 (12.5%) and group 2 (10.5%) (P = 0.604). Three complications were modified Clavien grade I, two were grade II, and one was grade IIIB [Table 3]. Mean hospital stay for group 1 (4.7 ± 1.6 days) was longer than that of group 2 (3 ± 1.5 days) (P < 0.001).
| Discussion|| |
Nephrolithiasis is one of the most common problems in the urological practice, which comprises about one-third of the surgical workload of an active urologic department . First described in 1976 by Fernstrom and Johansson , PCNL rapidly became the gold standard in the management of large renal stones. During the past 20 years, PCNL has undergone significant evolution regarding the miniaturization of instrumentation and access tract size . This has been done to such an extent, then one must ask how small is too small and do we actually need to go any smaller?
Much of the morbidity of PCNL is attributed to access formation and tract size in the form of blood loss, postoperative pain, and urine extravasation and leakage [16–19]. To limit the occurrence of such complications, various minimally invasive PCNL techniques have been developed, namely miniperc, ultraminiperc, and microperc.
Since its introduction in 1997, miniperc has been widely and regularly used for treatment of intermediate-sized and large-sized renal stones with high stone-free rates and reduced morbidity in relation to conventional PCNL ,,. Miniperc is a two-step PCNL, which is preferred by many urologists, where a single-step dilatation takes place instead of gradual dilatation in conventional PCNL, which decreases the shear effect on the renal parenchyma, which in turn minimizes the intraoperative bleeding and the overall morbidity .
In continued efforts to decrease the tract size, even further than that used during miniperc, microperc was developed, and also with the goal of minimizing PCNL morbidity such as postoperative pain and length of hospital stay. In comparison with miniperc, microperc is a single-step PCNL using the all-seeing needle to access into the renal collecting system without additional tract dilation. The small tract size and the avoidance of tract dilation in microperc are believed to limit the potential renal injury and minimize the bleeding complications. Another advantage of the microperc as described is the routine lack of postoperative nephrostomy, which has been shown to improve patient's comfort ,.
ESWL is a widely used treatment option for renal stones with variable stone clearance rates depending on stone and patient factors ,. Retrieval of the stone and its fragments is not possible in ESWL, a fact which is similar to microperc; however, the latter is carried out under vision aiming at disintegrating the stone into dust regardless of its hardness, which is then easily washed out, but ESWL results in small fragments where active removal of the stone is not accessible especially in cases of stones located in the unfavorable lower calyx . In addition, ESWL often requires repeated treatment sessions and therefore time and compliance in order to achieve stone clearance. In a large number of patients following ESWL treatment, residual fragments remain within the kidney and are believed to lead to recurrent stone formation .
RIRS is another treatment option that is also minimally invasive and uses natural orifices. Palmero et al.  reported a stone-free rate with RIRS in a series of 106 patients with moderate-sized stones (≥2 cm) to be 79.4% with a single treatment and 94.1% with retreatment, with overall complication rate of 6.7%. In another series of 70 patients, Singh et al.  reported a primary stone-free rate, with RIRS of 85%. Traxer and Thomas  reported 46.5% ureteral wall injury rate in a series that contained 359 patients, who underwent RIRS using ureteral access sheath, which adds more doubt to the safety of the maneuver. There are some limitations to RIRS in the management of lower calyceal stones secondary to an acute infundibulopelvic angle which can hamper stone retrieval by flexible ureteroscopes ,. Other drawbacks of RIRS include high costs and limited life expectancy and durability of the instruments .
The objective of this study was to compare the outcomes of two minimally invasive PCNL techniques, namely, miniperc and microperc. In their large multicenter study, Kiremitet al.  reported a stone-free rate of 88.8% after microperc in comparison with 83.6% after miniperc and an overall complication rate of 3.4% with microperc versus 7.3% with miniperc. In our comparative study, both techniques showed excellent efficacy in the treatment of medium-sized renal stones with a stone-free rate after single treatment of 84.2% with microperc versus 93.8% with miniperc, with no statistically significant difference between both groups (P = 0.262).
Given the large working sheath and instruments, it is not surprising that miniperc led to a similar stone clearance in much less operative time (P = 0.004). However, our results and those from other studies suggest microperc can achieve comparable efficacy to miniperc, while having a possibly better safety profile. The drawback of reduced sheath diameter in microperc is basically increased operative time owing to reduced irrigation flow, in addition to the need for more extensive stone disintegration. Moreover, higher intrarenal pressures can be generated during microperc, though to date this does not appear to result in any detectable untoward renal functional effects. The need for auxiliary measures was negligible after treatment in both groups. The mean hospital stay was significantly lower in the microperc cases (P < 0.001), which may have been attributable to the tubeless nature of the microperc technique.
The retrospective nature of this study is one limitation, as are the low number of included cases, the lack of randomization, and the potential selection bias. Nevertheless, the fact that all surgeries were performed by highly experienced stone surgeons should help to minimize result variation, and excellent operative results were appreciated for both treatment modalities.
| Conclusion|| |
Our current data show that microperc is emerging as an effective and safe treatment option for intermediate-sized kidney stones, with outcomes comparable even to miniperc which is already a well-established treatment with high safety profile in experienced hands. Studies are needed to better evaluate its cost-effectiveness, the need for auxiliary treatments over time, and its possible complementarity with RIRS when working with patients in the supine position.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Türk C, Petřík A, Sarica K, Seitz C, Skolarikos A, Straub M, et al
. EAU guidelines on interventional treatment for urolithiasis. Eur Urol 2016; 69:475–482.
Piskin MM, Guven S, Kilinc M, Arslan M, Goger E, Ozturk A. Preliminary, favorable experience with microperc in kidney and bladder stones. J Endourol 2012; 26:1443–1447.
Kukreja R, Desai M, Patel S, Bapat S, Desai M. First prize: factors affecting blood loss during percutaneous nephrolithotomy: prospective Study. J Endourol 2004; 18:715–722.
Jackman SV, Docimo SG, Cadeddu JA, Bishoff JT, Kavoussi LR, Jarrett TW. The 'mini-perc' technique: a less invasive alternative to percutaneous nephrolithotomy. World J Urol 1998; 16:371–374.
Kumar A, Kumar N, Vasudeva P, Kumar Jha S, Kumar R, Singh H. A prospective, randomized comparison of shock wave lithotripsy, retrograde intrarenal surgery and miniperc for treatment of 1 to 2 cm radiolucent lower calyceal renal calculi: a single center experience. J Urol 2015; 193:160–164.
Desai M, Mishra S. 'Microperc' micro percutaneous nephrolithotomy: evidence to practice. Curr Opin Urol 2012; 22:134–138.
Desai MR, Sharma R, Mishra S, Sabnis RB, Stief C, Bader M. Single-step percutaneous nephrolithotomy (microperc): the initial clinical report. J Urol 2011; 186:140–145.
Lahme S, Bichler KH, Strohmaier WL, Gotz T. Minimally invasive PCNL in patients with renal pelvic and calyceal stones. Eur Urol 2001; 40:619–624.
Mishra S, Sharma R, Garg C, Kurien A, Sabnis R, Desai M. Prospective comparative study of miniperc and standard PNL for treatment of 1 to 2 cm size renal stone. BJU Int 2011; 108:896–900.
Ganpule AP, Bhattu AS, Desai M. PCNL in the twenty- first century: role of Microperc, Miniperc, and Ultraminiperc. World J Urol 2015; 33:235–240.
de Fata FR, García-Tello A, Andrés G, Redondo C, Meilán E, Gimbernat H, et al
. Comparative study of retrograde intrarenal surgery and micropercutaneous nephrolithotomy in the treatment of intermediate-sized kidney stones. Actas Urol Esp 2014; 38:576–583.
Sabnis RB, Ganesamoni R, Doshi A, Ganpule AP, Jagtap J, Desai MR. Micropercutaneous nephrolithotomy (microperc) vs retrograde intrarenal surgery for the management of small renal calculi: a randomized controlled trial. BJU Int 2013; 112:355–361.
Clavien PA, Barkun J, De Oliveira ML, Vauthey JN, Dindo D, Schulick RD, et al
. The Clavien-Dindo classification of surgical complications: five-year experience. Ann Surg 2009; 250:187–196.
Pal RP, Mellon JK. Renal stone disease. The Foundation Years 2008; 4:199–203.
Fernstrom I, Johansson B. Percutaneous pyelolithotomy. A new extraction technique. Scand J Urol Nephrol 1976; 10:257–259.
Guven S, Istanbulluoglu O, Gul U, Ozturk A, Celik H, Aygün C, et al
. Successful percutaneous nephrolithotomy in children: multicenter study on current status of its use, efficacy and complications using Clavien classification. J Urol 2011; 185:1419–1424.
Michel MS, Trojan L, Rassweiler JJ. Complications in percutaneous nephrolithotomy. Eur Urol 2007; 51:899–906.
Seitz C, Desai M, Häcker A, Hakenberg OW, Liatsikos E, Nagele U, et al
. Incidence, prevention, and management of complications following percutaneous nephrolitholapaxy. Eur Urol 2012; 61:146–158.
Skolarikos A, de la Rosette J. Prevention and treatment of complications following percutaneous nephrolithotomy. Curr Opin Urol 2008; 18:229–234.
Knoll T, Wezel F, Michel MS, Honeck P, Wendt-Nordahl G. Do patients benefit from miniaturized tubeless percutaneous nephrolithotomy? A comparative prospective study. J Endourol 2010; 24:1075–1079.
Yamaguchi A, Skolarikos A, Buchholz N-PN, Chomon GB, Grasso M, Saba P, et al
. Operating times and bleeding complications in percutaneous nephrolithotomy: a comparison of tract dilation methods in 5537 patients in the Clinical Research Office of the Endourological Society Percutaneous Nephrolithotomy Global Study. J Endourol 2011; 25:933–939.
Helal M, Black T, Lockhart J, Figueroa TE. The Hickman peel-away sheath: alternative for pediatric percutaneous nephrolithotomy. J Endourol 1997; 11:171–172.
Albala DM, Assimos DG, Clayman RV, Denstedt JD, Grasso M, Gutierrez-Aceves J, et al
. Lower pole I: a prospective randomized trial of extracorporeal shock wave lithotripsy and percutaneous nephrostolithotomy for lower pole nephrolithiasis—initial results. J Urol 2001; 166:2072–2080.
Elbahnasy AM, Shalhav AL, Hoenig DM, Elashry OM, Smith DS, Mcdougall EM, et al
. Lower caliceal stone clearance after shock wave lithotripsy or ureteroscopy: the impact of lower pole radiographic anatomy. J Urol 1998; 159:676–682.
Osman MM, Alfano Y, Kamp S, Haecker A, Alken P, Michel MS, et al
. 5-year-follow-up of patients with clinically insignificant residual fragments after extracorporeal shockwave lithotripsy. Eur Urol 2005; 47:860–864.
Palmero J, Castelló A, Miralles J, de La Rosa IN, Garau C, Pastor J. Results of retrograde intrarenal surgery in the treatment of renal stones greater than 2 cm. Actas Urol Esp 2014; 38:257–262.
Singh BP, Prakash J, Sankhwar SN, Dhakad U, Sankhwar PL, Goel A, et al
. Retrograde intrarenal surgery vs extracorporeal shock wave lithotripsy for intermediate size inferior pole calculi: a prospective assessment of objective and subjective outcomes. Urology 2014; 83:1016–1022.
Traxer O, Thomas A. Prospective evaluation and classification of ureteral wall injuries resulting from insertion of a ureteral access sheath during retrograde intrarenal surgery. J Urol 2013; 189:580–584.
Hyams ES, Shah O. Percutaneous nephrostolithotomy versus flexible ureteroscopy/holmium laser lithotripsy: cost and outcome analysis. J Urol 2009; 182:1012–1017.
Knoll T, Jessen JP, Honeck P, Wendt-Nordahl G. Flexible ureterorenoscopy versus miniaturized PNL for solitary renal calculi of 10–30 mm size. World J Urol 2011; 29:755–759.
Knoll T, Buchholz N, Wendt-Nordahl G. Extracorporeal shockwave lithotripsy vs. percutaneous nephrolithotomy vs. flexible ureterorenoscopy for lower-pole stones. Arab J Urol 2012; 10:336–341.
Kiremit MC, Guven S, Sarica K, Ozturk A, Buldu I, Kafkasli A, et al.
Contemporary management of medium-sized (10–20 mm) renal stones: a retrospective multicenter observational study. J Endourol 2015;29(7):838–843.
[Table 1], [Table 2], [Table 3]