Urology Annals

: 2019  |  Volume : 11  |  Issue : 3  |  Page : 257--260

Outcome of early experience of miniperc technique in pediatric age group

Ehab Mohamad Galal1, Amr Abdelhamid1, Tarek Fath El-Bab1, Ahmed Ali1, Ahmad Anwar1, Ahmed Abdelbary2, Akrm A Elmarakbi2, Mohamed H Abdelhamid3, Ehab Tawfiek1,  
1 Department of Urology, Minia University Hospital, Minia, Egypt
2 Department of Urology, Beni-Suef University, Beni Suef, Egypt
3 Department of Urology, Cairo University, Giza, Egypt

Correspondence Address:
Dr. Ehab Mohamad Galal
Department of Urology, Minia University Hospital, P.O. Box 61511, Minia, Egypt


Background: The aim of this study is to report our experience with the Miniperc technique for treatment of renal stone in pediatric age group. Materials and Methods: From August 2012 to January 2015, 34 patients aged <15 years with renal stones <3 cm underwent Miniperc technique were included in our study. The procedure was done through 14 Fr sheath using 8/9.8 Fr semi-rigid ureteroscope, holmium laser, and pneumatic lithotriptor for stone fragmentation. Stone-free rate (SFR), operative time, hospital stay, and complication rate were evaluated. Results: A total of 34 Miniperc techniques were performed on children with a mean age of 8.8 ± 3.7 years. Stone size varied from 18 to 30 mm (mean 23 mm). Mean operative time was 50 min. The mean hospital stay was 48±12 hours. The overall SFR was 82.4% which increased after secondary procedures to 94%. Two postoperative complications recorded in the form of sepsis and bleeding that required no blood transfusion. Conclusion: Our initial experience concluded that Miniperc technique is a safe and effective treatment option for renal stones in pediatric population.

How to cite this article:
Galal EM, Abdelhamid A, El-Bab TF, Ali A, Anwar A, Abdelbary A, Elmarakbi AA, Abdelhamid MH, Tawfiek E. Outcome of early experience of miniperc technique in pediatric age group.Urol Ann 2019;11:257-260

How to cite this URL:
Galal EM, Abdelhamid A, El-Bab TF, Ali A, Anwar A, Abdelbary A, Elmarakbi AA, Abdelhamid MH, Tawfiek E. Outcome of early experience of miniperc technique in pediatric age group. Urol Ann [serial online] 2019 [cited 2022 Jan 26 ];11:257-260
Available from: https://www.urologyannals.com/text.asp?2019/11/3/257/256150

Full Text


The reported incidence of pediatric renal stones is 50 cases/100,000 children.[1] Treatment options for renal stones in pediatric population include shock wave lithotripsy (SWL), percutaneous nephrolithotomy (PCNL), retrograde intrarenal surgery, and laparoscopic and/or robotic approach.[2] Management of such cases usually poses challenges to a pediatric urologist to choose the ideal treatment modality with high stone clearance rate and low morbidity.[3] The European Association of Urology guidelines recommended the PCNL as the therapy of choice for complex renal stones and when unfavorable factors for SWL exist.[4] The standard PCNL tract may be too large for pediatric kidneys and meanwhile poses a significant risk of bleeding and increased morbidity.[5] Miniperc technique was introduced by Jackman et al. in an effort to reduce the morbidity related to standard PCNL.[6] The purpose of this study was to review our experience with the Miniperc technique in pediatric age group to assess its safety as well as appropriate inclusion criteria.

 Materials and Methods

Between August 2012 and January 2015, 34 patients (25 males and 9 females) with renal stones<3 cm underwent stone extraction using Miniperc technique. Indications for surgery included failed SWL, large stones that required repeated sessions, and patients whose families desired one-session therapy. The mean age of children was 8.8 ± 3.7 years ranged from 5 to 15 years. Informed consent from parents of all participants was written and specified in the operative consent. Approval for this study was obtained from the ethics committee of our hospital.

Initial evaluation included detailed history, routine hematological investigations including coagulation profiles, urine analysis, and culture. Radiologic examinations including plain X-ray of the kidneys, ureter, and bladder (KUB), renal ultrasound, intravenous urogram, or computed tomography (CT) were performed routinely to assess the stone characters, identify the anatomy of collecting system, and provide an anatomical proof for establishing percutaneous tract. Postoperative radiological screening was done at day 1, then after 1 and 3 months by KUB, and ultrasound and/or CT for the evaluation of residual stones and any reported complications. Postoperative complications were graded by the Clavien–Dindo classification.[7]

Miniperc surgical technique

Under general anesthesia and with administration of intravenous broad-spectrum antibiotic 1 h before induction, the child positioned in the dorsal lithotomy position and an 8.5 Fr pediatric Storz cystoscope was used for retrograde stenting of the affected kidney by 4–5 Fr ureteric catheters. After the patient turned to prone position, the desired calyx punctured, then the tract was dilated by means of coaxial progressive fascial dilators, and a 14 Fr working sheath was placed under fluoroscopy. We used 8/9.8 Fr rigid ureteroscope (R-URS) (Richard Wolf, Knittlingen, Germany) with pneumatic lithotripter (LithoClast™ Richard Wolf GmbH, Knittlingen, Germany) or 20 W holmium:YAG laser (Lumenis, Santa Clara, CA, USA), 200-μm laser fiber with an energy output of 0.8–1.5 J at 8–12 Hz for stone fragmentation. Big fragments >2 mm were removed with a forceps. Stone clearance was assessed under fluoroscopy, and finally, 5 Fr DJ stent was inserted through the tract (removed after 3–4 weeks) or ureteric catheter left in place according to surgeon's preference. Nephrostomy tube of suitable size may be used to drain the kidney in suspected bleeding or residual stones and removed accordingly after 2–3 days postoperatively.


Our study recorded 25 (73.6%) boys and 9 (26.4%) girls who underwent one-session single tract Miniperc technique. The mean patient's age was 8.8 ± 3.7 years. Fifty-three percent of the patients (18 of 34) had stones in the left kidney and 47% (16 of 34) in the right kidney. Previous ipsilateral open renal stone surgery was recorded in three children. Stones were solitary in 64% (pelvic in 53%, calyceal in 11%) and multiple (pelvic and calyceal) in 36%. Stone density was graded on three levels based on comparison with the adjacent rib (3: more dense detected in 70%, 2: isodense in 18%, and 1: less dense in 12%). Stone size varied from 18 to 30 mm (mean 23 mm). We reported the effect of different stone characters on stone-free rate (SFR), and there were no statistically significant differences regarding these characters [Table 1]. Mild-to-moderate hydronephrosis was noted in all patients. Pneumatic lithotripter and holmium: YAG laser were used in 16 and 18 patients, respectively. Mean operative time was 50 min. It was calculated from beginning of cystoscopy till fixation of the stent or tube. There were no intraoperative complications in all cases. Only two cases reported postoperative complications of Grade 2a (potentially life-threatening complications required medications only). Sepsis was reported in one case with renal pelvic and lower calyceal stone 2.5 cm and suspected due to prolonged procedure (90 min). Bleeding was recorded in another case who required no blood transfusion while nephrostomy tube was inserted for 3 days and removed after clamping and the child discharged with DJ stent removed after 3 weeks. The mean hospital stay was 48±12 hours. There is no consensus on the definition of SFR. It is usually considered as stone fragments smaller than 2 mm. The overall SFR was 82.4% (28 of 34 patients). The remaining 6 (17.6%) patients were considered unsuccessful due to residual stone fragments need auxiliary procedures. Of these patients, four performed SWL as the residual stone was 5 mm in one patient and three patients refusing second-look PCNL with complete stone clearance after one session. Two patients with 7 mm stone lower calyx refusing secondary procedure while follow-up of them up to 6 months revealed stable stone size without documented urinary tract infection (UTI). After secondary procedures, 94% of the patients achieved the stone-free status. Follow-up was completed for all patients after 1 month, while only 30 and 25 patients completed the follow-up after 3 and 6 months, respectively. Five patients recorded recurrent attacks of ipsilateral renal pain during follow-up. UTI without obstruction reported in one patient and completely eradicated after treatment according to culture and sensitivity, while the remaining four patients underwent noncontrast head CT and urine analysis without any detected cause.{Table 1}


The main goal in the management of pediatric stones is to achieve complete clearance, eradication of infection, and correction of any metabolic or congenital disorders. All stone treatment modalities are applicable in pediatric age group. The guidelines recommended SWL as the first-line treatment for pediatric renal stones ≤20 mm.[8] While due to lower re-treatment rates requiring less auxiliary procedures, PCNL has gradually become the mainstay replacing SWL for treatment of large stone burdens in children.[9] Although traditional PCNL carries the advantages of clear vision and high stone clearance, while in pediatric patients, it can still be associated with significant complications, such as uncontrolled hemorrhage attributed to using large instruments in smaller kidneys.[10] Performing the standard PCNL with a miniature endoscope via a small percutaneous tract (11–20 Fr) is termed as minimally invasive PCNL or Miniperc. Few reported series of Miniperc in children exists. Jackman et al. developed the novel percutaneous access technique Miniperc using a 13 Fr peel-away sheath and reported 85% SFR for 11 procedures in seven children with a mean age of 3.4 years.[11] In other small series, the Miniperc was done safely and effectively in children with a mean stone burden of 1.5 cm in most studies and SFR of 70%–95%.[12],[13],[14] In our initial experience with Miniperc, we evaluated the SFR in relation to different stone characters. There was no significant difference according to these characters. The mean stone size was 23 mm which was expected to lead to lower clearance, while the overall early SFR was 82.4% which increased to 94% after secondary procedures. This is may be due to stone dusting settings used during laser (increased frequency and lower wattage). The SFR in this study was comparable with other studies on Miniperc in children done through a 14–16 Fr sheath. Bilen et al.[15] reported 90% SFR using 14 Fr Miniperc in children with a mean age of 6.3 years. Wang et al.[16] reported their results of Miniperc on children aged under 3 years. All procedures were performed by single tract, including 245 14 Fr tracts, one 16 Fr tract, and one 12 Fr tract, respectively. Majority of cases had stone burden 1–2 cm. Mean operating time was 32.5 min (range 21–62 min). Complete SFR has been reported as 97.2%.

In our study, the mean operative time was comparable to that reported by Nischith and Saptarshi (58 min) in 20 Miniperc pediatric patients.[17] In another study of 26 cases of Miniperc through 14 Fr sheath using a 9.5 Fr (R-URS) with holmium:YAG laser lithotripsy, the operative time reported was 71.08 min, which considered by the authors as the drawback of Miniperc related to diminished field visibility and the need for prolonged lithotripsy to obtain small fragments suitable for extraction through the small sheath. However, they reported 19.2% of cases with stones size 3–4.8 cm.[18]

The aim of the Miniperc is to reduce complications such as blood loss, intraoperative–postoperative pain, and hospital stay.

As bleeding significantly correlated with operative time, stone complex, and sheath size in pediatric patients,[19] using 8/9.8 Fr (R-URS) via 14 Fr tract obviously reduced the damage of renal parenchyma and vessel. Many studies on Miniperc reported no blood transfusion.[13],[20],[21] However, one study required blood transfusion in 4 (15%) patients using a 14 Fr sheath.[22] In our study, there was only one patient of postoperative bleeding that required no blood transfusion. He had complex pelvic and middle calyceal stone about 2.8 cm. The small tract of the procedure with high intrapelvic pressure may lead to pyelovenous-lymphatic backflow that may be complicated by bacteremia and postoperative fever.[23] In this study, we lowered the intrapelvic pressure using operating instruments that are smaller than the access sheath to allow the leakage of irrigating fluids and also keep inflow of irrigants at gravity and never pressurized. This may be responsible for reporting only one case of sepsis due to prolonged procedure.

One of the limitations of our study is the small number of patients and it was conducted at single center. However, as it is one of few prospective studies about the use of Miniperc in pediatric age group with different stone characters, we believe that it will be of value to the literature. A comparative study with conventional PCNL with long follow-up period should be done.


With our initial experience, Miniperc is safe and not related to major blood loss or other serious complications and could be reasonable alternative for renal stones in children.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


1Sas DJ, Hulsey TC, Shatat IF, Orak JK. Increasing incidence of kidney stones in children evaluated in the emergency department. J Pediatr 2010;157:132-7.
2Ganpule AP, Mishra S, Desai MR. Percutaneous nephrolithotomy for pediatric urolithiasis. Indian J Urol 2010;26:549-54.
3Casale P, Grady RW, Joyner BD, Zeltser IS, Kuo RL, Mitchell ME, et al. Transperitoneal laparoscopic pyelolithotomy after failed percutaneous access in the pediatric patient. J Urol 2004;172:680-3.
4Tekgül S, Dogan HS, Hoebeke P, Kocvara R., Nijman R, Radmayr Chr, et al. Guidelines on Pediatric Urology Uroweb; 2014. Available from: http://Urology_LR.pdf. [Last accessed on 2014 Aug 31].
5Michel MS, Trojan L, Rassweiler JJ. Complications in percutaneous nephrolithotomy. Eur Urol 2007;51:899-906.
6Jackman SV, Docimo SG, Cadeddu JA, Bishoff JT, Kavoussi LR, Jarrett TW, et al. The “mini-perc” technique: A less invasive alternative to percutaneous nephrolithotomy. World J Urol 1998;16:371-4.
7Dindo D, Demartines N, Clavien PA. Classification of surgical complications: A new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg 2004;240:205-13.
8Tekgul S, Dogan HS, Erdem E, Hoebeke P, Kocvara R, Nijman JM, et al. Guidelines on Paediatric Urology. Available from: http://www.uroweb.org/wp-content/uploads/EAU-Guidelines-Paediatric-Urology-2015.pdf. [Last accessed on 2015 Mar 01].
9Smaldone MC, Corcoran AT, Docimo SG, Ost MC. Endourological management of pediatric stone disease: Present status. J Urol 2009;181:17-28.
10Wein AJ, Kavoussi LR, Novick AC, Partin AW, Peters CA. Campbell-Walsh Urology. Philadelphia, United States of America: Elsevier Saunders; 2007.
11Jackman SV, Hedican SP, Peters CA, Docimo SG. Percutaneous nephrolithotomy in infants and preschool age children: Experience with a new technique. Urology 1998;52:697-701.
12Wah TM, Kidger L, Kennish S, Irving H, Najmaldin A. MINI PCNL in a pediatric population. Cardiovasc Intervent Radiol 2013;36:249-54.
13Yan X, Al-Hayek S, Gan W, Zhu W, Li X, Guo H, et al. Minimally invasive percutaneous nephrolithotomy in preschool age children with kidney calculi (including stones induced by melamine-contaminated milk powder). Pediatr Surg Int 2012;28:1021-4.
14Bhageria A, Nayak B, Seth A, Dogra PN, Kumar R. Paediatric percutaneous nephrolithotomy: Single-centre 10-year experience. J Pediatr Urol 2013;9:472-5.
15Bilen CY, Koçak B, Kitirci G, Ozkaya O, Sarikaya S. Percutaneous nephrolithotomy in children: Lessons learned in 5 years at a single institution. J Urol 2007;177:1867-71.
16Wang F, An HQ, Li J, Tian CY, Wang YJ. Minimally invasive percutaneous nephrolithotomy in children less than three years of age: Five-year experience in 234 cases. Urol Int 2014;92:433-9.
17D'Souza N, Paul S. Mini percutaneous nephrolithotomy for renal calculi in paediatric patients: A review of twenty cases. Urol Ann 2016;8:16-9.
18Daw K, Shouman AM, Elsheemy MS, Shoukry AI, Aboulela W, Morsi HA, et al. Outcome of mini-percutaneous nephrolithotomy for renal stones in infants and preschool children: A prospective study. J Pediatr Urol 2015;86:1019-26.
19Zeren S, Satar N, Bayazit Y, Bayazit AK, Payasli K, Ozkeçeli R, et al. Percutaneous nephrolithotomy in the management of pediatric renal calculi. J Endourol 2002;16:75-8.
20Zeng G, Zhao Z, Zhao Z, Yuan J, Wu W, Zhong W, et al. Percutaneous nephrolithotomy in infants: Evaluation of a single-center experience. Urology 2012;80:408-11.
21Zeng G, Jia J, Zhao Z, Wu W, Zhao Z, Zhong W, et al. Treatment of renal stones in infants: Comparing extracorporeal shock wave lithotripsy and mini-percutaneous nephrolithotomy. Urol Res 2012;40:599-603.
22Bilen CY, Gunay M, Ozden E, Inci K, Sarikaya S, Tekgul S, et al. Tubeless mini percutaneous nephrolithotomy in infants and preschool children: A preliminary report. J Urol 2010;184:2498-502.
23Zhong W, Zeng G, Wu K, Li X, Chen W, Yang H, et al. Does a smaller tract in percutaneous nephrolithotomy contribute to high renal pelvic pressure and postoperative fever? J Endourol 2008;22:2147-51.