Stesura Seveso 345Archivio Italiano di Urologia e Andrologia 2020; 92, 4 ORIGINAL PAPER No conflict of interest declared. DOI: 10.4081/aiua.2020.4.345 Which factors affect the success of pediatric PCNL? Single center experience over 20 years Volkan Izol 1, Nihat Satar 1, Yildirim Bayazit 1, Fatih Gokalp 2, Nebil Akdogan 1, Ibrahim Atilla Aridogan 1 1 Department of Urology, Faculty of Medicine, University of Çukurova, Adana, Turkey; 2 Clinic of Urology, Osmaniye Government Hospital, Osmaniye, Turkey. rograde intrarenal surgery (RIRS) are the treatments of choice in children (2). Additionally, over the last two decades, percutaneous nephrolitotomy (PCNL), with low complications and high success rates, has become the standard treatment of choice for kidney stones > 2 cm and is an alternative procedure for stone size between 1- 2 cm at lower pole (2, 3). PCNL is an effective and safe procedure in pediatric patients (4-7). Nevertheless, serious complications such as bleeding requiring transfusion, organ injuries, pneu- mothorax, infection, and sepsis, still have been reported for this procedure (7). There are a few factors identified as affecting complications, including stone size, sheath size, number of punctures, presence of hydronephrosis, and prolonged operation time (8, 9). Recent studies of stone disease treatment showed increased success rates, and also decreased complication rates in association with increase of expertise in high volume centers (7, 8). In this retrospective study, we aimed to evaluate the impact of surgeons’ experience on complication rates, success rates, and the management of complications along a period of more then 20 years. MATERIALS AND METHODS Between June 1997 and June 2018, 573 pediatric patients with a total of 654 renal units underwent PCNL for renal stone disease. The patients with bilateral kid- ney stones were treated with staged procedures. All patients were assessed preoperatively with excretory urography, renal ultrasound, and/or non-enhanced spi- ral computerized tomography, and urine was collected for culture analysis before surgery. Written informed consent was achieved for all participants. After approvel by Cukurova University Ethics Committee, June 2018/78, preoperative data were obtained, including gender, age, operation time, sheath size, laterality, stone burden, hematocrit, and serum creatinine. The stone burden was calculated by the stone surface area formula. Intraoperative and postoperative data were obtained including pre/postoperative variation of glomerular fil- tration rate (GFR) (calculated with Cockcroft Gault equations), drop of hemoglobin levels, transfusion rate, complications according to the Clavien classification, operative time, length of hospital stay and stone-free rate (SFR) (10, 11). Objective: We aimed to investigate the impact of surgeons’ experience on pediatric percutaneous nephrolithotomy (PCNL) outcomes. Materials and methods: Between June 1997 and June 2018, 573 pediatric patients with 654 renal units underwent PCNL for renal stone disease by senior surgeons. Data were divided into two groups, group-1 (n = 267), first ten years period, group-2 (n = 387); second ten years period. Results: Mean ± SD age of patients was 7.6 ± 4.9 (1-17) years. The stone-free rates (SFR) assessed after 4 weeks were 74.9% vs. 83.4% in group-1 vs. group-2, respectively (p = 0.03). The mean operation time, fluoroscopy time, and the number of patients requiring blood transfusion significantly decreased in group 2 (100.4 ± 57.5 vs. 63.63 ± 36.3, 12.1 ± 8.3 vs. 8.3 ± 5.4, and 24.3% vs. 2.9%; p < 0.001, p < 0.001, and p = 0.002 in group-1 versus group-2, respectively). On multivariate analysis, increasing stone size increased operation time (p < 0.001), fluoroscopy time (p < 0.001), intraoperative and postoperative blood transfusion rates (p = 0.006 and p = 0.018, respectively), and hospital stay (p = 0.002) but was not associated with change of glomerular filtration rate (GFR) (p = 0.71). Sheath size also correlated with increased fluo- roscopy time (p < 0.001), operation time (p < 0.001), intraop- erative blood transfusion (p < 0.001) and hospital stay, but sheath size did not affect postoperative blood transfusion (p = 0.614) or GFR change (p = 0.994). Conclusions: The percutaneous nephrolithotomy (PCNL) is a minimally invasive procedure and is well accepted because of its lower complication rate and high efficiency for pediatric patients. Stone and sheath size are predictive factors for blood loss and hospital stay. During 20 years, our fluoroscopy time, operation time, blood loss, and complication rates decreased, and stone-free rate increased. KEY WORDS: Pediatric; Percutaneous; Urinary calculi; Endourology. Submitted 24 May 2020; Accepted 30 July 2020 INTRODUCTION Pediatric stone-disease is widespread in developing countries and Turkey (1). The surgical management of stone disease has changed because of technological advances in recent years. For renal stones smaller than 2 cm, extracorporeal shock wave lithotripsy (SWL) and ret- Summary Archivio Italiano di Urologia e Andrologia 2020; 92, 4 V. Izol, N. Satar, Y. Bayazit, F. Gokalp, N. Akdogan, I. Atilla Aridogan 346 Additionally, we divided the data into two groups. In group-1, PCNL was performed in the first ten years peri- od (1997-2007); in group-2, PCNL was performed in the second ten years period from 2008 to the present. Surgical technique All procedures were performed by four experienced sur- geons who had been working for at least 20 years in our clinic and staff surgeons under supervision of mentors. All patients received prophylactic antibiotics preopera- tively during anesthesia induction. After the placement of a 5 Fr ureteral open-end catheter, patients were posi- tioned in a prone position with proper constructional support by silicone rolls. The pelvicalyceal system was visualized by injecting the radiographic contrast dye through the ureteric catheter. The collecting system was punctured with a needle under fluoroscopy, a guidewire was inserted, and then the urinary tract was dilated with metal or Amplatz dilatators. After placement of an 18-30 Fr sheath, a 15Fr-19Fr rigid nephroscope or 9.5 Fr rigid ureteroscope was inserted into the collecting system. Stones were fragmented with a pneumatic lithotripter or laser and retrieved with rigid or flexible forceps or graspers. A 10 Fr nephrostomy tube was left in place if needed. We preferred the tubeless technique for selected cases such as those with short operation time, a single puncture for a tract, undamaged pelvicalyceal system, no major bleeding or residual stones at the end of the pro- cedure. On the second postoperative day, the patient underwent antegrade pyelography, or the nephrostomy tube was clamped if there was no residual fragment or extravasa- tion detected by imaging. Then, the nephrostomy tube was extracted. Patients were discharged after drainage from the nephrostomy tract was stopped. If the drainage from the nephrostomy tract continued longer than seven days, it was defined as prolonged drainage, and we inserted a double J stent. When drainage was stopped for several days, patients were discharged. Follow up The first visit for follow up was done at 4-6 weeks after discharge, including urinalysis, metabolic examination of 24-hour urine specimens, and urinary ultrasonogra- phy. Stone free rates (SFR) were evaluated at 4 week fol- low. We reported the result as a failure in presence of any asymptomatic residual stone fragment > 4 mm at 4 week follow up. We confirmed the result by using intra- venous urography in the first-year period and non- enhanced computerized tomography in the second ten years period. Statistical analysis SPSS, version 20.0, was used to perform statistical analy- sis. The Kolmogorov Smirnov test was used in the numerical computations provided the assumption of a normal distribution. For comparing the categorical measurements between the groups, the chi-square test was used. Mann-Whitney U, chi-square, ANOVA, and logistic regression were used for multivariate analysis. Statistical significance was defined as a p-value of less than 0.05. RESULTS Demographic data Five hundred seventy-three pediatric patients with 654 renal units were evaluated in the study. The mean ± SD age of patients was 7.6 ± 4.9 years. The mean stone bur- den was 371.8 ± 459.4 (95% CI: 343.0-415.5) mm3. There were 343 (52.5%) renal units with a single calyceal stone and 311 (47.5%) patients with multiple calyceal or staghorn stones. SFR was found 81.4% (n = 533). The mean hospital stay was 4.6 ± 4.2 days. In our practice, the usual hospital course for PCNL is 3-4 days in pediatric patients, but 173 (26.4%) patients stayed longer (7 to 27 days) due to leakage drainage, bleeding, infections, or other complications (Table 1). Operative outcomes On multivariate analysis, the perioperative parameters such as fluoroscopy time, bleeding, and operation time were associated with stone size and sheath size. Increasing stone size increased operation time (p < 0.001), fluoroscopy time (p < 0.001), intraoperative and postoperative blood transfusion rate (p = 0.006 and p = 0.018, respectively), and hospital stay (p = 0.002) but was not associated with GFR change (p = 0.71). Sheath size also correlated with th parameters and increased fluoroscopy time (p < 0.001), operation time (p < 0.001), intraoperative blood transfusion (p = 0.002) and hospital stay, but sheath size did not affect postop- Table 1. Demographic data of patients. Value No. of patients 654 Age (years)a 7.6 ± 4.9 Genderb M 167 (62.5%) F 100 (37.5%) Lateralityb Left 326 (49.8%) Right 328 (50.2%) Site of stoneb Single calyx 343 (52.5%) Multiple calyces 311 (47.5%) Operation timea 78.3 ± 49.0 Stone free rateb 533 (81.4%) aData was presented as mean ± SD; bData was presented as n (%). Table 2. Complications causing prolonged hospital stay. Group 1 Group 2 p value (1997-2007) (2008-2018) Infection and fever 26 (9.7%) 15 (3.8%) 0.02 Leakage drainage 10 (3.7%) 11 (2.8%) 0.52 Requiring stenting 6 (2.2%) 7 (1.8%) 0.69 Colon perforation 2 (0.7%) 1 (0.2%) 0.79 Collecting system perforation 1 (0.3%) 4 (1.0%) 0.34 Bleeding 78 (29.2%) 22 (5.6%) < 0.001 Requiring blood transfusion 65 (24.3%) 11 (2.8%) < 0.001 Transcathateter angiography 2 (0.7%) 1 (0.2%) 0.36 All data was presented as n (%). 347Archivio Italiano di Urologia e Andrologia 2020; 92, 4 Success of pediatric percutaneous nephrolithotomy erative blood transfusion (p = 0.614) or GFR change (p = 0.994). Furthermore, prolonged operation time increases fluoroscopy time (p < 0.001), intraoperative and postoperative blood transfusion (p < 0.001 and p = 0.008, respectively), and hospital stay (p < 0.001), but not associated with GFR change (p = 0.55). Stone size and sheath size were not associated with post- operative changes of GFR. SFR was correlated with oper- ation time (B: -0.013, p = 0.02) (Table 3). Table 4 shows the comparison of the outcomes of two subgroups of patients treated in two different period of time using dif- ferent-sized instruments. Mean operation time, fluo- roscopy time, and blood transfusion rate were signifi- cantly lower in group-2 (p < 0.001, p < 0.001, and p = 0.002, respectively). However, stone volume and sheath size also significantly decreased in group-2 (p < 0.001). SFR were 74.9% and 86.4% in group-1 and group-2, respectively (p = 0.03). Reoperation rates were 18 (6.7%) versus 11 (2.9%) in group-1 vs. group-2, respectively (p = 0.01). There was no significant change between preoperative and postop- erative mean GFR in both groups (2.51 ± 0.2 mL/min and 3.83 ± 0.3 mL/min; p = 0.584, p = 0.536 in group- 1 and group-2, respectively). The most common complications were low-grade com- plications, grade I (21.3%), and grade II (29.6%). Grade I and II complications were significantly higher group-1 than group-2 (p = 0.001 and p < 0.001). Grade III-a and III-b complications were seen in 16 (2.4%) and 5 (0.7%) patients, respectively, and there was no significant dif- ference between groups (p = 0.45, p = 0.34). Complications and management The most common complication was bleeding in both groups (29.2% and 5.6% in group-1 and group-2, respectively). Rates of hemorrhages requiring transfu- sions were significantly different between the two groups (24.3% and 2.9% in group-1 and group-2, respectively, p = 0.02). Three patients underwent angiography for severe bleeding after the procedure, and a ten-year-old child underwent embolization for a pseudoaneurysm of the kidney. Twenty-six (9.7%) children in group-1 and fifteen (3.8%) in group-2 had a fever after PCNL (p = 0.07). Patients took different antibiotic regimens after a positive urine culture. Twenty-one patients were followed up for prolonged drainage after removal of the nephrostomy tube. Thirteen patients, six (2.2%) in group-1 and seven (1.8%) in group-2, required double-J stenting. One patient required stenting for perirenal urinoma that resolved spontaneously. Collecting system perforations were seen in five patients, one (0.3%) in group-1 and four (1.0%) in group-2. Three patients had a long-stay- ing nephrostomy tube from four to seven days, which was extracted after no extravasation was demonstrated at anterograde pyelography. Two cases required open sur- gery, one underwent pyeloplasty for damaged ureter-pel- viv junction (UPJ) and the other underwent a primary repair of the renal pelvis. Two (0.7%) patients in group-1 and one (0.2%) in group- 2 had a colon perforation. One of them was treated with open surgery and a colostomy by the pediatric surgeon. The colostomy was closed after three months when anas- tomosis was done successfully. Two patients were treated conservatively, by withdrawal of the nephrostomy tube outside the kidney into the colon as a percutaneous colostomy tube and by insertion of a double-J ureteral stent for separating nephron-colic communication. Patients took intravenous broad-spectrum antibiotics and total parenteral nutrition. After 7-10 days, the patients started receiving oral feeding. The tube was removed after complete healing of the colon. One month after, the J stent was extracted under control of retrograde pyelog- raphy. One child underwent nephrectomy for a non- functioning kidney that was not producing urine in the Table 4. Difference characteristics of two chronological groups. 1997-2007 2008-2018 p value (n = 267) (n = 387) Age (years)a 8.5 ± 4.9 6.9 ± 4.7 Genderb M 167 (62.5%) 210 (54.2%) F 100 (37.5%) 177 (45.8%) Sideb Left 128 (47.9%) 198 (51.1%) Right 139 (52.1%) 189 (48.9%) Stone sizea (mm2): 480.8 ± 380.0 295.8 ± 196.5 p < 0.001 Sheath sizea: 27.87 ± 2.8 24.41 ± 2.6 p < 0.001 GFR change (mg/dl): 2.6 ± 0.2 3.8 ± 0.3 p = 0.425 Serum creatinine changea (mg/dl): 0.013 ± 0.0 0.001 ± 0.0 p = 0.717 Operation timea (min): 100.4 ± 57.5 63.63 ± 36.3 p < 0.001 Fluoroscopy timea (min): 12.19 ± 8.3 8.31 ± 5.4 p < 0.001 Hemorrhage requiring transfusionb: 65 (24.3%) 11 (2.9%) p = 0.002 Stone free ratesb SF 200 (74.9%) 323 (83.4%) p = 0.03 Failure 64 (24.2%) 56 (14.8%) Nephrostomy removal time (day): 2.93 2.57 p = 0.133 Postoperative Complications: Clavien Dindob p = 0.842 1 39 (14.6%) 26 (6.7%) p = 0.001 2 69 (25.8%) 15 (3.8%) p < 0.001 3a 8 (2.9%) 8 (2.0%) p = 0.45 3b 1 (0.3%) 4 (1.0%) p = 0.34 4a 2 (0.7%) 1 (0.2%) p = 0.36 5 0 0 aData was presented as mean ± SD; bData was presented as n (%). Table 3. Multivariate analysis of SFR compared to demographic and perioperative parameters. Unstandardized coefficients 95% Confidence interval B Std. error p Lower Upper Age .047 .056 .399 .939 1.170 Gender -.024 .300 .936 .543 1.756 Laterality -.264 .301 .380 .426 1.385 Weight -.017 .014 .226 .956 1.011 Stone size -.001 .001 .108 .998 1.000 Operation time -.013 .006 .021 .976 .998 Fluoroscopy time .000 .000 .781 .999 1.001 Sheath size .079 .070 .259 .944 1.241 Constant 1.367 1.614 .397 *Depended variable was SFR. Archivio Italiano di Urologia e Andrologia 2020; 92, 4 V. Izol, N. Satar, Y. Bayazit, F. Gokalp, N. Akdogan, I. Atilla Aridogan 348 postoperative days. Histopathological evaluation revealed xanthogranulomatous pyelonephritis. DISCUSSION Pediatric stone disease is an important issue, and the crit- ical point for preventing recurrence and relative compli- cations after surgery is stone clearance. There still is not a consensus on describing stone-free rates. SFR varied in the studies due to the differences between pediatric and adult kidney anatomy, variable stone size, use of differ- ent-sized instruments, and inclusion or exclusion of clin- ically insignificant residual fragment (CIRF) cases. A recent study by Çıtamak et al. presented their results at four years intervals over 17 years, and stone-free rates were 73.5%, 68.1%, 75.5%, and 74.0%, with no significant difference among the groups (p = 0.65) (12). Our study showed that our increasing clinical experience and use of small instruments incresed SFR after pediatric PCNL. Our SFR was significantly higher in group-2 than group-1 and reoperation rates were similar into groups. Similar to our study, Yadav et al. study reported that stone-free rates were increased over 15 years from 84.6% to 89.9% (13). The early pediatric PCNL series were performed using adult-size instruments. The improvements in the devices and techniques of PCNL facilitated urologists to perform this procedure (14, 15). In our study, the mean sheath size decreased from 28 Fr to 24 Fr over the years. Bilen et al. compared three different sized nephroscope, and stone-free rates were 69.5%, 80%, and 90% in the 26Fr, 20Fr, and miniperc groups, respectively (p < 0.005). The authors emphasized that the 26Fr and 20Fr groups include more patients with semi-staghorn and staghorn calculi (16). A novel systematic review showed that the minimal invasive PCNL (micro-ultra mini) success rate ranged between 85-100% (17). In our study, the total complication rate (Clavien I-IV) was 28.4%, and there was no significant difference between the two groups. Similar results were found in the CROES study which showed that the complication rate was 23.3% (7). Novel research showed the compli- cations were decreased over the years (33.8%, 23.6%, 19.6%, and 11.5%, respectively, for every four years, p < 0.001) (12). In the literature, the studies compared PCNL complications in children using different instru- ments, and the complications were graded according to the modified Clavien system, and similar to our research, most of the complications were grade I and II (5, 18, 19). Ozden et al., in a study of 100 patients using pediatric instruments, reported an overall complication rate of 25% (18). Another study by Guven et al. reported that the total complication rate was 29.1% (n = 140), and there was no significant difference between pediatric and adult instruments (p = 0.52) (5). Additionally, Bilen et al. also showed that complication rates were not significant- ly different in their study comparing three different sized instruments (16). Mishra et al. examined the outcomes of miniperc (MPCNL) versus standard conventional PCNL and concluded that the MPCNL is significantly superior to PCNL in bleeding and hospital stay time (19). Similar to our study, novel papers showed that recently present- ed small size percutaneous accesses, such as MPCNL and micro percutaneous method (Micro-PCNL), are safer than classic PCNL in children (2, 20). Our study demonstrat- ed that there had been no significant change in the treat- ment of complications until today, but we became less invasive due to our increased knowledge of complica- tions. The most common complications were bleeding and fever. Types and frequencies of complications were sim- ilar to those in adults (8, 17, 21). Zeren et al. study showed correlation of intraoperative bleeding with oper- ation time, sheath size, and stone size (8). Our research demonstrated that stone size and operation time corre- lated with intraoperative and postoperative blood trans- fusion. We also found that a larger sheath size is related to higher intraoperative blood transfusion rates and longer hospital stay. Similar to our study, Altintaş et al. study compared three different sheath sizes (17 Fr, 24 Fr, and 26 Fr) showing that sheath size was related to increased intraoperative bleeding although there was no significant difference of preoperative and postoperative creatinine levels (p = 0.873) (22). However, controver- sial to our study, the literature also reported that sheath size did not affect transfusion rates (12, 16, 23). Fever was the second common complication in our study. Previous studies reported that the postoperative fever rate was approximately present in 29% (18, 21). Bayrak et al. reported that postoperative fever rates in their study, comparing children to adults, were 5.4% and 5.6%, respectively (24). Çelik et al. showed that postoperative fever rates were similar and reported rates of 5.9% and 6.8% using pediatric (18Fr) and adult-sized (24Fr) nephroscope, respectively (25). In our study, postoperative fever rates were not signifi- cantly different in the two groups and similar to pub- lished literature. Herein, we compared different-sized instruments and experience time and found that PCNL is an operator- dependent procedure, which improves its results, pre- sumably due to increased operator experience and the involvement of a team with substantial prior knowledge. Furthermore, our results depend on advances to tech- nology that shifted the management of stone disease to minimal invasive modalities. We realized that we treated smaller stones in the second ten years period. The main reasons for this finding are: • Increasing of diagnosis of patients with small stone size due to the novel radiological tools and easier access to health care services. • In our clinic, use of a ESWL machine that uses fluo- roscopy for stone localization (with no ultrasound- guided ESWL machine around the region) • Technological advancement with development of small instruments for urologic endoscopic proce- dures. Limitations of the study included its retrospective nature and the absence of a metabolic evaluation and chemical analysis of the composition of the stone. The second sig- nificant limitation was insufficient data of follow up, especially on group-1 and no standardization of timing or use of imaging tools at follow up. Another limitation of the study was the performance of percutaneous pro- 349Archivio Italiano di Urologia e Andrologia 2020; 92, 4 Success of pediatric percutaneous nephrolithotomy cedures by more surgeons using different instruments at different periods being the experience of each surgeon a possible source of bias. However, a strenght of the study is that the data and results were obtained from a single large volume center. CONCLUSIONS Our study showed that the patient cohort became younger with smaller stone sizes over time. Concordantly, the fluoroscopy time, operation time, blood loss, and complications rates were decreased, and stone free-rates were increased with use of smaller instruments. The stone and sheath size are major factors to predict blood loss and hospital stay. REFERENCES 1. Bartosh SM. Medical management of paediatric stone disease. Urol Clin North Am. 2004; 31:575-87. 2. Türk C, Neisius A, Petr̆ík A, et al. 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Renal parenchymal injury after standard and mini percutaneous nephrostolithotomy. J Urol. 2001; 165:1693-5. 24. Bayrak O, Erturhan S, Seckiner I, et al. Reliability of percuta- neous nephrolithotomy in pediatric patients: comparison of compli- cations with those in adults. Korean J Urol. 2013; 54:383-7. 25. Celik H, Camtosun A, Dede O, et al. Comparison of the results of pediatric percutaneous nephrolithotomy with different sized instruments. Urolithiasis. 2017; 45:203-8. Correspondence Volkan Izol, MD Nihat Satar, MD Yildirim Bayazit, MD Nebil Akdogan, MD Ibrahim Atilla Aridogan, MD Department of Urology, Faculty of Medicine, University of Çukurova, Adana (Turkey) Fatih Gokalp, MD, FEBU (Corresponding Author) fatihgokalp85@gmail.com Osmaniye Government Hospital, Urology Clinic, 80020, Osmaniye (Turkey)