Abstract
Purpose:
The aim of our study is to evaluate the pediatric percutaneous nephrolithomy (PCNL) learning curve of a surgeon.
Patients and Methods:
The cases of the first 70 pediatric patients with renal stone disease who underwent PCNL by a surgeon who had performed 120 PCNLs on adults at our clinic were analyzed retrospectively. The patients were divided into two groups depending on their date of surgery (n=35), and the localization of the stone, stone burden, access numbers on the kidney, stone-free rates, blood transfusion in the perioperative-postoperative period, duration of hospitalization, and complications were recorded.
Results:
The mean of patients in group 1 was 11.45±3.93 (2–16) years, while the same value for group 2 was 8.42±4.21 (1–16) years (P<0.005). There was no statistically significant difference between the two groups regarding stone surface area (group 1: 332.57±192.46 [100–700] mm2; group 2: 322.85±165.20 [150–900] mm2), number of access, stone localization, duration of hospitalization, duration of surgery, blood replacement, and Double-J implantation (P>0.005). While the stone-free rate was 82.85% for group 1, it was 100% for group 2 (P>0.005).
Conclusions:
Pediatric PCNL can be performed safely after 120 adult PCNL procedures, although this number varies from one surgeon to another. After the first 35 pediatric PCNL experiences, PCNL can safely be performed even on very young children, and higher stone-free rates can be obtained.
Introduction
Endoscopic renal stone surgery, which has been in practice for the last 50 years, is the greatest and most significant development in urologic practice. These surgical innovations started with the definition of endoscopic surgical methods that were the least damaging to the kidneys. Percutaneous nephrolithotomy (PCNL) is one of the most important and most frequently used of these endoscopic surgery methods. 2 PCNL was first used for the pediatric population in 1985. Although there were hesitations about its use in the period when it was first used for pediatric stone disease, now it has become a routine surgical method and has replaced open surgery. 3
A certain learning curve is needed to start performing PCNL for adult patients. It has been reported that surgical notion is obtained after performing PCNL on 60 adult patients. 4 There is, however, no clear consensus on the issue for pediatric patients. The procedure is relatively harder in children than in adults because of the difficulty in accessing the organ because the kidney is smaller and mobile, because of the limited movement in the kidney, and because of less tolerance toward hemodynamic and hypothermic changes. It has been suggested that the mentioned difficulties that make pediatric cases special can be overcome by adequate surgical experience gained from adult cases. In our study, we aimed to demonstrate the pediatric PCNL learning curve of a surgeon who had performed 120 PCNLs in adults in our clinic.
Patients and Methods
This study covers the retrospective analysis of 70 patients with pediatric renal stone disease who underwent PCNL by the same surgeon between January 2007 and December 2011.
Urine for culture was obtained from all patients before the operation. Patients with urinary infections started treatment with antibiotics depending on their culture results, and procedures were planned after the sterilization of urine. All patients underwent metabolic evaluation that included urine pH, serum calcium, phosphorus, and uric acid determination. Measurement of 24-hour urinary calcium, phosphorus, uric acid, creatinine, and electrolytes was also performed. For patients for whom PCNL was planned, abdominal and pelvic plain radiography and noncontrast abdominal CT were performed. The stone burden was calculated in mm2 through the multiplication of the length with the width of the stone as seen in the preoperative plain abdominal radiograph.
The localization of the stone, the number of renal accesses, the type of lithotripter used, stone-free rates, blood transfusion in the perioperative-postoperative period, duration of hospitalization, and complications during the PCNL procedure were recorded (Table 1). Blood transfusion criteria were accepted fall in hemoglobin (Hb<10 g/dL) and hemodynamic instability.
All patients were evaluated with radiography of the kidneys, ureters, and bladder or noncontrast CT (those with nonopaque stones) in the early postoperative period regarding residual stone existence. Residual stone load was calculated in mm2.
All procedures were performed by the same surgeon (IS). The surgeon started performing pediatric PCNL procedure after 120 adult PCNL experiences.
Applied PCNL method
After the patient received general anesthesia in the supine position and then was placed in the lithotomy position, open-ended 3F or 4F ureteral catheters were inserted in the ureteral orifice of the kidney in which stones existed. The patient was then transferred to the prone position. To avoid hypothermia, irrigation fluids were warmed and the extremities were covered with warming blankets. Genitalia were covered with a lead protection panel. The pelvicaliceal system was imaged (scanned) by delivering a radiopaque substance through the ureteral catheter under fluoroscopic guidance. A suitable calix was inserted using a 19-gauge percutaneous input needle under fluoroscopy. Guidewire (Sensor Guidewire, 0.038 inches) was forced forward through the inside of the needle. Amplatz renal dilator (Marflow, Switzerland) materials were passed over the wire one by one gradually so as to enlarge the entrance point to the kidney as much as 26F (Karl Storz, Germany). Then 24F (R. Wolf, Germany) and 15.5F (R. Wolf, Germany) rigid nephroscopes were used to image endoscopically. The instruments were chosen according to patient age.
The stones were broken using pneumatic, ultrasonic, or combined lithotripsy with respect to stone size and then removed by using capture forceps. At the end of the process, a Foley catheter was placed through a nephrostomy sheath, and nephrostomy location was controlled by releasing an opaque substance through the Foley catheter.
The nephrostomy tube was removed after antegrade nephrostography was performed. Double-J (D-J) implantation was performed for a patient with a PCNL application in the case of persistent urine leakage from the nephrostomy tract after nephrostomy tube removal.
SPSS Windows version 11.5 software was used for analysis, and P values lower than 0.05 were accepted as significant. The Mann Whitney U test was used to compare the two groups.
Results
The first 35 patients who underwent PCNL because of pediatric renal stone disease constituted group 1, while the second group of 35 patients formed group 2. The mean age of patients in group 1 was 11.45±3.93 (2–16) years, while the mean age of patients in group 2 was 8.42±4.21 (1–16) years. The mean age of group 1 was higher than that of group 2 in a statistically significant way (P<0.005).
While the mean figure for stone surface area in group 1 of patients who underwent PCNL was 332.57±192.46 (100–700) mm2, the same figure for group 2 was 322.85±165.20 (150–900) mm2. There was no statistically significant difference between the two groups regarding stone surface area (P<0.005).
There was no statistically significant difference between PCNL group 1 and group 2 regarding laterality, the number of accesses (minimum: 1–maximum: 3) (group 1 mean: 1.22±0.49; group 2 mean: 1.05±0.23), stone localization (upper pole, lower pole, pelvis, staghorn), duration of hospitalization, and duration of surgical procedure (P>0.005).
When the two groups were compared regarding stone-free rate, it was seen that while 29 of 35 patients in group 1 (82.85%) were stone free, all the patients in group 2 (100%) became stone free. There was no statistical difference between the two groups regarding stone-free rates (P>0.005).
Five (14.28%) patients in group 1 received blood transfusion while two (5.71%) of the patients in group 2 received a blood transfusion. Three patients in group 1 and two patients in group 2 had D-J catheter implantation on obtaining nephrostomy results in the postoperative period showing prolonged urine leak from the nephrostomy tract. There was no decisive statistical difference between the two groups regarding minor complications such as blood replacement and D-J implantation (P>0.05). In addition, the effect of tract size and use of pediatric sized instruments on blood loss were analyzed, and there was no statistical difference (P>0.05).
The only major complication was seen in group 1. Colonic injury occurred with the patient in the prone position and on puncture of the lower pole. The colonic injury was diagnosed intraoperatively. Intraoperative consultation was undertaken with a pediatric surgeon, who advised primary repair. The patient became stone free and was discharged on postoperative day 4 without any additional complication.
Discussion
The goal of treatment in urinary system stone diseases is to obtain a rapid and high level of success through a minimally damaging treatment of the kidney. To this end, today PCNL has replaced open surgery because it offers short-term hospitalization and a low cost of treatment, provides patients with the opportunity for early convalescence in the postoperative period, needs minimal parenchymal injury, and does not cause cosmetic deformity with incision scars. 5
The routine performance of PCNL can be obtained after a certain learning curve, as is the case with all surgical procedures. The issue as to what constitutes the objective indicator of the PCNL learning curve is still being discussed. Some studies compared the duration of the procedure, the duration of fluoroscopy, success rates, and the amount of bleeding to this end. Although the procedure seems to be complicated and difficult at first sight, it can be performed successfully after the learning steps are completed thoroughly.
Tanriverdi and associates 4 have investigated the learning curve of a surgeon who had no previous PCNL experience in their study covering 104 patients. The authors concluded that the surgeon gained experience after 60 cases and that the duration of the procedure and fluoroscopy shortened in time. Ziaee and colleagues, 6 however, stated that a surgeon who never had solo PCNL experience had fewer complications and spent less time for the procedure after completing 45 cases. They determined that competence and excellence were achieved after 45 and 105 patients in PCNL procedures. Allen and coworkers, 7 on the other hand, underlined that a surgeon gained competence after 60 PCNL procedures while he or she became excellent after 115 cases.
PCNL, however, is relatively more difficult to perform on children than adults because of the difficulty to access the organ since the kidney is smaller and mobile, because of the limited movement of the kidney, and because of less tolerance toward hemodynamic and hypothermic changes. These difficulties decrease over time in pediatric patients thanks to experiences gained from surgery in adults because complications seen in PCNL procedures mainly take place during the first access (wrong tract choice and related bleeding, adjacent organ damage, renal pelvis rupture etc.). Tanriverdi and associates 4 stated that the most time-consuming part of the PCNL curve was the renal access and renal dilation. It is suggested that both complications related to the first access and the risk of hemodynamic and hypothermic instability related to prolonged procedural duration in pediatric patients decrease thanks to experiences gained from adult patients regarding this stage. In our study, although there is no statistical significance, the drop in the mean number of accesses in group 2 explains the decrease in the amount of bleeding in the group.
We have concluded that after 120 adult PCNL cases of experience, a safe and effective PCNL can be performed on the pediatric population. We choose 35 children in each group because we would like to show differences between early and late experience. When we compare the pediatric PCNL experience in itself, it is seen that because there was a statistically significant age difference between the first 35 and the last 35 cases, one starts to perform PCNL on younger children in group 2 with the experience gained. Further, the fact that patients in group 2 had a 100% stone-free rate attracts attention, although there is no statistically significant difference between the groups. The only major complication, colon perforation, took place in the first group.
Dogan and colleagues 8 underlined that PCNL can be performed on children of all ages in a safe and effective way. Guven and coworkers 9 also stated that PCNL can safely be performed on even 3-year-old children. In a study conducted by Kumar and colleagues, 10 the authors put forward that PCNL could be performed in a safe and effective way for pediatric staghorn stones. All of these procedures, however, are obtained after a certain amount of experience. We, in our study, underline that a surgeon needs to perform a certain number of adult PCNL procedures first to gain this experience. Although this number varies from one surgeon to another, we wanted to demonstrate that pediatric PCNL can safely be performed after 120 adult PCNL procedures. Because pediatric cases have their unique learning curves, one can mention 30 to 40 cases to pinpoint expertise for these cases.
Conclusion
As a result, to have routine pediatric PCNL procedures at a clinic, the surgeons first should start having adult PCNL procedures at their clinics. After that, they can begin performing pediatric PCNL procedures in a safe and effective way for children of all ages and for stones of all sizes through their experiences gained in years.
Footnotes
Disclosure Statement
No competing financial interests exist.