|Year : 2014 | Volume
| Issue : 1 | Page : 26-31
Training in percutaneous nephrolithotomy: A structured apprenticeship program
Rajendra B Nerli1, Shishir Devaraju1, Murigendra B Hiremath2
1 Department of Urology, KLES Kidney Foundation, KLE University's Jawaharlal Nehru Medical College, Belgaum, Karnataka, India
2 PG Department of Studies in Biotechnology and Microbiology, Karnatak University, Dharwad, Karnataka, India
|Date of Web Publication||7-Feb-2014|
Rajendra B Nerli
Department of Urology, KLES Kidney Foundation, KLE University's Jawaharlal Nehru Medical College, Belgaum - 590 010, Karnataka
Source of Support: None, Conflict of Interest: None
Introduction: Percutaneous nephrolithotomy (PCNL) achieves excellent stone-free rates with acceptable complication rates and is therefore the treatment of choice for large renal calculi. It is generally believed that the establishment of a proper access tract is the crucial step. It is also well-known that PCNL is a difficult surgical technique with reported long learning curves. Apprenticeship is the traditional way of acquiring surgical skills. We report our experience in structured apprenticeship training in PCNL at our center. Materials and Methods: During the study period July 2007 to June 2012, the residents were introduced to a structured apprenticeship training program in PCNL. Results: During the study period, five residents underwent this structured apprenticeship learning. Stone clearance rate of 85.54 ± 2.67 was achieved by all the residents. The stone clearance rate for solitary renal pelvic calculi was 100%. Secondary procedures were required in 15.27 ± 2.74 of cases, blood transfusion rates were 15.2 ± 3.2, and the complication rate was 8.55 ± 1.6. Using the surgical surrogate of operation theatre time and fluoroscopy time, it was observed that competence in PCNL was obtained after 21 cases. Conclusions: Today in the absence of cheap and effective alternative training systems, structured apprenticeship training under the supervision of dedicated trainers is an effective way to train trainees. This helps in reducing the learning curve of the trainees.
Keywords: Apprenticeship, percutaneous surgery, training, urinary stones
|How to cite this article:|
Nerli RB, Devaraju S, Hiremath MB. Training in percutaneous nephrolithotomy: A structured apprenticeship program. J Sci Soc 2014;41:26-31
| Introduction|| |
In a busy urologic department, it is believed that nearly 30% of the surgical workload is related to the management of renal and ureteric calculi.  The primary goal of surgical stone management is to achieve maximal stone clearance with minimal morbidity to the patient. With the introduction of shock wave lithotripsy (SWL) and the continuing advancements in the field of endourology have allowed most patients with renal stones to be treated in a minimally invasive fashion. Most patients harboring "simple" renal calculi <20 mm in size can be treated satisfactorily with SWL. However, in situations involving large renal calculi, stones within dependent or obstructed portions of the collecting system, stones of certain composition (cystine, calcium oxalate monohydrate, and brushite), and obesity or a body habitus that inhibits imaging and targeting of the stone, SWL is associated with poor stone clearance rates and patients are unlikely to achieve a successful outcome.  Today percutaneous nephrolithotomy (PCNL) has become a routinely used technique to treat patients with large or otherwise complex calculi. ,,,
Worldwide, PCNL represents 5% of renal stone surgery.  A significant number of urologists all over the world perform this surgery to treat renal calculi. With over 35 years of its application worldwide, PCNL remains an important/milestone technique with a very low complication rate and a very high success rate.  This remains the major reason or motivation to learn this procedure all the more. However, PCNL is not an easy procedure to learn and is associated with a steep learning curve.  The most important step of PCNL seems to be the ability to obtain an appropriate access to the renal collecting system, which reduces the risk of vascular injury and leads to a better stone-free rate. 
Several efforts have been made to enhance training for percutaneous surgery of the upper urinary tract and most of them have focused on obtaining percutaneous access. Very few data exists in literature on the teaching of renal percutaneous access and PCNL. As of now apprenticeship, inanimate simulators, virtual reality (VR) simulators, and robotics provide training perspectives in the 21 st century. In this paper, we aim to provide an insight into the apprentice training in percutaneous stone surgery at our center and look into proposals for curriculum training on PCNL.
| Materials and Methods|| |
During the study period July 2007 to June 2012, the residents were introduced to a structured apprenticeship training program [Table 1] in PCNL. During the first year of residency, the resident was exposed to the theoretical and practical knowledge of the technique and its indications. The resident observed, assisted, and performed percutaneous nephrostomy under fluoroscopy/ultrasonography (USG) guidance for patients presenting with obstructive systems needing drainage. These procedures were mentored by a staff/senior peer of the department.
|Table 1: Structured curriculum for the training in percutaneous nephrolithotomy |
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During the 2 nd year of residency, the resident was taught as to correct assessment of risk and benefits of PCNL. The art to communicate with the patient and relatives the nature of the procedure as well as alternatives, possible complications and consequences, were imparted. The resident observed, assisted, and performed PCNL in step-wise fashion under the direct mentorship of staff/senior resident. The resident was encouraged to participate in continuing medical education programs and also be able to identify ways to update knowledge and implement new technical skills.
During the final year of residency, the resident performed PCNL on his own or under supervision depending on trainee's skills. The case chosen for PCNL was of the resident's choice. Prior to the procedure, the resident presented the details of the case. The anatomy and the proposed puncture sites were defined. The number of puncture sites was also discussed. Patients on antiplatelet or anticoagulants were not included into the study. Similarly patients with severe cardiac disease were not included in the study. The procedures in a step-wise fashion involved solitary pelvic stones, partial staghorn calculi, and staghorn calculi not needing more than two punctures. The procedures were assessed for operating time, fluoroscopy time, blood-loss/need for intraoperative transfusions, stone clearance, need for secondary procedures, and complications. The student was taught to assess his own professional limitations and refer the patient to a more qualified colleague when indicated.
| Results|| |
During the study period, five residents underwent this structured apprenticeship learning. During the 1 st year, each resident had performed on an average 7.6 ± 1.14 percutenous nephrostomy (PCN's) under fluoroscopy/USG guidance. No complications were noted during this procedure. During the 2 nd year of training, the residents had performed a mean of 16.6 ± 1.52 PCNL under direct supervision and mentorship of the staff/senior peer. These cases were assisted by the staff members or senior residents of the department.
During the 3 rd and final year of residency the residents performed PCNL [Table 2] on their own or under supervision depending on the trainee skills.
The mean operation theatre time ranged from 70.79 to 81.19 min. The mean fluoroscopy time ranged from 12.61 to 15.11 min. Plotting the OT time versus the cases [Figure 1] it was possible to suggest competence in PCNL, which was obtained after a minimum of 21 cases. Similarly plotting the fluoroscopy time versus cases [Figure 2], competence in PCNL was obtained after a minimum of 21 cases.
Stone clearance rate of 85.5 ± 2.67 was achieved by all the residents. The stone clearance rate for solitary renal pelvic calculi was 100%. In cases of residual calculi, most of these residual stones were calyceal calculi, not easily accessible during the procedure. Blood transfusion rates were 15.2 ± 3.2 and the decision for intra/perioperative transfusions was made by the anesthetists. None of the patients had intra/perioperative hypotension secondary to bleeding. The initial PCNL procedure was abandoned in three patients because of intraoperative bleeding leading to poor vision.
Secondary procedures were required in 15.27 ± 2.74 of cases and included a second look procedure in four patients and SWL for patients with leftover stones. Most of the leftover stones were calyceal calculi which could not be accessed during the procedure. Most of these calculi were <7-8 mm in size and were cleared with a single sitting of SWL. Three of the four patients needing a second look procedure, had bleeding during the initial PCNL procedure making the vision poor; hence, the procedure was abandoned and a second sitting of PCNL done a few days later.
The complication rate was 8.55 ± 1.6 and most of the complications were minor, which included fever, urinary tract infection, perinephrostomy urinary leaks and pain. One patient had secondary hematuria and was readmitted 14 days after the initial procedure. The bleeding continued in episodes and the patient needed to undergo renal angiography and selective angioinfarction.
| Discussion|| |
PCNL is the preferred choice of treatment for large (>2 cm) renal or staghorn renal stones.  The planning and successful execution of the initial access into the kidney is crucial to the outcome of PCNL. In many institutions (especially in western hemisphere), the kidney is accessed by an interventional radiologist in the radiology department, requiring PCNL to be a staged procedure. A recent American survey revealed that only 11% of urologists performing PCNL routinely obtained percutaneous access by themselves.  Reasons for this trend may include the lack of training, a personal comfort level, and other parameters as may the availability of better equipment in the radiology suite or the costs related to the extra time to obtain access.  The urologist's ability to access the kidney in the operating room, permitting PCNL to be carried out in one stage, is advantageous for several reasons. The inefficiency of having the patient attend in the operating room for retrograde ureteric catheter insertion, then having to be transferred to the radiology suite to place the tract, and then returning to the operating room for stone removal, is eliminated. The urologist's selection of the optimum tract based on the intrarenal anatomy and the ability to make secondary tracts as required,  permit more effective stone removal. Watterson et al.,  also found access-related complications were fewer and stone-free rates improved when the urologist made the percutaneous access.
The PCNL procedure has a steep learning curve and if not performed properly, can be associated with a high complication rate in the beginning of the experience.  To define the surgical learning curve properly, it is important to determine surrogate markers to evaluate the surgical expertise and the number of procedures needed to gain surgical competence in the PCNL procedures. Very few publications are available today on this topic. To define the learning curve for PCNL there are some potential surrogate markers (or outcomes) which include stone clearance rate, complication rate, operation time, fluoroscopic screening time, and radiation dose. Using these markers, it has been suggested that competence at performing PCNL is reached after 60 cases and excellence is obtained after 115 cases.  Tanriverdi et al.,  have studied the learning curve of one surgeon prospectively, using many parameters, including stone-free rate and complication rate. The two markers showing improvement were the operation time and the fluoroscopic screening times. No further decrease in the operation time was observed after case number 60.
A drop in the mean fluoroscopy screening time was observed from a peak of 17.5 ± 3.2 min in the first 15 cases to 8.9 ± 4.3 min for cases 46 through 60. This decline continued in cases 61-104 but was not significant. These authors suggested that competence in PCNL is obtained after 60 cases.
A survey in the United States showed that residents were comfortable with percutaneous access after an average of 21.2 ± 4.5 access procedures.  Conversely, urologists who were comfortable performing percutaneous access after residency had performed significantly more percutaneous access procedures during their residency than those who were uncomfortable (24.4 ± 5.6 and 10.6 ± 3.1 procedures, respectively; P = 0.046).  Therefore, the authors suggested that performing ≥24 percutaneous access procedures during residency might increase resident proficiency immediately after residency. It is also well-known that residents trained to perform PCNL during residency were more comfortable with this procedure than those who did not receive training in PCNL during residency.  Our study shows that competence in PCNL was achieved by the residents after a minimum of 21 cases. We used the OT time and fluoroscopy time individually to assess the learning curves. A minimum of 20-25 cases of PCNL need to be performed by the resident under structured apprenticeship to make the resident competent and confident enough.
The most common method of acquiring surgical skills in PCNL today is by traditional apprenticeship which involves an extensive period of training with patients. The learning process begins with theoretical approach as written in books and journals. This is followed by mentored practice on patients until the trainee is mature enough to perform on his own. Nevertheless, an enormous gap exists between what can be read in books or taught by experts and the reality encountered when operating on patients. With the introduction of audiovisual technology, the apprentice has the opportunity to watch recorded real procedures before switching to real practice. Several models  have been developed to train urologists in the art of PCNL. Animal models closely mimic reality; however, training on animals is difficult to organize and not close enough to human reality and moreover is very expensive. Surgical stimulation is being increasingly considered for training and testing. Presently two types of surgical stimulators exist, inanimate and VR virtual stimulators.  Hacker et al.,  have used an ex vivo perfused porcine kidney, a chicken carcass, artificial stone, and all the equipment required for a PCNL procedure. Though the model is inexpensive, introducing animal organs in an operating room and the lack of kidney motion will limit application of this bench model. Since 1995, manually positioned and fully automated robots were introduced to assist in providing renal access for PCNL procedure; however, the size and complexity precluded their use in routine clinical practice.  Recently, a new technique using a portable mechanical gantry with a needle guiding device, C-arm fluoroscopy, and a laptop computer containing the software and graphic user interface for selecting the targeted calyx has been established.  Although the last technique is portable, light-weight, and simple to set up and operate, providing accuracy in gaining calyceal access, the cost of manufacturing the gantry and needle positioning mechanism is approximately US$1500 and, most importantly, it was tested on synthetic and animal models only. Very few teaching institutions in India have facilities for teaching PCNL on animal/VR models. In the absence of such training methods, it is the responsibility of trainers to develop effective apprenticeship program.
It is very important today that an urologist must learn how to perform a percutaneous access safely by himself.  The ability to secure a safe and precise percutaneous access is an essential step in performing PCNL, and many techniques to establish renal access have been described in the literature. Shergill et al.,  identified an easy technique to establish the correct depth of initial percutaneous needle insertion which they have labeled it as ''The 3-Finger Technique.'' They have successfully used this technique to demonstrate and teach PCNL access. The trainees were able to achieve percutaneous access without immediate or late complications. Despite the fact that several devices have evolved as educational tools, it needs to be determined whether these tools can be used for validation of surgeon's skills. It is necessary for young urologists and trainees to embrace new training technologies, attend workshops, and actively participate in their applications. A proper curriculum for training in PCNL needs to be established. Theoretical knowledge and information can be passed on successfully to trainees by the end of the residency program; however, the level of surgical skills and performance depends on the case load of the training center, the trainees individual skills, and preferences.
| Conclusion|| |
Training in PCNL is associated with a steep learning curve that is mainly related to obtaining renal access. The quality of training during residency is dependent on the availability of complete up-to-date equipment, recruitment of patients, mentorships, and the skills of the trainee. Learning curves in our apprenticeship program reach a plateau after 21 procedures performed by the resident on its own. In addition, the resident needs to participate in continuing education programs, workshops so as to maintain proficiency.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]