Abstract
Background:
The aim of this study was to report current practices of percutaneous nephrolithotomy (PCNL) among endourologists.
Methods:
An internet survey was administered to Endourological Society members. Responders were distributed into three groups according to the number of PCNL cases per year (<50, 50–100, >100). PCNL technical details as well as opinions regarding specific clinical case scenarios were evaluated and compared between groups.
Results:
We received 300 responses from 47 different countries. Prone position was used in 77% of cases, while 16% used supine position and only 7% used modified lateral decubitus. Most endourologists performed their own access. There were no significant differences between the three groups regarding patient position (p = 0.1), puncture acquisition by urologist or radiologist (p = 0.2) and fluoroscopic puncture technique (p = 0.2). Endourologists with high annual PCNL practice (>100) had least probability to utilize nephrostomy tube (p = 0.0005) or use balloon dilator (p = 0.0001). They also had the highest probability of performing mini-PERC (p = 0.0001).
Conclusions:
The majority of endourologists performing PCNL obtain their own access. Prone positioning is predominant, while totally tubeless PCNL are uncommon. Mini-PERC is gaining more popularity among endourologists. Most endourologists follow the guidelines for their choice of treatment modality in different sizes and locations of upper tract calculi.
Introduction
Upper urinary tract calculi affect up to 8.8% of population in the United States. 1 Treatment modalities for renal calculi currently revolve around stone size and location. Percutaneous nephrolithotomy (PCNL) is the gold standard for treating large renal calculi >2 cm.2,3 PCNL has become favored over open nephrolithotomy because of its lower morbidity. 4 However, in comparison with ureteroscopy (URS) or extra-corporeal shock wave lithotripsy (SWL), PCNL has been considered the most complicated stone surgery technique. 5
The routine use of PCNL in some places may be limited by the difficulty in gaining percutaneous access. Renal access can be challenging, and in some centers, it is performed by intervention radiologists. 6
Endourologists use different techniques and instruments in performing PCNL. Only a few studies in the literature report trends in the use of PCNL. Questions asked in these studies were limited and did not cover different techniques.7–9 In this study we report current practices of PCNL among endourologists all over the world through detailed questions covering the majority of steps and techniques.
Materials and methods
Using Survey Monkey, a web-based survey (Supplementary Data; available online at www.surveymonkey.com) was created and administered via blast e-mails to members of the Endourological Society. The survey questionnaire covered demographic data, number of cases performed annually and details pertaining to technique of PCNL practice as well as opinions regarding specific clinical case scenarios.
We asked our respondents to specify their range of PCNL practice in the total number of cases that they perform on an annual basis. We categorized them based on their annual cases flow to <50 cases per year, 50–100 cases per year and >100. PCNL technical details were evaluated and compared between the three groups.
Statistical analysis was performed using JMP™ (SAS Campus Drive Building T Cary, NC, USA). PCNL technical details were evaluated and compared between the three groups using Chi-square and Wilcoxon signed-rank tests with p < 0.05 considered statistically significant.
Results
We had 300 responses from Endourological Society members from 47 countries. The distribution of responders according to their location is shown in Table 1.
Geographical distribution of responders.
As shown in Table 2, the majority of respondents (77%) placed patients in the prone position, while 16% placed them in supine position and 7% or placed them in a modified lateral position. These results did not vary when categorized according to the case flow (p = 0.1).
Questions related to guidelines of stone management.
CT, computed tomography; KUB, kidney ureter bladder plain X ray; N/A, not applicable; PCNL, percutaneous nephrolithotomy; POD, postoperative day; U/S, ultrasound.
Access was performed by the urologist themselves in 82% of cases, performed by a radiologist in 7% and by both in 11% with no statistical difference among the three categories of respondents (p = 0.2). Access was achieved under fluoroscopic guidance in 75%, by both fluoroscopic and ultrasonic guidance in 21%, while only 4% reported that they depend on ultrasound solely to guide their access. This practice did not differ between subgroups of respondents (p = 0.9).
Stiff guidewire was used by 40%, while 32% used hydrophilic guidewire and 27% used a Teflon coated guidewire.
A safety guidewire was used by 69% of endourologists However, 56% of responders with high case volume did not use a safety guidewire.
Balloon dilators were used by 41%, compared with 32% who used Alken’s metal telescoping dilators followed by Amplatz polyurethane progressive dilators in 14% and one-shot Amplatz polyurethane dilators in 13%.
It was observed that 47% of our respondents perform mini-PERC. The majority of those who practice it were among the practitioners with higher cases flow (44%). There was a statistically significant difference between the more experienced group and the other two groups in omitting use of guidewire and post-PCNL nephrostomy (Table 2).
On a question regarding use of prophylactic antibiotic, 76% of respondents used single dose antibiotics before surgery, 15% used a 3-day course and 8% used a 7-day course prior to surgery.
PCNL monotherapy with multiple access was the most common staghorn stone treatment modality used by 47% of responders, followed by combined PCNL and flexible ureteroscopy by 33%, while PCNL monotherapy with single access was used by 20%. Interestingly 40% of our responders used combined flexible ureteroscopy and PCNL to clear complex staghorn stones.
Table 3 presents questions asked for choice of management modalities in view of guidelines. It was observed that 96% used PCNL for treatment of lower calyceal stones ⩾2 cm. Flexible ureteroscopy (46%) followed by PCNL (40%) followed by SWL (14%) were the choice for treatment of 1–2 cm lower calyceal stones.
Questions related to guidelines of stone management.
SWL, extra-corporeal shock wave lithotripsy; LAP, laparoscopic; PCNL, percutaneous nephrolithotomy; RIRS, retrograde intrarenal surgery; URS, ureteroscopy.
For lower calyceal stones <1 cm, 50% used flexible ureteroscopy, 47% used SWL and 3% used mini-PERC. Overall, two-thirds of responders used PCNL for treatment of pelvic stones of 2 cm.
Differences in doing a tubeless technique, getting access by urologist or radiologist, combined techniques, position, and access guidance among responders from different regions were not statistically significant in our study.
Variations in trends depending on the region of responders were shown in Table 4.
Regional variations in trends.
Discussion
In the treatment of renal calculi, PCNL is a complex minimally invasive approach. 10 Obtaining renal access is an important initial step. Our results indicate that the majority of responders from the Endourological Society established their own renal access. Interestingly, in our survey, 67% of North American responders obtained their own access. This figure is higher than other previous reports such as the Bird and colleagues survey in 2003 who reported 11% only. This is because their responders were all actively practicing members of the north central section of the American Urological Association including general urologists and trainees. Another study by Jayram and Matlaga, reported that 20.4% of North American certifying urologists obtained their own access in 2012. In this survey, responders were endourologists who are members of the Endourological Society with greater expertise in endourology that can explain our results compared with previous surveys.8,9 Ultimately the quality of access has a direct impact on the outcome of the procedure. In a study comparing urologist versus interventional radiologist-obtained renal access, significantly fewer access-related complications and better stone-free rates were achieved when the urologist gained access. 11 In another series with over 1200 patients, similar access-related complications and stone-free rates were achieved, despite more complex stones and challenging access in the urologists’ access group. 12
Many reports in the literature have discussed the success and safety of ultrasonic-guided access either in conjunction with fluoroscopy or solo ultrasonic-guided PCNL. Advocates of ultrasonic-guided access reported that its advantages over fluoroscopic guidance were avoidance of radiation risks and lower possible risk of adjacent organ injury.13–16 The choice of access guidance modality was not reported in previous surveys.7–9 However our data reflect that the trend among endourologists is still with the use of fluoroscopic-guided access.
The results of the present study emphasized the popularity of the prone position over supine PCNL. This may be explained by the higher stone-free rate and familiarity of the prone position.17,18 In previous surveys, the choice of patient position was not addressed.7–9 Our data confirmed that the combined PCNL with flexible ureteroscopy approach is gaining more popularity. This agrees with other studies reporting the advantages of the combined antegrade and retrograde approaches in the management of complex renal stones.19,20
There is a known debate regarding exit strategy in PCNL. Many studies reported safety of tubeless PCNL.19,21 Although studies indicated that tubeless PCNL may be well tolerated, it has not become routine practice, and importantly, the term ‘tubeless’ is often misleading and a postoperative stent or ureteral catheter is usually maintained. On the other hand, the advantages of tubeless PCNL were challenged with a 1-day nephrostomy tube.22–24 Our data and previous surveys, emphasized that absolute tubeless PCNL did not gain popularity.7–9
Questions for the choice of treatment options in different stone sizes and locations were also not covered in previous reports.7–9 The results emphasized that most endourologists follow the current guidelines in the management of urolithiasis. 25 Interestingly, our data indicated that the use of retrograde intrarenal surgery (RIRS) has an increasing role in contemporary practice in management of lower calyceal stones <1 cm and between 1–2 cm than SWL and in combination with PCNL in management of staghorn stones.
Recently, with advancement in technology and miniaturization of instruments, smaller access sheaths are now available and increasingly used. Different terminology was used to describe different sheaths sizes as mini-PERC, ultra-mini-PERC and micro-PERC procedures. Results of different series are promising.26–28 Interestingly, our survey data reflected that the use of mini-PERC is gaining more popularity. This was not covered in previous surveys.8,9
Our results confirmed that the case load per year has an impact on different techniques in PCNL. This was evident in differences between the three groups in the use of mini-PERC, and omitting the use of safety guidewires, and post-PCNL nephrostomy which were more in the more experienced group.
Differences in most of the trends among endourologists from different regions were not significant in our study. North American endourologists used more balloon dilators and ultrasonic lithotripter than endourologists from other regions. Asian endourologists did more mini-PERCs than other regions.
Limitations of the study may be in the application of a single choice answer rather than different choices with different grades, which would give a better interpretation of the results.
Conclusions
The majority of endourologists performing PCNL obtain their own access. Prone positioning is predominant, while totally tubeless PCNL is uncommon. Mini-PERC is gaining more popularity among endourologists. Most endourologists follow the guidelines for their choice of treatment modality in different sizes and locations of upper tract calculi.
Footnotes
Acknowledgements
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. This article does not contain any studies with animals performed by any of the authors. Informed consent was obtained from all individual participants included in the study.
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Conflict of interest statement
The authors declare that there is no conflict of interest.