Using the Modified Clavien Grading System to Classify Complications of Percutaneous Nephrolithotomy

Is percutaneous nephrolithotomy effective and safe in infants younger than 2 Years old? Comparison of mini standard percutaneous nephrolithotomy

BACKGROUND

In this study, we aimed to compare the operative outcomes, postoperative outcomes, stone-free status and complications of SPCNL and MPCNL in infants younger than two years of age.

METHODS

We retrospectively analyzed 163 patients younger than two years of age who underwent percutaneous nephrolithotomy (PCNL) in our institution between September 1999 and March 2022. The patients were divided into two groups depending on the tract size. The MPCNL group consisted of 73 patients with a tract of 22 Fr or less, and the SPCNL consisted of 90 patients with a tract greater than 22 Fr.

RESULTS

The median age of 163 patients included in the study was 17.3 (range 7-24) months. Although the median stone size was lower in the SPCNL group, no statistically significant difference was found between the two groups in terms of stone size (p = 0.073). The median operative time was 74.8 min in the MPCNL group and 62.8 min in the SPCNL group, with a statistically significant difference (p = 0.002). Stone free rates (SFR) were 89 % and 90.8 % in the MPCNL and SPCNL groups, and the clinically insignificant residual fragments (CIRF) rates were 11 % and 4.6 %, respectively (p = 0.064). The fluoroscopy time, nephrostomy withdrawal time, and hospitalization stay were similar in the two PCNL groups (p = 0.535, p = 0.253, and p = 0.143, respectively). Postoperative fever was similar in MPCNL and SPCNL groups (p = 0.504). Although bleeding (6.7%-2.7 %) and blood transfusion (3.3%-1.4 %) rates were higher in the SPCNL group, there was no statistically significant difference (p = 0.248 and p = 0.420, respectively). Prolonged urinary leakage occurred in 6 (8.2 %) patients in the MPCNL group and 1 (1.1 %) patient in the SPCNL group, with a statistically significant difference (p = 0.026).

CONCLUSIONS

With the development of MPCNL, the use of SPCNL in infants has decreased considerably. However, SPCNL continues to be an effective and reliable method when needed in suitable patients. Although PCNL in infants shows some differences from adults, it is an effective and safe method for suitable patients.

LEVEL OF EVIDENCE

Although we created our study by retrospectively examining the pediatric urology data that we created prospectively, our study is of a retrospective nature. Therefore the Level of Evidence is 3.

Evaluation of the effect of 9.5/11.5-fr ureteral access sheath use on acute kidney injury with the myo-inositol oxygenase biomarker in patients undergoing retrograde intrarenal surgery: a prospective, randomized, and controlled study

INTRODUCTION

We aimed to investigate whether a low intrarenal pressure provided by ureteral access sheath (UAS) use had a positive effect on the prevention of acute kidney injury through the evaluation of the myo-inositol oxygenase (MIOX).

MATERIAL AND METHODS

The patients were divided into two groups according to whether a 9.5/11.5-Fr UAS was used during retrograde intrarenal surgery (RIRS): UAS group and non-UAS group. RIRS was performed under gravity irrigation and manual pumping was not used. For the measurement of MIOX, 5 cc blood samples were taken from the patients preoperatively and four hours postoperatively.

RESULTS

Operation time and hospital stay were significantly longer in the UAS group. The mean preoperative and postoperative MIOX values were 0.77 ± 0.36 ng/ml and 0.74 ± 0.38 ng/ml, respectively, in the UAS group, and 0.74 ± 0.31 ng/ml and 0.83 ± 0.40 ng/ml, respectively, in the non-UAS group. The mean MIOX change was -0.29 ± 0.36 in the UAS group and 0.08 ± 0.44 in the non-UAS group, indicating no significant difference between the groups.

CONCLUSION

Even if UAS is not used, significant acute kidney injury is not observed under gravity irrigation and therefore, if we avoid manual pumping, the intrarenal pressure remains low, thus potentially rendering the use of 9,5/11,5-Fr UAS unnecessary.

Clinical Utility of S.T.O.N.E, Guy's Scoring System, and Renal Stone Complexity Scoring in Predicting Outcome of Single-Tract Percutaneous Nephrolithotomy

BACKGROUND

Several imaging-based scores have been developed to predict postoperative stone-free state (SFS) and complications. This study aimed to assess the accuracy of the S.T.O.N.E., Guy Scoring System (GSS), and Seoul National University Renal Stone Complexity (S-ReSCS) scores in predicting the outcomes of single-tract percutaneous nephrolithotomy (ST-PCNL). This scoring system holds paramount importance for low-income and low-middle-income countries (LMICs), as it is inexpensive and cost-effective for the healthcare system.

METHODOLOGY

This retrospective study was carried out with 147 participants. Based on the preoperative computerized tomographic (CT) scan, each patient's S.T.O.N.E. score, GSS, and S-ReSCS were recorded. The modified Clavien grading system was used to document intra- and postoperative complications.

RESULTS

The mean age of the sample population was 45 years. SFS was achieved in 110 (74.8%) patients. The number of calyces involved (p = 0.008), S.T.O.N.E. scoring (p = 0.001), GSS (p = 0.008), and S-ReSCS (0.001) correlated well with the SFS. Forty-nine (33.33%) patients developed complications. The most common complications fell within Clavien grade II. No statistical significance was noted between the S.T.O.N.E. score, GSS, and S-ReSCS with the modified Clavien grading system.

CONCLUSION

The S.T.O.N.E. scoring, GSS, and S-ReSCS have a high predictive value for achieving SFS in ST-PCNL. In addition, findings from LMICs are comparable with those from the rest of the world.

Mini-versus standard percutaneous nephrolithotomy in pediatric population: A randomized controlled trial

INTRODUCTION

Mini PCNL has gained popularity in adult patients due to reduction in the complication rate with comparable stone free rate. There is paucity of level 1 evidence regarding the benefit of mini PCNL in the pediatric group.

OBJECTIVE

We performed a randomised study to compare mini PCNL (mPCNL) with standard PCNL (sPCNL) for the management of renal calculi in patients less than 18 years of age in terms of safety, efficacy, and stone-free rate (SFR).

MATERIALS AND METHODS

A randomised controlled trial was performed on 50 children who underwent PCNL from June 2015 to March 2021, who were divided into two groups. Group I had 25 patients managed with mPCNL (sheath size 16.5 Fr) and Group II had 25 patients who underwent sPCNL (sheath size 26 Fr). Primary outcomes including stone free rates (SFR) and hemoglobin drop and secondary outcomes like operative time, complications, pain score, need of analgesia, incidence of nephrostomy site leak, hospital stay in days were compared between the two groups.

RESULTS

The mean age of patients in groups I and II was 9.4 ± 2.6 and 10.4 ± 2.26 years, respectively (p = 0.15). The mean stone sizes in both groups I and II were 18.6 ± 2.56 and 20.2 ± 3.58 mm, respectively (p > 0.05). The stone free rate for group I was 88% and for group II, 92% (p = 0.64). The average drop in hemoglobin was higher in group II compared to group I (1.1 ± 0.31 g/dl and 1.7 ± 0.23 g/dl respectively; p < 0.0001), however the mean blood transfusion rate was not significantly different in both groups. The operating time was shorter in group II compared to group I (p-value - 0.0030). The pain scores were lesser for the group I. Grade I complications were higher in group II as compared to group I (p-0.047); however, grade II complications were comparable in both groups. The mean hospital stay was not significantly different in both groups.

DISCUSSION

This study confirms the role of mini PCNL in pediatric patients with renal stones. The stone clearance rate of mini PCNL is equivalent to standard PCNL, with lesser blood loss and postoperative complications, however with longer operative time during mPCNL. The small number of the participants in both arms is a limitation of this study and may also reflect fewer children with urolithiasis being treated surgically even in a tertiary care referral centre.

CONCLUSIONS

Mini-PCNL offers equivalent stone free outcome with lower complications rate compared to the standard PCNL for all types of renal stones.

Comparative efficacy between retrograde intrarenal surgery with vacuum-assisted ureteral access sheath and minimally invasive percutaneous nephrolithotomy for 1-2 cm infectious upper ureteral stones: a prospective, randomized controlled study

Objective

To observe the efficacy and safety of retrograde intrarenal surgery combined with vacuum-assisted ureteral access sheath (V-UAS) and minimally invasive percutaneous nephrolithotomy (MPCNL) in patients with 1-2 cm infectious upper ureteral stone.

Patients and methods

A total of 173 patients with 1-2 cm infectious upper ureteral stone were prospectively randomized into two groups. Eighty-six in the V-UAS group and 87 cases as control in the MPCNL group. The SFRs at different times (Postoperative 1 day, 2nd week and 4th week) was considered as the primary outcome of the study. The secondary end points were operative time, postoperative hospital stay and operative complications.

Results

There was no obvious difference between two groups in patients' demographics and preoperative clinical characteristics (all P > 0.05). Postoperative data showed that the SFR at postoperative 1 day in the V-UAS group was significantly lower than that in the MPCNL group (73.2% vs. 86.2%, P = 0.034). However, there was no statistical significance between two groups in SFRs during postoperative 2 weeks and 4 weeks (All P > 0.05). The levels of WBC, CRP and PCT were all significant lower in the V-UAS group than those in the MPCNL group at the postoperative 24 h and 48 h (all P < 0.05). Postoperative complications included fever (≥38.5°C), bleeding, pain and urosepsis. In terms of the rates of fever, pain and urosepsis, MPCNL group were all significantly higher than those in the V-UAS group (10.3 vs. 2.4%, P = 0.031; 14.9 vs. 2.4%, P = 0.003; 4.6 vs. 0.0%, P = 0.044; respectively). No significant difference was found between two groups in bleeding. Meanwhile, postoperative hospital stay in the V-UAS group was more shorten than that in the MPCNL group (3.7 vs. 5.9 days, P < 0.001).

Conclusions

Our study showed that RIRS with V-UAS, a new partnership to treat 1-2 cm infectious upper ureteral stones, was satisfying as it achieved a high SFR rate and a low rate of infectious complications. This method was safe and reproducible in clinical practice.

The feasibility of ultrasound-guided mini-percutaneous nephrolithotomy for ESWL-resistant lower calyx renal stones of up to two centimeters: a single center experience

Lower pole renal stones present a significant challenge in urologic practice due to difficulty in accessing the calyx and eliminating fragments. Management options for these stones include watchful waiting for asymptomatic stones, extracorporeal shock wave lithotripsy (ESWL), ureterorenoscopy (URS), and percutaneous nephrolithotomy (PCNL). Mini-PCNL is a newer modification of conventional PCNL. The study aimed to assess the feasibility of mini-PCNL in treating lower pole renal stones equal to or less than 20mm that were not responsive to ESWL therapy. We included 42 patients (24 male and 18 female) with a mean age of 40±2.3 who underwent mini-PCNL at a single urology center between June 2020 and July 2022 and assessed operative and postoperative outcomes. The mean total operative time was 47±3.11 minutes, ranging from 40 to 60 minutes. The stone-free rate was 90%, and the overall complication rate was 26%, which included minor bleeding (5%), hematuria (7%), pain (12%), and fever (2%). The mean hospital stay was 80±3.34 hours (3-4 days). Our findings suggest that mini-PCNL is an effective treatment option for lower pole renal stones that are not responsive to ESWL therapy. The immediate stone-free rate was high, with minimum non-serious complications.

Minipercutaneous Nephrolithotomy in the Management of Large and Complex Renal Calculi in Children: How Effective Is It?

Purpose: To evaluate the efficacy and safety of minipercutaneous nephrolithotomy (PCNL) in the management of large and complex calculi in children. Patients and Methods: From May 2017 to April 2021, a total of 41 pediatric cases were diagnosed with large/complex renal stones (partial-total staghorn) and following a detailed biochemical evaluation and thorough radiological examination (plain abdominal radiograph, urinary ultrasound, noncontrast and/or computed tomography), all cases underwent mini-PCNL procedure for the minimal invasive management of these calculi. Preoperative, intraoperative, and postoperative data were analyzed and reported in detail. Results: A total of 41 procedures were performed in 26 boys and 15 girls (male/female = 1.73). While the age of the kids ranged from 2.5 to 10 years (mean 6.74 ± 2.76), mean size of the stones was 16.28 ± 3.43 mm (range 11-24) with a mean stone density value of 816 HU (range 550-1350). Evaluation of the success rates in terms of complete stone clearance on postoperative day 1 revealed that while 73.2% (30/41), residual fragments have been noted in 11 cases (26.8%). Size of the residual fragments ranged from 2 to 7 mm (mean 4.3). Of those children, 10 cases required flexible ureteroscopy for stone removal, and in 1 case, placement of Double-J was adequate for spontaneous passage. During a 3-month follow-up, the stone-free rate (SFR) increased to 100% without any residual fragment left. Conclusions: Mini-PCNL with holmium laser lithotripsy is an effective and safe treatment alternative in the minimal invasive management of large/complex kidney stones in children with high SFRs.

Prevalence of the Retro-Renal Colon: A Systematic Review and Meta-Analysis with Implications for Percutaneous Nephrolithotomy

BACKGROUND

This systematic review and meta-analysis aims to determine the prevalence of the retrorenal colon (RRC) and its implications in percutaneous nephrolithotomy with the overall objective of promoting the prevention of associated iatrogenic complications.

METHODS

A systematic search of literature was conducted on the electronic databases PubMed, ScienceDirect, and Hinari to identify studies eligible for inclusion. Search results were screened by title and abstract, and those potentially relevant were evaluated by full text. Studies were deemed eligible for inclusion if they reported clear extractable data regarding the prevalence of the retro-renal colon. A meta-analysis was completed using MetaX1 to calculate the pooled prevalence of the retro-renal colon. Sub-group analysis was performed based on geographical regions from which the studies originated, imaging modality, and patient position.

RESULTS

174 records were screened and a total of 10 records included in the analysis with retrospective cohort studies being the most common study design. A male predominance was seen in most sample sizes that had reported data on gender demographics ranging from 41.5-62%. The most common imaging modality utilized was computerized tomography (CT) scan followed by ultrasound. The range of the unweighted prevalence of retro-renal colon across all studies that had absolute numbers reported was from 3.5-25%. One of the studies reported a colonic perforation rate of 0.3% in patients without CT images.

CONCLUSION

The retro-renal colon is a relatively common finding with observed preponderance to females and left lateralization. The presence of RRC increases the likelihood of colon perforations while gaining percutaneous access to the kidney. Pre-procedural imaging can help detect its presence and choose an appropriate route of entry. USG and CT have both been found useful as a modality to pick up RRC.

Efficacy and safety of percutaneous nephrolithotripsy in elderly patients: a retrospective study

Background

Percutaneous nephrolithotripsy (PCNL) is difficult to perform for elderly patients; thus, this study aimed to assess its efficacy and safety in elderly patients aged > 70 years, note any associations between outcomes and patient characteristics, and summarize relevant themes and observations.

Methods

Data from patients older than 70 years who had undergone PCNL for upper urinary tract calculi between January 2016 and January 2021 was retrospectively analyzed. Risk factors for postoperative complications and residual stones were analyzed using multivariate logistic regression.

Results

A total of 116 elderly patients underwent 122 PCNL operations, of which six underwent secondary PCNL operations, and all of which were successfully completed. The average age was 74.6 ± 4.3 years; the average stone size and operation time were 3.5 ± 1.8 (1.2–11 cm), and 71.8 ± 34.1 min, respectively. Of the participants, 16 or 13.8% had postoperative complications and 29 (25%) had residual stones after operation. The stone free rate was 75%. Multivariate analysis revealed that an American Score of Anesthesiology III was an independent risk factor for postoperative complications (odds ratio [OR] = 4.453, p = 0.031), and staghorn calculi were independent risk factors for postoperative residual calculi (OR = 31.393, p = 0.001).

Conclusion

PCNL was shown to be safe and effective for elderly patients aged > 70 years. Further, ASA III was an independent risk factor for postoperative complications, and staghorn calculi were independent risk factors for postoperative residual calculi in elderly patients.

Supine PCNL-5 year experience in a tertiary care center

OBJECTIVE

The prone position for percutaneous nephrolithomy (PCNL) has been widely practiced. There has been a shift from prone position to supine position which showed numerous benefits. The aim of our study is to describe the 5 year experience from the perspective of a tertiary care center using a modified Galdakao supine Valdivia position for total tubeless ultra mini supine PCNL, total tubeless supine PCNL, tubeless supine PCNL, and standard supine PCNL.

MATERIAL AND METHODS

We retrospectively reviewed the data of 90 patients who underwent supine PCNL at the tertiary care center during the period of 5 years from January 2017 to January 2021. The data collection was done from patients' medical records. Pre operatively, complete examination of the patients with laboratory investigations were done. The modified Clavien classification system was used to classify the perioperative complications of PCNL.

RESULTS

Operative time was lowest for ultra mini supine PCNL (50 ± 10.4 min) compared to standard supine PCNL (58 ± 11.2 min). Stones were single in 54 patients and multiple in 40 patients with 4 patients with staghorn stones. The size of the stones in the largest dimension ranged from 1.2 to 5.5 cm.Complete clearance was achieved in 84 (89.7%) patients. Seven patients (7.2%) developed mild fever and four patients (4.5%) required blood transfusion.

CONCLUSION

We found supine PCNL to be an immensely convenient, time-saving practice, and with higher stone free rate compared to prone PCNL. The different techniques of supine PCNL were also useful in patients with horseshoe kidney and calyceal diverticulum which resulted in good outcomes in these patients.

Ptotic Right Retro-renal Liver Lobe Injury During Supine Percutaneous Nephrolithotomy Managed by Hemostatic Sponge

Percutaneous nephrolithotomy is an invasive procedure applied to large and complex stones in the prone or supine position. Various complications—but mostly fever or bleeding—can be seen during and after the procedure. Neighboring organ injuries are rare during access. Liver injuries are rarely seen and have a better clinical prognosis than other organ injuries. We present the management of liver injury with ptosis of the retro-renal right lobe as a complication during supine percutaneous nephrolithotomy.

Percutaneous nephrolithotomy outcomes based on body mass index: A 5-year retrospective study in an Indonesian tertiary hospital

Objectives:

The aim of this study was to evaluate the impact of body mass index (BMI) on percutaneous nephrolithotomy (PCNL) outcomes and complications for nephrolithiasis.

Patients and methods:

Patients with a history of PCNL surgery from 2012 to 2017 in Dr. Soetomo General-Academic Hospital were retrospectively evaluated. Patients were then categorized into four groups: underweight (BMI <18.5 kg/m2), normal (BMI 18.5 to 24.99 kg/m2), overweight (BMI ⩾25–29.9 kg/m2), and obese (BMI ⩾30 kg/m2). The association between BMI, subjects’ characteristics, length of stay, stone-free rate (SFR), and complications were analyzed using one-way analysis of variance (ANOVA) and univariate logistic regression.

Results:

The study included 430 male patients (58%) and 310 female patients (42%). They were classified based on their BMI into underweight ( n = 5, 1%), normal weight ( n = 291, 39%), overweight ( n = 271, 37%), and obese ( n = 173, 23%) groups. The underweight BMI group had a higher average blood loss ( p=0.002) compared to the other groups; however, the univariate logistic regression showed that BMI had no significant effect on SFR ( p=0.491).

Conclusion:

PCNL is safe and feasible to be performed in patients with different BMI as obesity has no impact on the outcomes and complications associated with PCNL.

Level of evidence

3

Tips and Tricks to Improve Ergonomics, Efficacy, Versatility, and Overcome Limitations of Micro Percutaneous Nephrolithotomy

Percutaneous Nephrolithotomy (PCNL) has evolved over the decades from Standard to Mini to Ultramini PCNL to Micro-perc, with miniaturisation being the dominant theme and supine approach gaining momentum world over.

Aim: In literature, miniaturised PCNL with microperc needle access system has raised concerns of intrarenal pressure and has some limitations with its success for larger stones. Our tips and tricks explain how to overcome these pitfalls by utilising the full construct of the needle system to its maximum potential. These will in turn help make the procedure versatile, precise, ergonomical, and enhance a surgeon's experience with improved outcomes for patients especially in large renal stones.

Materials and Methods: We describe the limitations of microperc needle access as stated in literature and proposals by the co-authors using microperc for miniaturised access on how to overcome the same.

Results: A simplified table describing the limitations and tips and tricks on overcoming these is provided for quick reference.

Conclusion: As Technological advancements and techniques for miniaturised access in urolithiasis improve, we believe our suggestions will help surgeons overcome the quoted limitations of microperc needle access for miniaturised PCNL, making this a versatile, safe and efficacious technique even in large and complex stones. A multi centre trial will be the best way to validate the suggestions proposed in this article.

Is Percutaneous Nephrolithotomy the Modality of Choice Versus Extracorporeal Shockwave Lithotripsy for a 20 to 30 mm Single Renal Pelvic Stone with ≤1000 Hounsfield Unit in Adults? A Prospective Randomized Comparative Study

Objectives: To compare the efficacy, complications, and costs of percutaneous nephrolithotomy (PNL) and extracorporeal shock wave lithotripsy (SWL) in the treatment of a 20 to 30 mm single renal pelvic stone with a density ≤1000 HU. Patients and Methods: Eighty patients were prospectively randomized to receive either PNL or SWL during May 2017 to April 2019. The relevant demographic and clinical characteristics were compared. Results: The mean age in the PNL and SWL groups was 43.25 ± 15.16 and 44.18 ± 12.08 years, respectively. The mean stone sizes were 25.2 ± 3.9 and 24.6 ± 2.3 mm, respectively. The stone-free rate (SFR) was significantly different after the primary procedures (92.5% vs 37.5%, respectively; p < 0.04), but it was comparable after 3 months (97.5% vs 90%, respectively; p = 0.723), with a higher rate of auxiliary procedures after SWL (p = 0.017). On multivariate analysis, stone density was the only significant variable for the SFR in the SWL group (p = 0.004). Complications occurred in 27.5% and 22.5% of cases, respectively (p = 0.796). The mean costs of SWL (650.23 ± 424.74 United States Dollars [US$]) were significantly lower than those of PNL (1137.65 ± 224.43 US$; p < 0.0001). Conclusions: The SFRs for PNL and SWL were not significantly different after 3 months in the treatment of a 20 to 30 mm single renal pelvic stone with ≤1000 HU, although PNL provided a significantly higher rate after its primary procedure. SWL was significantly less costly, but it mandated a significantly higher number of auxiliary procedures than PNL.

Safety and efficacy of superior calyceal access versus inferior calyceal access for pelvic and/or lower calyceal renal calculi- a prospective observational comparative study

Objective

To compare efficacy and safety between superior calyceal access and inferior calyceal access for pelvic and/or lower calyceal renal stones.

Methods

Consecutive patients presenting with Pelvic and/or inferior calyceal renal calculi were allocated to the superior calyceal access (group 1) or inferior calyceal access (group 2) treatment arm. Allocation of treatment access was based on the surgeon’s preference. Variables studied included stone free rate, operating time, intraoperative and postoperative complications. Statistical analysis was executed using SPSS, Version 16.0. The statistical significance was evaluated at 5% level of significance (p value < 0.05).

Results

Between July 2018 and February 2019, 63 patients were included in each group. The percutaneous inserted guidewire entered the ureter in 92% in group1 and 74.6% in group 2 (p = 0.034). Stone fragments migrated to the middle calyx in 3.2% in group1 and 9.5% in group 2 (p = 0.033). A second puncture was required in one patient in group 1 and in 5 patients in group 2 (p = 0.04). The operative duration (minutes) was 13.46 ± 1.09 in the group 1 while 16.58 ± 1.44 in the group 2 (p = 0.002). Thoracic complications (hydropneumothorax) occurred to 2 patients in superior calyceal access group managed with intercostal tube drainage (p = 0.243).Post operatively blood transfusion was required in two patients in group 2 (p = 0.169). Angioembolization was done in one patient among the inferior calyceal access approach (p = 0.683). Complete stone clearance assessed at 3 months was 96.8% in group 1 and 85.7% in group 2 (p = 0.046).

Conclusions

Superior calyceal access is a safe and most efficacious in terms of achieving complete stone clearance rate with reduced operative time, minimal blood loss, less need for a second puncture and auxiliary procedures at minimal complications.

Study registration

Clinical trials registry – INDIA; CTRI/2018/07/014,687.

Characterization of Flow-Caused Intrarenal Pressure Conditions During Percutaneous Nephrolithotomy In Vitro

PURPOSE

To investigate renal pelvic pressures during percutaneous nephrolithotomy (PCNL) in the standard, mini, and ultramini PCNL systems.

METHODS

We studied an ultramini PCNL system (UMP, outer shaft diameter 13F), a mini PCNL system (MPCNL, shaft 18F, nephroscope 12F), and a standard PCNL system (SPCNL, shaft 27F, nephroscope 24F). Pressure profiles were first investigated in an open model setup, subsequently in a closed model, and finally in an ex vivo porcine kidney. Measurements were determined with the nephroscope in an advanced and pulled-back position for all models.

RESULTS

In the advanced position, maximum pressures of 41.61 ± 0.20 mmHg (UMP), 15.61 ± 0.15 mmHg (MPCNL), and 15.46 ± 0.14 mmHg (SPCNL) were measured in the closed model. In the pulled-back position, maximum pressures were 16.04 ± 0.22 mmHg (UMP), 17.02 ± 0.11 mmHg (MPCNL), and 20.50 ± 0.11 mmHg (SPCNL). In the ex vivo porcine kidney model, maximum pressures were 13.81 ± 6.04 mmHg (UMP), 5.64 ± 0.21 (MPCNL), and 9.21 ± 0.52 (SPCNL) with the nephroscope pushed to end position. After retracting the nephroscope from the outer shaft, pressures in all systems did not exceed 10 mmHg.

CONCLUSIONS

The maximum pressures achieved with the three PCNL systems in all three models were kept below the 30 mmHg critical threshold value. High pressures were only determined for the UMP system with the nephroscope pushed to its end position. This was attributed to the conical shape of the nephroscope, which occupies the space between the nephroscope and outer shaft, resulting in outflow obstruction.