The New Generation Mini-PCNL System - Monitoring and Controlling of Renal Pelvic Pressure by Suctioning Device for Efficient and Safe PCNL in Managing Renal Staghorn Calculi

International Alliance of Urolithiasis (IAU) consensus on miniaturized percutaneous nephrolithotomy

Over the past three decades, there has been increasing interest in miniaturized percutaneous nephrolithotomy (mPCNL) techniques featuring smaller tracts as they offer potential solutions to mitigate complications associated with standard PCNL (sPCNL). However, despite this growing acceptance and recognition of its benefits, unresolved controversies and acknowledged limitations continue to impede widespread adoption due to a lack of consensus on optimal perioperative management strategies and procedural tips and tricks. In response to these challenges, an international panel comprising experts from the International Alliance of Urolithiasis (IAU) took on the task of compiling an expert consensus document on mPCNL procedures aimed at providing urologists with a comprehensive clinical framework for practice. This endeavor involved conducting a systematic literature review to identify research gaps (RGs), which formed the foundation for developing a structured questionnaire survey. Subsequently, a two-round modified Delphi survey was implemented, culminating in a group meeting to generate final evidence-based comments. All 64 experts completed the second-round survey, resulting in a response rate of 100.0%. Fifty-eight key questions were raised focusing on mPCNLs within 4 main domains, including general information (13 questions), preoperative work-up (13 questions), procedural tips and tricks (19 questions), and postoperative evaluation and follow-up (13 questions). Additionally, 9 questions evaluated the experts' experience with PCNLs. Consensus was reached on 30 questions after the second-round survey, while professional statements for the remaining 28 key questions were provided after discussion in an online panel meeting. mPCNL, characterized by a tract smaller than 18 Fr and an innovative lithotripsy technique, has firmly established itself as a viable and effective approach for managing upper urinary tract stones in both adults and pediatrics. It offers several advantages over sPCNL including reduced bleeding, fewer requirements for nephrostomy tubes, decreased pain, and shorter hospital stays. The series of detailed techniques presented here serve as a comprehensive guide for urologists, aiming to improve their procedural understanding and optimize patient outcomes.

Intelligent control of pressure based on ureteral access sheaths: renal pelvic pressure during flexible ureteroscope perfusion at different sites

OBJECTIVE

This study aimed to evaluate the accuracy and effectiveness of renal pelvic pressure (RPP) control during flexible ureteroscopic perfusion at various sites.

METHODS

Flexible ureteroscopy for the intelligent control of RPP was based on a ureteral access sheath (UAS) that integrated pressure measurement and suction functions (with automatic adjustment). Eleven consecutive patients with indurating nephrostomy tubes were enrolled. The nephrostomy tube was connected to a disposable invasive blood pressure sensor. The RPP was zeroed after the pressure stabilized. The flow rate and control value were set at 100 ml/min and - 5 mmHg, respectively. An 8.5 Fr flexible ureteroscope was irrigated at the renal pelvis, as well as the upper, middle, and lower calyces of the kidney for 1 min.

RESULTS

All 11 patients with upper urinary tract calculi underwent successful UAS placement. Pressures measured by the sheath and fistula during perfusion were - 5.07 ± 1.41 and - 4.89 ± 1.07 mmHg at the renal pelvis, -5.16 ± 1.36 and - 5.12 ± 1.32 mmHg at the upper calyces, -4.98 ± 0.87 and - 5.39 ± 1.01 mmHg at the middle calyces, as well as -4.95 ± 1.56 and - 5.64 ± 1.24 mmHg at the lower calyces, respectively. There were no significant differences in pressure between the sheath and fistula groups or in sheath and fistula pressures among parts. The RPP fluctuated; however, all values were within the safe limit of 20 mmHg.

CONCLUSION

The UAS-based pressure monitoring technology can accurately and reliably monitor and control RPP within a set range.

Assessment of Effectiveness and Safety of Aspiration-Assisted Nephrostomic Access Sheaths in PCNL and Intrarenal Pressures Evaluation: A Systematic Review of the Literature

Background: Different suction-assisted nephrostomic sheaths have been developed for percutaneous nephrolithotomy (PCNL). Objectives: (1) To examine PCNL techniques performed with different aspiration-assisted sheaths (Clear Petra® sheath, Superperc, SuperminiPCNL, and a miniPCNL patented sheath), with specific regard to effectiveness and safety outcomes in adult and paediatric patients; (2) to extrapolate intrarenal pressure (IRP) data during these procedures. Methods: A systematic literature search was performed in accordance with PRISMA guidelines. Relevant articles up to 8 February 2024 were included. Results: Twenty-five studies were selected, thirteen retrospective and twelve prospective. The use of four different aspirating sheaths for miniPCNL was reported: Clear Petra® sheath, Superperc, SuperminiPCNL, and a miniPCNL patented sheath. Stone free rates (SFRs) across techniques ranged from 71.3% to 100%, and complication rates from 1.5% to 38.9%. Infectious complication rates varied from 0 to 27.8% and bleeding complication rates from 0 to 8.9%. Most complications were low grade ones. The trend among studies comparing aspiration- and non-aspiration-assisted miniPCNL was towards equivalent or better SFRs and lower overall infectious and bleeding complication rates in suction techniques. Operation time was consistently lower in suction procedures, with a mean shortening of the procedural time of 19 min. Seven studies reported IRP values during suction miniPCNL. Two studies reported satisfactory SFRs and adequate safety profiles in paediatric patient cohorts. Conclusions: MiniPCNL with aspirating sheaths appears to be safe and effective in both adult and paediatric patients. A trend towards a reduction of overall infectious and bleeding complications with respect to non-suction procedures is evident, with comparable or better SFRs and consistently shorter operative times. The IRP profile seems to be safe with the aid of aspirating sheaths. However, high quality evidence on this topic is still lacking.

The safety and efficacy of Sotn ureteroscopy for renal and upper ureteral calculi: a prospective multicenter randomized controlled trial

BACKGROUND

Sotn ureteroscopy is a new lithotripsy procedure developed on the basis of ureteroscopy and includes a rigid ureteral access sheath, standard mirror, lithotripsy mirror, and Sotn perfusion aspirator. Thus, we performed a prospective multicenter randomized controlled trial comparing the safety and efficacy of Sotn ureteroscopy in the treatment of renal and upper ureteral calculi.

METHODS

In this study, 224 patients with renal and upper ureteral calculi were randomly divided equally into study and control groups from March 2018 to March 2022. All the patients were approved by the hospital ethics committee (proof number: ZF-2018-164-01 and ZF-2018-165-01) of the Second Affiliate Hospital of Guangzhou University of Chinese Medicine in China. The primary outcome was stone-free rate (SFR) assessed by computed tomography on the 1st day and month after treatment and operation duration. The secondary outcome was postoperative complication rate.

RESULTS

In total, for upper ureteral calculi, the SFR of 1 day after operation of the Sotn ureteroscopy group was significantly higher than the rigid ureteroscopy group (83.6% vs. 60%, P=0.006). Moreover, operative time (33.7±1.80 vs. 52.9±2.73 min, P<0.005) of the Sotn ureteroscopy group was significantly lower than the rigid ureteroscopy group. Additionally, the SFR of 1 day after operation and operative time for the study group (Sotn ureteroscopy combined with flexible ureteroscopy) and the control group (flexible ureteroscopy alone) were 63.2% and 36.8% (P=0.005), 65.6±4.06 and 80.3±4.91 (P=0.023), respectively. However, there were no significant differences in the SFR of 1 month after operation, success rate of ureteral access sheath placement, and postoperative complications between the two groups (P>0.05). In subgroups with stone diameters ≥1.5 cm and stone CT values ≥1000 Hounsfield units, Sotn ureteroscopy showed more advantages in terms of the SFR of 1 day after operation. Importantly, complications such as ureteral injury, sepsis, fever, and severe hematuria were not statistically different between the two groups (P>0.05).

CONCLUSIONS

For renal and upper ureteral calculi, Sotn ureteroscopy has the advantage of a higher SFR of 1 day after the operation and a shorter operative time, suggesting that the Sotn ureteroscopy may have further potential applications in clinics.

Prevention of complications in endourological management of stones: What are the basic measures needed before, during, and after interventions?

Objective

This narrative review aims to describe measures to minimise the risk of complications during percutaneous nephrolithotomy (PCNL), ureteroscopy, and retrograde intrarenal surgery.

Methods

A literature search was conducted from the PubMed/PMC database for papers published within the last 10 years (January 2012 to December 2022). Search terms included "ureteroscopy", "retrograde intrarenal surgery", "PCNL", "percutaneous nephrolithotomy", "complications", "sepsis", "infection", "bleed", "haemorrhage", and "hemorrhage". Key papers were identified and included meta-analyses, systematic reviews, guidelines, and primary research. The references of these papers were searched to identify any further relevant papers not included above.

Results

The evidence is assimilated with the opinions of the authors to provide recommendations. Best practice pathways for patient care in the pre-operative, intra-operative, and post-operative periods are described, including the identification and management of residual stones. Key complications (sepsis and stent issues) that are relevant for any endourological procedure are then be discussed. Operation-specific considerations are then explored. Key measures for PCNL include optimising access to minimise the chance of bleeding or visceral injury. The role of endoscopic combined intrarenal surgery in this regard is discussed. Key measures for ureteroscopy and retrograde intrarenal surgery include planning and technique to minimise the risk of ureteric injury. The role of anaesthetic assessment is discussed. The importance of specific comorbidities on each step of the pathway is highlighted as examples.

Conclusion

This review demonstrates that the principles of meticulous planning, interdisciplinary teamworking, and good operative technique can minimise the risk of complications in endourology.

Experimental study of a new technique for minimally invasive percutaneous nephrolithotomy: intelligent pressure-controlled minimally invasive percutaneous nephrolithotomy

BACKGROUND

To test the reliability and safety of a newly invented technique for minimally invasive percutaneous nephrolithotomy, intelligent pressure-controlled minimally invasive percutaneous nephrolithotomy (IPC-MPCNL).

METHODS

Eighteen kidneys of nine female pigs were randomly divided into three groups. Those in Groups A and B underwent IPC-MPCNL through the new system composed of a pressure-measuring MPCNL suctioning sheath and an irrigation and suctioning platform with pressure feedback control. The infusion flow rate was 500 ml/min in Group A and 750 ml/min in Group B. Those in Group C underwent MPCNL at an infusion flow rate of 500 ml/min. The renal pelvic pressure (RPP) monitored by a ureteral catheter and that monitored by the pressure-measuring sheath in Groups A and B were compared. The RPP in Group C was monitored by a ureteral catheter.

RESULTS

The RPP measured by the pressure-measuring sheath and that measured by the ureteral catheter in Group A was - 5.59 ± 1.95 mmHg and 4.46 ± 2.08 mmHg, respectively. The RPP measured by the pressure-measuring sheath and that measured by the ureteral catheter in Group B was - 4.00 ± 2.01 mmHg and 5.92 ± 2.05 mmHg, respectively. Hence, the RPPs measured by the pressure-measuring sheath in Groups A and B were consistent with those measured by the ureteral catheter. The RPP in Group C was 27.75 ± 5.98 mmHg (large fluctuations).

CONCLUSIONS

IPC-MPCNL can be used to accurately monitor the RPP and maintain it within a preset safe range via suction. The new technique and the new system are safe and reliable.

Experimental and clinical applications and outcomes of using different forms of suction in retrograde intrarenal surgery. Results from a systematic review

OBJECTIVE

To identify the latest advances in suction devices and evaluate their effect in Retrograde intrarenal surgery (RIRS) and ureteroscopy for stones.

BASIC PROCEDURES

A systematic literature search was performed on 4th January 2023 using Scopus, PubMed, and EMBASE. Only English papers were included; both pediatric and adult studies were accepted. Duplicate studies, case reports, letters to the editor, and meeting abstracts were excluded.

MAIN FINDINGS

Twenty-one papers were selected. Several methods have been proposed for suction use in RIRS, such as through the ureteral access sheath or directly to the scope. Artificial intelligence can also regulate this system, monitoring pressure and perfusion flow values. All the proposed techniques showed satisfactory perioperative results for operative time, stone-free rate (SFR), and residual fragments. Moreover, the reduction of intrarenal pressure (induced by aspiration) was also associated with a lower infection rate. Even the studies that considered kidney stones with a diameter of 20 mm or higher reported higher SFR and reduced postoperative complications. However, the lack of well-defined settings for suction pressure and fluid flow prevents the standardization of the procedure.

CONCLUSION

Aspiration device in the surgical treatment of urinary stones favours a higher SFR, reducing infectious complications, as supported by the included studies. RIRS with a suction system provided to be a natural successor to the traditional technique, regulating intrarenal pressure and aspirating fine dust.

Upper urinary tract pressures in endourology: a systematic review of range, variables and implications

OBJECTIVES

To systematically review the literature to ascertain the upper tract pressures generated during endourology, the relevant influencing variables and clinical implications.

MATERIALS AND METHODS

A systematic review of the MEDLINE, Scopus and Cochrane databases was performed by two authors independently (S.C., N.D.). Studies reporting ureteric or intrarenal pressures (IRP) during semi-rigid ureteroscopy (URS)/flexible ureterorenoscopy (fURS)/percutaneous nephrolithotomy (PCNL)/miniaturized PCNL (mPCNL) in the period 1950-2021 were identified. Both in vitro and in vivo studies were considered for inclusion. Findings were independently screened for eligibility based on content, with disagreements resolved by author consensus. Data were assessed for bias and compiled based on predefined variables.

RESULTS

Fifty-two studies met the inclusion criteria. Mean IRP appeared to frequently exceed a previously proposed threshold of 40 cmH₂ O. Semi-rigid URS with low-pressure irrigation (gravity <1 m) resulted in a wide mean IRP range (lowest reported 6.9 cmH₂ O, highest mean 149.5 ± 6.2 cmH₂ O; animal models). The lowest mean observed with fURS without a ureteric access sheath (UAS) was 47.6 ± 4.1 cmH₂ O, with the maximum peak IRP being 557.4 cmH₂ O (in vivo human data). UAS placement significantly reduced IRP during fURS, but did not guarantee pressure control with hand-operated pump/syringe irrigation. Miniaturization of PCNL sheaths was associated with increased IRP; however, a wide mean human IRP range has been recorded with both mPCNL (lowest -6.8 ± 2.2 cmH₂ O [suction sheath]; highest 41.2 ± 5.3 cmH₂ O) and standard PCNL (lowest 6.5 cmH₂ O; highest 41.2 cmH₂ O). Use of continuous suction in mPCNL results in greater control of mean IRP, although short pressure peaks >40 cmH₂ O are not entirely prevented. Definitive conclusions are limited by heterogeneity in study design and results. Postoperative pain and pyrexia may be correlated with increased IRP, however, few in vivo studies correlate clinical outcome with measured IRP.

CONCLUSIONS

Intrarenal pressure generated during upper tract endoscopy often exceeds 40 cmH₂ O. IRP is multifactorial in origin, with contributory variables discussed. Larger prospective human in vivo studies are required to further our understanding of IRP thresholds and clinical sequelae.

Current evidence for suction in endourological procedures: comprehensive review of literature

PURPOSE OF REVIEW

To identify the latest advances on the utilization of suctioning devices in the surgical treatment of urinary stones.

RECENT FINDINGS

Advances are being made to incorporate suction and pressure control capabilities in percutaneous and ureteroscopic lithotripsy. Multiple retrospective studies and few prospective studies have shown that suctioning with minimally invasive percutaneous nephrolithotomy, commonly referred to as Super MiniPerc, can lead to better stone-free rates (SFR) and shorter operative time with lower incidence of infectious complications. Suctioning during retrograde intrarenal surgery (RIRS) has mainly been achieved through suctioning ureteral access sheath. Here as well, the incorporation of suction improved the SFR, but most importantly, reduced the risk of postoperative infectious complications.

SUMMARY

Theoretically suction in endourological procedures could facilitate stone debris removal and could reduce intrarenal pressure at the same time allowing for increased irrigation flow potentially decreasing operation time and infectious complications. These claims are supported in contemporary clinical studies, reporting superior SFR and reduced postoperative infectious complications in both percutaneous nephrolithotomy and RIRS.

Intrarenal pressures during percutaneous nephrolithotomy: a porcine kidney model

BACKGROUND

Increased intrarenal pressure during endoscopic lithotripsy is associated with increased adverse outcomes. The objective of this study was to evaluate the effect of various devices on IRP during percutaneous intrarenal surgery in ex vivo porcine kidney models.

METHODS

Whole intact porcine urinary tracts were harvested. Intrarenal pressure was measured using cystometrometry software. Intrarenal pressure during PCNL was recorded using variations of percutaneous access sheath size, irrigation height of 100 cm and 60 cm, use of a ureteric catheter and use of suction. The primary outcome was absolute IRP measurements. Secondary outcomes were comparisons of IRP between techniques.

RESULTS

Using a 30 Fr vs 26 Fr access sheath and 26 Fr nephroscope the mean pressure at an irrigation height of 60 cm was significantly lower than 100 cm (p = 0.0013 vs p < 0.0001, respectively). Pressure's during mini-PCNL were significantly higher than conventional PCNL in all variations. Using the 16.5 Fr access sheath and 12 Fr nephroscope produced a significantly lower pressure at a 60 cm irrigation height than 100 cm (p = 0.0010). IRP was significantly lower with a ureteric catheter in place vs no ureteric catheter at 100 cm (p = 0.0015) and at 60 cm (p = 0.0040).

CONCLUSIONS

Using standard PCNL tract sizes intrarenal pressure varied significantly depending on the height of the irrigation fluid. Mini-PCNL is at higher risk of pathological pressure, however, the use of a ureteric catheter significantly decreased pressure. To maintain safe IRP during PCNL urologists should be aware of these significant variations.

Comparison of the Efficacy of ShuoTong Ureteroscopy and Simple Flexible Ureteroscopy in the Treatment of Unilateral Upper Ureteral Calculi

Background: ShuoTong ureteroscopy (Sotn-ureteroscopy, ST-URS), a new lithotripsy operation method developed on the basis of ureteroscopy, is widely used to treat ureteral stones in China. Its composition includes rigid ureteral access sheath, standard mirror, lithotripsy mirror, and ShuoTong perfusion aspirator (ST-APM). Here, we compared the efficacy and safety of the ST-URS and the flexible ureteroscope (F-URS) holmium laser lithotripsy in the treatment of unilateral upper ureteral calculi. Methods: Retrospective analysis was conducted on the clinical data of 280 patients who met the inclusion 1) urinary tract CT was diagnosed with unilateral single upper ureteral calculi above the L4 lumbar spine; 2) patient age was from 18 to 80 years old; 3) patients were informed and consented to this study; and 4) patients were approved by the hospital ethics committee (proof number: KY-2019-020) and the exclusion criteria for unilateral upper ureteral calculi in the First Affiliated Hospital of Xiamen University from January 2018 to November 2020, and they were divided into the ST-URS group and the flexible ureteroscopy (F-URS) group. Results: The stone-free rate of 1 day after operation of the ST-URS group was significantly higher than the F-URS group (63.71 vs. 34.62%, P < 0.0001). The operative time (38.45 vs. 46.18 min, P = 0.005) and hospitalization cost (27,203 vs. 33,220 Yuan, P < 0.0001) of the ST-URS group were significantly lower than the F-URS group. There were no significant differences in the success rate of ureteral access sheath placement, operative blood loss, stone-free rate of 1 month after operation, postoperative complications, postoperative hospital stay, and postoperative visual analog scale (VAS) pain score between the two groups (P > 0.05). In subgroups of a diameter of calculi ≥ 1.5 cm, calculi CT numerical value ≥ 1,000 Hounsfield unit and the preoperative hydronephrosis range ≥ 3.0 cm, ST-URS shows more advantages in the operative time, stone-free rate of 1 day after the operation, the hospitalization cost, and the incidence of postoperative complications. Conclusion: In unilateral upper ureteral stones treated with a holmium laser, compared with the simple F-URS, the ST-URS has a shorter operative time, lower hospitalization cost, and a higher stone-free rate of 1 day after the operation, suggesting that the ST-URS could be more widely applied in clinics.

Role of Intrarenal Pressure in Modern Day Endourology (Mini-PCNL and Flexible URS): a Systematic Review of Literature

PURPOSE OF REVIEW

To review the latest evidence about intrarenal pressures (IRPs) generated during flexible ureteroscopy (fURS) and mini percutaneous nephrolithotomy (mPCNL) and present tools and techniques to maintain decreased values.

RECENT FINDING

fURS and PCNL constitute the primary means of stone treatment. New flexible ureterorenoscopes with small diameter and miniaturized PCNL instruments achieve optimal stone-free rates (SFRs) while decreasing invasiveness and morbidity. Nevertheless, endourologists must remain cognizant regarding the dangers of increased IRPs to avoid complications. Current research presents essential information for urologists regarding this topic. During fURS, using a ureteral access sheath (UAS), we avoid extremely high IRPs with all irrigation types. During mPCNL, pressure remains low, mainly using the purging effect or a vacuum-assisted sheath. Devices of intraoperative IRP measurement and intelligent pressure control have proven their feasibility, accuracy and efficacy. These will have an increasing role to play in the future management of stone disease.

Percutaneous nephrolithotomy with suction: is this the future?

PURPOSE OF REVIEW

The armamentarium of percutaneous nephrolithotomy (PCNL) and the strategy to perform the procedure is constantly evolving. The innovation and development in techniques lead to further miniaturization in PCNL devices and change the lithotripsy and stone removal strategy. Suctioning in PCNL offers urologist a new conception in renal stone management. The present review evaluates the latest results on efficacy, safety and feasibility of suctioning PCNL techniques.

RECENT FINDINGS

Recent literature reported the outcomes of different suctioning PCNL techniques. Most of these studies demonstrated good efficacy when comparing conventional PCNL. Suctioning PCNL improving the lithotripsy efficiency to enhance the stone-free rate (SFR) and reducing renal pelvic pressure to attenuate postoperative infectious complications. The advantage of suction also helps overcome the limitation of potentially higher intrarenal pressure and prolonged operative time in Mini-PCNL.

SUMMARY

PCNL with suctioning represents a valuable new tool in the armamentarium of modern endourologists. This innovative approach can offer improved safety and efficacy with lower complications rates and higher cost effectiveness than the traditional PCNL technique.

Clinical Assessment of Risk Factors for Renal Atrophy After Percutaneous Nephrolithotomy

Background

This study explored the risk factors for renal atrophy after percutaneous nephrolithotomy (PCNL), and provides a reference for clinical prevention of renal atrophy after PCNL.

Material/Methods

According to the inclusion and exclusion criteria, the clinical data of 816 patients who underwent PCNL in our hospital from May 2013 to February 2018 were retrospectively collected. Depending on whether the patient had kidney atrophy, they were divided into a renal atrophy group and a non-renal atrophy group. We collected and analyzed data on patient sex, age, kidney location, duration of disease, stone size, hydronephrosis, renal calculus position (renal ureteral junction or multiple pyelonephritis-associated stones), operation time, intraoperative blood loss, perfusion pressure, and pyonephrosis. The indicators with statistically significant differences were selected and multivariate logistic regression analysis was carried out to determine the risk factors for renal atrophy.

Results

Among 816 patients, 49 had renal atrophy and the incidence rate was 6.01%. Univariate analysis and multivariate logistic regression analysis showed that independent risk factors for renal atrophy after PCNL were: duration of the disease longer than 12 months (OR=4.216, P=0.003, 95% CI: 1.714, 7.354), perfusion pressure >30 mmHg (OR=3.895, P=0.001, 95% CI: 1.685, 8.912), moderate and severe hydronephrosis (OR=5.122, P<0.001, 95% CI: 1.847, 9.863), stones located at the junction of the renal pelvis (OR=3.787, P=0.001, 95% CI: 1.462, 7.654), stones located in multiple calyces (OR=4.531, P=0.014, 95% CI: 1.764, 8.196), and pyonephrosis (OR=10.143, P<0.001, 95% CI: 2.214, 16.248).

Conclusions

The main risk factors for renal atrophy after PCNL are: course of disease more than 12 months, moderate and severe hydronephrosis, pyonephrosis, multiple calyceal stones, stones at the junction of the renal pelvis, and intraoperative high perfusion pressure.

Suction Use During Endourological Procedures

PURPOSE OF REVIEW

Equipment used in endourology is constantly evolving due to increasing incidence of urolithiasis. Suctioning has been used mainly in PCNL in conjunction with ultrasonic and ballistic devices for stone removal. Recently technological advances permitted the use of suctioning in more endourological techniques. This review aims to summarize the literature regarding these advancements and analyze the upcoming results.

RECENT FINDINGS

Several centers have conducted experimental and clinical studies on suctioning use during PCNL, mPCNL, and ureteroscopy and concluded that it is an effective and safe adjustment that improves stone-free rates and limits complication rates after these procedures. Suctioning use during common endourological procedures led to improved safety and efficacy among several indications. Due to the observational nature and small sample size of many studies, larger RCTs are needed to make safe conclusions.

Tract sizes in percutaneous nephrolithotomy: does miniaturization improve outcome?

PURPOSE OF REVIEW

To provide a summary of surgical outcomes in percutaneous nephrolithotomy (PCNL) according to various techniques and tract sizes.

RECENT FINDINGS

Recent literature in this field concluded that standard PCNL (sPCNL) remains the optimal treatment for stones between 1 and 2.5 cm and can be managed with tracts 14-20 F, whereas small stones less than 1.5 cm can be treated with tracts under 14 F. According to new datasets, smaller tracts can be equally effective in the treatment and might offer the possibility to reduce bleeding, length of hospital stay, postoperative pain as well as overall complication rates when compared with sPCNL. On the other hand, longer operative time as well as lower stone-free rates, which have been the main drawbacks of the miniaturized approach, have recently shown to be comparable with sPCNL.

SUMMARY

At present, tract size is a highly debatable topic in percutaneous stone therapy. New systems for miniaturized PCNL have been developed to achieve comparable stone-free rates while reducing the incidence of common complications. The adoption of these techniques demands skilled surgeons and institutional investment for the acquisition of new equipment.

The Comparison Study of Flexible Ureteroscopic Suctioning Lithotripsy With Intelligent Pressure Control Versus Minimally Invasive Percutaneous Suctioning Nephrolithotomy in Treating Renal Calculi of 2 to 3 cm in Size

Purpose. To compare the efficacy and safety of flexible ureteroscopic suctioning lithotripsy (FURS) using patented designed intelligent irrigation and suctioning intraluminal pressure-control platform and integrated pressure-measuring suctioning ureteral access sheath versus minimally invasive suctioning percutaneous nephrolithotomy (MPCNL) in treating renal calculi at 2 to 3 cm in size. Methods. Ninety-one patients who met the criteria were included in the study. Among these, 46 patients underwent transurethral flexible ureteroscopic lithotripsy and the other 45 patients underwent MPCNL. We retrospectively analyzed the clinical data for the 2 groups and parameters including stone clearance rate, complication rate, average operative time, average postoperative hospitalization duration, and average postoperative hemoglobin level decrease were compared. Results. The hospitalization time for the FURS group was 3.53 ± 1.25 days, which was statistically shorter than that of the MPCNL group, which was 6.54 ± 2.36 days. There was significantly more patients needing pain medication postoperatively in the MPCNL group with statistical difference between the 2 groups ( P = .015). Also, there was more significant hemoglobin level drop in the MPCNL group with statistical difference between the 2 groups. However, there were no statistical differences between the 2 groups on average operative time and stone clearance rate. Conclusion. Both the operative methods are safe and efficacious in treating solitary renal calculus at 2 to 3 cm in size. However, FURS has more advantages including shorter hospital stay, less complication, and less bleeding.

The Influence of Super-Mini Percutaneous Nephrolithotomy on Renal Pelvic Pressure In Vivo

OBJECTIVE

Renal pelvic pressure (RPP) is expected to rise during percutaneous procedures. A very small tract size was expected to bring high RPP, and super-mini percutaneous nephrolithotomy (SMP) uses a 14F sheath, which is even smaller than that used in mini-percutaneous nephrolithotomy, so the RPP in SMP was more worrisome. Interestingly, the sheath had suction, which aimed to decrease the RPP, so we measured the RPP in an in vivo model to explore the relationship of implying negative pressure through the sheath with the RPP.

METHODS

Seventy-four consecutive patients were enrolled for RPP measurement during SMP between April 2016 and July 2017. Prospective RPP measurements were recorded using the MINDRAY-PM9000 monitor by connecting its baroceptor of the invasive blood pressure channel to a retrogradely inserted renal pelvic open-ended ureteric catheter. RPP data were collected each second by a computer program. All data were evaluated statistically with SPSS 13.0 software.

RESULTS

During SMP with a 14F irrigation-suction sheath, the average RPP was 19.51 ± 5.83 mm Hg. The median accumulative time of RPP ≥30 mm Hg was 55 (3-345) seconds. Postoperative fever was recorded in four patients (5.4%). A receiver operating characteristic -curve analysis showed that when suction pressure was set to 0.03 Mpa (≈230 mm Hg), irrigation pressure between 200 and 250 mm Hg, and the irrigation flow to 320 mL/minute, the accumulative high RPP was more likely <50 seconds, and the sensitivity and specificity were 75.0% and 66.7%, respectively.

CONCLUSIONS

The RPP in SMP remains <30 mm Hg. Controlling the pressures as well as the flow of irrigating saline is important for the safety and efficiency of percutaneous procedures.

Pressure matters 2: intrarenal pressure ranges during upper-tract endourological procedures

PURPOSE

To perform a review on the latest evidence related to intrarenal pressures (IRPs) generated during upper-tract endourology, and present different tools to maintain decreased values, to decrease complication rates.

METHODS

A literature search was performed using PubMed, restricted to original English-written articles, including animal, artificial model and human studies. Different keywords were: percutaneous nephrolithotomy, PCNL, ureteroscopy, URS, RIRS, irrigation flow, irrigation pressure, intrarenal pressure, intrapelvic pressure and renal-pelvic pressure.

RESULTS

IRPs reported during retrograde intrarenal surgery (RIRS), PCNL, miniPCNL, and microPCNL range 40.8-199.35, 3-40.8, 10-45 and 15.37-41.21 cm H₂O, respectively. By utilizing ureteral access sheaths (UASs) IRPs usually remain lower than 30 cm H₂O at an irrigation pressure (IP) of ≤ 100 cm H₂O but could increase to > 40 cm H₂O at an IP of 200 cm H₂O. By utilizing the minimally invasive PCNL system, IRPs remain low at 20 cm H₂O even at high IPs. Utilizing endoluminal isoproterenol during RIRS, could reduce IRP increases with a rate of 27-107%, and maintain low IRPs values, usually below 50 cm H₂O.

CONCLUSIONS

Increased IRP values have been reported during RIRS and UASs constitute the most efficient tool for decreasing them. IRPs during mini-PCNL can be decreased utilizing the vacuum-cleaner and purging effects but might remain uncontrolled during micro- and ultra-mini PCNL. Intraluminal pharmacological treatment could play a role in IRP decrease, with isoproterenol being the most studied agent.

A Novel Flexible Ureteroscopy with Intelligent Control of Renal Pelvic Pressure: An Initial Experience of 93 Cases

BACKGROUND

Flexible ureteroscopic lithotripsy (URS) is rapidly becoming a first-line therapy for patients with renal and ureteral calculi. Most current medical infusion devices can only monitor infusion flow and pressure, but not renal pelvic pressure (RPP).

PATIENTS AND METHODS

We designed a patented intelligent system to facilitate flexible URS that included an irrigation and suctioning platform and a ureteral access sheath (UAS) with a pressure-sensitive tip, enabling regulation of the infusion flow precisely and control of the vacuum suctioning by computerized real-time recording and monitoring of RPP. A stable RPP was ensured by pressure feedback technology. Ninety-three patients with renal or ureteral calculi participated in the study and received flexible URS. Gravel particles were sucked out automatically during the flexible URS. Patients were evaluated on postoperative days 1 and 30 by X-ray of kidneys, ureters, and bladder to assess stone-free status.

RESULTS

In 81 of the 93 patients, only one surgery was needed to remove the stone. There were nine cases who failed the first surgery due to difficulty in placing the UAS, but flexible URS was performed in these patients after indwelling a Double-J stent to the ureter with the calculus for 2 weeks. Three cases were converted to percutaneous nephrolithotomy due to significant ureteral stenosis. For the 90 patients who underwent flexible URS, the actual RPP was controlled under 20 mmHg with clear operative visualization. The stone-free rates at postoperative days 1 and 30 were 90.0% (81/90) and 95.6% (86/90), respectively. Clavien I complications were noted in 13 cases, while Clavien II complications were noted in two cases. No major complications (Clavien III-V) were noted.

CONCLUSIONS

Our patented system is technically feasible, safe, and efficient for treating upper urinary calculi. The advantages include breaking stones effectively and low complication rates because of its automatic control of RPP.