[Minimally invasive percutaneous nephrolitholapaxy (MIP)]

Comparison of lithotripsy methods during mini-PNL: is there a role for ballistic lithotripsy in the era of high-power lasers

BACKGROUND

For renal stones > 20 mm, percutaneous nephrolithotomy (PNL) offers the best stone clearance rates with acceptable complication rates. This study aimed to compare the efficiency of high-power holmium YAG laser and ballistic lithotripsy during mini-PNL.

METHODS

Data from 880 patients who underwent mini-PNL for renal stones was investigated retrospectively. The study utilized propensity score matching to create two groups: laser lithotripsy (n = 440) and ballistic lithotripsy (n = 440). The groups were matched based on stone size, Guy's stone score, and stone density. The main objectives of the study were to assess the stone-free rate (SFR), duration of surgery, and complication rates.

RESULTS

The average age of the population was 51.4 ± 7.1 years, with a mean stone size of 28.6 ± 8.3 mm and a mean stone density of 1205 ± 159 HU. There were no significant differences between the groups. The SFRs of the laser lithotripsy and ballistic lithotripsy were 92.5% and 90.2%, respectively (p = 0.23). The laser lithotripsy group had a notably shorter surgery time (40.1 ± 6.3 min) compared to the ballistic lithotripsy group (55.6 ± 9.9 min) (p = 0.03). Complication rates were similar (p = 0.67).

CONCLUSIONS

Our study shows that a high-power holmium YAG laser provides quicker operation time compared to ballistic lithotripsy. However, ballistic lithotripsy is still an effective and safe option for stone fragmentation during mini-PNL. In places where a high-power holmium YAG laser is not available, ballistic lithotripters are still a safe, effective, and affordable option for mini-PNL.

Impact of Renal Access Angle and Speed of Nephroscope Retrieval Movements on the Vortex Effect

OBJECTIVE

To analyze the influence of different renal access angles (AAs) and nephroscope retrieval speeds on the efficacy of the vortex effect (VE) in mini-percutaneous nephrolithotomy (mini-PCNL). This study aimed to understand the poorly understood physical components of the VE.

MATERIALS AND METHODS

A Pexiglas™ (KUS®) model was built based on the dimensions of a 15/16 F mini-PCNL set (Karl Storz). The flow rate was continuous via an automatic pump and calibrated to achieve hydrodynamic equivalence to the real equipment. One experiment consisted of manually retrieving all 30 stone phantoms (3 mm diameter) utilizing only the VE. Cumulative time to retrieve all stones was measured. An accelerometer recorded instant speeds of the nephroscope every 0.08 seconds (s), and 3 experiments were performed at each angle (0°, 45°, and 90°). A logistic regression model was built utilizing maximum speeds and access angles to predict the effectiveness of the VE.

RESULTS

Mean cumulative time for complete stone retrieval was 28.1 seconds at 0° vs 116.5 seconds at 45° vs 101.4 seconds at 90° (P < .01). We noted significantly higher speeds at 0° compared to 45° and 90° (P < .01); however, differences in average and maximum speed between 45° and 90° were not statistically significant (P = .21 and P = .25, respectively). The regression model demonstrated a negative association between increasing maximum speed and VE's effectiveness (OR 0.547, CI 95% 0.350-0.855, P < .01). When controlling for maximum speed, the 0° angle had significantly higher chances of achieving at least a partially effective VE.

CONCLUSION

Increasing the renal access angle or nephroscope extraction speed negatively impacts the effectiveness of the VE. This significantly increased procedure time in the laboratory model, suggesting that the VE is less effective at higher sheath angles.

The Vortex Effect in Minimally Invasive Percutaneous Nephrolithotomy

OBJECTIVE

To describe the physical principles of the vortex effect to better understand its applicability in minimally invasive percutaneous nephrolithotomy (MIP) procedures.

METHODS

Two acrylic phantom models were built based on the cross-sectional area (CSA) ratio of a MIP nephroscope and access sheaths (15/16F and 21/22F MIP-M, Karl Storz). The nephroscope phantom was 10 mm in diameter. The access sheaths had diameters of 14 mm (CSA ratio: 0.69) and 20 mm (CSA ratio: 0.30). The models were adapted to generate hydrolysis, and hydrogen bubbles enhanced flow visualization on a green laser background. After calibration, the experimental flow rate was set to 12.0 mL/s. Three 30-second trials assessing the flow were performed with each model. Computational fluid dynamic simulations were completed to determine the speed and pressure profiles.

RESULTS

In both models, as the incoming fluid from the nephroscope phantom attempted to move toward the collecting system, a stagnation point was demonstrated. No fluid entered the collecting system phantom. Utilizing the 14 mm sheath, we observed a random generation of several vortices and a pressure gradient (PG) of 114.4 N/m2 between the nephroscope's tip and stagnation point. In contrast, examining the 20 mm sheath revealed a significantly smaller PG (19.4 N/m2) and no noticeable vortices were noted.

CONCLUSION

The speed of the fluid and equipment geometry regulate the PG and the vortices field, which are responsible for the production of the vortex effect. Considering the same flow rate, a higher ratio between the CSA of the nephroscope and access sheath results in improved efficacy of the vortex effect.

Is There Still a Place for Percutaneous Nephrolithotomy in Current Times?

Background: Percutaneous nephrolithotomy (PCNL) and its miniaturized modifications are usually considered the standard surgical options for large (>20 mm) staghorn and infected stones. Moreover, PCNL is a viable alternative to retrograde intrarenal surgery (RIRS) for smaller stones (<20 mm) in the presence of anatomical malformations or inaccessible lower pole stones. However, due to the advancements in laser and scope technology, RIRS is expanding its indications with the potential benefits of lower complications and a shorter hospital stay. Methods: A literature search using the PUBMED database from inception to June 2022 was performed to explore the current role of PCNL in endourology. The analysis involved a narrative synthesis. Results: PCNL confirmed its role in the treatment of large and complex stones; moreover, miniaturized PCNL has become more competitive, gaining space among classic indications of flexible ureteroscopy. Conclusions: considering all the evaluated subgroups, we can conclude that PCNL is an old fascinating procedure and is here to stay.

Application of a three-dimensional visualization model in intraoperative guidance of percutaneous nephrolithotomy

OBJECTIVES

To establish a three-dimensional visualization model of percutaneous nephrolithotomy, apply it to guiding intraoperative puncture in a mixed reality environment, and evaluate its accuracy and clinical value.

METHODS

Patients with percutaneous nephrolithotomy indications were prospectively divided into three-dimensional group and control group with a ratio of 1:2. For patients in three-dimensional group, positioning markers were pasted on the skin and enhanced computed tomography scanning was performed in the prone position. Holographic three-dimensional models were made and puncture routes were planned before operation. During the operation, the three-dimensional model was displayed through HoloLens glass and visually registered with the patient's body. Puncture of the target renal calyx was performed under three-dimensional-image guiding and ultrasonic monitoring. Patients in the control group underwent routine percutaneous nephrolithotomy in the prone position under the monitoring of B-ultrasound. Deviation distance of the kidney, puncture time, puncture attempts, channel coincidence rate, stone clearance rate, and postoperative complications were assessed.

RESULTS

Twenty-one and 40 patients were enrolled in three-dimensional and control group, respectively. For three-dimensional group, the average deviation between virtual and real kidney was 3.1 ± 2.9 mm. All punctures were performed according to preoperative planning. Compared with the control group, the three-dimensional group had shorter puncture time (8.9 ± 3.3 vs 14.5 ± 6.1 min, P < 0.001), fewer puncture attempts (1.4 ± 0.6 vs 2.2 ± 1.5, P = 0.009), and might also have a better performance in stone clearance rate (90.5% vs 72.5%, P = 0.19) and postoperative complications (P = 0.074).

CONCLUSIONS

The percutaneous nephrolithotomy three-dimensional model manifested acceptable accuracy and good value for guiding puncture in a mixed reality environment.

The Matryoshka technique in percutaneous nephrolithotomy

OBJECTIVE

Miniaturized percutaneous nephrolithotomy (PCNL) reduces the risk of haemorrhagic complications, but the limited field of work represents a drawback. To obtain the best outcomes, the percutaneous access size should be intraoperatively tailored. Our purpose is to describe the indications and the procedural steps of the Matryoshka technique and to report its clinical outcomes.

MATERIALS AND METHODS

We performed a retrospective analysis of the data from consecutive Matryoshka PCNL procedures from October 2016 to January 2018. Collected data included patients' history, stone characteristics, intra- and post-operative items, stone clearance and need for retreatment. The main indication to the Matryoshka technique is the inability to securely position a guidewire due to an obstruction or narrowness in the pyelocalyceal system. This technique begins by puncturing the calyx hosting the stone and advancing a hydrophilic guidewire through the needle. If the guidewire cannot proceed beyond the stone, the Matryoshka technique is employed for tract stabilization. The tract is carefully dilated with small-bore instruments and a cautious lithotripsy is performed to create enough space to introduce the guidewire beyond the stone under visual control. Once the access has been stabilized the surgeon can upsize the tract to the optimum to complete the procedure. Additionally, the technique can be employed when an intraoperative reassessment induces the surgeon to further dilate the tract to quicken the procedure.

RESULTS

Sixteen patients were included, with a median stone volume of 3.49 cm3. Median operative time was 112 minutes. Three Clavien I-II (postoperative fever) and one Clavien IIIB (colon perforation) complications were reported. No blood transfusions were recorded. Three patients underwent scheduled retreatment as part of a multistep procedure. Out of the remaining 13 patients, 10 (76.9%) obtained a complete stone clearance.

CONCLUSIONS

The Matryoshka technique helps the urologist to obtain a secure percutaneous access and makes PCNL flexible and progressive, potentially minimizing the risk of access-related complications.

Minimally invasive percutaneous nephrolithotomy (PCNL): Techniques and outcomes

Minimally invasive percutaneous nephrolithotomy (PCNL) was introduced to decrease the morbidity of the standard PCNL (sPCNL). Thereafter, many modifications and techniques have been presented with the introduction of different miniaturized PCNL (mPCNL) techniques, such as micro-PCNL and ultra-mini-PCNL (UMP). As of present, none of the techniques has displaced the sPCNL. Nonetheless, mini-PCNL has continuously widening indications and has been proposed to have significant advantages over sPCNL. In the current review, each technique is presented while discussing the advantages and disadvantages of each approach. A comprehensive review of the current literature has been performed. Articles related to the topic were retrieved and critically analyzed. Less peri-operative bleeding and shorter hospital stay were the most important advantages advocated for mini-PCNL. Although the performance of mini-PCNL is safe, the utilization of micro-PCNL and UMP should be done with caution.

Multitract percutaneous nephrolithotomy in staghorn calculus

Staghorn calculi are branched stones which occupy a majority portion of the pelvicaliceal system. An untreated staghorn calculus over time can damage the kidney and deteriorate its function and/or cause life threatening sepsis. Total stone clearance is an important goal in order to eradicate any infective focus, relieve obstruction, prevent recurrence and preserve the kidney function. Percutaneous nephrolithotomy (PCNL) is currently the accepted first-line treatment option for staghorn calculi. The options available are single-tract PCNL with an auxiliary procedure like shockwave lithotripsy, single-tract PCNL with flexible nephroscopy, or multitract PCNL. Each has its own pros and cons. But the ultimate goal of treatment for any patient with staghorn calculi should be safety, cost-effectiveness, and to achieve total stone clearance. With this article, we review the management of staghorn calculi with multiple percutaneous (“multitract”) access, its advantages and disadvantages and its current position by studying the various published materials across the globe.

iPad-assisted percutaneous nephrolithotomy (PCNL): a matched pair analysis compared to standard PCNL

PURPOSE

To compare iPad-assisted (Apple Inc., Cupertino, USA) percutaneous access to the kidney to the standard puncturing technique for percutaneous nephrolithotomy (PCNL).

METHODS

For the iPad-assisted PCNL, a computed tomography is performed prior to surgery, using fiducial radiopaque markers. The important anatomical structures (i.e. kidney, stones) are segmented using specific software enabling the superimposition of images semi-transparently on the iPad by marker-based navigation. Twenty-two patients underwent an iPad-assisted percutaneous puncture of the kidney for PCNL. Twenty-two patients of the clinical database from the Urological Department SLK Hospital Heilbronn, who underwent the standard puncturing technique, were matched to these patients. Matching criteria were age, gender, stone volume, body mass index, stone site and the absence of anatomical variation. Puncture time, radiation exposure and number of attempts for a successful puncture were evaluated. All procedures were performed by two experienced urologists. The standard puncturing method consisted of a combination of ultrasound and fluoroscopy guidance. Chi-square and t test were used to ensure that there was no difference in the matching criteria between the groups. To compare the two methods, U test, Kruskal-Wallis and Chi-square test were used.

RESULTS

Examination of radiation exposure showed a significant difference between the two groups in favour of the standard puncturing method (p < 0.01) and puncture time (p = 0.01). However, there was no significant difference in puncturing attempts (p = 0.45).

CONCLUSION

The iPad-assisted navigation, with the objective being to puncture the renal collecting system, represents a new technique (IDEAL criteria 2b), which proved to be applicable in clinical practice, but still has potential for technical improvement.

Miniaturisation of PCNL

Conventional PCNL leads to a high stone-free rate but is associated with a significant treatment morbidity. To decrease the morbidity of PCNL but to achieve an equal stone-free rate, in 2001 a miniaturised version of a conventional PCNL (Mini-PCNL) was introduced. Meanwhile numerous modifications of the Mini-PCNL were reported. The ongoing experience with the Mini-PCNL technique showed that Mini-PCNL is not only a miniaturisation but also a different method to remove the stones, as the stones come out of the calyceal system only by means of the irrigation flow without any further need of forceps or baskets. Due to a limited number of papers in the literature, the guidelines so far do not distinguish between conventional and Mini-PCNL, although the Mini-PCNL already became a frequent treatment modality in daily routine worldwide. From the current point of view, Mini-PCNL can be recommended to treat all kinds of upper urinary tract stones exceeding a diameter of 10 mm. In this context, Mini-PCNL is a treatment alternative to flexible ureterorenoscopy, SWL and conventional PCNL. The available literature shows that the morbidity of Mini-PCNL is less and the stone-free rate is equal to that of conventional PCNL. It seems that there is no limitation to Mini-PCNL in the treatment of upper urinary tract stones. The future will show what kind of further miniaturisation of the Mini-PCNL procedure will be appropriate.

Implementation of minimally invasive percutaneous nephrolithotomy (MIP): comparison of the initial learning curve with the later on clinical routine in a tertiary centre

OBJECTIVE

We report on the comparison of clinical results of the early phase of implementation of minimally invasive PNL (MIP) in a mentor-based approach with the later on clinical routine in a tertiary centre.

PATIENTS AND METHODS

From January 2010 until January 2015 MIP was performed in 190 patients. Stone and patient characteristics were recorded in prospective manner. Perioperative complications were recorded within the Clavien-Classification. The first 120 consecutive patients undergoing MIP were evaluated and divided into three groups of 40 patients each. Mentor-based introduction of MIP was done within the first 40 patients (group A). Further patients were treated on routine clinical practice basis (group B and C). Treatment outcome was compared within the three groups.

RESULTS

The groups did not significantly differ with regard to patient characteristics, operation time and decline in haemoglobin. In the mentor-based series mean stone size was 21.7 ± 12.6 vs. 15.6 ± 7.9 and 16.1 ± 8.4 mm in group B and C (p = 0.033). Primary stone-free rates were 65, 87.5 and 87.5% for the three groups (p = 0.015). Stone-free rate was higher in smaller and simple stones. Overall, complication rate was 41.7% including 36.7% Clavien grade I and II complications.

CONCLUSIONS

MIP can be implemented safe and effectively with mentor-based approach. MIP has a high safety profile, which allows high safety and efficacy of MIP at the time of implementation.

Use of a Novel Flexible Mini-nephroscope in Minimally Invasive Percutaneous Nephrolithotomy

OBJECTIVE

To assess the feasibility and safety of a novel flexible mini-nephroscope in minimally invasive percutaneous nephrolithotomy (PCNL). Presumably, limiting the size and number of tracts during PCNL has the potential of decreasing the morbidity of the procedure. We present our experience with this new technique.

MATERIALS AND METHODS

A retrospective analysis of patients with multiple kidney stones treated with mini-PCNL combined with a novel flexible mini-nephroscope was performed. Minimally invasive PCNL was done with rigid 12 F MIP-M nephroscope, followed by flexible mini-nephroscopy for smaller stones in other inaccessible calyces. Record was made of the operating time, stone-free rates, postoperative pain, morbidity, hospital stay, time to recovery, complication rates, and ancillary procedures. Matched-pair analysis was done with cases operated by flexible ureteroscopy performed with Flex X-2 or Flex X-c scope.

RESULTS

Twenty-five patients in the study group were matched with 25 cases from the flexible ureteroscopy group. Both groups were comparable in terms of age, laterality, and mean composite stone burden. The mean operating time was 40.1 ± 10.6 minutes in the mini-PCNL group and 51.2 ± 8.8 minutes in the flexible ureteroscopy group. Mean hospital stay was similar in both groups. The primary stone clearance rate of 92% (23 of 25) in the mini-PCNL group was better than the clearance rate of 80% (20 of 25) in the flexible ureteroscopy group. Eight percent in the mini-PCNL group required ancillary procedures as compared with 20% of cases in the flexible ureteroscopy group. Postoperative pain and analgesia requirement in these patients was minimal. There were no significant complications.

CONCLUSION

Flexible mini-nephroscope is an effective adjuvant to minimally invasive PCNL in achieving high clearance rate with minimum morbidity.

The vacuum cleaner effect in minimally invasive percutaneous nephrolitholapaxy

INTRODUCTION

Percutaneous stone removal increasingly plays an important role among the different approaches of interventional stone therapy, particularly since the development of miniaturized instruments is resulting in lower morbidity for the patients. One major drawback of smaller instruments is the increased difficulty of stone retrieval after disintegration due to the reduced tract diameter. This results in longer operation time and the need of additional tools such as disposable retrieval baskets. One of the key factors in the development of minimally invasive percutaneous nephrolitholapaxy (MIP) was the design of an Amplatz sheath which provides a built-in vacuum cleaner effect for stone retrieval.

METHODS

A series of flow analyses with the gauges and shapes of the most commonly used nephroscopes and sheaths in percutaneous nephrolitholapaxy was performed by computational fluid dynamics. Flow velocity and direction in front of the nephroscope were computed and visualized by the software.

RESULTS

In our study, the vacuum cleaner effect developed exclusively when a round-shaped nephroscope was used (Nagele Miniature Nephroscope System, Karl Storz GmbH & Co. KG) and depended on the relation between nephroscope diameter and inner sheath diameter. The strongest effect was observed with a 12 F nephroscope and an inner sheath diameter of 15 F. It did not develop when an oval- or crescent-shaped nephroscope was used. In front of the distal end of the round-shaped nephroscope, a slipstream develops, induced by the excursive change of width of the fluid flow on the outlet of the flushing canal. This allows the adhesion of a stone fragment in the eddy while the fluid flow is circulating around the stone.

CONCLUSION

This study illustrates and explains the vacuum cleaner effect which has been detected in the development of the Nagele Miniature Nephroscope System used in MIP. It combines the reduced morbidity of smaller kidney puncture diameters with the benefit of quick and complete stone removal.

Risk factors for septic shock after mini-percutaneous nephrolithotripsy with holmium laser

OBJECTIVE

To evaluate the risk factors for septic shock after mini-percutaneous nephrolithotripsy (MPCNL) and provide a theoretic basis for the prevention of septic shock after MPCNL.

METHODS

A total of 834 patients who underwent MPCNL from June 2004 to April 2012 were retrospectively analyzed. The χ(2) test and a logistic regression were used to identify key risk factors for septic shock after MPCNL.

RESULT

The incidence of septic shock after MPCNL was 2.40%. Logistic regression analysis identified female sex (odds ratio, 1.055E8; P <.001) and diabetes mellitus (odds ratio, 4.192; P = .001) as independent risk factors for post-MPCNL septic shock.

CONCLUSION

Female sex and diabetes mellitus are the key risk factors for septic shock after MPCNL. Routine administration of antibiotics preoperatively might reduce the incidence of septic shock.

Minimally invasive percutaneous nephrolithotomy: an alternative to retrograde intrarenal surgery and shockwave lithotripsy

PURPOSE

There is a lack of studies comparing shock wave lithotripsy (SWL), retrograde intrarenal surgery (RIRS) and minimally invasive percutaneous nephrolithotomy (MIP) in renal stone treatment. This study compared treatment outcome, stone-free rate (SFR) and stone-free survival (SFS) with regard to stone size and localization.

METHODS

This analysis included 482 first-time-treated patients in the period 2001-2007. Detailed clinical information, stone analysis and metabolic evaluation were evaluated retrospectively. Outcome, SFR and SFS were analyzed with regard to size (<1 vs. ≥1 cm) and localization (lower vs. non-lower pole).

RESULTS

Higher SFRs in lower and non-lower pole stones ≥1 cm were confirmed for RIRS and MIP (p < 0.0001). A regression model confirmed a higher risk of non-lower pole stone persistence for SWL versus RIRS (OR: 2.27, p = 0.034, SWL vs.

MIP (OR

3.23, p = 0.009) and larger stone burden ≥1 versus <1 cm (OR: 2.43, p = 0.006). In accordance, a higher risk of residual stones was found in the lower pole for SWL versus RIRS (OR: 2.67, p = 0.009), SWL versus

MIP (OR

4.75, p < 0.0001) and stones ≥1 cm versus <1 cm (OR: 3.02, p = 0.0006). In RIRS and MIP patients, more complications, stenting, prolonged disability, need/duration of hospitalization and analgesia were noticed (p < 0.05). Overall SFS increased from SWL, RIRS, to MIP (p < 0.001). SWL showed lower SFS for non-lower pole (p = 0.006) and lower pole stones (p = 0.007).

CONCLUSIONS

RIRS and MIP were shown to have higher stone-free rates and SFS compared to SWL. The price for better outcome was higher, considering tolerable complication rates. Despite larger preoperative stone burden, MIP achieved high and long-term treatment success.