Miniaturization in percutaneous nephrolithotomy: What is new?

Objective: To summarize recent advancements in mini-percutaneous nephrolithotomy (mini-PCNL) in surgical technique, stone removal strategy, lithotripsy, and surgical model from the current literature. Methods: We conducted a narrative review of relevant English-language articles up to October 2022 using the PubMed and Web of Science databases. The following keywords were used in the search: "percutaneous nephrolithotomy", "minimally invasive percutaneous nephrolithotomy", "mini-PCNL", "mini-perc", "mPCNL", and "miniaturization". Results: A series of new progress has been made in many aspects of mini-PCNL, such as further reduction of tract size-needle perc and further improvement of robotic-assisted PCNL-artificial intelligence-powered robotic devices. Conclusion: Many studies and trials have been conducted to reduce morbidity and increase the safety and effectiveness of mini-PCNL. It is crucial to realize that miniaturization of PCNL requires not only a smaller percutaneous tract size, but also an adjustment strategically in renal access, stone removal, lithotripsy, and surgical model in general. More large-scale prospective research needs to be carried out to further validate and optimize the safety and effectiveness of mini-PCNL.

A prospective comparative study to evaluate safety and efficacy of pneumatic versus laser lithotripsy in mini-percutaneous nephrolithotomy.

OBJECTIVE: The choice of lithotripter is an important part of planning in mini-percutaneous nephrolithotomy (mini perc) as the operating time is prolonged due to reduced sheath size and smaller working channel. Previous studies mostly reported the use of laser lithotripter for stone fragmentation while the literature on pneumatic lithotripter use in miniperc is scant. METHODS: In this study, we compared the efficacy and safety of the laser lithotripter (LL) vs pneumatic lithotripter (PL) in miniperc for small to medium-sized renal/upper ureteric stones (size: 1-2 cm). All consecutive patients who underwent miniperc from September 2020 to August 2022 were included in the study. Laser lithotripter was used in 81 patients (group LL), while pneumatic was used in 75 patients (group PL). The preoperative, operative, and postoperative findings were compared. RESULTS: Baseline patient characteristics (age, sex, body mass index, and co-morbid illness) and stone characteristics (size, stone number, laterality, presence of staghorn calculi, presence of hydronephrosis, Guy's stone scores) were comparable between the two groups (P>0.05). The mean operative time was comparable (P=0.38) while the mean fragmentation time was significantly higher in the PL group (35.42±6.34 vs 28.96±2.82 minutes; P<0.01). 29.3% required forceps/basket for stone removal in PL group as compared to 7.4% in LL group (P=0.02). Mean VAS (Visual Analog Scale) score on the first post-operative day, stone clearance, drop in hemoglobin, average hospital stay, stone clearance at 3 months postoperative, and complications were comparable (P>0.05). CONCLUSION: Lithotripsy with pneumatic lithotripter can be used as an equally effective and safe alternative to laser lithotripter in mini-perc for treatment of small-medium sized renal/upper ureteric calculi.

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.

Single-Center Experience with Swiss LithoClast® Trilogy for Kidney Stones.

INTRODUCTION: PCNL remains the gold standard for larger kidney stones. Reducing the operating time of PCNL and its complication rate seems to be the next logical step in optimizing this classical technique. To achieve these objectives, some new methods of lithotripsy emerge. We present the data of a single, high-volume, academic center with combined ultrasonic and ballistic lithotripsy in PCNL using the Swiss LithoClast® Trilogy device. MATERIALS AND METHODS: We designed a prospective, randomized study including patients who underwent PCNL or miniPerc with lithotripsy using the new EMS Lithoclast Trilogy or EMS Lithoclast Master. The procedure was carried out with all patients in prone position, by the same surgeon. The working channel size was 24 Fr-15.9 Fr. We evaluated the stones' features, operative time, fragmentation time, complications, stone clearance rate and stone-free rate. RESULTS: Our study included 59 patients, 38 females and 31 males, of an average age of 54.5 years old. The Trilogy group included 28 patients and the comparator included 31 patients. Urine culture was positive in seven cases which required seven days of antibiotics. The mean stone diameter was 35.6 mm with a mean Hounsfield unit (HU) of 710.1. The average number of stones was 2.08 (6 complete staghorn stones and 12 partial staghorn stones). A total of 13 patients presented a JJ stent (46.4%). We found a very significant difference in all the parameters favoring the Trilogy device. The most important result in our opinion is the probe active time, which was almost six times shorter in the Trilogy group. The stone clearance rate was about double in the Trilogy group, leading to shorter overall and intra-renal operating times. The overall complication rate was 17.9% in the Trilogy group and 23% in the Lithoclast Master group. The mean hemoglobin drop was 2.1 g/dL with a mean creatinine rise of 0.26 mg/dL. CONCLUSIONS: Swiss LithoClast® Trilogy, a device combining ultrasonic and ballistic energy, is a safe and efficient method of lithotripsy for PCNL, proving statistically significant benefits over its predecesor. It can achieve the goal of reducing complication rates and operative times for PCNL.

Mini-Perc for Renal Stones-A Single Center Experience and Literature Review.

AIM: The aim of this study was to analyze the outcomes of miniaturized nephrolithotomy (mini-perc) in the management of renal stones with a diameter smaller than 20 mm. MATERIALS AND METHODS: We retrospectively reviewed the records of 102 patients who underwent mini-perc between March 2015 and March 2020 in our department. The primary objective was the stone-free rate, but we also analyzed the retreatment rate, complications, hospital stay, operative time and reduction in hemoglobin level. All these patients had this technique as their first-line treatment, in a prone position, using a 16 Fr sheath size. Data were compared to a series of patients from the literature, treated with conventional PCNL. RESULTS: The patients had calculus limited to either a single calyx or just extending to the renal pelvis, and stone size was less than 20 mm in its maximal dimension. The intrarenal stone location was in the upper calyx in 7 cases, middle calyx in 20 cases and lower calyx in 46 cases, and there were 29 patients with renal pelvis stone. The male to female ratio was 1.5:1, and the median age was 48.4 years. The average stone size was 17.4 mm in diameter (ranging between 9 and 20 mm) and all cases underwent Ho-YaG laser lithotripsy, ballistic energy and combined ultrasonic and ballistic lithotripsy. At the end of the procedure, an antegrade double J stent was placed under fluoroscopy for a maximum of 2 weeks in 42 cases, while 9 cases needed a nephrostomy tube 12-14 F. A total of 51 cases were totally tubeless. Our median operative time was 61 min (ranging from 35 to 75 min). The median hospitalization stay was 3.8 days. The stone free rate was 90.1% after one procedure, only nine (8.8%) cases needed a "second look" flexible ureteroscopy, and the final stone-free rate was 98% (absence of detectable calculi on ultrasound, KUB or non-contrast CT scan). The overall complication rate was 6.86% (Clavien classification I-57.14%; II-28.5%; III-14.2%), while no Clavien IV or V complications were reported. No patient required a blood transfusion, and mean hemoglobin loss was 0.81 mg/dL. Overall, our results are better than similar data for conventional PCNL in the literature. CONCLUSIONS: The "mini-perc" technique is an effective procedure for the treatment of the renal lithiasis that is less or equal to 2 cm. The results demonstrated that this minimally invasive technique is associated with a higher stone-free rate and minimal complications.

Totally tubeless single access tract mini-percutaneous nephrolithotripsy in treatment of large burden > 2-cm and/or complex renal stones: a case series of 62 patients.

BACKGROUND: Limited literature has focused on the use of totally tubeless mini-percutaneous nephrolithotomy (PCNL) for the treatment of large renal stones. We present our findings of treating patients with large and/or complex renal stones using single renal access totally tubeless mini-PCNL. METHODS: From March 2018 to May 2021, 62 consecutive cases in which single tract totally tubeless mini-PCNL was used to treat complex renal stones were enrolled, all with calculi > 2 cm. All procedure of puncture and dilation were guided by fluoroscope. The complexity of stones was assessed according to the Guy's Scoring System (GSS). The surgical duration, length of hospital stay, analgesia requirement, stone-free rate, and perioperative morbidity were assessed. RESULTS: The mean preoperative stone burden was 36.69 ± 19.76 mm (above 2 cm in all cases), mean surgical duration was 61.93 ± 40.84 min (range 15-180 min), and mean hematocrit reduction was 4.67 ± 2.83%. Postoperative Nalbuphine was used in 6 patients. The mean length of stay was 2.46 ± 1.19 days (range 2-8 days), and the postoperative stone-free rate was 83.9% (52/62), and 87.1% (54/62) after auxiliary ESWL. The overall complication rate was 14.5%, the majority of complications being postoperative transient fever. CONCLUSION: For the treatment of large bursen > 2 cm and/or complex renal stones, totally tubeless single tract mini-PCNL ensures a feasible SFR, low morbidity and short hospital stay. According to the low complication rate in our study, the totally tubeless manner was not associated with an increased risk of postoperative morbidity, and patients benefited from decreased postoperative analgesics use.

Anterograde Mini-Percutaneous Retropelvic Extra-Luminal Endopyelotomy: A Novel Approach to Uretero-Pelvic Junction Obstruction.

Background Uretero-pelvic junction obstruction (UPJO) is a common cause of upper tract urinary obstruction. This condition is generally treated with various surgical options which include endoscopic (retrograde or anterograde), laparoscopic, open or robotic-assisted approaches. Herein, we describe a novel endoscopic retropelvic extra-luminal approach using a mini (14 Fr) nephroscope. Methods A 30-year-old male presented with symptomatic left UPJO and inferior pole renal stones, which were identified on computed tomography (CT) imaging. Mercaptuacetyltriglycine (MAG3) renogram demonstrated a functioning left kidney. With the patient positioned supine, a mini-perc (Karl-Storz) nephroscope was used to access the renal pelvis via the percutaneous route. The retropelvic space was thereafter accessed. Using a Holmium-YAG laser, the UPJO was splayed using an extra-luminal approach. Results Clear endoscopic vision, minimal bleeding, and overall satisfactory identification of the UPJO were achieved. At the 12-month follow-up, the patient remained stent and symptom-free. On follow-up CT imaging and MAG3 renogram, the system remained dilated with no obstruction noted. Conclusion Percutaneous anterograde retropelvic extra-luminal endopyelotomy is a novel approach that should be considered in patients with secondary renal calculi. This is the first report of the procedure being successfully performed utilizing the mini-perc access route.

Flexible ureteroscopy versus miniaturized percutaneous nephrolithotomy for renal stones of 1-2 cm.

Technological advances and innovation in endourology have significantly reduced the indications of extracorporeal shockwave lithotripsy in the management of moderate-sized renal stones. In the last decade, we have witnessed a trend towards the use of finer scopes for percutaneous procedures instead of standard percutaneous nephrolithotomy (PCNL) (≥22 Fr). Miniaturized PCNL (mPCNL), i.e. miniPCNL (12-20 Fr), ultra-miniPCNL (11-13 Fr), mini-microPCNL (8 Fr), and microPCNL (<5 Fr), is increasingly being used. Concomitant developments in laser technology have provided a safe and effective stone fragmentation modality for use via flexible ureteroscopes (fURS). Technological advances in the design of fURS have improved not only the optics (fiber optic to chip-on-the-tip technology digital image) but also the ergonomics. Both the endourological techniques are extremely effective and safe, as shown in a multitude of good-quality studies. There are some differences in stone-free rate and complications. mPCNL in general has a higher stone-free rate, albeit with a slightly higher incidence of hemorrhagic complications. fURS often requires longer stenting time and longer period to achieve stone clearance, whereas mPCNL often needs ureteral catheter for only 24 hours and has a higher first day stone-free rate. fURS is a 1 day procedure compared to mPCNL, which requires patients to stay hospitalized for 2-3 days. It is therefore important to tailor the indications of these two procedures to the individual patient's needs.

Safety and efficacy of a single middle calyx access (MCA) in mini-PCNL.

To compare outcomes of a single middle calyx access (MCA) with a single upper or lower calyceal access in mini-PCNL. From May 2015 through August 2018, patients' files who underwent a single renal access mini-PCNL were retrospectively reviewed. All patients underwent fluoroscopic-guided access (16-20 F) in the prone position. They were categorized into group 1 (MCA) and group 2 (either upper or lower calyceal access). Compared preoperative items included stone location, size, number and complexity (according to Guy's score). The compared outcome parameters were complication and stone-free rates. The study comprised 512 consecutive patients, 374 patients in group 1 and 138 in group 2. A single MCA was utilized to access 95% of proximal ureteral calculi, 89% for ureteropelvic junction stones, and 84% for stones present in the pelvicalyceal system and ureter. MCA was used in 89% of complete staghorn stones and 73% of multiple stones. the Stone-free rates (93% vs 90.6%, P = 0.350) and the complications rates (8% vs 7.2%, P = 0.772) were comparable between group 1 and 2 despite that MCA was used for most cases with complex stones. Complications severity were also comparable (P = 0.579). Mini-PCNL performed through a single MCA is effective and safe. This access can be used for the treatment of renal and upper ureteral calculi of different complexities and locations.

Miniaturized percutaneous nephrolithotomy versus retrograde intrarenal surgery in the treatment of renal stones with a diameter <15 mm: A 3-year open-label prospective study.

AIM: The aim of this study is to compare the outcomes of miniaturized percutaneous nephrolithotomy (mini-perc) and retrograde intrarenal surgery (RIRS) in management of renal stones with a diameter <15 mm. MATERIALS AND METHODS: This was an open-label prospective study that included a total of 80 cases underwent mini-perc (n = 40) and RIRS (n = 40) between July 2014 and August 2017. The primary outcome objective was stone-free rate, retreatment rate, complications, hospital stay, operative time, and reduction in hemoglobin level. Data were analyzed using SPSS version 16.0 Software. RESULTS: Overall, 80 patients were enrolled in this study. The mean age was 40.12 and 38.20 years, and the mean stone size was 1.15 and 1.30 cm in mini-perc and RIRS group, respectively. Majority of the study participants were males. Overall, mini-perc and RIRS had stone clearance rates of 100% and 95.4%, respectively. Two patients required retreatment in RIRS group. The duration of hospital stay and the rate of complication was similar in both the groups. Operative duration was more in RIRS group. Decrease in hemoglobin level was more in mini-perc group. CONCLUSIONS: Results demonstrated that both modalities were associated with high stone clearance rates with minimal complications. RIRS was associated with less reduction in hemoglobin and could be used as standard treatment modality for small renal calculi.

Tract Sizes in Miniaturized Percutaneous Nephrolithotomy: A Systematic Review from the European Association of Urology Urolithiasis Guidelines Panel.

CONTEXT: Miniaturized instruments for percutaneous nephrolithotomy (PNL), utilizing tracts sized ≤22 Fr, have been developed in an effort to reduce the morbidity and increase the efficiency of stone removal compared with standard PNL (>22 Fr). OBJECTIVE: We systematically reviewed all available evidence on the efficacy and safety of miniaturized PNL for removing renal calculi. EVIDENCE ACQUISITION: The review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. Since it was not possible to perform a meta-analysis, the data were summarized in a narrative synthesis. EVIDENCE SYNTHESIS: After screening 2945 abstracts, 18 studies were included (two randomized controlled trials [RCTs], six nonrandomized comparative studies, and 10 case series). Thirteen studies were full-text articles and five were only available as congress abstracts. The size of tracts used in miniaturized procedures ranged from 22 Fr to 4.8 Fr. The largest mean stone size treated using small instruments was 980mm2. Stone-free rates were comparable in miniaturized and standard PNL procedures. Procedures performed with small instruments tended to be associated with significantly lower blood loss, while the procedure duration tended to be significantly longer. Other complications were not notably different between PNL types. Study designs and populations were heterogeneous. Study limitations included selection and outcome reporting bias, as well as a lack of information on relevant confounding factors. CONCLUSIONS: The studies suggest that miniaturized PNL is at least as efficacious and safe as standard PNL for the removal of renal calculi. However, the quality of the evidence was poor, drawn mainly from small studies, the majority of which were single-arm case series, and only two of which were RCTs. Furthermore, the tract sizes used and types of stones treated were heterogeneous. Hence, the risks of bias and confounding were high, highlighting the need for more reliable data from RCTs. PATIENT SUMMARY: Removing kidney stones via percutaneous nephrolithotomy (PNL) using smaller sized instruments (mini-PNL) appears to be as effective and safe as using larger (traditional) instruments, but more clinical research is needed.