Direct Endoscopic Visualization Combined with Ultrasound Guided Access during Percutaneous Nephrolithotomy: A Feasibility Study and Comparison to a Conventional Cohort

Prone vs supine percutaneous nephrolithotomy: does position affect renal pelvic pressures?

The purpose of this study was to measure and compare renal pelvic pressure (RPP) between prone and supine percutaneous nephrolithotomy (PCNL) in a benchtop model. Six identical silicone kidney models were placed into anatomically correct prone or supine torsos constructed from patient CT scans in the corresponding positions. A 30-Fr renal access sheath was placed in either the upper, middle, or lower pole calyx for both prone and supine positions. Two 9-mm BegoStones were placed in the respective calyx and RPPs were measured at baseline, irrigating with a rigid nephroscope, and irrigating with a flexible nephroscope. Five trials were conducted for each access in both prone and supine positions. The average baseline RPP in the prone position was significantly higher than the supine position (9.1 vs 2.7 mmHg; p < 0.001). Similarly, the average RPP in prone was significantly higher than supine when using both the rigid and flexible nephroscopes. When comparing RPPs for upper, middle, and lower pole access sites, there was no significant difference in pressures in either prone or supine positions (p > 0.05 for all). Overall, when combining all pressures at baseline and with irrigation, with all access sites and types of scopes, the mean RPP was significantly higher in the prone position compared to the supine position (14.0 vs 3.2 mmHg; p < 0.001). RPPs were significantly higher in the prone position compared to the supine position in all conditions tested. These differences in RPPs between prone and supine PCNL could in part explain the different clinical outcomes, including postoperative fever and stone-free rates.

Ultrasound-Guided PCNL - Why Are We Still Performing Exclusively Fluoroscopic Access?

PURPOSE OF REVIEW

While urologists are traditionally taught to perform percutaneous nephrolithotomy (PCNL) utilizing exclusively fluoroscopy, ultrasound has emerged as a safe alternative. This article showcases the major reasons why ultrasound-guided access should be considered the first-line approach for performing access for PCNL.

RECENT FINDINGS

There continues to be a need to further reduce radiation exposure in the management of kidney stone patients. This review showcases how performing ultrasound-guided PCNL has been associated with a shorter learning curve, increased patient safety, and the ability to perform x-ray free PCNL. Ultrasound-guided PCNL is not only an achievable skill for urologists to learn but provides multiple advantages over traditional fluoroscopic access. As every effort should be given to help reduce radiation exposure for kidney stone patients as well as performing surgeons and operating theater personnel, endourologists should strive to add this technique to their armamentarium.

Comparison between prone and supine nephrolithotomy in pediatric population: a double center experience

PURPOSE

Stone disease in the pediatric age is an increasing issue. Percutaneous Nephrolithotomy (PNL) can be used for larger and complex stones. As in adults it can be performed in the supine or prone position.

METHODS

We retrospectively reviewed two centers' experience in prone and supine PNL in children to analyze its results and complications.

RESULTS

33 patients underwent prone and 19 supine procedures. Patients in the prone group were younger than in the supine, while no significant differences were found in stone burden, access size, operative time or complications. Complications were: 8 and 4 Clavien 1 for the prone and supine group, respectively, one case of urosepsis (4b) in the prone and 2 cases of Clavien 3 in the supine group (double J stent placement for renal colic and ureteroscopy for steinstrasse). Tubeless procedures and mean nephrostomy time were in favor of the supine group, whereas fluoroscopy time and ureteral drainage stay were in support of the prone group. Stone free rate was better in the supine group (83.3 vs 66.6%), possibly reflecting the capability to perform a combined approach in 12 patients (allowing to reach all the calyx with simultaneous anterograde and retrograde access) or younger age in the prone group (13 vs 2 patients ≤5 years), with no differences in stone burden.

CONCLUSIONS

Supine approach seems to guarantee higher stone-free rates. Larger series are necessary to determine what the best technique is in terms of X-ray exposure, operative time and complications.

Feasibility of contrast-enhanced ultrasound and flank position during percutaneous nephrolithotomy in patients with no apparent hydronephrosis: a randomized controlled trial

Purpose

To investigate the puncture accuracy and feasibility of contrast-enhanced ultrasound (CEUS) guided percutaneous nephrolithotomy (PCNL) in flank position for patients with no apparent hydronephrosis.

Methods

Between May 2018 and June 2020, 72 kidney stone patients with no or mild hydronephrosis were randomized into two groups: a CEUS-guided PCNL group and a conventional ultrasound (US)-guided group. Patients’ demographics and perioperative outcomes were compared, including the success rate of puncture via calyceal fornix, the success rate of a single-needle puncture, puncture time, operative time, postoperative hemoglobin loss, stone-free rate, incidence of complications and postoperative stay.

Results

The success rate of puncture via calyceal fornix for CEUS-guided group was significantly higher than that for conventional US-guided group (86.1 vs. 47.2%, p = 0.002). Patients performed with CEUS-guided PCNL required shorter renal puncture time than those guided with conventional US (36.5 s vs. 61.0 s, p < 0.001). The median postoperative hemoglobin loss in the CEUS-guided group was significantly lower than that in conventional US-guided group (2.5 vs. 14.5 g/L, p < 0.01). There was no statistically significant difference in the success rate of a single-needle puncture, operative time, stone-free rate, incidence of complications and postoperative stay between the two groups.

Conclusion

CEUS guidance facilitates identification of the renal calyx fornix, and benefits more precise renal puncture and less hemoglobin loss in PCNL. CEUS-guided PCNL in flank position is a feasible approach to the treatment of kidney stone patients with no apparent hydronephrosis.

Trial registration number: ChiCTR1800015417.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00345-022-03933-4.

Percutaneous nephrolithotomy - the puncture

OBJECTIVE

To determine what importance is given to the puncture and assistive technologies in percutaneous nephrolithotomy (PNL) in the current urological literature.

METHODS

PubMed was searched for English publications and reviews for the keywords: 'percutaneous nephrolithotomy', 'percutaneous nephrostomy', 'puncture'. The search was limited to the last 5 years, January 2016 until February 2021. Based on 183 abstracts, 121 publications were selected, read, and reviewed. References, older or seminal papers were read and cited if they contributed to a better understanding. A total of 198 references form the basis of this narrative review.

RESULTS

The puncture is frequently referred to as the most crucial part of PNL. In contrast, the influence of the puncture on the failure rate of PNL and the specific puncture-related complications seems to be low in the single-digit percentage range. However, there are no universally accepted definitions and standards measuring the quality of puncture. Consequently, the impact of the puncture on general PNL complications, on stone scores predicting success rates and on learning curves evaluating surgeons' performance have not been systematically studied. Assistive technologies rely on fluoroscopy and ultrasonography, the latter of which is becoming the preferred imaging modality for monitoring the entire procedure. Needle bending, a problem relevant to all puncture techniques, is not addressed in the urological literature.

CONCLUSIONS

The importance attached to puncture in PNL in the current urological literature is subjectively high but objectively low. Some basics of puncture are not well understood in urology. Disciplines other than urology are more actively involved in the development of puncture techniques.

Ureteroscopy-assisted puncture for ultrasonography-guided renal access significantly improves overall treatment outcomes in endoscopic combined intrarenal surgery

OBJECTIVES

To assess the impact and availability of ureteroscopy-assisted puncture for percutaneous renal access during ultrasonography-guided miniaturized (mini)-endoscopic combined intrarenal surgery for large volume renal and/or proximal ureteral stones.

METHODS

We conducted a multi-institutional retrospective cohort study for urolithiasis treatment. Data from a total of 313 patients who underwent mini-endoscopic combined intrarenal surgery to treat renal and/or ureteral stones between January 2016 and April 2020 were collected. We compared the outcomes between ultrasonography-guided mini-endoscopic combined intrarenal surgery with and without ureteroscopy-assisted puncture (ureteroscopy-assisted puncture(+) group [n = 126] and ureteroscopy-assisted puncture(-) group [n = 187] group, respectively). The primary outcome was requirement for additional surgical intervention. Secondary outcomes were stone-free rate, complications and total procedure, fluoroscopy, hospital stay, and postoperative ureteral stent placement durations.

RESULTS

The ureteroscopy-assisted puncture(+) group had a lower additional surgical intervention rate and a higher stone-free rate immediately after and 3 months after surgery than the ureteroscopy-assisted puncture(-) group (5.6% vs 19.7%, P < 0.001; 82.5% vs 65.8%, P = 0.001; 59.5% vs 44.6%, P = 0.011). The median total procedure, fluoroscopy, and postoperative ureteral stent placement durations were 18 min, 3 min, and 5 days shorter, respectively, in the ureteroscopy-assisted puncture(+) group. Multivariate analyses showed that ureteroscopy-assisted puncture was associated with a decreased risk of additional surgical intervention (odds ratio 0.31, P = 0.011) and postoperative infection (odds ratio 0.34, P = 0.003) and decreased total procedure (estimate = -11 min; P = 0.011), fluoroscopy (estimate = -3 min; P = 0.034), and postoperative ureteral stent placement (estimate = -8 days; P = 0.011) durations. Female patients and those with smaller stone volumes or without hydronephrosis were identified as ideal ureteroscopy-assisted puncture candidates.

CONCLUSIONS

Ureteroscopy-assisted puncture during mini-endoscopic combined intrarenal surgery could provide favorable surgical outcomes, especially in female patients without collecting system obstruction.

Retained Digital Flexible Ureteroscope During Percutaneous Nephrolithotomy

Background: During percutaneous nephrolithotomy, retrograde flexible ureteroscopy can be utilized to facilitate repositioning of stones, enable direct vision percutaneous access, minimize radiation exposure, reduce operating times, and improve stone-free rates. Although advancements in technique and flexible ureteroscope technology for the past decades have rendered complications rare, herein we report a case of a retained ureteroscope during percutaneous nephrolithotomy that was effectively managed endoscopically. Case Presentation: A 59-year-old Caucasian gentleman with a history of recurrent bilateral nephrolithiasis presents for a left-sided percutaneous nephrolithotomy for a large stone burden >4 cm. A ureteral access sheath was used and retrograde ureteroscopy was performed to first reposition several stones into the renal pelvis. During manipulation, we were unexpectedly unable to retract the ureteroscope from the access sheath. We describe procedural details leading up to the event and subsequent intraoperative management using an antegrade approach. Conclusion: A retained flexible ureteroscope is a rare but serious intraoperative complication that may require invasive open surgical management. However, careful endoscopic management may be feasible in select cases, allowing for preservation of ureter and instrument.

[Navigation systems for the percutaneous access to the kidney]

BACKGROUND

Percutaneous access to the renal pelvis still remains the most difficult step before nephrolitholapaxy (PCNL). New imaging techniques, such as 3D imaging and various navigation instruments such as electromagnetic, sonographic, CT-controlled and marker-based/iPAD try to simplify this step and reduce complications.

OBJECTIVES

In this review, various new techniques for puncturing the renal collecting system are presented and their advantages and disadvantages are evaluated.

MATERIALS AND METHODS

A systematic literature search was carried out in MEDLINE, whereby only puncture techniques that have already been evaluated in clinical studies were included.

RESULTS

Five different navigation methods for puncturing the renal pelvis before PCNL were found.

CONCLUSION

Intraoperative navigation can be useful when puncturing the collecting system. The combination of ultrasound and fluoroscopy currently remains the gold standard. However, there is still a need for further, primarily clinical, prospective studies to determine which new imaging technology and navigation systems will prevail and thus facilitate the access route to the kidney, especially in the case of special anatomical conditions.

Percutaneous kidney stone surgery and radiation exposure: A review

During the past 3 decades, radiation exposure (RE) has increased drastically among patients undergoing percutaneous nephrolithotomy (PCNL), thus potentially causing new cases of cancer each year. The effective dose received by patients comes from pre- and post-operative computed tomography (CT) and intraoperative fluoroscopy (FL). We reviewed literature to find novel techniques and approaches that help to decrease RE of patients and personnel. We performed PubMed search using keywords percutaneous nephrolithotomy, intraoperative fluoroscopy, radiation exposure, imaging, percutaneous access, ultrasound, computed tomography, endoscopy, reconstruction, innovations, and augmented reality. Forty-four relevant articles were included in this review. As much as 20% of patients with first diagnosed urolithiasis exceed background RE level almost 17-fold. For diagnosing purposes using low-dose and ultra-low-dose CT, as well as low-dose dual energy scan protocols can be efficient ways to decrease RE while maintaining decent accuracy. Patients with urinary stones can be effectively monitored with digital tomosynthesis, ultrasound alone or ultrasound combined with plain film of the abdomen. Percutaneous access (PCA) into the kidney can be performed with reduced or even no RE, using novel PCA methods. REs from conventional imaging techniques during diagnosis and treatment increase probability of non-stochastic radiation effects. Urologists should be aware of protocols that decrease RE from CT and FL in diagnosis and management of urinary stones. Consideration of recently developed imaging modalities and PCA techniques will also aid in adherence to the “as low as reasonably achievable” principle.

The "all-seeing needle" micro-PCNL versus flexible ureterorenoscopy for lower calyceal stones of ≤ 2 cm

The objectives of the study are to compare the safety and efficacy of "all-seeing needle" optical puncture system micro-percutaneous nephrolithotomy (micro-PCNL) and flexible ureterorenoscopy (FURS) for the treatment of lower calyceal stones of ≤ 2 cm and to determine the advantages and disadvantages of each. 116 patients in total with lower calyceal stones of ≤ 2 cm were randomly divided into two equal groups, "all-seeing needle" optical puncture system micro-PCNL and FURS. In both groups, holmium laser was utilized for lithotripsy. The perioperative parameters were compared between the two groups. Compared to the "all-seeing needle" micro-PCNL group, the mean operative time was significantly longer in the FURS group (P = 0.000). However, there was no significant difference between the two groups with respect to mean hemoglobin reduction (P = 0.087), complications (P = 0.731) and LOS (P = 0.856). The overall SFR of the "all-seeing needle" micro-PCNL group and FURS group was 84.5% (49/58) and 79.3% (46/58), respectively, without any significant difference between the groups (P = 0.469). For treating lower calyceal stones of ≤ 2 cm, the "all-seeing needle" micro-PCNL group had shorter operative time than FURS, while no significant differences between the two groups with respect to mean hemoglobin reduction, complications, LOS and SFR were found.