Avoiding "Needless" nephrectomy: What is the role of small renal mass biopsy in 2024?

Current guidelines do not mandate routine preoperative renal mass biopsy (RMB) for small renal masses (SRMs), which results in a considerable rate (18%-26%) of needless nephrectomy/partial nephrectomy for benign renal tumors. In light of this ongoing practice, a narrative review was conducted to examine the role of routine RMB for SRM. First, arguments justifying the current non-biopsy approach to SRM are critically reviewed and contested. Second, as a standalone procedure, RMB is critically assessed; RMB was found to have higher sensitivity, specificity, and an equal or lower complication rate when compared with other commonly preoperatively biopsied solid organ tumors (e.g., breast, prostate, lung, pancreas, thyroid, and liver). Based on the foregoing information, we propose a paradigm shift in SRM management, advocating for an updated policy in which partial nephrectomy or nephrectomy for SRM invariably occurs only after a preoperative biopsy confirms that a SRM is indeed malignant.

Alkaline Water: Help or Hype for Uric Acid and Cystine Urolithiasis?

PURPOSE: The consumption of alkaline water, water with an average pH of 8 to 10, has been steadily increasing globally as proponents claim it to be a healthier alternative to regular water. Urinary alkalinization therapy is frequently prescribed in patients with uric acid and cystine urolithiasis, and as such we analyzed commercially available alkaline waters to assess their potential to increase urinary pH. MATERIALS AND METHODS: Five commercially available alkaline water brands (Essentia, Smart Water Alkaline, Great Value Hydrate Alkaline Water, Body Armor SportWater, and Perfect Hydration) underwent anion chromatography and direct chemical measurements to determine the mineral contents of each product. The alkaline content of each bottle of water was then compared to that of potassium citrate (the gold standard for urinary alkalinization) as well as to other beverages and supplements used to augment urinary citrate and/or the urine pH. RESULTS: The pH levels of the bottled alkaline water ranged from 9.69 to 10.15. Electrolyte content was minimal, and the physiologic alkali content was below 1 mEq/L for all brands of alkaline water. The alkali content of alkaline water is minimal when compared to common stone treatment alternatives such as potassium citrate. In addition, several organic beverages, synthetic beverages, and other supplements contain more alkali content than alkaline water, and can achieve the AUA and European Association of Urology alkali recommendation of 30 to 60 mEq per day with ≤ 3 servings/d. CONCLUSIONS: Commercially available alkaline water has negligible alkali content and thus provides no added benefit over tap water for patients with uric acid and cystine urolithiasis.

Surgical Force: Initial Study and Clinical Implications in the Assessment of Ureteral Access Sheath Induced Injury.

Purpose: Ureteral access sheaths (UAS) pose the risk of severe ureteral injury. Our prior studies revealed forces ≤6 Newtons (N) prevent ureteral injury. Accordingly, we sought to define the force urologists and residents in training typically use when placing a UAS. Materials and Methods: Among urologists and urology residents attending two annual urological conferences in 2022, 121 individuals were recruited for the study. Participants inserted 12F, 14F, and 16F UAS into a male genitourinary model containing a concealed force sensor; they also provided demographic information. Analysis was completed using t-tests and Chi-square tests to identify group differences when passing a 16F sheath UAS. Participant traits associated with surpassing or remaining below a minimal force threshold were also explored through polychotomous logistic regression. Results: Participant force distributions were as follows: ≤4N (29%), >6N (45%), and >8N (32%). More years of practice were significantly associated with exerting >6N relative to forces between 4N and 6N; results for >8N relative to 4N and 8N were similar. Compared to high-volume ureteroscopists (those performing >20 ureteroscopies/month), physicians performing ≤20 ureteroscopies/month were significantly less likely to exert forces ≤4N (p = 0.017 and p = 0.041). Of those surpassing 6N and 8N, 15% and 18%, respectively, were high-volume ureteroscopists. Conclusions: Despite years of practice or volume of monthly ureteroscopic cases performed, most urologists failed to pass 16F access sheaths within the ideal range of 4N to 6N (74% of participants) or within a predefined safe range of 4N to 8N (61% of participants).

Efficient and Accurate Computed Tomography-Based Stone Volume Determination: Development of an Automated Artificial Intelligence Algorithm.

PURPOSE: Given the shortcomings of current stone burden characterization (maximum diameter or ellipsoid formulas), we sought to investigate the diagnostic accuracy and precision of a University of California, Irvine-developed artificial intelligence (AI) algorithm for determining stone volume determination. MATERIALS AND METHODS: A total of 322 noncontrast CT scans were retrospectively obtained from patients with a diagnosis of urolithiasis. The largest stone in each noncontrast CT scan was designated the "index stone." The 3D volume of the index stone using 3D Slicer technology was determined by a validated reviewer; this was considered the "ground truth" volume. The AI-calculated index stone volume was subsequently compared with ground truth volume as well with the scalene, prolate, and oblate ellipsoid formulas estimated volumes. RESULTS: There was a nearly perfect correlation between the AI-determined volume and the ground truth (R=0.98). While the AI algorithm was efficient for determining the stone volume for all sizes, its accuracy improved with larger stone size. Moreover, the AI stone volume produced an excellent 3D pixel overlap with the ground truth (Dice score=0.90). In comparison, the ellipsoid formula-based volumes performed less well (R range: 0.79-0.82) than the AI algorithm; for the ellipsoid formulas, the accuracy decreased as the stone size increased (mean overestimation: 27%-89%). Lastly, for all stone sizes, the maximum linear stone measurement had the poorest correlation with the ground truth (R range: 0.41-0.82). CONCLUSIONS: The University of California, Irvine AI algorithm is an accurate, precise, and time-efficient tool for determining stone volume. Expanding the clinical availability of this program could enable urologists to establish better guidelines for both the metabolic and surgical management of their urolithiasis patients.

Electromotive Drug Administration in the Porcine Renal Pelvis: First Report.

Introduction: Electromotive Drug Administration (EMDA) amplifies drug delivery deep into targeted tissues. We tested, for the first time, the ability of EMDA to deliver methylene blue into the urothelium of the renal pelvis. Materials and Methods: In an anesthetized female pig, both proximal ureters were transected two inches distal to the ureteropelvic junction. An 8F dual lumen catheter and a 5F fenestrated catheter with an indwelling silver wire were inserted into both renal pelvises following which methylene blue (0.1%) was infused at a rate of 5 mL/min for 20 minutes. In one pelvis, a 4 mA positive pulsed electrical current was applied to the silver wire. Results: In contrast to the control pelvis, the EMDA side macroscopically exhibited dense homogeneous staining; microscopy revealed penetration of methylene blue into the urothelium/lamina propria. Conclusion: In the porcine renal pelvis, application of EMDA increased the penetration of a charged molecule into the urothelium/lamina propria.

Comparison of Ureteral Stent Biomaterials: Encrustation Profile in Lithogenic Artificial Urine Models.

Ureteral stent encrustation significantly limits indwelling time and can lead to downstream urological problems. However, no ideal polymeric biomaterials have been shown to completely resist encrustation in long-term urine exposure. Recently, 2-hydroxyethyl methacrylate (HEMA)-coated Pellethane was reported as a promising biomaterial resistant to encrustation. This study compared HEMA-coated Pellethane to commercially available stents under two different artificial urine environments. To evaluate the degree and composition of encrustation on HEMA-coated Pellethane, Boston Scientific Tria, Bard InLay Optima, Cook Universa Hydrogel, and Cook Black Silicone stents were used at various dwelling times in two different artificial urine environments. In a batch-flow model, samples of stents were suspended in an artificial urine solution (AUS) at 37 °C. Every 24 h for 11 weeks, 50% of the AUS would be replaced with fresh components using a programmable peristaltic pump system. The stent materials were removed at suitable time intervals and air-dried for 24 h under sterile conditions before follow-up analysis. SEM was used to assess the degree of encrustation, and inductively coupled plasma mass spectrometry (ICP-MS) was employed to quantify the encrusted compositions, specifically for calcium, magnesium, and phosphorus. We measured the weight gain over time due to encrusted deposits on the stents and quantified the amount of Ca, Mg, and P deposited on each encrusted stent. After the 11 week trial, HEMA-coated Pellethane showed the most average mass change. SEM showed that HEMA-coated Pellethane was fully encrusted in just 2 weeks in the AUS environments, and ICP-MS showed that Ca is the most abundant deposit. Among all the tested stents, Black Silicone performed the best. The two AUSs were formulated to encrust more rapidly than physiological conditions. HEMA-coated Pellethane is not an ideal stent material, while silicone is a promising material for advancing ureteral stents.

Evaluation of Renal Function and Stent Durability Following Resonance Stent Placement for Benign Disease.

Introduction: The metal-based Resonance stent (RS) has traditionally been placed in patients with malignant ureteral obstruction; as such, the long-term utility of RS among patients with benign ureteral obstruction (BUO) remains underinvestigated. Methods: We retrospectively reviewed our database for patients with BUO who underwent RS placement between 2010 and 2020. The impact of chronic RS placement on renal function was evaluated by estimated serum creatinine-based glomerular filtration rate (eGFR), furosemide renal scan, and CT-based renal parenchymal volume measurement. The number of and reason for RS stent exchanges during the follow-up period, incidence of encrustation, and the average indwell time were recorded. A cost analysis of placing the RS vs a polymeric stent was performed. Results: Among 43 RS patients with BUO, at a mean follow-up of 26 months, there was no change in eGFR (p = 0.99), parenchymal volume (p = 0.44), or split renal function of the stent-bearing side on renal scan (p = 0.48). The mean RS indwell time was 9.7 months. Eleven patients (26%) underwent premature stent replacement (6 cases) or removal (5 cases). Stents in 9 patients (32%) were encrusted, of which 4 (44%) required laser lithotripsy. Overall, 25 patients (58%) and 12 patients (28%) had a mean stent indwell time of ≥6 months and ≥12 months, respectively. Placing an RS resulted in a 52%, 37%, and 5.6% cost reduction compared with a regular polymeric stent placement, where it was exchanged every 6, 4, or 3 months, respectively. Conclusions: RS deployment in the patient with a BUO results in cost-effective maintenance of renal function and of renal parenchymal volume at a mean follow-up of 2 years; however, only 28% of patients fulfilled the 1-year criterion for RS indwell time.

Electromotive Drug Administration in the Ureter in an In Vivo Animal Model: Initial Report.

Introduction: Electromotive drug administration (EMDA) delivers a drug deeply into targeted tissues, such as the bladder. EMDA has never been applied to the ureter. Methods: In four in vivo porcine ureters, a unique EMDA catheter containing a silver conducting wire was advanced for the infusion of methylene blue. In two ureters, a pulsed current was delivered through an EMDA machine, whereas the other two ureters served as a control. After 20 minutes of infusion, the ureters were harvested. Results: In the EMDA ureter, there was diffuse staining of the urothelium; penetration of methylene blue occurred in the lamina propria and muscularis propria. In the control ureter, there was only patchy staining of the urothelium. Conclusion: In this first report of ureteral EMDA, a charged molecule penetrated beyond the urothelium into the lamina propria and muscularis propria of the porcine ureter.

A Review of the Recommendations and Strength of Evidence for Clinical Practice Guidelines on the Management of Small Renal Masses.

Introduction: With the rise in the detection of incidental small renal masses (SRM), the management paradigm for these patients has become an issue of increasing concern. We aim to identify areas of consensus, controversy, and opportunities for improvement among recently published guidelines and assess the strength of evidence for the management of SRMs. Methods: We reviewed practice guidelines for SRMs promulgated by the American Urological Association, European Association of Urology, National Comprehensive Cancer Network, American Society of Clinical Oncology, European Society for Medical Oncology, and the Chinese Society of Clinical Oncology. Levels of evidence and strength of recommendations for evaluation, management and follow-up were analyzed with regard to consensus, conflict, and neglect. Results: There is consensus among guidelines for the initial evaluation and treatment of SRMs; however, discrepancies exist with regard to indications for active surveillance, thermal ablation, and timing/method of follow-up after treatment. Routine renal mass biopsy is not recommended by any guideline. Overwhelmingly, guideline statements are based on low to moderate levels of evidence; only 23% of the reviewed guidelines were based on high-level evidence, 38% based on moderate-level, and 39% on low-level evidence or expert opinion. Conclusions: Despite all six guidelines sharing a consensus on most management topics regarding SRMs, the ongoing lack of high-level evidence precludes gold standard recommendations in the areas of diagnosis, treatment, and follow-up. More high-quality studies are needed to develop a stronger, data-supported universal guideline for the management of SRMs.

Evaluation of silk fibroin-based urinary conduits in a porcine model of urinary diversion.

Background: The primary strategy for urinary diversion in radical cystectomy patients involves incorporation of autologous gastrointestinal conduits into the urinary tract which leads to deleterious consequences including chronic infections and metabolic abnormalities. This report investigates the efficacy of an acellular, tubular bi-layer silk fibroin (BLSF) graft to function as an alternative urinary conduit in a porcine model of urinary diversion. Materials and methods: Unilateral urinary diversion with stented BLSF conduits was executed in five adult female, Yucatan mini-swine over a 3 month period. Longitudinal imaging analyses including ultrasonography, retrograde ureteropyelography and video-endoscopy were carried out monthly. Histological, immunohistochemical (IHC), and histomorphometric assessments were performed on neoconduits at harvest. Results: All animals survived until scheduled euthanasia and displayed moderate hydronephrosis (Grades 1-3) in reconstructed collecting systems over the course of the study period. Stented BLSF constructs supported formation of vascularized, retroperitoneal tubes capable of facilitating external urinary drainage. By 3 months post-operative, neoconduits contained α-smooth muscle actin+ and SM22α+ smooth muscle as well as uroplakin 3A+ and pan-cytokeratin + urothelium. However, the degree of tissue regeneration in neotissues was significantly lower in comparison to ureteral controls as determined by histomorphometry. In addition, neoconduit stenting was necessary to prevent stomal occlusion. Conclusion: BLSF biomaterials represent emerging platforms for urinary conduit construction and may offer a functional replacement for conventional urinary diversion techniques following further optimization of mechanical properties and regenerative responses.

Porcine Bladder Replacement with a Bilayer Silk Fibroin Enhanced Prosthetic Reservoir: A Feasibility Study.

Introduction: The creation of synthetic reservoirs for bladder replacement has been limited by challenges of interfacing synthetic materials and native tissue. We sought to overcome this challenge by utilizing a novel bilayer silk fibroin scaffold (BLSF) as an intermediary toward the development of an acellular prosthetic reservoir. Methods: Under institutionally approved protocols, 3D-printed reservoirs were implanted in six juvenile female pigs after cystectomy. BLSF was attached to the in situ prosthetic reservoir serving as an intermediary to native ureteral and urethral tissue anastomoses. Our first protocol allowed four pigs to be survived up to 7 days, and the second protocol allowed two pigs to be survived for up to 1 year. At the first sign of functional decline or the end of the study period, the animals were euthanized, and kidneys, ureters, prosthetic bladder, and urethra were harvested en bloc for histopathology analysis. Results: The first two pigs had anastomotic urine leaks because of design flaws resulting in early termination. The third pig had acute renal failure resulting in early termination. The artificial bladder design was modified in subsequent iterations. The fourth pig survived for 7 days and, upon autopsy, had intact urethral and ureteral anastomoses. The fifth and sixth pigs survived for 11 and 12 weeks, respectively, before they were sacrificed because of failure to thrive. One animal developed an enteric fistula. The other animal had an intact anastomosis, and the BLFS was identified at the ureteral and urethral anastomoses on histopathologic analysis. Conclusions: Replacing the porcine bladder with a prosthetic bladder was achieved for up to 3 months, the second longest survival period for a nonbiologic bladder alternative. BLSF was used for the first time to create an interface between synthetic material and biologic tissue by allowing ingrowth of urothelium onto the acellular alloplastic bladder.

Comparison of Superpulse Thulium Fiber Laser vs Holmium Laser for Ablation of Renal Calculi in an In Vivo Porcine Model.

Introduction and Objectives: We sought to compare the effectiveness and efficiency of the superpulse thulium fiber laser (sTFL to the holmium: yttrium-aluminum-garnet [Ho:YAG] laser for ureteroscopic "dusting" of implanted renal stones in an in vivo porcine model. Methods: Twenty-four porcine kidneys (12 juvenile female Yorkshire pigs) were randomized to Ho:YAG or sTFL treatment groups. Canine calcium oxalate stones were scanned with computed tomography to calculate stone volume and stone density; the stones were randomized and implanted into each renal pelvis via an open pyelotomy. In all trials, a 14F, 35 cm ureteral access sheath was placed. With a 9.9F dual lumen flexible ureteroscope, laser lithotripsy was performed using dusting settings: Ho:YAG 200 µm laser fiber at 16 W (0.4 J, 40 Hz) or sTFL 200 µm laser fiber at 16 W (0.2 J, 80 Hz). Lithotripsy continued until no fragments over 1 mm were observed. No stone basketing was performed. Throughout the procedures, intrarenal and renal pelvis temperatures were measured using two percutaneously positioned K-type thermocouples, one in the upper pole calyx and one in the renal pelvis. After the lithotripsy, the ureteropelvic junction was occluded, the kidneys were bivalved, and all residual fragments were collected, dried, weighed, and then measured with an optical laser particle sizer. Results: Implanted stones were similar in volume and density in both groups. Intraoperative collecting system temperatures were similar for both groups (all <44°C). Compared to Ho:YAG, sTFL ablated stones faster (9 vs 27 minutes, p < 0.001) with less energy expenditure (8 vs 26 kJ, p < 0.001), and a greater stone clearance rate (73% vs 45%, p = 0.001). After sTFL lithotripsy, 77% of the remaining fragments were ≤1 mm vs 17% of fragments ≤1 mm after Ho:YAG treatment (p < 0.001). Conclusions: In an in vivo porcine kidney, using dusting settings, sTFL lithotripsy resulted in shorter ablation times, higher stone clearance rates, and markedly smaller stone fragments than Ho:YAG lithotripsy.

Beyond Efficiency: Surface Electromyography Enables Further Insights into the Surgical Movements of Urologists.

Introduction: Surgical skill evaluation while performing minimally invasive surgeries is a highly complex task. It is important to objectively assess an individual's technical skills throughout surgical training to monitor progress and to intervene when skills are not commensurate with the year of training. The miniaturization of wireless wearable platforms integrated with sensor technology has made it possible to noninvasively assess muscle activations and movement variability during performance of minimally invasive surgical tasks. Our objective was to use electromyography (EMG) to deconstruct the motions of a surgeon during robotic suturing (RS) and distinguish quantifiable movements that characterize the skill of an experienced expert urologic surgeon from trainees. Methods: Three skill groups of participants, novice (n = 11), intermediate (n = 12), and expert (n = 3), were enrolled in the study. A total of 12 wireless wearable sensors consisting of surface EMGs and accelerometers were placed along upper extremity muscles to assess muscle activations and movement variability, respectively. Participants then performed a RS task. Results: EMG-based parameters, total time, dominant frequency, and cumulative muscular workload, were significantly different across the three skill groups. We also found nonlinear movement variability parameters such as correlation dimension, Lyapunov exponent trended differently across the three skill groups. Conclusions: These findings suggest that economy of motion variables and nonlinear movement variabilities are affected by surgical experience level. Wearable sensor signal analysis could make it possible to objectively evaluate surgical skill level periodically throughout the residency training experience. Clinical Trial Registration Number: HS# 2018-4407.

Multidisciplinary Approach and Outcomes of Pretreatment Small (cT1a) Renal Mass Biopsy: Single-Center Experience.

Purpose: We evaluated our experience of a multidisciplinary approach to renal mass biopsy (RMB) for small renal masses (SRMs) employing in-office ultrasound (US)-guided biopsy by urology (24%), CT, or US biopsy by interventional radiology (IR) (79%), and endoscopic ultrasound (EUS)-guided biopsy by gastroenterology (GI) (4%). Materials and Methods: A single-institution retrospective review of patients who underwent RMB for SRM from May 2013 to August 2019 was conducted. Data regarding patient demographics, tumor characteristics, biopsy technique, histopathology, and management were collected. Diagnostic rates, concordance with final pathology, complications, and outcomes were analyzed. Results: Of the 192 biopsies reviewed, 63% biopsies were malignant, 20% were benign, and 17% were nondiagnostic. Based on biopsy results, 71 patients (37%) elected active surveillance. Thirty-eight (20%) patients underwent cryoablation, 56 (29%) underwent partial nephrectomy, 14 (7%) underwent radical nephrectomy, and the remaining patients were treated elsewhere. The rate of surgery for benign pathology after pretreatment RMB was 3%. The concordance rate between biopsy and final pathology was 99% for malignancy, 96% for specific pathology subtype, and 85% for renal cell carcinoma grade. Median time from diagnosis to definitive treatment was 97 days (urology: 76, IR: 110 and GI: 54, p = 0.002). Three (1.6%) Clavien I complications were reported. Conclusion: Our multidisciplinary approach to RMB for clinical stage T1a demonstrated favorable safety and diagnostic rates, which effectively directed management strategies and minimized surgery for benign disease. Urologist-performed office biopsies significantly shortened the time from diagnosis to definitive treatment. Our experience with GI EUS biopsy has demonstrated feasibility and safety for tumors that were otherwise not accessible percutaneously.

Retrograde Cystonephroscopy for Complex Renal Calculi Using Novel Dual-Action Aspiration, Irrigation Cystoscope: Initial Case Series.

Introduction: Percutaneous nephrolithotomy is the gold standard treatment for kidney stones ≥2 cm; however, it remains an invasive procedure with significant risks especially in individuals with severe medical comorbidities. In contrast, while ureteroscopy is far less morbid, a major impediment to its use for larger calculi is the inability to evacuate the many fragments created during laser lithotripsy. Herein, we describe two patients with large-volume calculi and a third high-risk patient with a smaller stone who were treated with cystonephroscopy using a recently released, 16F flexible cystoscope equipped with dual aspiration and irrigation capabilities. Materials and Methods: Three consecutive female patients underwent retrograde cystonephroscopy from June 2021 to July 2021 with a novel 16F aspiration-enabled flexible cystoscope. Demographic data were collected. Preoperative and postoperative CT scan images were reviewed to determine linear stone dimensions and scalene ellipsoid volume. Results: The three female patients had an average age of 72.3 years and an American Society of Anesthesiologists (ASA) physical status score of 3. The mean preoperative stone volume was 4950 mm3. The average postcystonephroscopy stone volume was 217 mm3, resulting in a total stone clearance rate of 97%. No major complications occurred. The average procedure time was 176 minutes. Conclusions: Among the three high-risk female patients, two with large-volume calculi, retrograde cystonephroscopy with a novel aspiration-enabled cystoscope allowed for the procedure to be effectively completed solely via a retrograde approach.

The Impact of One Week of Pre-Stenting on Porcine Ureteral Luminal Circumference.

Objectives: Larger ureteral access sheaths (UASs) have the potential to improve ureteroscopic stone removal outcomes but are often avoided by surgeons because of concerns of ureteral injury. Using our novel UAS force sensor and previously defined force thresholds for ureteral injury, we sought to evaluate the impact of 1 week of stenting on the maximum safe dilation of ureteral luminal circumference. Methods: Twelve juvenile female Yorkshire pigs (24 ureters) were evaluated. The inner (i.e., luminal) circumference of each ureter was determined using Cook urethral dilators ranging from 8F to 24F in 2F increments, 37 cm in length. Each dilator was sequentially passed while applying the UAS force sensor to measure insertion force before and after 1 week of stent placement. Each ureter was randomized to receive either a 4.7F or 7.0F stent (20 cm). Maximum ureteral luminal circumference was defined as effective passage of the dilator to the ureteropelvic junction with ≤6 newtons (N) of force (the force threshold previously defined by porcine and clinical studies to avoid ureteral damage). After passage of the largest dilator at 6 N, flexible ureteroscopy was performed and a post-ureteroscopic lesion scale (PULS) was recorded. Results: After 1 week of stent placement, the median ureteral luminal circumference increased to 15F representing a mean increase of 3.8F ± 2.8F (p < 0.001). Twenty-one (88%) of the pre-stented ureters had an increase in luminal circumference, with 12 ureters (50%) dilated to ≥16F (p = 0.032), 6 ureters (25%) dilated to ≥18F, and in 2 cases a maximum size of 24F was recorded. The PULS grade was ≤2 in all cases, indicating no high-grade ureteral injuries. Laterality and stent size did not impact ureteral luminal circumference after pre-stenting (p = 0.232 and p = 0.337, respectively). Conclusions: One week of ureteral stenting resulted in nearly a 4F increase in the luminal circumference of porcine ureters.

The Life and Death of Percutaneous Stone Removal: "Looking Back-Looking Forward".

Although percutaneous nephrolithotomy (PCNL) is less morbid than open surgery, it still carries risks of significant complications as well as injury to the renal parenchyma. Flexible ureteroscopic stone removal, although causes no appreciable damage to the renal parenchyma, has limitations, most notably, a lower stone-free rate than PCNL. Advances in our knowledge regarding ureteral physiology combined with technical developments applied to ureteral access sheath deployment and size may well propel retrograde intrarenal surgery to the forefront of kidney stone removal, regardless of stone size or location.