Comparison of metabolic parameters between pure-uric acid and mixed-uric acid kidney stone formers.

PURPOSE: We seek to compare clinical and 24-h urine parameters between pure-uric acid (UA) and UA-CaOx stone formers in our practice and explore how any differences in metabolic profiles could suggest different prevention strategies between the two groups. METHODS: We retrospectively reviewed patients with either pure- or mixed-UA nephrolithiasis from 2020 to 2023 at a tertiary care center. We included patients with a 24-h urine collection and a stone analysis detecting any amount of UA. Patients were organized into two cohorts: (1) those with 100% UA stones and (2) < 100% UA stones. Differences in demographic characteristics were compared between pure-UA and UA-CaOx stone formers. Twenty-four hour urine metabolic parameters as well as metabolic abnormalities were compared between the pure-uric acid and mixed-uric acid groups. RESULTS: We identified 33 pure-UA patients and 33 mixed-UA patients. Patient demographics were similar between the groups (Table 1). Pure- and mixed-UA patients had a similar incidence of metabolic syndrome, diabetes, history of stones, and stone burden. Table 1 Demographic and baseline characteristics among pure- and mixed-uric acid stone formers Pure-uric acid stones (n = 33) Mixed-uric acid stones (n = 33) p-value Median age [IQR] 63.00 [58.00-72.50] 63.00 [53.50-68.00] 0.339 Median BMI [IQR] 28.79 [25.81-33.07] 27.96 [25.81-29.55] 0.534 Gender, n (%) 1.000  Male 21 (63.6) 21 (63.6)  Female 12 (36.4) 12 (36.4) Metabolic syndrome, n (%) 17 (51.5) 16 (48.5) 0.806 Diabetes, n (%) 13 (39.4) 12 (36.4) 0.800 History of stones, n (%) 23 (69.7) 22 (66.7) 0.792 Median total stone burden, mm [IQR] 12.00 [6.00-26.50] 13.00 [7.05-20.00] 0.995 Median serum uric acid, mg/dL [IQR] 6.20 [4.80-7.15] 5.90 [4.98-6.89] 0.582 IQR Interquartile range BMI Body Mass Index n number We found the pure-UA cohort to have 24-h lower urine volume (1.53 vs. 1.96 L/day, p = 0.045) and citrate levels (286 vs. 457 mg/day, p = 0.036). UA-CaOx stone formers had higher urinary calcium levels (144 vs. 68 mg/day, p = 0.003), higher urinary oxalate levels (38 vs. 30 mg/day, p = 0.017), and higher median urinary calcium oxalate super-saturation (3.97 vs. 3.06, p = 0.047). CONCLUSIONS: Pure-UA kidney stone formers have different urinary metabolic parameters when compared with UA-CaOx stone formers, thus requiring different and tailored medical management.

Drivers of calcium oxalate stone formation in the octogenarian population.

INTRODUCTION: American Urological Association (AUA) guidelines suggest metabolic testing via 24-h urine studies in high-risk, interested first-time stone formers, and recurrent stone formers. If metabolic testing is not available or otherwise not feasible, clinicians may need to utilize empiric therapy. Debility and social barriers, particularly in the elderly population, may limit the practicality of metabolic testing, and therefore, empiric therapy is of particular importance. The aim of this study is to identify whether unique urinary metabolic abnormality profiles exist for octogenarians with calcium oxalate kidney stones, as this may guide empiric stone prevention therapy more precisely in this population. MATERIALS AND METHODS: Patients with calcium oxalate stones from a single academic kidney stone center in New York, NY, were retrospectively identified in our prospectively managed database. Patient data, including demographic, clinical information, and baseline 24-h urine studies, were collected before initiating any treatment. Subjects were stratified by age (≤ 40, 41-59, 60-79, and ≥ 80 years) to compare the metabolic urinary abnormality profiles between octogenarians and other age groups. Subgroup analyses were also performed to compare results by gender and by the presence of underlying kidney dysfunction. Comparative statistical analysis was carried out using Chi-square tests, Mann-Whitney U tests, and t-tests where appropriate. RESULTS: Hypocitraturia, low urine pH, and low urine volume were most common in older patients, particularly in octogenarians. Hypercalciuria, hypernatriuria, and hyperuricosuria were more apparent in younger groups. CONCLUSION: With increasing age, hypocitraturia, low urine pH, and low urine volume were more prevalent on 24-h urine metabolic testing. We hypothesize increased comorbidity, including medical renal disease, polypharmacy, and dehydration are possible factors contributing to this unique profile. We suggest that empiric therapy targeted towards this profile is important in very elderly stone formers in whom 24-h urine testing may not be possible. Increased hydration, increased fruit and vegetable intake, and low-dose alkali therapy are easy measures to accomplish this.

The T-Tilt Position: A Novel Modified Patient Position to Improve Stone-Free Rates in Retrograde Intrarenal Surgery.

PURPOSE: Residual fragments following retrograde intrarenal surgery can lead to future stone episodes. The lower pole of the kidney presents a unique challenge as it is the most difficult location for retrograde intrarenal surgery. We investigated a modified patient position to increase stone-free rate by analyzing presence of residual fragments. We randomized patients into standard position and the T-Tilt position (15° Trendelenburg and 15° airplane away from the surgical side kidney). MATERIALS AND METHODS: In this prospective, randomized study, patients were randomized into the standard or T-Tilt position. Demographics, comorbidities and operative parameters were collected. Stone-free rate was determined with renal ultrasound and x-ray at 1-month followup. Postoperative complications were recorded up to 1 month. Variables were compared using Kruskal-Wallis test for continuous variables and chi-square test for categorical variables. RESULTS: A total of 138 patients were analyzed: 75 standard patients and 63 T-Tilt patients. The groups had similar patient and stone factors. The most common stone position was the lower pole (68.0% standard, 74.6% T-Tilt). Stone-free rates were significantly different: standard position was 76.7% and T-Tilt position was 92.1% (p=0.015). Stone-free rates for isolated lower pole stones were significantly different as well: standard position was 68.2% and T-Tilt position was 95.6% (p <0.001). Clavien-Dindo scores did not differ significantly (p=0.262). CONCLUSIONS: The T-Tilt patient position was associated with higher stone-free rates. It is an atraumatic, cost-effective technique. These results suggest that modifying patient positioning during retrograde intrarenal surgery improves stone-free rates.

The impact of metabolic syndrome components on urinary parameters and risk of stone formation.

PURPOSE: To investigate the relationship between metabolic syndrome (MS) and urinary abnormalities in stone-forming patients. Additionally, to delineate whether severity of urinary derangements is impacted by the number of co-occurring MS components. METHODS: Stone-forming patients who underwent initial metabolic workup prior to medical intervention at a comprehensive stone clinic were retrospectively reviewed and included in the study. Patients were given a six point (0-5) Metabolic Syndrome Severity Score (MSSS) based on the number of co-occurring MS components and split into six respective groups. Baseline clinical characteristics and metabolic profiles were compared between groups. RESULTS: Four-hundred-ninety-five patients were included in the study. Median age and median BMI was 58 years and 27.26 kg/m2, respectively. Several significant metabolic differences were noted, most notably a downward trend in median urinary pH (p < 0.001) and an upward trend in median urinary supersaturation uric acid (p < 0.001) across groups as MSSS increased. Multivariate analysis demonstrated an independent association between higher MSSS and increasing number of urinary abnormalities. A second multivariate analysis revealed that all MS components except hyperlipidemia were independently associated with low urinary pH. Additionally, obesity was independently associated with the greatest number of urinary abnormalities and had the strongest association with hyperuricosuria. CONCLUSIONS: Prior research has attributed the strong association of nephrolithiasis and MS to high prevalence of UA nephrolithiasis and low urinary pH. Our findings indicate that all MS components with the exception of hyperlipidemia were independently associated with low urinary pH suggesting a mechanism independent from insulin resistance.

Is Totally Tubeless Percutaneous Nephrolithotomy a Safe and Efficacious Option for Complex Stone Disease?

Background: Percutaneous nephrolithotomy is the gold standard treatment for large, complex intrarenal stones. Historically, this was performed using a nephrostomy tube (PCN) and/or internalized ureteral stent at the end of the procedure. However, totally tubeless nephrolithotomy (tt-PCNL) is a novel technique where no tubes (no stent nor nephrostomy tube) are left post-operatively. We review the literature on this subject regarding peri-operative outcomes, post-operative outcomes, and potential complications of the procedure, discuss our technique, and make recommendations on implementation for centers not currently utilizing the procedure. Materials and methods: We performed a comprehensive search of the literature on totally tubeless nephrolithotomy using MEDLINE database search. Our search included prior review articles, meta-analyses, systematic reviews, primary research articles, case reports, and case studies. Results: In comparison to prior approaches where a stent or nephrostomy tube is placed, tt-PCNL has a similar complication rate and better post-operative outcomes. Totally tubeless PCNL has similar operative times and similar changes in hemoglobin. However, it had shorter length of stays across all studies. The mean difference in length of stay in the studies reviewed was 1.96 days. Additionally, tt-PCNL had decreased post-operative analgesic requirements and pain scores. Conclusions: This review highlights totally tubeless percutaneous nephrolithotomy as a safe and feasible surgical technique with improved outcomes in properly selected patients.

Review of efficacy and safety of same-day discharge after percutaneous nephrolithotomy.

PURPOSE: Prior literature reviews have assessed the efficacy and safety of outpatient percutaneous nephrolithotomy (PCNL) with "outpatient" defined as discharge within twenty-four hours of surgery. To our knowledge, this is the first literature review analyzing ambulatory PCNLs (aPCNL) defined as hospital discharge on the same day as surgery. This review aims to assess the efficacy and safety of same-day discharge after PCNL. METHODS: We conducted a search in the PubMed database for key search terms including "ambulatory PCNL", "ambulatory percutaneous nephrolithotomy", "outpatient PCNL", "outpatient percutaneous nephrolithotomy", and "day surgery percutaneous nephrolithotomy". We reviewed articles defining "ambulatory" as discharge the same day the PCNL was performed. 13 papers were identified in our search. RESULTS: Overall, we found no difference in complication rates, emergency department visits, and postoperative admissions when comparing outpatient PCNL to inpatient PCNL, and to previously published statistics for inpatient PCNL. Some studies even showed lower rates of adverse outcomes in ambulatory cohorts when compared to inpatient cohorts. Additionally, ambulatory PCNL conferred significant healthcare savings over inpatient PCNL. CONCLUSION: This literature review suggests that ambulatory PCNL can be safely performed in both optimal and suboptimal surgical candidates with no significant increase in complications. Additional high-quality studies are warranted to further the evidence surrounding outpatient PCNL and its outcomes.

Selecting an Endourology Society Fellowship Program: The Candidates' Perspectives.

Introduction: Understanding the factors that influence the decision of urology residents to pursue an Endourology Society (ES) fellowship and the criteria used by applicants to rank programs may help residents and program directors (PDs) optimize the match process. In the present study, we surveyed current ES fellows to gain better insight surrounding their decision-making process. Materials and Methods: A survey was emailed to all ES fellows, comprising Endourology and Stone Disease (ESD), Laparoscopic and Robotic Surgery (MIS), and combination of ESD/MIS (COM) programs. A Likert scale ranging from 1 to 5 was used. The survey captured demographics such as geographic region, program type, duration, applicants' reasons for pursuing fellowship, criteria for ranking programs, and perceived improvements in surgical comfort levels at the end of their training. Results: Out of the 60 fellows who were surveyed, 40 (66.7%) responded. Among the respondents, 9 (22.5%) pursued ESD, 10 (25%) pursued MIS, and 21 (52.5%) pursued COM programs. The primary reason for seeking a fellowship was to improve surgical skills while increasing earning potential and enhancing research opportunities were deemed the least important. Fellows enrolled in 1-year programs were less likely to pursue fellowships for academic reasons. The two most significant factors in selecting a program were both related to gaining operative experience. Lastly, there was an increase in the level of comfort performing all endourological surgeries independently after fellowship. Conclusions: ES fellowship is seen as an opportunity to hone surgical skills and increase job competitiveness. When selecting a program, operative experience is the most important factor, and fellowship improves operative confidence. The information obtained from this study may mutually help guide future applicants and PDs in the decision process of the Endourology Match.

Adjuvant intraluminal therapies for upper tract urothelial carcinoma.

Upper urinary tract urothelial carcinomas (UTUCs) are often identified and first treated endoscopically. After proper risk stratification, adjuvant treatment may be recommended. Consequently, as adjuvant therapy becomes more common place in the oncological armamentarium, we seek to better characterize its existing and future therapeutic landscape. In this article, we present an overview of the most up-to-date information about intracavitary instillations as an adjuvant therapy in the context of UTUC. We reviewed the current literature on the epidemiology, disease characteristics, treatment, and outcomes of UTUC with a particularly focus on intraluminal adjuvant therapy for UTUC. This review provides a comprehensive overview of the most recent available data regarding adjuvant therapies used for UTUC. Intraluminal therapy plays an increasingly important role in the management of UTUC. Mitomycin C is the most common adjuvant treatment for UTUC with bacillus Calmette-Guerin (BCG) being utilized to a lesser extent. UGN-101 is a novel topical gel-based therapy that has shown promising results and thus recently garnered Food and Drug Administration (FDA) approval for UTUC. Other treatments such as BCG-IFN, gemcitabine, docetaxel, and drug-eluting stents (DES) may play a future role in UTUC treatment given further research. It is important to caveat that current studies on topical adjuvant treatments demonstrate varying degrees of effectiveness. This is largely due to limited research on UTUC, consisting of small sample sizes, and mostly retrospective experiences. Accordingly, further clinical trials are needed to evaluate the true benefit of these treatments.

Comprehensive analysis of factors associated with significant blood loss during percutaneous nephrolithotomy.

INTRODUCTION: The objective of this study is to conduct a thorough investigation of the risk factors associated with blood loss during PCNL, within the setting of a US urban tertiary care center. MATERIALS AND METHODS: We conducted a retrospective analysis of our endourology database to identify adult patients who underwent PCNL for stone extraction at our tertiary stone center between October 2014 and December 2022. Patients were categorized into two groups based on the extent of blood loss: significant blood loss (SBL) and no significant blood loss (NSBL). The cut-off value for SBL was determined as the median change in hematocrit levels from preoperative to postoperative among patients who required postoperative transfusions. Several factors were evaluated, including stone dimensions, operative details, the presence of preoperative drains, patient position, type of access, access site, number of accesses, tract size, tract length, stone location, number of stones, operative time, and the S.T.O.N.E. Nephrolithometry Scoring System. RESULTS: Our analysis included a total of 695 procedures performed on 674 distinct patients who met our inclusion criteria. Of these, 102 patients (14.7%) were included in the SBL group. Patients in the SBL group had a higher mean number of accesses (1.57 vs. 1.29, P<0.001), were positioned prone more often (96.0% vs. 88.6%, P = 0.025), and underwent fluoroscopic-guided access more frequently (89.9% vs. 64.8%, P<0.001). Additionally, significant differences were observed in stone morphology, with the SBL group having higher rates of complete staghorn stones (42.2% vs. 27.0%, P = 0.019) and lower rates of partial staghorn stones (27.7% vs. 36.8%, P = 0.019). A larger proportion of patients in the SBL group required a 16 French nephrostomy tube for postoperative drainage (13.3% vs. 10.4%, P = 0.041). Lastly, the SBL group had a longer mean operative time compared to the NSBL group (P<0.001). Multiple logistic regression analysis identified stone volume (P = 0.039), number of accesses (P = 0.047), and operative time (P = 0.006) as independent risk factors associated with SBL status. CONCLUSION: Surgical complexity factors such as stone volume, number of accesses, and operative time are linked to a higher risk of SBL during PCNL. Stone volume and the requirement for multiple accesses can usually be estimated with reasonable accuracy before surgery.

The effects of continuing aspirin on blood loss and postoperative outcomes in percutaneous nephrolithotomy.

BACKGROUND: Percutaneous nephrolithotomy (PCNL) is an effective surgery for complex kidney stones yet with inherent bleeding risks. It remains unclear whether aspirin should be discontinued prior to PCNL. We aimed to further substantiate the safety of continuing aspirin during PCNL surgery and to determine whether aspirin status affects postoperative outcomes following PCNL. METHODS: We retrospectively queried our endourology database for patients who underwent PCNL from October 2017 to December 2022 at our high-volume tertiary referral center. The three groups were based on aspirin status at the time of PCNL: no aspirin (NA), discontinued aspirin (DA), and continued aspirin (CA). Data collected included demographics, preoperative characteristics, operative parameters, pre and postoperative lab values, transfusions, and complications. RESULTS: A total 648 patients were divided into these study groups: 525 NA patients (81.0%), 55 DA (8.5%), and 68 CA (10.5%). The DA and CA groups were of similar comorbidities, and both were more comorbid at baseline than NA. Postoperative change in lab values and complications did not differ significantly. Rates of postoperative blood transfusion were higher in the CA and DA groups compared to NA and approached statistical significance. There were no significant differences in any postoperative outcomes between the DA and CA groups alone. CONCLUSIONS: In patients on chronic aspirin therapy, continuing aspirin appears equally safe to discontinuing aspirin prior to PCNL. Most patients should not forego the benefits of continuous aspirin for the theoretical risk of bleeding. Patients on prolonged aspirin therapy may be more likely than those who are not on chronic aspirin therapy to require blood transfusions. However, regardless of whether aspirin use is stopped, this may be caused by patient comorbidities rather than higher rates of blood loss.

Reverse Trendelenburg Positioning Minimizes Stone Retropulsion During Ureteroscopic Laser Lithotripsy: A Prospective Randomized Study.

Purpose: Retropulsion of stone fragments during ureteroscopic laser lithotripsy (URSLL) remains a challenge for urologists and is associated with increased operative time and reduced stone-free rate (SFR). In this study, we compared the rate of retropulsion of ureteral stones during URSLL between the standard dorsal lithotomy (SDL) position and dorsal lithotomy position with reverse Trendelenburg (RT). Materials and Methods: Patients with ureteral stones requiring surgical intervention between May 2019 and January 2022 were randomized to undergo URSLL in either SDL or RT positions. The primary outcome of this study was stone retropulsion. Secondary outcomes included retropulsion to the kidney, SFR, operative time, 30-day emergency department visits and complications, and the need for conversion from semirigid to flexible ureteroscope. Differences between groups were evaluated using the chi-square test, Fisher exact test, Kruskal-Wallis test, or t-test. Results: A total of 114 patients were included in the study, with 57 patients in each group. There were no differences between groups in terms of baseline demographics or stone characteristics. Retropulsion was significantly less frequent in the RT group (68.4% vs 10.5%, p < 0.01). Similarly, the RT group was favored for lower risk of retropulsion into the kidney (40.4% vs 5.3%, p < 0.01), operative time (43.5 vs 33.0 minutes, p = 0.02), and need for ureteroscope conversion (16.7% vs 2.2%, p = 0.04). There was no difference in the SFR (100% vs 95%, p = 0.49). Conclusions: RT positioning during URSLL for ureteral stones significantly decreases the rate of stone retropulsion, operative time, and the need for conversion from semirigid to flexible ureteroscope.

The Role of Experience: How Case Volume and Endourology-Fellowship Training Impact Surgical Outcomes for Ureteroscopy.

Introduction: Surgical experience is associated with superior outcomes in complex urologic cases, such as prostatectomy, nephrectomy, and cystectomy. The question remains whether experience is predictive of outcomes for less complex procedures, such as ureteroscopy (URS). Our study examined how case volume and endourology-fellowship training impacts URS outcomes. Methods: We retrospectively reviewed URS cases from 2017 to 2019 by high ureteroscopy volume urologists (HV), low ureteroscopy volume urologists (LV), endourology-fellowship trained (FT), and non-endourology FT (NFT) urologists. Surgical outcomes including stone-free rate (SFR), complication and reoperation rates, and postoperative imaging follow-up were analyzed between groups. Results: One thousand fifty-seven cases were reviewed across 23 urologists: 6 HV, 17 LV, 3 FT, and 20 NFT. Both FT and HV operated on more complex cases with lower rates of pre-stented patients. HV also operated on patients with higher rates of renal stones, lower pole involvement, and prior failed procedures. Despite this, FT and HV showed between 11.7% and 14.4% higher SFR, representing 2.7- to 3.6-fold greater odds of stone-free outcomes for primary and secondary stones. Additionally, HV and FT had a 4.9% to 7.8% lower rate of postoperative complications and a 3.3% to 4.3% lower rate of reoperations, representing 1.9- to 4.0-fold lower odds of complications. Finally, their patients had a 1.6- to 2.1-fold higher odds of postoperative imaging follow-up with a greater proportion receiving postoperative imaging within the recommended 3-month postoperative period. Conclusions: More experienced urologists, as defined by higher case volume and endourology-fellowship training, had higher SFR, lower complication and reoperation rates, and better postoperative imaging follow-up compared with less experienced urologists. Although less experienced urologists had outcomes in-line with clinical and literature standards, continued training and experience may be a predictor of better outcomes across multiple URS modalities.

Criteria Used by Endourology Society Fellowship Program Directors for the Selection and Evaluation of Fellows.

Introduction: An understanding of which trainee factors Endourology Society (ES) fellowship program directors (PDs) value may help urology residents optimize their fellowship candidacy and help current fellows optimize their fellowship performance. In the present study, we evaluated which factors are most important to ES PDs in selecting fellowship candidates and evaluating current fellows. Materials and Methods: A survey was constructed using Research Electronic Data Capture (REDCap) software and emailed to PDs of fellowships registered with the ES. Fellowships in the ES include Endourology/kidney stone disease (ESD) programs, robotic-laparoscopic surgery programs (MIS), and combination programs. A Likert scale ranging from 1 (not important) to 5 (extremely important) was used to rank the criteria for selecting and evaluating fellows. The survey captured program demographics such as geographic region, program type, and program duration. Results: Of the 52 ES PDs, 35 (67%) responded. Respondents represented 8 (23%) ESD programs, 7 (20%) MIS programs, and 20 (57%) combination programs. Furthermore, 16 (46%) represented 1-year programs and 19 (54%) represented 2-year programs. The top-five factors for candidate selection were perceived fit of the applicant, perceived level of applicant interest, initial interview, personal emails from applicants' advocates, and personal phone calls from applicants' advocates. Advocacy on behalf of the applicant appeared to be especially important for 2-year fellowships. The top-five factors for the evaluation of fellows in training were patient interactions, professionalism, attitude/demeanor, operative skills, and interactions with ancillary staff. Research productivity was of greater importance for the evaluation and selection of 2-year fellows and ESD fellows. Conclusions: Applicants for ES fellowships should focus on the initial interview and recruiting supportive mentors to advocate for their applications, particularly for 2-year programs. Although PDs value both clinical skills and research productivity, research productivity was more important for 2-year programs and ESD programs. Further research into applicant perspectives on the fellowship application process is warranted.

Do Infection-Associated Stone Subtypes Behave the Same Clinically? A Retrospective Bicenter Study.

Introduction and Objectives: Infection-associated renal stones are commonly composed of magnesium-ammonium-phosphate (MAP) and carbonate apatite (CA). The clinical implications of these two different, but closely related stone types, are unknown. We sought to compare the clinical, microbiologic, and metabolic characteristics of patients with MAP and CA stone types. Methods: We retrospectively reviewed the medical records of patients from two centers (one in the United States and one in Israel) who underwent ureteroscopy or percutaneous nephrolithotomy between 2012 and 2020 and identified patients with a predominant stone analysis component of CA or MAP and clinical data supporting an infection stone. We analyzed and compared demographic data, medical history, postoperative fever, stone and urinary microbiology, and 24-hour urine studies. Results: A total of 79 and 75 patients met the inclusion criteria for the MAP and CA cohorts, respectively. No significant difference was found in patient demographics or comorbidities between the MAP and CA cohort. Female predominance was noted in both. Although there were no significant differences in 24-hour urine parameters between the cohorts, hypercalciuria was common in both cohorts (38% and 32% of patients in the MAP and CA cohorts, respectively). Gram-negative bacteria were more common in the MAP stone cultures. Postoperative fever was significantly more common in the MAP cohort (14.7% vs 3.8%, p < 0.016). Conclusions: MAP and CA stone formers share similar demographic characteristics with a clear female predominance. MAP stones patients appear more likely to develop postoperative fever, possibly related to a higher occurrence of gram-negative bacteria in the stone cultures of the MAP cohort. Although there were no significant differences among metabolic parameters, hypercalciuria was noted in approximately a third of the cohort. The clinical significance of this finding is yet to be determined.

Understanding the link between kidney stones and cancers of the upper urinary tract and bladder.

Kidney stones are one of the most common renal pathologies. While emerging evidence has implicated a potential association between kidney stones and upper urinary tract cancers (including renal cancer), there is limited understanding as to the common underlying biological pathways functionally linking the etiology of kidney stone formation and the incidence, development, and progression of urinary tract cancers. From a clinical perspective, kidney stone disease can be a barrier to oncologic care due to renal obstruction. From the epidemiological perspective, risk factors associated with both conditions include smoking, alcohol consumption, diet, and gender. Herein, we review the association between renal calculi and malignancy of the upper urinary tract and discuss the current understanding of (a) potential shared mechanisms, and (b) the impact this has on shared therapeutic management of both conditions.

Is metformin use associated with changes in urinary parameters in stone formers?

INTRODUCTION: Diabetes mellitus (DM) is associated with an increased risk of nephrolithiasis and is often treated with metformin. The relationship between metformin and nephrolithiasis formation remains unclear, as studies have demonstrated conflicting results. METHODS: We conducted a cross-sectional analysis of stone-forming patients at our stone clinic prior to the initiation of stone-directed medical management. Patients were grouped based on diabetic status and diabetic medication regimen. Outcomes evaluated were 24-hour urinary parameters and specimen stone type using univariate Kruskal-Wallis and Chi-squared analyses. Multivariate analyses controlling for metabolic syndrome components and HbA1c were performed. RESULTS: Data were available for 505 patients, of whom 147 were diabetic and 358 were not. On multivariate analyses controlling for HbA1c and other comorbidities, diabetic patients on metformin still had worse urinary parameters, including urine pH, than non-diabetic patients (pH=-0.33, -0.37, p<0.05). Patients with DM on metformin did not exhibit significant differences in 24-hour urine findings compared to patients with DM not on metformin (p>0.05 for all urinary parameters). CONCLUSIONS: Stone-forming patients with DM on metformin were associated with urinary abnormalities similar to those not on metformin. Cohort studies comparing urinary parameters of patients prospectively started on metformin are necessary to further elucidate metformin's role, if any, in combatting nephrolithiasis.

Emergent Stenting for Obstructive Nephrolithiasis During the COVID-19 Pandemic Compared to the Prepandemic Era.

COVID-19 has rapidly evolved into a global pandemic. In an attemp to reduce transmission, patients were advised to avoid in-person medical evaluations when possible. Accordingly, we hypothesize that fewer patients have sought care and undergone treatment for emergent urological conditions such as nephrolithiasis. We performed a retrospective chart review of patients undergoing emergent ureteral stent placement for obstructive nephrolithiasis from March 15, 2020 through May 31, 2020 and compared them to similar patients from a year earlier. We found that notably fewer patients underwent emergent stent placement during the COVID-19 era and that these patients were notably sicker. These findings suggest that indirect sequelae of the pandemic include delays in seeking care for conditions unrelated to the virus. Strategies such as increased use of in-office stenting and improved patient counseling may help reduce delays in care and improve clinical outcomes for patients with nephrolithiasis during subsequent peaks in the ongoing pandemic.

Thulium fiber laser utilization in urological surgery: A narrative review.

The thulium fiber laser (TFL) is a novel technology under active investigation as an conceivable alternative to the Holmium:yttrium-aluminum-garnet (Ho:YAG) laser, which is currently the gold standard for an array of urologic procedures. The purpose of this review is to discuss the existing literature on the functionality and effectiveness of TFL in urological practice. We conducted a search of the PubMed, Medline, Web of Science Core Collection, SCOPUS, Embase (OVID), and Cochrane Databases for all full articles and systematic reviews on the TFL. We found a total of 35 relevant pieces of literature. The early research findings pertaining to the TFL exhibit numerous potential advantages over the Ho:YAG laser. In vitro and ex vivo studies have highlighted the TFL's ability to utilize smaller laser fibers, obtain faster stone ablation rates, and achieve less retropulsion when tested against the Ho:YAG laser in lithotripsy. Currently, there is limited in vivo research that investigates the utilization of the TFL. The in vivo results that are available, however, look promising both for laser lithotripsy and soft tissue ablation. Indeed, the existing literature suggests that the TFL has great potential and may possess numerous technological advantages over the Ho:YAG laser, especially in laser lithotripsy. Although these early studies are promising, randomized control trials are needed to assess the full applicability of the TFL in urology.