POCUS-first for nephrolithiasis: A Monte Carlo simulation illustrating cost savings, LOS reduction, and preventable radiation.

OBJECTIVES: Non-contrast computed tomography (NCCT) is the gold standard for nephrolithiasis evaluation in the emergency department (ED). However, Choosing Wisely guidelines recommend against ordering NCCT for patients with suspected nephrolithiasis who are <50 years old with a history of kidney stones. Our primary objective was to estimate the national annual cost savings from using a point-of-care ultrasound (POCUS)-first approach for patients with suspected nephrolithiasis meeting Choosing Wisely criteria. Our secondary objectives were to estimate reductions in ED length of stay (LOS) and preventable radiation exposure. METHODS: We created a Monte Carlo simulation using available estimates for the frequency of ED visits for nephrolithiasis and eligibility for a POCUS-first approach. The study population included all ED patients diagnosed with nephrolithiasis. Based on 1000 trials of our simulation, we estimated national cost savings in averted advanced imaging from this strategy. We applied the same model to estimate the reduction in ED LOS and preventable radiation exposure. RESULTS: Using this model, we estimate a POCUS-first approach for evaluating nephrolithiasis meeting Choosing Wisely guidelines to save a mean (±SD) of $16.5 million (±$2.1 million) by avoiding 159,000 (±18,000) NCCT scans annually. This resulted in a national cumulative decrease of 166,000 (±165,000) annual bed-hours in ED LOS. Additionally, this resulted in a national cumulative reduction in radiation exposure of 1.9 million person-mSv, which could potentially prevent 232 (±81) excess cancer cases and 118 (±43) excess cancer deaths annually. CONCLUSION: If adopted widely, a POCUS-first approach for suspected nephrolithiasis in patients meeting Choosing Wisely criteria could yield significant national cost savings and a reduction in ED LOS and preventable radiation exposure. Further research is needed to explore the barriers to widespread adoption of this clinical workflow as well as the benefits of a POCUS-first approach in other patient populations.

Racial disparities in analgesic use amongst patients presenting to the emergency department for kidney stones in the United States.

INTRODUCTION: We sought quantify racial disparities in use of analgesia amongst patients seen in Emergency Departments for renal colic. METHODS: We identified all individuals presenting to the Emergency Department with urolithiasis from 2003 to 2015 in the nationally representative Premier Hospital Database. We included patients discharged in ≤1 day and excluded those with chronic pain or renal insufficiency. We assessed the relationship between race/ethnicity and opioid dosage in morphine milligram equivalents (MME), and ketorolac, through multivariable regression models adjusting for patient and hospital characteristics. RESULTS: The cohort was 266,210 patients, comprised of White (84%), Black (6%) and Hispanic (10%) individuals. Median opioid dosage was 20 MME and 55.5% received ketorolac. Our adjusted model showed Whites had highest median MME (20 mg) with Blacks (-3.3 mg [95% CI: -4.6 mg to -2.1 mg]) and Hispanics (-6.0 mg [95% CI: -6.9 mg to -5.1 mg]) receiving less. Blacks were less likely to receive ketorolac (OR: 0.72, 95% CI: 0.62-0.84) while there was no difference between Whites and Hispanics. CONCLUSIONS: Black and Hispanic patients in American Emergency Departments with acute renal colic receive less opioid medication than White patients; Black patients are also less likely to receive ketorolac.

Testosterone replacement therapy is associated with an increased risk of urolithiasis.

PURPOSE: To determine whether TRT in men with hypogonadism is associated with an increased risk of urolithiasis. METHODS: We conducted a population-based matched cohort study utilizing data sourced from the Military Health System Data Repository (a large military-based database that includes beneficiaries of the TRICARE program). This included men aged 40-64 years with no prior history of urolithiasis who received continuous TRT for a diagnosis of hypogonadism between 2006 and 2014. Eligible individuals were matched using both demographics and comorbidities to TRICARE enrollees who did not receive TRT. The primary outcome was 2-year absolute risk of a stone-related event, comparing men on TRT to non-TRT controls. RESULTS: There were 26,586 pairs in our cohort. Four hundred and eighty-two stone-related events were observed at 2 years in the non-TRT group versus 659 in the TRT group. Log-rank comparisons showed this to be a statistically significant difference in events between the two groups (p < 0.0001). This difference was observed for topical (p < 0.0001) and injection (p = 0.004) therapy-type subgroups, though not for pellet (p = 0.27). There was no significant difference in stone episodes based on secondary polycythemia diagnosis, which was used as an indirect indicator of higher on-treatment testosterone levels (p = 0.14). CONCLUSION: We observed an increase in 2-year absolute risk of stone events among those on TRT compared to those who did not undergo this hormonal therapy. These findings merit further investigation into the pathophysiologic basis of our observation and consideration by clinicians when determining the risks and benefits of placing patients on TRT.

Unsupervised Machine Learning to Identify Risk Factors of Pyeloplasty Failure in Ureteropelvic Junction Obstruction.

Introduction: In adult patients with ureteropelvic junction obstruction (UPJO), little data exist on predicting pyeloplasty outcome, and there is no unified definition of pyeloplasty success. As such, defining pyeloplasty success retrospectively is particularly vulnerable to bias, allowing researchers to choose significant outcomes with the benefit of hindsight. To mitigate these biases, we performed an unsupervised machine learning cluster analysis on a dataset of 216 pyeloplasty patients between 2015 and 2023 from a multihospital system to identify the defining risk factors of patients that experience worse outcomes. Methods: A KPrototypes model was fitted with pre- and perioperative data and blinded to postoperative outcomes. T-test and chi-square tests were performed to look at significant differences of characteristics between clusters. SHapley Additive exPlanation values were calculated from a random forest classifier to determine the most predictive features of cluster membership. A logistic regression model identified which of the most predictive variables remained significant after adjusting for confounding effects. Results: Two distinct clusters were identified. One cluster (denoted as "high-risk") contained 111 (51.4%) patients and was identified by having more comorbidities, such as old age (62.7 vs 35.7), high body mass index (BMI) (26.9 vs 23.8), hypertension (66.7% vs 17.1%), and previous abdominal surgery (72.1% vs 37.1%) and was found to have worse outcomes, such as more frequent severe postoperative complications (7.2% vs 1.0%). After adjusting for confounding effects, the most predictive features of high-risk cluster membership were old age, low preoperative estimated glomerular filtration rate (eGFR), hypertension, greater BMI, previous abdominal surgery, and left-sided UPJO. Conclusions: Adult UPJO patients with older age, lower eGFR, hypertension, greater BMI, previous abdominal surgery, and left-sided UPJO naturally cluster into to a group that more commonly suffers from perioperative complications and worse outcomes. Preoperative counseling and perioperative management for patients with these risk factors may need to be thought of or approached differently.

Initial Safety and Feasibility of Steerable Ureteroscopic Renal Evacuation: A Novel Approach for the Treatment of Urolithiasis.

Background: There is a need to reliably render urolithiasis patients completely stone free with minimal morbidity. We report on the initial safety and feasibility with steerable ureteroscopic renal evacuation (SURE) in a prospective study using basket extraction as a comparison. Materials and Methods: A pilot randomized controlled study was conducted comparing SURE with basket extraction postlaser lithotripsy. SURE is performed using the CVAC™ Aspiration System, a steerable catheter (with introducer). The safety and feasibility of steering CVAC throughout the collecting system under fluoroscopy and aspirating stone fragments as it was designed to do were evaluated. Fluoroscopy time, change in hemoglobin, adverse events through 30 days, total and proportion of stone volume removed at 1 day, intraoperative stone removal rate, and stone-free rate (SFR) at 30 days through CT were compared. Results: Seventeen patients were treated (n = 9 SURE, n = 8 Basket). Baseline demographics and stone parameters were not significantly different between groups. One adverse event occurred in each group (self-limiting ileus for SURE and urinary tract infection for Basket). No mucosal injury and no contrast extravasation were observed in either group. The CVAC catheter was steered throughout the collecting system and aspirated fragments. There was no significant difference in fluoroscopy time, procedure time, change in hemoglobin, or stone removal rate between groups. SURE removed more and a greater proportion of stone volume at day 1 vs baskets (202 mm3 vs 91 mm3, p < 0.01 and 84% vs 56%, p = 0.022). SURE achieved 100% SFR at 30 days vs 75% for baskets, although this difference was not statistically significant (p = 0.20). Conclusions: This initial study suggests SURE is safe, feasible, and may be more effective in stone removal postlaser lithotripsy compared to basketing. More development is needed, and larger clinical studies are underway.

Changing the Status Quo: Developing a Virtual Sub-Internship in the Era of COVID-19.

PROBLEM: Subinternships are integral to medical education as tools for teaching and assessing fourth-year medical students. Social distancing due to COVID-19 has precluded the ability to offer in-person subinternships - negatively impacting medical education and creating uncertainty surrounding the residency match. With no precedent for the development and implementation of virtual subinternships, the Society of Academic Urologists (SAU) developed an innovative and standardized curriculum for the Virtual Subinternship in Urology (vSIU). METHODS: The vSIU committee's mandate was to create a standardized curriculum for teaching foundational urology and assessing student performance. Thirty-three members from 23 institutions were divided into working groups and given 3 weeks to develop 10 modules based on urologic subspecialties, Accreditation Council for Graduate Medical Education core competencies, technical skills training and student assessment. Working groups were encouraged to develop innovative learning approaches. The final curriculum was assembled into the "vSIU Guidebook." RESULTS: The vSIU Guidebook contains 212 pages - 64 pages core content and 2 appendices (patient cases and evaluations). It outlines a detailed 4-week curriculum with a sufficient volume of resources to offer a completely adaptable virtual course with the same rigor as a traditional subinternship. Modules contain curated teaching resources including journal articles, lectures, surgical videos and simulated clinical scenarios. Innovative learning tools include reflective writing, mentorship guidelines, videoconference-based didactics, surgical simulcasting and virtual technical skills training. The guidebook was disseminated to program directors nationally. NEXT STEPS: The vSIU is the first virtual subinternship in any specialty to be standardized and offered nationally, and it was implemented by at least 19 urology programs. This curriculum serves as a template for other specialties looking to develop virtual programs and feedback from educators and students will allow the curriculum to evolve. As the pandemic continues to challenge our paradigm, this rapid and innovative response exemplifies that the medical community will continue to meet the needs of an ever-changing educational landscape.

Determining Variable Costs in the Acute Urolithiasis Cycle of Care Through Time-Driven Activity-Based Costing.

OBJECTIVE: To characterize full cycle of care costs for managing an acute ureteral stone using time-driven activity-based costing. METHODS: We defined all phases of care for patients presenting with an acute ureteral stone and built an overarching process map. Maps for sub-processes were constructed through interviews with providers and direct observation of clinical spaces. This facilitated calculation of cost per minute for all aspects of care delivery, which were multiplied by associated process times. These were added to consumable costs to determine cost for each specific step and later aggregated to determine total cost for each sub-process. We compared costs of eight common clinical pathways for acute stone management, defining total cycle of care cost as the sum of all sub-processes that comprised each pathway. RESULTS: Cost per sub-process included $920 for emergency department (ED) care, $1665 for operative stent placement, $2368 for percutaneous nephrostomy tube placement, $106 for urology clinic consultation, $238 for preoperative center visit, $4057 for ureteroscopy with laser lithotripsy (URS), $2923 for extracorporeal shock wave lithotripsy, $169 for clinic stent removal, $197 for abdominal x-ray, and $166 for ultrasound. The lowest cost pathway ($1388) was for medical expulsive therapy, whereas the most expensive pathway ($8002) entailed a repeat ED visit prompting temporizing stent placement and interval URS. CONCLUSION: We found a high degree of cost variation between care pathways common to management of acute ureteral stone episodes. Reliable cost accounting data and an understanding of variability in clinical pathway costs can inform value-based care redesign as payors move away from pure fee-for-service reimbursement.

Stone forming risk factors in patients with type Ia glycogen storage disease.

PURPOSE: Patients with type Ia glycogen storage disease have an increased recurrent nephrolithiasis rate. We identified stone forming risk factors in patients with type Ia glycogen storage disease vs those in stone formers without the disease. MATERIALS AND METHODS: Patients with type Ia glycogen storage disease were prospectively enrolled from our metabolic clinic. Patient 24-hour urine parameters were compared to those in age and gender matched stone forming controls. RESULTS: We collected 24-hour urine samples from 13 patients with type Ia glycogen storage disease. Average +/- SD age was 27.0 +/- 13.0 years and 6 patients (46%) were male. Compared to age and gender matched hypocitraturic, stone forming controls patients had profound hypocitraturia (urinary citrate 70 vs 344 mg daily, p = 0.009). When comparing creatinine adjusted urinary values, patients had profound hypocitraturia (0.119 vs 0.291 mg/mg creatinine, p = 0.005) and higher oxalate (0.026 vs 0.021 mg/mg creatinine, p = 0.038) vs other stone formers. CONCLUSIONS: Patients with type Ia glycogen storage disease have profound hypocitraturia, as evidenced by 24-hour urine collections, even compared to other stone formers. This may be related to a recurrent nephrolithiasis rate greater than in the overall population. These findings may be used to support different treatment modalities, timing and/or doses to prevent urinary lithiasis in patients with type Ia glycogen storage disease.

Care Setting as a Modifiable Predictor of Perioperative Cost and Outcomes following Elective Urinary Stone Surgery.

INTRODUCTION: We sought to identify predictors of index surgical care setting and to determine if care setting influences risk adjusted perioperative costs and/or 30-day revisits following elective surgery for urinary stones. METHODS: Using 2014 HCUP (Healthcare Cost and Utilization Project) all payer claims data from New York and Florida, we retrospectively identified 29,433 patients undergoing index ureteroscopy or shock wave lithotripsy. We used inverse probability of treatment weighting adjusted multivariable logistic and gamma regression to assess the association between index surgical care setting and 30-day revisits and total costs, respectively. RESULTS: Most urinary stone procedures (70.8%) were performed in the ambulatory setting. Underinsurance was associated with lower odds of undergoing surgery in the ambulatory setting (Medicaid vs private: OR 0.44, 95% CI 0.37-0.53; p <0.001; self-pay vs private: OR 0.21, 95% CI 0.17-0.26; p <0.001). Adjusted mean index surgical and 30-day acute care costs were significantly lower among ambulatory vs inpatient/emergency department cases ($4,746.10 vs $10,669.26 and $5,434.42 vs $11,729.39, both p <0.001), respectively. Ambulatory surgery was independently associated with lower odds of experiencing a 30-day revisit (OR 0.82, 95% CI 0.72-0.94; p=0.005). CONCLUSIONS: Urinary stone cases managed surgically in an ambulatory setting had lower risk adjusted costs and odds of a 30-day revisit compared to those managed in an inpatient setting. Our findings support use of ambulatory rather than inpatient based elective surgery for uncomplicated urinary stones. We invite clinicians and policymakers alike to reconsider clinical and nonclinical factors that influence pathways of care.

Impact of long-term potassium citrate therapy on urinary profiles and recurrent stone formation.

PURPOSE: Potassium citrate therapy has become one of the cornerstones of medical stone management. We elucidated the long-term effects of potassium citrate on urinary metabolic profiles and its impact on stone formation rates. MATERIALS AND METHODS: We performed a retrospective cohort study in patients treated at the Comprehensive Kidney Stone Center at our institution between 2000 and 2006. Patients with pre-therapy and post-therapy 24-hour urinary profiles available who remained on potassium citrate for at least 6 months were included in the analysis. RESULTS: Of the 1,480 patients with 24-hour urinary profiles 503 met study inclusion criteria. Mean therapy duration was 41 months (range 6 to 168). Overall a significant and durable change in urinary metabolic profiles was noted as soon as 6 months after the onset of therapy. These changes included increased urinary pH (5.90 to 6.46, p <0.0001) and increased urinary citrate (470 to 700 mg a day, p <0.0001). The stone formation rate also significantly decreased after the initiation of potassium citrate from 1.89 to 0.46 stones per year (p <0.0001). There was a 68% remission rate and a 93% decrease in the stone formation rate. CONCLUSIONS: Potassium citrate provides a significant alkali and citraturic response during short-term and long-term therapy with the change in urinary metabolic profiles sustained as long as 14 years of treatment. Moreover, long-term potassium citrate significantly decreases the stone formation rate, confirming its usefulness in patients with recurrent nephrolithiasis.

The impact of robotic surgery on pelvic lymph node dissection during radical prostatectomy for localized prostate cancer: the Brown University early robotic experience.

INTRODUCTION: Open pelvic lymph node dissection (PLND) remains the gold standard in patients with intermediate and high-risk prostate cancer undergoing radical retropubic prostatectomy (RRP). Recently, our institution has adopted robotic assistance for performing radical prostatectomy. We sought to determine whether robot-assisted laparoscopic PLND yields comparable numbers of lymph nodes compared to open PLND. METHODS: The medical records of patients undergoing open or robot-assisted laparoscopic radical prostatectomy (RALRP) with concurrent pelvic lymph node dissection (PLND) between 2003 and 2008 were reviewed. Demographic factors including age, PSA, and Gleason score were recorded. Pathology reports were reviewed to determine the number of pelvic lymph nodes obtained during PLND. Lymph node yield was further evaluated based on surgeon. Student's t-test was used to compare the number of lymph nodes obtained with each method. RESULTS: A total of 61 patients undergoing open RRP with PLND and 62 patients undergoing RALRP with PLND were included. The mean number of lymph nodes obtained via open PLND was 7.3 while the mean number obtained via robotic PLND was 3.3. These means were significantly different with a p value < 0.001. One patient in the open cohort (1.6%) and two patients in the robotic cohort (3.2%) had micrometastatic disease on PLND. CONCLUSION: Robot-assisted laparoscopic PLND yielded fewer lymph nodes compared to open PLND at the time of radical prostatectomy for organ confined disease. Patients with higher risk disease may benefit from open prostatectomy with PLND early in a program's robotics experience. These findings may be related to the relative youth of our robotics program and further comparisons as our data mature will be revealing.

Hounsfield units on computed tomography predict calcium stone subtype composition.

INTRODUCTION: Hounsfield unit (HU) determination of urinary stones on noncontrast computed tomography (NCCT) has been shown to predict stone composition. However, no in vivo studies have attempted to radiographically separate the various calcium stone compositions. We investigate the efficacy of HU measurement on NCCT to determine if it can differentiate the various calcium stone subtypes. PATIENTS AND METHODS: Of the 684 patients who had undergone ureteroscopy at our institution from 1/2003 to 10/2007, 100 were identified with a documented NCCT, a chemical stone analysis and a stone size >5 mm but <2 cm. RESULTS: Stone compositions were categorized as 100-80% calcium oxalate monohydrate (CaOMH) (n = 24), <80-60% CaOMH (n = 21), <60-50% CaOMH (n = 11) calcium oxalate dihydrate (CaODH) (n = 16), apatite (n = 9), brushite (n = 4), cystine (n = 2) and uric acid (n = 13). Mean HU were 879 +/- 230, 769 +/- 295, 717 +/- 304, and 517 +/- 203 for the 100-80% CaOMH, <80-60% CaOMH, <60-50% CaOMH and CaODH groups, respectively. The average HU for the apatite, brushite, cystine and uric acid groups were 844 +/- 346, 1,123 +/- 254, 550 +/- 74 and 338 +/- 145, respectively. The CaOMH groups together had a significantly higher HU than the CaODH group (p < 0.05) and a significantly lower HU than the brushite group (p < 0.05). CONCLUSIONS: HU measurement of urinary stones on NCCT may be used to separate some calcium stone subtypes, specifically CaOMH and CaODH. This information may be useful in counseling patients on treatment options for patients requiring intervention.

Renal parenchyma thickness: a rapid estimation of renal function on computed tomography.

PURPOSE: To define the relationship between renal parenchyma thickness (RPT) on computed tomography and renal function on nuclear renography in chronically obstructed renal units (ORUs) and to define a minimal thickness ratio associated with adequate function. MATERIALS AND METHODS: Twenty-eight consecutive patients undergoing both nuclear renography and CT during a six-month period between 2004 and 2006 were included. All patients that had a diagnosis of unilateral obstruction were included for analysis. RPT was measured in the following manner: The parenchyma thickness at three discrete levels of each kidney was measured using calipers on a CT workstation. The mean of these three measurements was defined as RPT. The renal parenchyma thickness ratio of the ORUs and non-obstructed renal unit (NORUs) was calculated and this was compared to the observed function on Mag-3 lasix Renogram. RESULTS: A total of 28 patients were evaluated. Mean parenchyma thickness was 1.82 cm and 2.25 cm in the ORUs and NORUs, respectively. The mean relative renal function of ORUs was 39%. Linear regression analysis comparing renogram function to RPT ratio revealed a correlation coefficient of 0.48 (p < 0.001). The linear regression equation was computed as Renal Function = 0.48 + 0.80 * RPT ratio. A thickness ratio of 0.68 correlated with 20% renal function. CONCLUSION: RPT on computed tomography appears to be a powerful predictor of relative renal function in ORUs. Assessment of RPT is a useful and readily available clinical tool for surgical decision making (renal salvage therapy versus nephrectomy) in patients with ORUs.

Ureteral stenting and urinary stone management: a systematic review.

PURPOSE: Ureteral stents are widely used in many urological procedures. We evaluated the recent literature, providing an update on materials and stent designs, and indications for stent placement and stent complications, including the management of such stent related problems. MATERIALS AND METHODS: A thorough literature search on ureteral stents was performed. Pertinent new and review/updated articles published in the English literature from 2000 through 2006 were systematically reviewed. RESULTS: Following uncomplicated ureteroscopy or shock wave lithotripsy routine stenting does not appear to affect the stone-free rate. However, stent related morbidity is often seen. Patients at greatest risk for complications are those undergoing bilateral stentless ureteroscopy, those with recent or recurrent urinary tract infections and pregnant patients. The placement of indwelling stents in these patients should be considered. The development of stent materials and designs has been directed toward decreasing stent related morbidity, such as pain, discomfort, bladder irritability, infection and encrustation. Changes in stent design and materials show great promise. Initial evaluations suggest improvements in patient comfort as well as decreased encrustation. Forgotten stents can lead to significant morbidity as a result of severe encrustation. Most cases can be managed endoscopically, often requiring multiple procedures. CONCLUSIONS: Stenting is not mandatory after uncomplicated simple ureteroscopy and shock wave lithotripsy. Patients with stents seem to have significantly more bladder and lower urinary tract symptoms than those in whom stents are not placed. However, there is a subgroup of patients who likely benefit from stenting following a procedure because of the increased risk of complications. The ideal ureteral stent biomaterial has yet to be discovered and an area of promising development is the drug eluting stent to prevent infection and encrustation.

Efficacy of intravesical ropivacaine injection on urinary symptoms following ureteral stenting: a randomized, controlled study.

PURPOSE: Previous studies suggest that intravesical administration of nonsteroidal anti-inflammatory drugs may reduce the troublesome voiding symptoms and pain related to ureteral stenting. The objective of this study was to investigate the effectiveness of a long-acting local anesthetic, ropivacaine, injected submucosally into the bladder to control ureteral stent-associated symptoms. MATERIALS AND METHODS: A randomized, single-blinded, study approved by our Institutional Review Board of adult patients scheduled for ureteroscopic stone surgery and possible stent placement was conducted. Patients were randomized to either the treatment cohort, who received five injections of 2 mL 0.5% ropivacaine around the ureteral orifice or to the control cohort, who received five injections of 2 mL of 0.9% normal saline in identical locations. Pain scale questionnaires were provided to each subject preoperatively and at postoperative hours 2, 4, 8, 24, and 48 as well as on the day of stent removal. Student's t test and Wilcoxon signed rank sum tests were used for Gaussian and nonparametric data, respectively. RESULTS: Twenty-two patients were randomized evenly into the two cohorts. The ropivacaine group consisted of 11 patients (eight men and three women) with a mean age of 56.2 years (standard deviation [SD] = 12, range 27-69), and the saline group consisted of eleven patients (six men and five women) with a mean age of 47.8 years (SD = 6.6, range 37-58). Intraoperative parameters appeared similar between the two cohorts. Intraoperative and postoperative narcotic usage was not different between the two groups, except at postoperative hour 2 when it favored the ropivacaine cohort (P = 0.05). Trends favoring ropivacaine in flank pain, bladder pain, genitalia pain, and hematuria domains were seen as long as 8 hours and up to the day of stent removal. Trends of less magnitude and duration were seen in the dysuria domain. No differences were seen in the frequency and urgency domains. CONCLUSIONS: Our preliminary investigation with intravesical injection of ropivacaine before ureteroscopic surgery demonstrated trends toward decreased pain and voiding symptoms in this small-sample study. Inclusion of a larger sample should definitively address the effectiveness of intravesical ropivacaine and its impact on stent-related symptoms.