The relationship between the force applied and perceived by the surgeon during ureteral access sheath placement: ex-vivo experimental model.

PURPOSE: To define a peak force of insertion (PFOI) threshold for ureteral damage during ureteral access sheath (UAS) placement on an experimental ureteral orifice model. METHODS: A specially designed water tank using 2 laparoscopic 5 mm ports and 2 different size (10 Fr and 8 Fr) sealing cap adaptors (SCA) as ureteral orifices was used to perform the test. A 10-12 Fr UAS was fixed to a load cell and the force of insertion (FOI) was continuously recorded with a digital force gauge.13 experts in the field of endourology who participated performed 3 UAS insertions. The FOI was recorded initially with 10 Fr followed by 8 Fr SCA. On the final insertion, the orifice was obstructed, leaving a 5 cm length to insert the UAS. The experts were asked to "Stop at the point they anticipate ureteral damage, and they would not proceed in real life". RESULTS: Using 10 Fr SCA the PFOI was 2.12 ± 0.58 Newton (N) (range:1.48-3.48) while 8 Fr SCA showed a PFOI 5.76 ± 0.96 N (range:4.05-7.35). Six of the experts, said they would stop proceeding when they reached above 5.1 N. Three experts had PFOI < 5.1 N and the other 4 stated they would go with PFOIs of 5.88, 6.16, 6.69 and 7.35 N when using SCA of 8 Fr.The highest load they would stop proceeding had a PFOI of 6.09 ± 1.87 N (range: 2.53-10.74). CONCLUSION: The PFOI threshold for ureteral damage inserting UAS of the experts is variable. Although FOI is a subjective perception, experience suggests that ureteral injury may occur at an average of 6.05 N perceived by surgeons' tactile feedback. In-vivo measurement of UAS PFOI may confirm a threshold.

International Alliance of Urolithiasis (IAU) guideline on staghorn calculi management.

BACKGROUND: The stone burden based management strategy reported in the guidelines published by different associations is well known for a long time. Staghorn calculi, representing the largest burden and most complex stones, is one of the most challenging cases to practicing urologists in clinical practice. The International Alliance of Urolithiasis (IAU) has released a series of guidelines on the management of urolithiasis. PURPOSE: To develop a series of recommendations for the contemporary management management of staghorn calculi and to provide a clinical framework for urologists treating patients with these complex stones. METHODS: A comprehensive literature search for articles published in English between 01/01/1976 and 31/12/2022 in the PubMed, OVID, Embase and Medline database is performed. A series of recommendations are developed and individually graded following the review of literature and panel discussion. RESULTS: The definition, pathogenesis, pathophysiology, preoperative evaluation, intraoperative treatment strategies and procedural advice, early postoperative management, follow up and prevention of stone recurrence are summarized in the present document. CONCLUSION: A series of recommendations regarding the management of staghorn calculi, along with related commentary and supporting documentation offered in the present guideline is intended to provide a clinical framework for the practicing urologists in the management of staghorn calculi.

International Alliance of Urolithiasis guideline on retrograde intrarenal surgery.

OBJECTIVES: To set out the second in a series of guidelines on the treatment of urolithiasis by the International Alliance of Urolithiasis that concerns retrograde intrarenal surgery (RIRS), with the aim of providing a clinical framework for urologists performing RIRS. MATERIALS AND METHODS: After a comprehensive search of RIRS-related literature published between 1 January 1964 and 1 October 2021 from the PubMed database, systematic review and assessment were performed to inform a series of recommendations, which were graded using modified GRADE methodology. Additionally, quality of evidence was classified using a modification of the Oxford Centre for Evidence-Based Medicine Levels of Evidence system. Finally, related comments were provided. RESULTS: A total of 36 recommendations were developed and graded that covered the following topics: indications and contraindications; preoperative imaging; preoperative ureteric stenting; preoperative medications; peri-operative antibiotics; management of antithrombotic therapy; anaesthesia; patient positioning; equipment; lithotripsy; exit strategy; and complications. CONCLUSION: The series of recommendations regarding RIRS, along with the related commentary and supporting documentation, offered here should help provide safe and effective performance of RIRS.

Efficacy of Intramuscular Ketorolac for Preventing Renal Colic Post Stent Removal: Randomized Controlled Trial.

PURPOSE: The treatment of stones ureteroscopically is associated with postoperative pain, thought to be due largely to the use of ureteral stents. In some, stent removal precipitates renal colic that can last from minutes to hours. We sought to determine if intramuscular ketorolac could reduce post-stent removal renal colic. MATERIALS AND METHODS: We performed a prospective, randomized, double-blind, placebo-controlled trial assessing the effects of ketorolac administered at time of stent removal. Patients were randomized to receive an intramuscular ketorolac 30 mg or placebo immediately prior to stent removal. Patients were contacted 1 and 7 days after stent removal to assess pain, need for opioids, emergency department or clinic visits and the need for surgical/medical interventions. RESULTS: A total of 124 patients (62 patients each in the control and treatment groups) were included in the study. The groups were comparable in demographic/operative characteristics. No difference in mean pain scores or proportion of patients who experienced severe pain at 1 and 7 days post stent removal was detected between groups. However, use of ketorolac resulted in significantly fewer renal colic-related unplanned emergency department/clinic visits in the treatment group (2%) compared with the control group (13%, p=0.032). CONCLUSIONS: Although administration of ketorolac prior to stent removal does not significantly reduce overall subjective pain experienced post stent removal compared to placebo, it does reduce the likelihood of severe renal colic requiring emergency department or office visits. Eligible patients may benefit from routine use of ketorolac injection at the time of stent removal.

Causes and prevention of kidney stones: separating myth from fact.

Despite high-level evidence supporting the use of pharmacotherapy therapy for the prevention of kidney stones, adherence to medications is often poor because of side-effects, inconvenience and cost. Furthermore, with a desire for more 'natural' products, patients seek dietary and herbal remedies over pharmacotherapy. However, patients are often unaware of the potential side-effects, lack of evidence and cost of these remedies. Therefore, in the present review we examine the evidence for a few of the commonly espoused non-prescription agents or dietary recommendations that are thought to prevent stone formation, including lemonade, fish oil (omega fatty acids), Phyllanthus niruri and the Dietary Approaches to Stop Hypertension (DASH) diet. While the present review includes only a few of the stone-modulating recommendations available to the lay community, we focussed on these four due to their prevalent use. Our goal is not to only dispel commonly held notions about stone disease, but also to highlight the lack of high-level evidence for many commonly utilised treatments.

Artificial intelligence in stone disease.

PURPOSE OF REVIEW: Artificial intelligence (AI) is the ability of a machine, or computer, to simulate intelligent behavior. In medicine, the use of large datasets enables a computer to learn how to perform cognitive tasks, thereby facilitating medical decision-making. This review aims to describe advancements in AI in stone disease to improve diagnostic accuracy in determining stone composition, to predict outcomes of surgical procedures or watchful waiting and ultimately to optimize treatment choices for patients. RECENT FINDINGS: AI algorithms show high accuracy in different realms including stone detection and in the prediction of surgical outcomes. There are machine learning algorithms for outcomes after percutaneous nephrolithotomy, extracorporeal shockwave lithotripsy, and for ureteral stone passage. Some of these algorithms show better predictive capabilities compared to existing scoring systems and nomograms. SUMMARY: The use of AI can facilitate the development of diagnostic and treatment algorithms in patients with stone disease. Although the generalizability and external validity of these algorithms remain uncertain, the development of highly accurate AI-based tools may enable the urologist to provide more customized patient care and superior outcomes.

Impact of Implementing Contrast-Enhanced Ultrasound for Antegrade Nephrostogram After Percutaneous Nephrolithotomy.

OBJECTIVES: To report results from a quality improvement (QI) project evaluating diagnostic performance, hospital resource use, and patient response data for postoperative contrast-enhanced ultrasound (CEUS) antegrade nephrostogram after percutaneous nephrolithotomy. METHODS: For this Health Insurance Portability and Accountability Act-compliant, Institutional Review Board-approved study, QI data were deidentified and analyzed. On the first postoperative day after percutaneous nephrolithotomy, patients underwent both CEUS and fluoroscopic antegrade nephrostogram. For CEUS, 1.0 mL of Lumason (sulfur hexafluoride lipid type A microspheres; Bracco Diagnostics, Inc, Monroe Township, NJ) was injected via an indwelling nephrostomy tube, with ureteral patency confirmed by identifying intravesical ultrasound (US) contrast. Diagnostic performance for ureteral patency and contrast extravasation was calculated (with fluoroscopy as the reference standard). The examination time, room time, physician time, hospital costs, and patient response data were compared. The mean, standard deviation, 95% confidence interval, differences in mean, and 95% confidence interval of differences were calculated. RESULTS: Eighty-one examinations were performed in 73 patients during the QI period. The sensitivity and specificity of CEUS for ureteral patency were 96% and 57%, respectively. There was no significant difference in time metrics between modalities, and the cost analysis showed lower direct and indirect costs for CEUS. Patient responses revealed lower levels of comfort for CEUS relative to fluoroscopy, without significant differences in reported pain or effort levels. CONCLUSIONS: Contrast-enhanced US showed very high sensitivity for ureteral patency; the relatively low specificity may have resulted from false-negative results in fluoroscopy. The hospital costs and resource use of CEUS compared favorably to fluoroscopy. Contrast-enhanced US also offers inherent advantages, including portability and lack of ionizing radiation.

Clinical and radiographic outcomes following salvage intervention for ureteropelvic junction obstruction.

PURPOSE: We aimed to assess failure rates of salvage interventions and changes in split kidney function (SKF) following failed primary repair of ureteropelvic junction obstruction (UPJO). MATERIALS AND METHODS: A retrospective review of adult patients at an academic medical center who underwent salvage intervention following primary treatment for UPJO was performed. Symptomatic failure was defined as significant flank pain. Radiographic failure was defined as no improvement in drainage or a decrease in SKF by ≥7%. Overall failure, the primary outcome, was defined as symptomatic failure, radiographic failure, or both. RESULTS: Between 2008-2017, 34 patients (median age 38 years, 50% men) met study criteria. UPJO management was primary pyeloplasty/secondary endopyelotomy for 21/34 (62%), primary pyeloplasty/secondary pyeloplasty for 6/34 (18%), and primary endopyelotomy/secondary pyeloplasty for 7/34 (21%). Median follow-up was 3.3 years following secondary intervention. Patients undergoing primary pyeloplasty/secondary endopyelotomy had significantly higher overall failure than those undergoing primary pyeloplasty/secondary pyeloplasty (16/21 [76%] vs. 1/6 [17%], p=0.015). Among patients undergoing secondary endopyelotomy, presence of a stricture on retrograde pyelogram, stricture length, and SKF were not associated with symptomatic, radiographic, or overall failure. Serial renography was performed for 28/34 (82%) patients and 2/28 (7%) had a significant decline in SKF. CONCLUSIONS: Following failed primary pyeloplasty, secondary endopyelotomy had a greater overall failure rate than secondary pyeloplasty. No radiographic features assessed were associated with secondary endopyelotomy failure. Secondary intervention overall failure rates were higher than reported in the literature. Unique to this study, serial renography demonstrated that significant functional loss was overall infrequent.

Impact of Potassium Citrate vs Citric Acid on Urinary Stone Risk in Calcium Phosphate Stone Formers.

PURPOSE: To our knowledge no medication has been shown to be effective for preventing recurrent calcium phosphate urinary stones. Potassium citrate may protect against calcium phosphate stones by enhancing urine citrate excretion and lowering urine calcium but it raises urine pH, which increases calcium phosphate saturation and may negate the beneficial effects. Citric acid can potentially raise urine citrate but not pH and, thus, it may be a useful countermeasure against calcium phosphate stones. We assessed whether these 2 agents could significantly alter urine composition and reduce calcium phosphate saturation. MATERIALS AND METHODS: In a crossover metabolic study 13 recurrent calcium phosphate stone formers without hypercalciuria were evaluated at the end of 3, 1-week study phases during which they consumed a fixed metabolic diet and received assigned study medications, including citric acid 30 mEq twice daily, potassium citrate 20 mEq twice daily or matching placebo. We collected 24-hour urine specimens to perform urine chemistry studies and calculate calcium phosphate saturation indexes. RESULTS: Urine parameters did not significantly differ between the citric acid and placebo phases. Potassium citrate significantly increased urine pH, potassium and citrate compared to citric acid and placebo (p <0.01) with a trend toward lower urine calcium (p = 0.062). Brushite saturation was increased by potassium citrate when calculated by the relative supersaturation ratio but not by the saturation index. CONCLUSIONS: Citric acid at a dose of 60 mEq per day did not significantly alter urine composition in calcium phosphate stone formers. The long-term impact of potassium citrate on calcium phosphate stone recurrence needs to be studied further.

Do Urinary Cystine Parameters Predict Clinical Stone Activity?

PURPOSE: An accurate urinary predictor of stone recurrence would be clinically advantageous for patients with cystinuria. A proprietary assay (Litholink, Chicago, Illinois) measures cystine capacity as a potentially more reliable estimate of stone forming propensity. The recommended capacity level to prevent stone formation, which is greater than 150 mg/l, has not been directly correlated with clinical stone activity. We investigated the relationship between urinary cystine parameters and clinical stone activity. MATERIALS AND METHODS: We prospectively followed 48 patients with cystinuria using 24-hour urine collections and serial imaging, and recorded stone activity. We compared cystine urinary parameters at times of stone activity with those obtained during periods of stone quiescence. We then performed correlation and ROC analysis to evaluate the performance of cystine parameters to predict stone activity. RESULTS: During a median followup of 70.6 months (range 2.2 to 274.6) 85 stone events occurred which could be linked to a recent urine collection. Cystine capacity was significantly greater for quiescent urine than for stone event urine (mean ± SD 48 ± 107 vs -38 ± 163 mg/l, p <0.001). Cystine capacity significantly correlated inversely with stone activity (r = -0.29, p <0.001). Capacity also correlated highly negatively with supersaturation (r = -0.88, p <0.001) and concentration (r = -0.87, p <0.001). Using the suggested cutoff of greater than 150 mg/l had only 8.0% sensitivity to predict stone quiescence. Decreasing the cutoff to 90 mg/l or greater improved sensitivity to 25.2% while maintaining specificity at 90.9%. CONCLUSIONS: Our results suggest that the target for capacity should be lower than previously advised.

Update of the ICUD-SIU consultation on stone technology behind ureteroscopy.

INTRODUCTION: Ureteroscopy is now the most frequent treatment used around the world for stone disease. Technological advancement, efficiency, safety, and minimally invasiveness of this procedure are some of the reasons for this change of trend. MATERIALS AND METHODS: In this review of the literature, a search of the PubMed database was conducted to identify articles related to ureteroscopy and accessories. The committee assigned by the International Consultation on Urological Disease reviewed all the data and produced a consensus statement relating to the ureteroscopy and all the particularities around this procedure. CONCLUSION: This manuscript provides literatures and recommendations for endourologists to keep them informed in regard to the preoperative, intraoperative, and postoperative consideration in regard of a ureteroscopy.

Surgical Management of Stones: American Urological Association/Endourological Society Guideline, PART II.

PURPOSE: This Guideline is intended to provide a clinical framework for the surgical management of patients with kidney and/or ureteral stones. The summary presented herein represents Part II of the two-part series dedicated to Surgical Management of Stones: American Urological Association/Endourological Society Guideline. Please refer to Part I for introductory information and a discussion of pre-operative imaging and special cases. MATERIALS AND METHODS: A systematic review of the literature (search dates 1/1/1985 to 5/31/2015) was conducted to identify peer-reviewed studies relevant to the surgical management of stones. The review yielded an evidence base of 1,911 articles after application of inclusion/exclusion criteria. These publications were used to create the Guideline statements. Evidence-based statements of Strong, Moderate, or Conditional Recommendation were developed based on benefits and risks/burdens to patients. Additional directives are provided as Clinical Principles and Expert Opinions when insufficient evidence existed. RESULTS: The Panel identified 12 adult Index Patients to represent the most common cases seen in clinical practice. Three additional Index Patients were also created to describe the more commonly encountered special cases, including pediatric and pregnant patients. With these patients in mind, Guideline statements were developed to aid the clinician in identifying optimal management. CONCLUSIONS: Proper treatment selection, which is directed by patient- and stone-specific factors, remains the greatest predictor of successful treatment outcomes. This Guideline is intended for use in conjunction with the individual patient's treatment goals. In all cases, patient preferences and personal goals should be considered when choosing a management strategy.

Surgical Management of Stones: American Urological Association/Endourological Society Guideline, PART I.

PURPOSE: This Guideline is intended to provide a clinical framework for the surgical management of patients with kidney and/or ureteral stones. The summary presented herein represents Part I of the two-part series dedicated to Surgical Management of Stones: American Urological Association/Endourological Society Guideline. Please refer to Part II for an in-depth discussion of patients presenting with ureteral or renal stones. MATERIALS AND METHODS: A systematic review of the literature (search dates 1/1/1985 to 5/31/2015) was conducted to identify peer-reviewed studies relevant to the surgical management of stones. The review yielded an evidence base of 1,911 articles after application of inclusion/exclusion criteria. These publications were used to create the Guideline statements. Evidence-based statements of Strong, Moderate, or Conditional Recommendation were developed based on benefits and risks/burdens to patients. Additional directives are provided as Clinical Principles and Expert Opinions when insufficient evidence existed. RESULTS: The Panel identified 12 adult Index Patients to represent the most common cases seen in clinical practice. Three additional Index Patients were also created to describe pediatric and pregnant patients with such stones. With these patients in mind, Guideline statements were developed to aid the clinician in identifying optimal management. CONCLUSIONS: Proper treatment selection, which is directed by patient- and stone-specific factors, remains the greatest predictor of successful treatment outcomes. This Guideline is intended for use in conjunction with the individual patient's treatment goals. In all cases, patient preferences and personal goals should be considered when choosing a management strategy.

A prospective, multi-institutional study of flexible ureteroscopy for proximal ureteral stones smaller than 2 cm.

PURPOSE: Flexible ureteroscopy is rapidly becoming a first line therapy for many patients with renal and ureteral stones. However, current understanding of treatment outcomes in patients with isolated proximal ureteral stones is limited. Therefore, we performed a prospective, multi-institutional study of ureteroscopic management of proximal ureteral stones smaller than 2 cm to better define clinical outcomes associated with this approach. MATERIALS AND METHODS: Adult patients with proximal ureteral calculi smaller than 2 cm were prospectively identified. Patients with concomitant ipsilateral renal calculi or prior ureteral stenting were excluded from study. Flexible ureteroscopy, holmium laser lithotripsy and ureteral stent placement was performed. Ureteral access sheath use, laser settings and other details of perioperative and postoperative management were based on individual surgeon preference. Stone clearance was determined by the results of renal ultrasound and plain x-ray of the kidneys, ureters and bladder 4 to 6 weeks postoperatively. RESULTS: Of 71 patients 44 (62%) were male and 27 (38%) were female. Mean age was 48.2 years. ASA(®) score was 1 in 12 cases (16%), 2 in 41 (58%), 3 in 16 (23%) and 4 in 2 (3%). Mean body mass index was 31.8 kg/m(2), mean stone size was 7.4 mm (range 5 to 15) and mean operative time was 60.3 minutes (range 15 to 148). Intraoperative complications occurred in 2 patients (2.8%), including mild ureteral trauma. Postoperative complications developed in 6 patients (8.7%), including urinary tract infection in 3, urinary retention in 2 and flash pulmonary edema in 1. The stone-free rate was 95% and for stones smaller than 1 cm it was 100%. CONCLUSIONS: Flexible ureteroscopy is associated with excellent clinical outcomes and acceptable morbidity when applied to patients with proximal ureteral stones smaller than 2 cm.

Diet: from food to stone.

Dietary factors have been shown to influence urine composition and modulate the risk of kidney stone disease. With the rising prevalence of stone disease in many industrialized nations, dietary modification as therapy to improve lithogenic risk factors and prevent stone recurrence has gained appeal, as it is both relatively inexpensive and safe. While some dietary measures, such as a high fluid intake, have been shown in long-term randomized clinical trials to have durable effectiveness, other dietary factors have been subjected to only short-term clinical or metabolic studies and their efficacy has been inferred. Herein, we review the current literature regarding the role of diet in stone formation, focusing on both the effect on urinary stone risk factors and the effect on stone recurrence.

Animal protein and the risk of kidney stones: a comparative metabolic study of animal protein sources.

PURPOSE: We compared the effect of 3 animal protein sources on urinary stone risk. MATERIALS AND METHODS: A total of 15 healthy subjects completed a 3-phase randomized, crossover metabolic study. During each 1-week phase subjects consumed a standard metabolic diet containing beef, chicken or fish. Serum chemistry and 24-hour urine samples collected at the end of each phase were compared using mixed model repeated measures analysis. RESULTS: Serum and urinary uric acid were increased for each phase. Beef was associated with lower serum uric acid than chicken or fish (6.5 vs 7.0 and 7.3 mg/dl, respectively, each p <0.05). Fish was associated with higher urinary uric acid than beef or chicken (741 vs 638 and 641 mg per day, p = 0.003 and 0.04, respectively). No significant difference among phases was noted in urinary pH, sulfate, calcium, citrate, oxalate or sodium. Mean saturation index for calcium oxalate was highest for beef (2.48), although the difference attained significance only compared to chicken (1.67, p = 0.02) but not to fish (1.79, p = 0.08). CONCLUSIONS: Consuming animal protein is associated with increased serum and urine uric acid in healthy individuals. The higher purine content of fish compared to beef or chicken is reflected in higher 24-hour urinary uric acid. However, as reflected in the saturation index, the stone forming propensity is marginally higher for beef compared to fish or chicken. Stone formers should be advised to limit the intake of all animal proteins, including fish.

Medical management of kidney stones: AUA guideline.

PURPOSE: The purpose of this guideline is to provide a clinical framework for the diagnosis, prevention and follow-up of adult patients with kidney stones based on the best available published literature. MATERIALS AND METHODS: The primary source of evidence for this guideline was the systematic review conducted by the Agency for Healthcare Research and Quality on recurrent nephrolithiasis in adults. To augment and broaden the body of evidence in the AHRQ report, the AUA conducted supplementary searches for articles published from 2007 through 2012 that were systematically reviewed using a methodology developed a priori. In total, these sources yielded 46 studies that were used to form evidence-based guideline statements. In the absence of sufficient evidence, additional statements were developed as Clinical Principles and Expert Opinions. RESULTS: Guideline statements were created to inform clinicians regarding the use of a screening evaluation for first-time and recurrent stone formers, the appropriate initiation of a metabolic evaluation in select patients and recommendations for the initiation and follow-up of medication and/or dietary measures in specific patients. CONCLUSIONS: A variety of medications and dietary measures have been evaluated with greater or less rigor for their efficacy in reducing recurrence rates in stone formers. The guideline statements offered in this document provide a simple, evidence-based approach to identify high-risk or interested stone-forming patients for whom medical and dietary therapy based on metabolic testing and close follow-up is likely to be effective in reducing stone recurrence.

How much is a kidney worth? Cost-effectiveness of routine imaging after ureteroscopy to prevent silent obstruction.

PURPOSE: The 2012 American Urological Association (AUA) Clinical Effectiveness Protocols for Imaging in the Management of Ureteral Calculous Disease recommends routine postoperative imaging after ureteroscopy. We evaluated the cost-effectiveness of routine postoperative imaging after ureteroscopy. MATERIALS AND METHODS: We searched the literature to determine the risk of complications after routine ureteroscopy for stones, including the incidence of postoperative pain, stricture and silent obstruction. Sequelae of renal loss due to undiagnosed silent obstruction may include chronic kidney disease, end stage renal disease and cardiovascular disease. Imaging and procedure costs were obtained from Medicare reimbursement rates and the literature. The costs and prevalence of lifetime complications associated with silent loss of 1 kidney were obtained from the renal donor transplant literature. A decision tree was constructed to calculate the cost of a strategy of routinely imaging all patients after ureteroscopy vs selective imaging based on postoperative pain. We performed 1-way and 2-way sensitivity analyses. RESULTS: The average cost per patient of a strategy of routine imaging after ureteroscopy in all patients was $5,326 vs $5,196 for a strategy of selective imaging based on postoperative pain. Assuming a 2% rate of silent obstruction, the cost per kidney saved would be $6,262. CONCLUSIONS: While routine postoperative imaging carries a $130 per patient incrementally higher cost over that of a strategy of selective imaging in patients with postoperative pain, preventing renal loss and its attendant morbidity justifies the additional modest cost.