Recurrence rates of urinary calculi according to stone composition and morphology

Research landscape and pharmacological mechanisms of traditional Chinese medicines in treating and preventing urolithiasis: Unearthing an anti-urolithic treasure trove

ETHNOPHARMACOLOGICAL RELEVANCE

Urolithiasis represents a predominant concern within urology due to its high recurrence rate and consequential surgical complications. Traditional Chinese Medicine (TCM), with a history spanning over 2000 years in treating kidney diseases, not only offers a less invasive and cost-effective option for treating and preventing urolithiasis, but also serves as a pharmacological treasure trove for the development of anti-urolithic drugs.

AIM OF THE STUDY

With the continuous deepening of research on the anti-urolithic effects of Chinese medicines, the pharmacological mechanisms of TCMs against urolithiasis are continuously evolving. Therefore, it is essential to summarize the current research status, clinical effectiveness, and mechanisms of TCM in treating and preventing urolithiasis, to ascertain its potential in anti-urolithic treatments, and to provide a reference for future anti-urolithiasis drug research.

METHODS

The electronic databases such as PubMed, Web of Science, and China National Knowledge Infrastructure (CNKI) have been utilized to retrieve relevant literature spanning from 2000 to September 2023, using keywords "Traditional Chinese Medicine" and "Urolithiasis". Then we conducted a visual analysis of the current status of related research, as well as a systematic organization of the therapeutic effects and underlying mechanisms of anti-urolithic TCMs.

RESULTS

Through the organization of research models, therapeutic effects, and active ingredients of 31 potential anti-urolithic TCMs, we have systematically summarized the underlying mechanisms of TCMs in management of urolithiasis. Mechanistically, Chinese herbs facilitate stone expulsion by enhancing diuresis, instigating anti-spasmodic effects, and promoting ureteral peristalsis when addressing calculi. They also harbor the potential to dissolve pre-existing stones. In terms of stone recurrence prevention, TCM compounds obstruct stone formation through targeting the sequence of crystal adhesion, nucleation, growth, and aggregation to inhibit stone formation. Additionally, TCM's significant roles include stifling oxidative stress, augmenting urinary stone inhibitors, and harmonizing oxalate metabolism, all of which are critical actions in stone prevention.

CONCLUSION

The anti-urolithic mechanism of TCM is multifaceted. Investigating the anti-urolithiasis mechanisms of TCM not only illuminates the potential of Chinese medicine in treating and preventing urolithiasis, but also uncovers active molecules and targets for drug treatment against calculus formation.

The immune factors have complex causal regulation effects on kidney stone disease: a mendelian randomization study

PURPOSE

Previous studies have reported the potential impact of immune cells on kidney stone disease (KSD), but definitive causal relationships have yet to be established. The purpose of this paper is to elucidate the potential causal association between immune cells and KSD by Mendelian randomization (MR) analysis.

METHODS

In our study, a thorough two-sample Mendelian randomization (MR) analysis was performed by us to determine the potential causal relationship between immune cell traits and kidney stone disease. We included a total of four immune traits (median fluorescence intensity (MFI), relative cellular (RC), absolute cellular (AC), and morphological parameters (MP)), which are publicly available data. GWAS summary data related to KSD (9713 cases and 366,693 controls) were obtained from the FinnGen consortium. The primary MR analysis method was Inverse variance weighted. Cochran's Q test, MR Egger, and MR-Pleiotropy RESidual Sum and Outlier (MR-PRESSO) were used to assess the stability of the results.

RESULTS

After FDR correction, the CD8 on HLA DR + CD8br (OR = 0.95, 95% CI = 0.93-0.98, p-value = 7.20 × 10- 4, q-value = 0.088) was determined to be distinctly associated with KSD, and we also found other 25 suggestive associations between immune cells and KSD, of which 13 associations were suggested as protective factors and 12 associations were suggested as risk factors. There was no horizontal pleiotropy or significant heterogeneity in our MR analysis, as determined by the p-value results of our Cochrane Q-test, MR Egger's intercept test, and MR-PRESSO, which were all > 0.05.

CONCLUSIONS

Our study has explored the potential causal connection between immune cells and KSD by Mendelian randomization analysis, thus providing some insights for future clinical studies.

Kidney stone growth through the lens of Raman mapping

Bulk composition of kidney stones, often analyzed with infrared spectroscopy, plays an essential role in determining the course of treatment for kidney stone disease. Though bulk analysis of kidney stones can hint at the general causes of stone formation, it is necessary to understand kidney stone microstructure to further advance potential treatments that rely on in vivo dissolution of stones rather than surgery. The utility of Raman microscopy is demonstrated for the purpose of studying kidney stone microstructure with chemical maps at ≤ 1 µm scales collected for calcium oxalate, calcium phosphate, uric acid, and struvite stones. Observed microstructures are discussed with respect to kidney stone growth and dissolution with emphasis placed on < 5 µm features that would be difficult to identify using alternative techniques including micro computed tomography. These features include thin concentric rings of calcium oxalate monohydrate within uric acid stones and increased frequency of calcium oxalate crystals within regions of elongated crystal growth in a brushite stone. We relate these observations to potential concerns of clinical significance including dissolution of uric acid by raising urine pH and the higher rates of brushite stone recurrence compared to other non-infectious kidney stones.

STUB1 exacerbates calcium oxalate-induced kidney injury by modulating reactive oxygen species-mediated cellular autophagy via regulating CFTR ubiquitination

The formation of calcium oxalate (CaOx) crystals in the kidneys leads to renal epithelial damage and the progression of crystalline nephropathy. This study investigated the role of STIP1 homology and U-box protein 1 (STUB1), an E3 ubiquitin ligase, and cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel, in CaOx-related renal damage and autophagy regulation. HK-2 cells were treated with various doses of CaOx monohydrate (COM) to simulate kidney injury in vitro. Cell viability, reactive oxygen species (ROS) production, and apoptosis were assessed. The regulation of CFTR ubiquitination by STUB1 was confirmed by immunoprecipitation. An in vivo model was established by injecting mice with glyoxylate. COM treatment dose-dependently decreased cell viability, increased TNF-α and ROS production, and induced apoptotic cell death in HK-2 cells. COM-treated cells also showed decreased CFTR protein expression. CFTR overexpression improved cell viability and reduced ROS production in COM-stimulated HK-2 cells. Bioinformatics analysis predicted CFTR's ubiquitination binding site for STUB1. Further analysis confirmed the role of STUB1 as a ubiquitin ligase in CFTR degradation. Knockdown of STUB1 upregulated CFTR expression, while STUB1 overexpression had the opposite effect. Knockdown of CFTR reversed the impact of STUB1 deficiency on autophagy. The in vivo experiments showed that CFTR overexpression attenuated kidney tissue damage and CaOx deposition in mice. STUB1-mediated CFTR ubiquitination plays a crucial role in mitigating calcium oxalate-related renal damage by regulating autophagy. Targeting the STUB1/CFTR axis may hold therapeutic potential for treating kidney injury associated with calcium oxalate deposition.

Advancements in stone classification: unveiling the beauty of urolithiasis

PURPOSE

Urolithiasis has become increasingly prevalent, leading to higher disability-adjusted life years and deaths. Various stone classification systems have been developed to enhance the understanding of lithogenesis, aid urologists in treatment decisions, and predict recurrence risk. The aim of this manuscript is to provide an overview of different stone classification criteria.

METHODS

Two authors conducted a review of literature on studies relating to the classification of urolithiasis. A narrative synthesis for analysis of the studies was used.

RESULTS

Stones can be categorized based on anatomical position, size, medical imaging features, risk of recurrence, etiology, composition, and morphoconstitutional analysis. The first three mentioned offer a straightforward approach to stone classification, directly influencing treatment recommendations. With the routine use of CT imaging before treatment, precise details like anatomical location, stone dimensions, and Hounsfield Units can be easily determined, aiding treatment planning. In contrast, classifying stones based on risk of recurrence and etiology is more complex due to dependencies on multiple variables, including stone composition and morphology. A classification system based on morphoconstitutional analysis, which combines morphological stone appearance and chemical composition, has demonstrated its value. It allows for the rapid identification of crystalline phase principles, the detection of crystalline conversion processes, the determination of etiopathogenesis, the recognition of lithogenic processes, the assessment of crystal formation speed, related recurrence rates, and guidance for selecting appropriate treatment modalities.

CONCLUSIONS

Recognizing that no single classification system can comprehensively cover all aspects, the integration of all classification approaches is essential for tailoring urolithiasis patient-specific management.

Genes polymorphism as risk factor of recurrent urolithiasis: a systematic review and meta-analysis

INTRODUCTION

Urolithiasis is one of the most prevalent diseases worldwide. Its prevalence is rising, both in developing and developed countries. It is known that genetic factors play big roles in the development of urolithiasis. One of the suspected factors is gene polymorphism. This study aims to find an accurate estimate of the association between genetic polymorphism and the risk of recurrent urolithiasis.

METHODS

A systematic review and meta-analysis were performed on 12 studies from 3 databases that investigated gene polymorphism as an risk factor of urolithiasis. The review was done using Review Manager® version 5.3.

RESULTS

Insignificant heterogenicity was found in this study. Populations from Asia and the Middle East are more likely to experience recurrent urolithiasis. Additionally, variation in the VDR and urokinase genes, particularly in the Asian population, increases the risk of developing recurrent urolithiasis.

CONCLUSIONS

Gene polymorphisms have significant roles in the development of urolithiasis, especially in the Middle Eastern region.

2022 Recommendations of the AFU Lithiasis Committee: Summary of indications

The spontaneous elimination rate of ureteral stones decreases with their size, but also in function of their location. The objectives of stone surveillance are to detect the occurrence of a complication (e.g., fever, clinical tolerance) and to verify the potential stone migration/elimination. The use of urological procedures and the choice of technique are based on many different factors. Kidney stone surveillance is proposed mainly to people with low risk of progression or complications (size<4mm and/or lower calyx location and non-infection stone). Surveillance may be extended to patients with larger stones, in function of the clinical context and comorbidities. Conversely, a urological procedure may also be proposed to patients with stones<4mm for professional (e.g., soldier, pilot, expatriate) or social reasons or if travelling is planned. The choice of technique is based on the stone composition (if already known) and density, the advantages and limitations of each technique, and also the clinical context, while trying to choose the least invasive procedure for a stone-free objective. METHODOLOGY: These recommendations were developed using two methods: the Clinical Practice Recommendations method (CPR) and the ADAPTE method, depending on whether the question was considered in the European Association of Urology (EAU) recommendations (https://uroweb.org/guidelines/urolithiasis) [EAU 2022] and their adaptability to the French context. This chapter is based on the references used in the chapters on the different techniques (extracorporeal shock wave therapy, ureteroscopy, percutaneous nephrolithotomy, medical expulsive therapy, postural therapy, chemolysis by alkalinization) as well as the American Urological Association (AUA) and EAU recommendations.

2022 recommendations of the AFU Lithiasis Committee: Objectives, results, residual stones and fragments

The main objectives of interventional stone treatment are stone removal, symptom elimination, and kidney function preservation. After treatment of kidney stones (extracorporeal shock wave lithotripsy [ESWL], or endoscopy), fragments may remain in the kidney, either deliberately left in place or due to treatment failure (i.e. residual stone [RS], resistant to ESWL, left or inaccessible by endoscopy), or due to failure to eliminate the obtained fragments (i.e. residual fragments [RF]). Their management may differ. The most commonly used definition of RF in the literature is based on a size cut-off (≤4mm) and on three criteria: spontaneous clearance rate, secondary intervention rate, and disease progression rate. RF may be spontaneously eliminated (42%), persist and increase in size (32%), or become complicated and require a secondary urological procedure (36%). Like for the initial treatment, it is important to consider the stone composition for the treatment decision-making concerning RS/RF. METHODOLOGY: These recommendations were developed using two methods: the Clinical Practice Recommendation (CPR) method and the ADAPTE method, depending on whether the question was considered in the European Association of Urology (EAU) recommendations (https://uroweb.org/guidelines/urolithiasis) (EAU, 2022) and their adaptability to the French context.

2022 Recommendations of the AFU Lithiasis Committee: Endoscopic description of renal papillae and stones

Endoscopic observation is performed during treatments by flexible ureteroscopy to differentiate in situ between renal papillary abnormalities and stones based on their concordance with Daudon's morphological/composition descriptions adapted to endoscopy. These intraoperative visual analyses are now an integral part of the urinary stone disease diagnostic approach in addition to the morphological/structural and spectrophotometric analysis that remains the reference exam, but that loses information on the stone component representativeness due to the development of in situ laser lithotripsy. These are the first practical recommendations on the endoscopic description of renal papillae and stones. METHODOLOGY: These recommendations were developed using two methods: the Clinical Practice Recommendations (CPR) and the ADAPTE method, depending on whether the question was considered in the European Association of Urology (EAU) recommendations (https://uroweb.org/guidelines/urolithiasis [EAU Guidelines on urolithiasis. 2022]) and their adaptability to the French context.

Establishment of a new predictive model for the recurrence of upper urinary tract stones

PURPOSE

To construct a nomogram for evaluation of the recurrence risk of upper urinary tract stones in patients.

METHODS

We retrospectively reviewed the clinical data of 657 patients with upper urinary tract stones and divided them into stone recurrence group and non-recurrence group. Blood routine, urine routine, biochemical, and urological CT examinations were searched from the electronic medical record, relevant clinical data were collected, including age, BMI, stones number and location, maximum diameter, hyperglycemia, hypertension, and relevant blood and urine parameters. The Wilcoxon rank-sum test, independent sample t test, and Chi-square test were used to preliminarily analyze the data of the two groups, then LASSO and logistic regression analysis were used to find out the significant difference indicators. Finally, R software was used to draw a nomogram to construct the model, and ROC curve was drawn to evaluate the sensitivity and specificity.

RESULTS

The results showed that multiple stones (OR: 1.832, 95% CI 1.240-2.706), bilateral stones (OR: 1.779, 95% CI 1.226-2.582), kidney stones (OR: 3.268, 95% CI 1.638-6.518), and kidney ureteral stones (OR: 3.375, 95% CI 1.649-6.906) were high risk factors. And the stone recurrence risk was positively correlated with creatinine (OR: 1.012, 95% CI 1.006-1.018), urine pH (OR: 1.967, 95% CI 1.343-2.883), Apo B (OR: 4.189, 95% CI 1.985-8.841) and negatively correlated with serum phosphorus (OR: 0.282, 95% CI 0.109-0.728). In addition, the sensitivity and specificity of the prediction model were 73.08% and 61.25%, diagnosis values were greater than any single variable.

CONCLUSION

The nomogram model can effectively evaluate the recurrence risk of upper urinary stones, especially suitable for stone postoperative patients, to help reduce the possibility of postoperative stone recurrence.

Risk Profile of Patients with Brushite Stone Disease and the Impact of Diet

This study examined the profile of patients and the impact of diet on the risk of brushite stone formation under controlled, standardized conditions. Sixty-five patients with brushite nephrolithiasis were enrolled in the study. Metabolic, dietary, and 24 h urinary parameters were collected under the habitual, self-selected diet of the patients and the balanced mixed, standardized diet. The [13C2]oxalate absorption, ammonium chloride, and calcium loading tests were conducted. All patients had at least one abnormality on the usual diet, with hypercalciuria (84.6%), increased urine pH (61.5%), and hyperphosphaturia (43.1%) being the most common. Absorptive hypercalciuria was present in 32.1% and hyperabsorption of oxalate in 41.2%, while distal renal tubular acidosis (dRTA) was noted in 50% of brushite stone formers. The relative supersaturation of brushite did not differ between patients with and without dRTA. Among all recent brushite-containing calculi, 61.5% were mixed with calcium oxalate and/or carbonate apatite. The relative supersaturation of brushite, apatite, and calcium oxalate decreased significantly under the balanced diet, mainly due to the significant decline in urinary calcium, phosphate, and oxalate excretion. Dietary intervention was shown to be effective and should be an integral part of the treatment of brushite stone disease. Further research on the role of dRTA in brushite stone formation is needed.

Development of convenient crystallization inhibition assays for structure-activity relationship studies in the discovery of crystallization inhibitors

Kidney stone diseases are increasing globally in prevalence and recurrence rates, indicating an urgent medical need for developing new therapies that can prevent stone formation. One approach we have been working on is to develop small molecule inhibitors that can interfere with the crystallization process of the chemical substances that form the stones. For these drug discovery efforts, it is critical to have available easily accessible assay methods to evaluate the potential inhibitors and rank them for structure-activity relationship studies. Herein, we report a convenient, medium-to-high throughput assay platform using, as an example, the screening and evaluation of inhibitors of L-cystine crystallization for the prevention of kidney stones in cystinuria. The assay involves preparing a supersaturated solution, followed by incubating small volumes (<1 mL) of the supersaturated solution with test inhibitors for 72 hours, and finally measuring L-cystine concentrations in the supernatants after centrifugation using either a colorimetric or fluorometric method. Compared to traditional techniques for studying crystallization inhibitors, this miniaturized multi-well assay format is simple to implement, cost-effective, and widely applicable in determining and distinguishing the activities of compounds that inhibit crystallization. This assay has been successfully employed to discover L-cystine diamides as highly potent inhibitors of L-cystine crystallization such as LH708 with an EC50 of 0.058 μM, 70-fold more potent than L-CDME (EC50 = 4.31 μM).

Sulfated Undaria pinnatifida Polysaccharide Promotes Endocytosis of Nano-Calcium Oxalate Dihydrate by Repairing Subcellular Organelles in HK-2 Cells

The clinical manifestation of primary hyperoxaluria includes hyperoxaluria and recurrent urinary calculi. In this study, an oxidative damage model was constructed based on oxalate damage to the human renal proximal tubular epithelial cells (HK-2), and a comparative study was carried out on four different sulfated levels of Undaria pinnatifida polysaccharides (UPP0, UPP1, UPP2, and UPP3 with sulfate group [-OSO₃^-] contents of 1.59%, 6.03%, 20.83%, and 36.39%, respectively) on the repair of oxidatively damaged HK-2 cells. The results showed that after repair by UPPs, cell viability was enhanced, healing ability was improved, the intracellular superoxide dismutase level and mitochondrial membrane potential were increased, malondialdehyde, reactive oxygen species, and intracellular Ca²⁺ levels were reduced, cellular autophagy was reduced; lysosomal integrity was improved, and cytoskeleton and cell morphology were restored. The ability of repaired cells to endocytose nano-calcium oxalate dihydrate crystals (nano-COD) was enhanced. The activity of UPPs was closely related to their -OSO₃^- content. A too high or too low -OSO₃^- content was not conducive to polysaccharide activity, and only UPP2 exhibited the best cell repair ability and strongest ability to promote the cell endocytosis of crystals. UPP2 may be used as a potential agent to inhibit CaOx crystal deposition caused by high oxalate concentration.

GeoBioMed perspectives on kidney stone recurrence from the reactive surface area of SWL-derived particles

Shock wave lithotripsy (SWL) is an effective and commonly applied clinical treatment for human kidney stones. Yet the success of SWL is counterbalanced by the risk of retained fragments causing recurrent stone formation, which may require retreatment. This study has applied GeoBioMed experimental and analytical approaches to determine the size frequency distribution, fracture patterns, and reactive surface area of SWL-derived particles within the context of their original crystal growth structure (crystalline architecture) as revealed by confocal autofluorescence (CAF) and super-resolution autofluorescence (SRAF) microscopy. Multiple calcium oxalate (CaOx) stones were removed from a Mayo Clinic patient using standard percutaneous nephrolithotomy (PCNL) and shock pulse lithotripsy (SPL). This produced approximately 4-12 mm-diameter PCNL-derived fragments that were experimentally treated ex vivo with SWL to form hundreds of smaller particles. Fractures propagated through the crystalline architecture of PCNL-derived fragments in a variety of geometric orientations to form rectangular, pointed, concentrically spalled, and irregular SWL-derived particles. Size frequency distributions ranged from fine silt (4-8 μm) to very fine pebbles (2-4 mm), according to the Wentworth grain size scale, with a mean size of fine sand (125-250 μm). Importantly, these SWL-derived particles are smaller than the 3-4 mm-diameter detection limit of clinical computed tomography (CT) techniques and can be retained on internal kidney membrane surfaces. This creates clinically undetectable crystallization seed points with extremely high reactive surface areas, which dramatically enhance the multiple events of crystallization and dissolution (diagenetic phase transitions) that may lead to the high rates of CaOx kidney stone recurrence after SWL treatment.

Flexible Ureterorenoscopy Versus Shockwave Lithotripsy for Kidney Stones ≤2 cm: A Randomized Controlled Trial

BACKGROUND

No clear recommendations are available on whether retrograde intrarenal surgery (RIRS) via flexible ureterorenoscopy or shockwave lithotripsy (SWL) should be preferred for kidney stones ≤2 cm, except for lower-pole stones.

OBJECTIVE

To compare outcomes between RIRS and SWL.

DESIGN, SETTING, AND PARTICIPANTS

This was a single-center randomized controlled trial from March 2015 to May 2018. Patients with a single 6-20-mm kidney stone were enrolled (NCT02645058).

INTERVENTION

Patients were randomized to RIRS or SWL.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was the single-procedure stone-free rate (SFR) at 1 mo. Two levels of success were set: fragments ≤4 mm (SFR-4) and no residual fragments (SFR-0). Secondary endpoints were the SFR at 6 mo and 1 yr and rates of complications and further treatments.

RESULTS AND LIMITATIONS

A total of 138 patients underwent treatment (70 RIRS vs 68 SWL). In comparison to SWL, RIRS SFR results were higher at 1 mo (SFR-4 70.0% vs 45.6%; p = 0.004; SFR-0 50.0% vs 26.5%; p = 0.004) and 6 mo (SFR-4 79.7% vs 63.6%; p = 0.038; SFR-0 59.4% vs 40.9%; p = 0.032). There was no difference in SFR measures between the groups at 1 yr (SFR-4 p = 0.322; SFR-0 p = 0.392). Overall complications were comparable (p = 0.207), but the complication rate for stones >10 mm was higher for the SWL group (p = 0.021). The need for further treatment was comparable (p = 0.368). In terms of patient satisfaction, 86.8% and 77.1% of patients would choose SWL and RIRS again, respectively (p = 0.24).

CONCLUSIONS

RIRS achieved better SFRs in comparison to SWL at 1 and 6 mo, but not at 1 yr. The RIRS complication rate was lower for stones >10 mm. SWL remains a viable alternative, especially for 6-10-mm stones, providing comparable results to RIRS in the long term.

PATIENT SUMMARY

We compared outcomes for the treatment of kidney stones ≤2 cm with two techniques: flexible ureteroscopy, in which a flexible telescope is passed through the urethra and bladder to reach the ureter between the bladder and kidney; and shockwave lithotripsy, in which shockwaves are applied to the skin over the location of the kidney stone. Ureteroscopy achieved better stone-free results at 1 and 6 months, but not at 1 year.

Temperature profiles during ureteroscopy with thulium fiber laser and holmium:YAG laser: Findings from a pre-clinical study

OBJECTIVE

The aim of this study was to investigate temperature profiles in both the renal pelvis and parenchyma during Thulium Fiber Laser (TFL) and Holmium:yttrium-aluminium-garnet (Ho:YAG) laser activation in an ex-vivo porcine model.

METHODS

Three porcine kidneys with intact renal pelvis and proximal ureters were used in the study. A temperature sensor was inserted through a nephrostomy tube into the renal pelvis and a second sensor was inserted directly into the renal parenchyma. Temperatures were recorded during continuous laser activation for 180 s, and for an additional 60 s after deactivation. TFL (150 μm and 200 μm) and Ho:YAG (270 μm) laser delivered power at settings of 2.4 W, 8 W, 20 W and 30 W.

RESULTS

Intrapelvic temperatures correlated directly to power settings. Higher power produced higher temperatures. For example, using a 150 μm fiber at 2.4 W resulted in a 2.6 °C rise from baseline (p = 0.008), whereas using the same fiber at 20 W produced a rise in temperature of 19.9 °C (p = 0.02). Larger laser fibers caused significantly higher temperatures compared to smaller fibers using equivalent power settings, e.g. mean temperature at 20 W using 150 μm was 39.6 °C compared to 44.9 °C using 200 μm, p < 0.001. There was a significant increase in parenchymal temperatures when applying 20 W and 30 W of laser power with the two larger fibers.

CONCLUSION

In this ex-vivo study, renal temperatures correlated directly to power settings. Higher power produced higher temperatures. Furthermore, larger laser fibers caused higher temperatures. These findings could help guide selection of safe power settings for ureteroscopic lithotripsy, but future clinical studies are needed for confirmation.

Effect of theobromine on dissolution of uric acid kidney stones

Purpose

Uric acid renal lithiasis has a high prevalence and a high rate of recurrence. Removal of uric acid stones can be achieved by several surgical techniques (extracorporeal shock wave lithotripsy, endoscopy, laparoscopy, open surgery). These stones can also be eliminated by dissolution within the kidneys, because the solubility of uric acid is much greater when the pH is above 6. At present, N-acetylcysteine with a urinary basifying agent is the only treatment proposed to increase the dissolution of uric acid stones. In this paper, we compare the effect of theobromine and N-acetylcysteine on the in vitro dissolution of uric acid calculi in artificial urine at pH 6.5.

Methods

The dissolution of uric acid renal calculi was performed in a temperature-controlled (37 °C) chamber. A peristaltic pump was used to pass 750 mL of synthetic urine (pH 6.5) through a capsule every 24 h. Stone dissolution was evaluated by measuring the change in weight before and after each experiment.

Results

N-acetylcysteine increased the dissolution of uric acid calculi, but the effect was not statistically significant. Theobromine significantly increased the dissolution of uric acid calculi. Both substances together had the same effect as theobromine alone. The addition of theobromine to a basifying therapy that uses citrate and/or bicarbonate is a potential new strategy for the oral chemolysis of uric acid stones.

Conclusion

Theobromine may prevent the formation of new stones and increase the dissolution of existing stones.

Efficacy of Flexible Ureteroscopic Lithotripsy and Percutaneous Nephrolithotomy in the Treatment of Complex Upper Urinary Tract Nephrolithiasis

Objective

A case-control study was conducted to compare the efficacy and prognostic factors of flexible ureteroscopic lithotripsy (FURL) and percutaneous nephrolithotomy (PCNL) when treating complex upper urinary tract renal calculi based on a retrospective cohort study.

Methods

The study period was from October 2019 to December 2021. A retrospective study was carried out on 100 patients with complicated upper urinary tract nephrolithiasis who underwent surgery in the Urology Department of our hospital. They were assigned into two groups: FURL and PCNL groups. The intraoperative blood loss, operation time, hematuria duration, hospital stay, primary stone removal rate, incidence of intraoperative and postoperative complications, VAS score, level of inflammatory factors, and micturition function were compared. According to the postoperative prognosis, the patients were reassigned into two groups: good prognosis group (n = 38) and poor prognosis group (n = 106). The factors related to poor prognosis after FURL and PCNL were screened, and multivariate loglistic regression analysis was adopted to determine the risk factors.

Results

The primary stone clearance rate in the PCNL group was significantly higher than that in the FURL group, and there was no significant difference in the incidence of intraoperative and postoperative complications between the two groups (P > 0.05). The intraoperative blood loss and the duration of hematuria in the PCNL group were significantly shorter than those in the FURL group, and the operation time and postoperative hospital stay in the FURL group were longer than those in the FURL group. The postoperative VAS score in the study group was significantly lower than that in the control group (P < 0.05). The levels of CRP, IL-1, TNF-α, and NF-κB in both groups decreased after operation, and the level of inflammatory factors in the PCNL group was significantly lower than that in the FURL group (P < 0.05). The indexes of IPSS and Q max in the PCNL group were significantly lower than those in the control group 3 months after operation. The index of micturition function in the PCNL group was significantly lower than that in the FURL group. Preoperative use of immunosuppressant, preoperative stone fever, positive preoperative urine culture, preoperative urinary leukocyte count ≥ 544 × L, intraoperative urinary opacity, and pus fur were significantly correlated with poor prognosis of ureteral patients (P < 0.05). Preoperative stone fever, high preoperative urinary leukocyte count, intraoperative urinary turbidity, and suppurative fur were independent risk factors for postoperative SIRS in patients with ureteral calculi.

Conclusion

PCNL is effective when treating complex upper urinary tract renal calculi. Compared with FURL, PCNL can remarkably reduce intraoperative blood loss and hematuria duration, can enhance micturition function, and will not remarkably increase the incidence of intraoperative and postoperative complications, high safety. High white blood cell count in urine before operation, fever due to stone before operation, turbid urine, and purulent fur during operation are independent risk factors for postoperative adverse outcome in patients with complex upper urinary tract renal calculi. Patients should be fully treated before surgery.

Application of CTU-Assisted Doppler Ultrasound Puncture in Nontube Percutaneous Nephrolithotomy, Its Effect on Patients' Complications, and Its Clinical Value

Objective

To research the application of CTU-assisted Doppler ultrasound puncture in uncatheterized PCNL, its influence on patients' complications, and its clinical value in a case-control study.

Methods

One hundred and forty-four patients who went through percutaneous nephrolithotomy (PCNL) from March 2019 to June 2021 in our hospital were arbitrarily assigned into the CTU group (n = 72) and CT plain scan group (n = 72). CTA+CTU was adopted to determine the puncture passage in the CTU group, and CT scan was employed in the CT group. The intraoperative blood loss, postoperative blood loss, operation time, hospital stay, primary stone removal rate, and the incidence of intraoperative and postoperative complications were compared. The visual analogue score (VAS) was employed to assess the degree of postoperative wound pain.

Results

The first-stage stone removal rate in the CTU group was 95.83% (69/72), which was remarkably higher compared to the CT plain scan group, which was 81.94% (59/72), and the difference was statistically significant (P < 0.05). The overall rates of intraoperative complications were 6.94% (5/72) in the CTU group and 18.06% (13/72) in the CT plain scan group, respectively, which exhibited great differences (P < 0.05). In addition, the overall rates of intraoperative complications were 2.78% (2/72) in the CTU and 13.89% (10/72) in the CT plain scan group, respectively, and the difference was statistically significant (P < 0.05). The operation time and postoperative hospital stays in the CTU group were remarkably shorter compared to the CT group, and the difference was statistically significant (P < 0.05). The intraoperative and postoperative blood loss of CTU group displayed obvious less than that of the CT group, and the difference was statistically significant (P < 0.05). The VAS were compared 24 hours after surgery. After operation, the VAS of 24 hours after operation in the CTU group (0.92 ± 0.12) were remarkably lower compared to the CT group (1.22 ± 0.15), and the difference was statistically significant (P < 0.05). Discussion. PCNL is constantly being optimized by CTU-assisted Doppler ultrasound puncture to improve stone clearance rates, reduce postoperative bleeding, be less painful, provide rapid recovery, and provide safe and feasible results. It is therefore worthwhile to standardize and then widely promote it in clinical practice.

Prophylaxis of Recurrent Stone Disease in Outpatient Clinics in Germany: A Quality-of-Care Concern

INTRODUCTION

The aim of the study was to survey current practices for preventing recurrent stone disease in an outpatient clinic setting in Germany.

METHODS

Two invitations to complete an anonymous REDCap® survey were emailed to members of the occupational union of German urologists who work as outpatient urologists ("Berufsverband Deutscher Urologen e.V."). The survey included questions on diagnostic modalities and counselling to prevent stone disease.

RESULTS

A total of 130 outpatient urologists completed the survey. 84.6% of urologists give general advice to first-time stone formers. Recommendations comprise increased fluid uptake in 100%, two-thirds advice on calcium and oxalate intake, and one-third on salt and protein intake. 64.6% perform a metabolic evaluation for high-risk stone formers. However, patients with risk factors other than repeat stone disease are often overlooked. Urologists agreed that a lack of time (73.1%) and reimbursement (64.6%), as well as insufficient patient compliance (60.8%), pose significant challenges. The majority of urologists agreed that training is required.

CONCLUSION

General recommendations for stone formers are usually provided, but nutritional advice tends to be incomplete. Our results raise quality-of-care concerns: Metabolic evaluation of stone formers at high risk of recurrence is uncommon. Structural changes are required due to time constraints, and poor remuneration must be addressed to improve patient care.

Risk factors for kidney stone disease recurrence: a comprehensive meta-analysis

Background

Kidney stone disease (KSD) is a common illness that causes an economic burden globally. It is easy for patients to relapse once they have suffered from this disease. The reported recurrence rate of KSD ranged from 6.1% to 66.9%. We performed this meta-analysis to identify various potential risk factors for the recurrence of KSD.

Methods

The PubMed, Embase and Web of Science databases were searched using suitable keywords from inception to Mar 2022. A total of 2,663 records were collected initially. After screening the literature according to the inclusion and exclusion criteria, 53 articles (40 retrospective studies; 13 prospective studies) including 488,130 patients were enrolled. The study protocol was registered with PROSPERO (No. CRD42020171771).

Results

The pooled results indicated that 12 risk factors including younger age (n = 18), higher BMI (n = 16), family history of kidney stones (n = 12), personal history of kidney stones (n = 11), hypertension (n = 5), uric acid stone (n = 4), race of Caucasian (n = 3), suspected kidney stone episode before the first confirmed stone episode (n = 3), surgery (n = 3), any concurrent asymptomatic (nonobstructing) stone (n = 2), pelvic or lower pole kidney stone (n = 2), and 24 h urine test completion (n = 2) were identified to be associated with KSD recurrence. In the subgroup analysis, patients with higher BMI (OR = 1.062), personal history of nephrolithiasis (OR = 1.402), or surgery (OR = 3.178) had a higher risk of radiographic KSD recurrence.

Conclusions

We identified 12 risk factors related to the recurrence of KSD. The results of this analysis could serve to construct recurrence prediction models. It could also supply a basis for preventing the recurrence of KSD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12894-022-01017-4.

Sex Differences and the Risk of Kidney Stones

A significant increase in the prevalence of kidney stones has been observed worldwide. In the past decades, this expansion was more pronounced among women than men. The precise mechanisms involved in the differences in the risk profile of stone disease between men and women have not been fully elucidated. Diet and lifestyle only partially can explain the differences, and the combination of factors such as the influence of sex hormones, genetics, and disorders in acid-base handling and urine pH, as well as differences in calcium tubular reabsorption and stone composition in men and women, may contribute to differences in the risk profile. In this review, we summarize the sex differences in the pathophysiologic basis of kidney stones, which may contribute to a more focused approach.

Discriminating the origin of calcium oxalate monohydrate formation in kidney stones via synchrotron microdiffraction

Nephrolithiasis is a multifactor disease that produces nephrolites in the kidneys. Calcium oxalate hydrate (dihydrated, COD, or monohydrated, COM) stones are the most common ones with more than sixty percent incidence worldwide. They are related to different pathologies, COD with hypercalciuria and COM with hyperoxaluria. COD is an unstable species and transforms into COM (herein named TRA to distinguish the origin of the monohydrated species). TRA and COM are chemically and crystallographically identical leading to misdiagnosis and recurrence increase. In the current study, the composition and crystalline structures of several calcium oxalate stones, classified by morpho-constitutional analysis, were examined by IR and synchrotron through-the-substrate micro-X-ray diffraction (tts-μXRD). Both IR and linear diffractogram studies were able to distinguish between the monohydrated and dihydrated phases but not between COM and TRA, as expected. The analysis of 2D diffraction patterns revealed that TRA showed a lower degree of crystallinity and less texture with respect to COM which can be used as a signature to distinguish between the two. This study confirms that despite the subtle differences between COM and TRA, the origin of the monohydrate oxalates can be unraveled using tts-μXRD. This valuable information should be taken into account in order to improve patients' diagnosis and reduce recurrence by considering and treating the origin of the formed stones.

An empirical study on hospital-based prevention of recurrent urinary stone disease in Germany

Purpose

Urinary stone disease is a common disease with a prevalence of 4.7% in Germany. The incidence increased over the last decades, and recurrence rates are up to 50% in the first 5 years after diagnosis. Adequate preventive measures can avoid up to 46% of stone recurrences. These numbers outline the importance of prevention. Especially among high-risk stone formers, specific diagnostics and measures are required. Published data indicate the divergence between the importance of prevention and its implementation in everyday clinical practice. This is the first survey among German urological departments highlighting medical care concerning the prevention of recurrent urinary stone disease, identifying challenges and providing recommendations for improvements.

Methods

Two hundred and seventy urological hospital departments in Germany were anonymously surveyed about measurements to prevent recurrent stone disease. The questionnaire comprised 23 items dealing with diagnostics, counselling, knowledge among doctors concerning preventive measures and difficulties in preventing recurrent urinary stone disease.

Results

Sixty-three urological departments (23.8%) answered the survey. The majority perform stone analysis at first and repeat events. Most patients with urinary stone disease receive general advice on preventive measures during their hospitalization. General recommendations focus on fluid intake and lifestyle changes. However, specific diets are infrequently recommended by inpatient urologists. Diagnostics to identify high-risk stone formers are mostly insufficient, and guideline-compliant urine tests are uncommon.

Conclusion

The quality of secondary prevention needs to improve considerably. The focus should be put on identifying high-risk stone formers and offering those patients specific counselling. Furthermore, general advice on dietary recommendations should be extended.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00345-021-03813-3.

In Search of an Efficient Complexing Agent for Oxalates and Phosphates: A Quantum Chemical Study

Limiting gastrointestinal oxalate absorption is a promising approach to reduce urinary oxalate excretion in patients with idiopathic and enteric hyperoxaluria. Phosphate binders, that inhibit gastrointestinal absorption of dietary phosphate by the formation of easily excretable insoluble complexes, are commonly used as a treatment for hyperphosphatemia in patients with end-stage renal disease. Several of these commercially available phosphate binders also have affinity for oxalate. In this work, a series of metallic cations (Li⁺, Na⁺, Mg²⁺, Ca²⁺, Fe²⁺, Cu²⁺, Zn²⁺, Al³⁺, Fe³⁺ and La³⁺) is investigated on their binding affinity to phosphate and oxalate on one side and anionic species that could be used to administer the cationic species to the body on the other, e.g., acetate, carbonate, chloride, citrate, formate, hydroxide and sulphate. Through quantum chemical calculations, the aim is to understand the competition between the different complexes and propose possible new and more efficient phosphate and oxalate binders.

Using micro computed tomographic imaging for analyzing kidney stones

Stone analysis is a critical part of the clinical characterization of urolithiasis. This article reviews the strengths and limitations of micro CT in the analysis of stones. Using micro CT alone in a series of 757 stone specimens, micro CT identified the 458 majority calcium oxalate specimens with a sensitivity of 99.6% and specificity of 95.3%. Micro CT alone was also successful in identifying majority apatite, brushite, uric acid, and struvite stones. For some minor minerals-such as apatite in calcium oxalate or calcium salts in uric acid stones-micro CT enables the detection of minute quantities well below 1%. The addition of a standard for calibrating X-ray attenuation values improves the ability of micro CT to identify common stone minerals. The three-dimensional nature of micro CT also allows for the visualization of surface features in stones, which is valuable for the study of stone formation.

Endoscopic Papillary Abnormalities and Stone Recognition (EPSR) during Flexible Ureteroscopy: A Comprehensive Review

Introduction: The increasing efficiency of the different lasers and the improved performance of endoscopic devices have led to smaller stone fragments that impact the accuracy of microscopic evaluation (morphological and infrared). Before the stone destruction, the urologist has the opportunity to analyze the stone and the papillary abnormalities endoscopically (endoscopic papillary recognition (EPR) and endoscopic stone recognition (ESR)). Our objective was to evaluate the value for those endoscopic descriptions. Methods: The MEDLINE and EMBASE databases were searched in February 2021 for studies on endoscopic papillary recognition and endoscopic stone recognition. Results: If the ESR provided information concerning the main crystallization process, EPR provided information concerning the origin of the lithogenesis and its severity. Despite many actual limitations, those complementary descriptions could support the preventive care of the stone formers in improving the diagnosis of the lithogenesis mechanism and in identifying high-risk stone formers. Conclusion: Until the development of an Artificial Intelligence recognition, the endourologist has to learn EPSR to minimize the distortion effect of the new lasers on the stone analysis and to improve care efficiency of the stone formers patients.

Validation of The Japanese Version of The Wisconsin Stone Quality of Life Questionnaire (WISQOL): Results from SMART Study Group

BACKGROUND

The Wisconsin Stone Quality of Life questionnaire (WISQOL) is a health-related quality of life measure designed for patients with urinary stones. It has been translated and used in several languages. This study aimed to validate the Japanese version of the WISQOL (J-WISQOL).

MATERIALS AND METHODS

The J-WISQOL was translated and validated using a multistep process proposed by the World Health Organization that involved forward translation, back-translation, and pilot testing with a group of patients. This study enrolled 150 patients with urinary stones who visited three academic hospitals for stone treatment. We assessed convergent validity of correlation patterns and internal consistency of the J-WISQOL and Short-Form 36-item survey version 2 (SF-36v2).

RESULTS

Overall, 150 patients were enrolled. The mean total score of the J-WISQOL was 108.18 ± 20.26 (raw score min-max, 28-140), suggesting that the onset and symptoms of urinary stones reduced the health-related quality of life in the patients. The J-WISQOL showed good internal consistency (Cronbach's α = 0.96) and inter-domain associations (Spearman's correlation coefficient r = 0.67-0.94). The J-WISQOL was correlated with the SF-36v2 in all domains: social, emotional, health, and vitality impact (r = 0.47-0.66).

CONCLUSION

The J-WISQOL is a reliable instrument for evaluating health-related quality of life measures in patients with urinary stones. It could be a useful quality of life questionnaire for urinary stones in Japan.

Towards automatic recognition of pure and mixed stones using intra-operative endoscopic digital images

OBJECTIVE

To assess automatic computer-aided in situ recognition of the morphological features of pure and mixed urinary stones using intra-operative digital endoscopic images acquired in a clinical setting.

MATERIALS AND METHODS

In this single-centre study, a urologist with 20 years' experience intra-operatively and prospectively examined the surface and section of all kidney stones encountered. Calcium oxalate monohydrate (COM) or Ia, calcium oxalate dihydrate (COD) or IIb, and uric acid (UA) or IIIb morphological criteria were collected and classified to generate annotated datasets. A deep convolutional neural network (CNN) was trained to predict the composition of both pure and mixed stones. To explain the predictions of the deep neural network model, coarse localization heat-maps were plotted to pinpoint key areas identified by the network.

RESULTS

This study included 347 and 236 observations of stone surface and stone section, respectively; approximately 80% of all stones exhibited only one morphological type and approximately 20% displayed two. A highest sensitivity of 98% was obtained for the type 'pure IIIb/UA' using surface images. The most frequently encountered morphology was that of the type 'pure Ia/COM'; it was correctly predicted in 91% and 94% of cases using surface and section images, respectively. Of the mixed type 'Ia/COM + IIb/COD', Ia/COM was predicted in 84% of cases using surface images, IIb/COD in 70% of cases, and both in 65% of cases. With regard to mixed Ia/COM + IIIb/UA stones, Ia/COM was predicted in 91% of cases using section images, IIIb/UA in 69% of cases, and both in 74% of cases.

CONCLUSIONS

This preliminary study demonstrates that deep CNNs are a promising method by which to identify kidney stone composition from endoscopic images acquired intra-operatively. Both pure and mixed stone composition could be discriminated. Collected in a clinical setting, surface and section images analysed by a deep CNN provide valuable information about stone morphology for computer-aided diagnosis.

Clinical and Metabolic Correlates of Pure Stone Subtypes

Background: There are multiple stone types, with each forming under different urinary conditions. We compared clinical and metabolic findings in pure stone formers (SFs) to understand whether there are consistent factors that differentiate these groups in terms of underlying etiology and potential for empiric treatment. Materials and Methods: Pure SFs based on infrared spectroscopic analysis of stones obtained at our institution between January 2002 and July 2018 with a corresponding 24-hour urinalysis were retrospectively evaluated. Results: One hundred twenty-one apatite (AP), 54 brushite (BRU), 50 calcium oxalate (CaOx) dihydrate, 104 CaOx monohydrate, and 82 uric acid (UA) patients were analyzed. AP, BRU, and CaOx dihydrate patients were younger than CaOx monohydrate and UA patients. The UA patients had the highest male predominance (76.8%), whereas AP patients were predominantly female (80.2%). UA was most associated with diabetes mellitus (45.3%), and CaOx monohydrate with cardiovascular disease (27.2%) and malabsorptive gastrointestinal conditions (19.2%). BRU patients had the highest prevalence of primary hyperparathyroidism (17%). AP, BRU, and CaOx dihydrate patients demonstrated high rates of hypercalciuria (66.1%, 79.6%, 82%). AP and BRU patients had the highest urinary pH. AP patients exhibited the highest rate of hypocitraturia, whereas CaOx dihydrate patients exhibited the lowest (55.4%, 30%). CaOx monohydrate patients had the highest rate of hyperoxaluria (51.9%). UA patients had the lowest urinary pH. There were no observable differences in the rates of hyperuricosuria or hypernatriuria. Conclusions: These results demonstrate that pure stone composition correlates with certain urinary and clinical characteristics. These data can help guide empiric clinical decision making.

Study of risk factor of urinary calculi according to the association between stone composition with urine component

Urolithiasis is a common urinary disease with high recurrence. The risk factor for the recurrence of calculi is not very clear. The object of the present study was to evaluate the association between calculi composition and urine component and analyse the risk factor for the recurrence of urolithiasis. In this study, a total of 223 patients with calculi and healthy control were enrolled, and the components of the calculi and urina sanguinis collected before surgery were analysed. Of the 223 patients, 157 were males and 66 were females. According to the stone composition, the case group was subdivided into three groups. 129 patients had single calcium oxalate stones, 72 had calcium oxalate stones mixed with other stones and 22 had other type of stones excluding calcium oxalate stones. Urine biochemicals were analysed and the associations were found between the chemicals in each group. Multivariate logistic analysis demonstrated that reduced urinary magnesium and uric oxalic acid were independent risk factors when comparing all cases with normal controls. Only decreased urinary magnesium was found to be a risk factor comparing the single calcium oxalate group with normal control group. Low level of urinary magnesium and uric oxalic acid were found to be risk factors comparing the mixed calcium oxalate group with normal control group. No risk factor was found comparing the other stone group with normal control group. In conclusion, there were clear relationships between stone components and urine chemicals. Urine chemicals might be risk factors to predicate the occurrence of urolithiasis.

A 13 year hospital based study on the Trend of Urinary Stone Disease in Uttarakhand, India

Background

The present retrospective study on urinary stone disease in the Uttarakhand state was necessitated as no study has been done yet.

Methods

A 13 year retrospective study (from 2005 to 2018) was conducted on the urinary stones removed from the patients, admitted at Himalayan Institute of Medical Sciences, Dehradun. The incidence of the disease, site of stones in urinary tract upon diagnosis, composition of removed stones and occurrence of a possible co-relationship between the incidence of the urinary stone disease at different times, age, sex, religion of the patients was investigated.

Results

The frequency of occurrence of urinary stones in males was found to be almost three times more as compared to their female counterparts. The above trend was consistent over the entire period of the study. Interestingly, in the Muslim and Sikh population of the area, females were found to be less prone to the problem as compared to their Hindu counterparts. However, in all religious groups, 21-40 years old subjects were found to be most susceptible to the problem and approximately 90% of the urinary stones were recovered from the kidneys and primarily composed of calcium oxalate.

Conclusion

The co-relationship between the occurrence of urinary stones with age, sex of the patients, their religion & site of stones on diagnosis was found to be statistically significant.

Effects of dexmedetomidine on immune function, renal function and inflammatory factors of patients undergoing percutaneous nephrolithotomy under general anesthesia

The present study was designed to determine the effects of dexmedetomidine on immune function, renal function and inflammatory factors in patients undergoing percutaneous nephrolithotomy under general anesthesia. A total of 177 patients with kidney calculi who underwent percutaneous nephrolithotomy in The Second Affiliated Hospital of Fujian Medical University were enrolled, in which 91 patients were treated with dexmedetomidine during surgery (research group) and 86 patients were not sedated during surgery (control group). The vital signs, renal function, inflammatory factors and immune function during surgery between the two groups were compared. Patients in the research group showed improved vital signs, renal function, inflammatory factors and immune function compared with the control group (P<0.05), and also experienced a significantly shorter hospitalization time (P<0.001). Therefore, the present results suggested that with a relatively high safety profile, use of dexmedetomidine for sedation can effectively protect renal and immune functions, and reduce the inflammatory response of patients during percutaneous nephrolithotomy. Thus, dexmedetomidine may have be potentially applied in clinical practice.

Value of the color Doppler imaging mode in improving physicians' diagnostic performance in patients with mid-ureteric stones larger than 5 mm: a retrospective study

The aim of this study was to retrospectively evaluate the value of the color Doppler flow imaging mode compared to the gray-scale mode for diagnosing mid-ureteric stones larger than 5 mm. We consecutively collected images from 79 patients possibly suffering from mid-ureteric stones under gray-scale and color Doppler flow imaging modes. Using computed tomography as the gold standard, all the included images were reviewed in a blinded manner for the confirmation of ureteral stones by 15 physicians divided into three groups according to their clinical experience level (resident, attending, and senior). During the evaluation process, the evaluation consistency was calculated and compared using Kendall's coefficient of concordance (Kendall's W). Moreover, diagnostic performance considering gray-scale and color imaging modes was compared. Especially for the diagnosis of mid-ureteric stones larger than 5 mm, the Kendall's W for the combined gray-scale and color Doppler flow imaging ultrasound scanning modes was greater than that for the gray-scale mode (P < 0.05). Additionally, significant improvements in the diagnostic sensitivity, negative predictive value, and accuracy were noted with color Doppler imaging (P < 0.05). Under isolated gray-scale mode, the resident group had reduced diagnostic sensitivity and negative predictive value and poorer accuracy compared with the attending and senior groups (P < 0.05). In contrast, no significant differences in the combined gray-scale and color Doppler flow imaging modes were noted among all groups (P > 0.05). In summary, the color Doppler flow imaging mode is useful for the diagnosis of mid-ureteric stones larger than 5 mm, especially in the resident group.

Tea and coffee consumption and the risk of urinary stones-a systematic review of the epidemiological data

OBJECTIVE

To explore the relationship between the consumption of coffee and tea with urolithiasis. We evaluated large epidemiological and small clinical studies to draw conclusions regarding their lithogenic risk.

METHODS

A systematic review was performed using the Medline and Scopus databases, in concordance with the PRISMA statement. English, French, and Spanish language studies regarding the consumption of caffeinated and decaffeinated coffee and tea, and the relationship to urinary stone disease were reviewed. Case reports and letters, unpublished studies, posters, and comments were excluded.

RESULTS

As per the inclusion criteria, 13 studies were included in the final review. Most studies, including four large prospective studies and one meta-analysis, reported a reduced risk of stone formation for coffee and tea. Caffeine has a diuretic effect and increases the urinary excretion of calcium, but if these losses are compensated for, moderate caffeine intakes may have little or no deleterious effects. Green and Herbal teas infused for short time had low oxalate content compared to black tea.

CONCLUSION

There is no evidence that moderate consumption of coffee raises the risk for stone formation in healthy individuals, provided the recommended daily fluid intake is maintained. The currently available literature supports in general a protective role for tea against the stone formation, mainly for green tea. However, heterogeneity of published data and lack of standardization needs to be addressed before final and clear conclusions can be given to patients and to the public in general.

Toward improved endoscopic examination of urinary stones: a concordance study between endoscopic digital pictures vs microscopy

Objective

To improve endoscopic recognition of the most frequently encountered urinary stone morphologies for a better aetiological approach in lithiasis by urologists.

Materials and Methods

An expert urologist intraoperatively and prospectively (between June 2015 and June 2018) examined the surface, the section, and the nucleus of all encountered kidney stones. Fragmented stones were subsequently analysed by a biologist based on both microscopic morphological (i.e. binocular magnifying glass) and infrared (i.e. Fourier transform‐infrared spectroscopy) examinations (microscopists were blinded to the endoscopic data). Morphological criteria were collected and classified for the endoscopic and microscopic studies. The Wilcoxon–Mann–Whitney test was used to detect differences between the endoscopic and microscopic diagnoses. A diagnosis for a given urinary stone was considered ‘confirmed’ for a non‐statistically significant difference.

Results

A total of 399 urinary stones were included in this study: 51.4% of the stones had only one morphological type, while 48.6% were mixed stones (41% had at least two morphologies and 7.6% had three morphologies). The overall matching rate was 81.6%. Diagnostics were confirmed for the following morphologies: whewellite (Ia or Ib), weddellite (IIa or IIb), uric acid (IIIa or IIIb), carbapatite‐struvite association (IVb), and brushite (IVd).

Conclusions

Our preliminary study demonstrates the feasibility of using endoscopic morphology for the most frequently encountered urinary stones and didactic boards of confirmed endoscopic images are provided. The present study constitutes the first step toward endoscopic stone recognition, which is essential in lithiasis. We provide didactic boards of confirmed endoscopic images that pave the way for automatic computer‐aided in situ recognition.

Calcium oxalate kidney stones, where is the organic matter?: A synchrotron based infrared microspectroscopy study

Kidney stones are collections of microcrystals formed inside the kidneys, which affect 6% to 12% of the population worldwide, with an increasing recurrence (50%-72%) after the first episode. The most abundant type is calcium oxalate (66%), described as monohydrated (COM) and dihydrated (COD). An issue in their chemistry is the transformation process of the metastable specie (COD) into the stable one, which is chemically, and in appearance, monohydrated. Since the origin of these species is different, it is important to differentiate between the transformation stage (and what stabilize COD) to understand the physiopathology and prevent the patients' recurrence. This work focuses on the organic matter distribution along these nephroliths by synchrotron radiation-based infrared microspectroscopy. Differences in the asymmetric stretching of the aliphatic hydrocarbons suggest that lipids may participate in the stabilization of COD and as inhibitors of COM formation/development; however, the presence of proteins in the nucleus could indicate a promoting role.

Comparison of Supersaturation Outputs from Different Programs and Their Application in Testing Correspondence with Kidney Stone Composition

Introduction: Relative supersaturation (SS) for calcium oxalate (CaOx), calcium phosphate (CaP), and uric acid (UA) has been used for assessing urinary crystallization and estimated by programs, including EQUIL, Joint Expert Speciation System (JESS), and Lithorisk. We compared outputs from these programs and their correspondence with stone composition. Materials and Methods: SS of CaOx, CaP, and UA, using EQUIL, JESS, and Lithorisk were calculated from stone-forming patients. Pearson correlation coefficients were used to ascertain the correspondence between the outputs. Fractional regression models evaluated the relationship between SS and the percentage of each compound in the stones. Results: Two hundred eleven patients were included. Pearson correlation coefficients for CaOx (r ≥ 0.96), CaP (r ≥ 0.99), and UA SS (r ≥ 0.99) showed a high correspondence between all programs. We observed a significant correspondence between CaOx SS and the percentage of CaOx dihydrate in the stone (p < 0.001), as well as between the percentage of brushite and apatite and CaP SS. UA SS showed the strongest correspondence with the percentage of UA in the stones (p < 0.001). Conclusions: Good correlation between EQUIL, JESS, and Lithorisk was observed and good correspondence with stone composition. The magnitude of the association demonstrated by fractional regression models supports evidence for applying SS in clinical practice.

Comparison of Two Dietary Supplements for Treatment of Uric Acid Renal Lithiasis: Citrate vs. Citrate + Theobromine

Background. Uric acid (UA) renal lithiasis has a high rate of recurrence and a prevalence ranging from 10% and 15%, depending on the population. The most important etiological factor is persistence of urinary pH below 5.5 and one of the most common treatments is alkalization with citrate. Recent studies demonstrated that theobromine, which is abundant in chocolate and cocoa, is a potent inhibitor of UA crystallization. Aim. The aim was to compare the efficacy of citrate versus citrate + theobromine as treatment for UA lithiasis. Methods. This randomized cross-over trial investigated the efficacy of two treatments in 47 patients with UA renal lithiasis. Urine volume, pH, UA excretion, theobromine excretion, and risk of UA crystallization (RUAC) at baseline and at the end of each intervention period were measured. Results. Each treatment significantly reduced the risk of UA crystallization compared to basal values. The RUAC after citrate + theobromine was lower than the RUAC after citrate, although this difference was not statistically significant. Conclusion. The combined consumption of citrate and theobromine may be a promising strategy for the prevention of UA kidney stones.