Uric acid nephrolithiasis: current concepts and controversies

Management of hypertension addressing hyperuricaemia: introduction of nano-based approaches

Uric acid (UA) levels in blood serum have been associated with hypertension, indicating a potential causal relationship between high serum UA levels and the progression of hypertension. Therefore, the reduction of serum UA level is considered a potential strategy for lowering and mitigating blood pressure. If an individual is at risk of developing or already manifesting elevated blood pressure, this intervention could be an integral part of a comprehensive treatment plan. By addressing hyperuricaemia, practitioners may subsidize the optimization of blood pressure regulation, which illustrates the importance of addressing UA levels as a valuable strategy within the broader context of hypertension management. In this analysis, we outlined the operational principles of effective xanthine oxidase inhibitors for the treatment of hyperuricaemia and hypertension, along with an exploration of the contribution of nanotechnology to this field.

Metabolic Evaluation and Recurrence Prevention for Urinary Stone Patients: An EAU Guidelines Update

BACKGROUND AND OBJECTIVE

The aim of this review was to define patients who are at high risk of recurrence of urolithiasis, to delineate diagnostic and therapeutic algorithms for each type of stone, and to clarify general guidelines and recommendations for prevention of recurrence.

METHODS

A professional research librarian carried out literature searches for all sections of the urolithiasis guidelines, covering the timeframe between 1976 and June 2023.

KEY FINDINGS AND LIMITATIONS

For every patient with urolithiasis, an attempt should be made to analyse the stone. Patients should be given general instructions on how to prevent recurrence, including adequate fluid and calcium intake, and low consumption of sodium and protein. Identifying and correcting the causative factors is a cornerstone in preventing the recurrence of urolithiasis. Diagnostic and therapeutic algorithms by stone composition are available. Every patient should undergo baseline metabolic screening, while patients with calcium stones, who are at high risk of relapse and complications, should undergo extensive metabolic screening with two 24-h urine collections and should receive targeted therapy. Patients with uric acid, infection, or cystine stones are at high risk of relapse. All patients at high risk of recurrence should be closely monitored, especially those not complying with therapy in the long term.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Metabolic stone evaluation and patient follow-up are highly recommended to prevent urolithiasis recurrence.

The awareness of renal stones amongst Syrian refugees in northern Jordan

Kidney Stone Disease (KSD) is a globally prevalent condition that can be effectively addressed through proper education. This study investigated the awareness of kidney stones among refugees residing in northern Jordan. A questionnaire was administered to 487 refugees of diverse ages and socioeconomic backgrounds. Notably, 97.3% of the respondents had not attended university, and 30.8% held unskilled jobs. Upon familiarizing themselves with the signs and symptoms of kidney stones, 16.22% of men and 12.32% of women reported experiencing such symptoms. This revealed a significant association, suggesting that men might be more susceptible to developing kidney stones than women due to a lack of medical follow-up and examination for men in the camp. However, 38.77% of individuals were uncertain whether they had kidney stones. Furthermore, 38.96% of refugees were unsure about which healthcare professional to consult when experiencing kidney stone symptoms. This report highlights a serious issue with refugees' knowledge of the symptoms, causes, and treatments for kidney stones. The results indicate that Syrian refugees face challenges in acquiring adequate disease awareness, potentially related to issues of migration and war, including low levels of education, limited income, living in camps, and difficulties accessing treatments when needed. Implementing additional policies is necessary to address these challenges among Syrian refugees; however, further studies are needed to validate these findings.

Association between chinese visceral adiposity index and risk of kidney stones in a health screening population: an ultrasonography based cross-sectional study

BACKGROUND

Obesity is an important risk factor for kidney stones(KS). Chinese Visceral Adiposity Index (CVAI), as a specific indicator for visceral obesity in the Chinese population, can more accurately assess the visceral fat content in Chinese individuals compared to Visceral Adiposity Index (VAI). However, the association between CVAI and risk for KS has not been studied.

METHODS

A total of 97,645 participants from a health screening cohort underwent ultrasound examinations for the diagnosis of kidney stones, along with measurements of their CVAI. Logistic regressions were utilized to determine the relationship between different quartiles of CVAI and the incidence of kidney stones. Simultaneously, subgroup analysis and the computation of dose-response curves were employed to pinpoint susceptible populations.

RESULTS

Among the participants, 2,888 individuals (3.0%) were diagnosed with kidney stones. The mean CVAI values ± standard deviation for the four groups were: Q1 (18.42 ± 19.64), Q2 (65.24 ± 10.39), Q3 (98.20 ± 9.11), and Q4 (140.40 ± 21.73). In the fully adjusted multivariable model, CVAI was positively correlated with urolithiasis (OR = 1.001; 95% CI = 1.000, 1.002). Compared with the first quartile of CVAI, the population in the fourth quartile of CVAI had a higher prevalence of kidney stones (OR = 1.231; 95% CI = 1.066, 1.415). Through subgroup analysis, a positive correlation between CVAI and the risk of kidney stones was found in non-smokers (OR = 1.001, 95%CI:1.000, 1.002), non-drinkers (OR = 1.001, 95%CI:1.000, 1.002), non-hypertensive subgroups (OR = 1.003, 95%CI:1.002, 1.003), and non-diabetes subgroups (OR = 1.001, 95%CI:1.000, 1.002).

CONCLUSION

The findings suggest that CVAI could be a reliable and effective biomarker for assessing the potential risk of kidney stone prevalence, with significant implications for the primary prevention of kidney stones and public health.

A case of post-renal acute kidney injury caused by bilateral ureterolithiasis

Key Clinical Message

Bilateral ureterolithiasis is rare but can cause acute kidney injury (AKI). Clinicians should first examine for post-renal causes of AKI, even if the patient lacks subjective symptoms.

Abstract

This letter describes a case of bilateral ureterolithiasis which presented with post-renal acute kidney injury (AKI) and was successfully treated by bilateral retrograde ureteric stenting. Clinicians should be aware of post-renal AKI caused by bilateral ureterolithiasis when acute worsening of renal function with oliguria is observed.

Changes in Urinary Uric Acid Concentration after Dotinurad Administration to Patients with Hyperuricemia: A Post Hoc Analysis of Two Clinical Trials in Japan

Dotinurad has been approved in Japan as a selective urate reabsorption inhibitor for the treatment of gout and hyperuricemia. The relationship between uric acid crystallization and the use of uricosuric drugs is widely acknowledged; however, the relationship between changes in urinary uric acid concentration and urine pH or volume has not been sufficiently analyzed. Therefore, we investigated the changes in urinary uric acid concentration following dotinurad administration as well as the relationship between urine pH or volume and urinary uric acid concentration. This post hoc analysis used data from 2 clinical trials that included 12 and 26 patients with hyperuricemia who received dotinurad treatment (for 7 days on an inpatient basis and 14 weeks on an outpatient basis, respectively). The urinary uric acid concentration transiently increased in the early stages of dotinurad use and when its dose was increased, but decreased over time. No uric acid concentrations exceeded the soluble limit at any urine pH. An inverse correlation was observed between urine volume and urinary uric acid concentration. This study highlights the significance of adequately managing urinary uric acid concentrations by increasing urine volume and alkalinizing urine to prevent uric acid crystallization during dotinurad administration.

Structural analysis and attenuates hyperuricemic nephropathy of dextran from the Imperata cylindrica Beauv. var. major (Nees) C. E. Hubb

ICPC-a was from the Imperata cylindrica with a molecular weight of 45 kDa, which was composed of α-D-1,3-Glcp and α-D-1,6-Glcp. The ICPC-a showed thermal stability, maintaining its structural integrity up to 220°C. X-ray diffraction analysis confirmed its amorphous nature, while scanning electron microscopy revealed a layered morphology. ICPC-a significantly ameliorated uric acid stimulation-induced HK-2 cell injury and apoptosis and reduced uric acid levels in mice with hyperuricemic nephropathy. ICPC-a protected against renal injury by inhibiting lipid peroxidation levels, increasing antioxidant damage and defense levels, inhibiting secretion of pro-inflammatory factors, regulating purine metabolism, PI3K-Akt signaling pathway, NF-κB signaling pathway, inflammatory bowel disease, mTOR signaling pathway, and MAPK signaling pathway. These findings indicate that ICPC-a is a promising natural substance with multiple targets, multiple pathways of action, and without toxicity, making it a valuable subject for further research and development.

Clinical characteristics of surgically managed patients with asymptomatic renal stones: Comparison of patients with symptomatic renal stones

PURPOSE

This study aimed to compare the characteristics of asymptomatic and symptomatic nephrolithiasis in patients who underwent surgical treatment for kidney stones.

MATERIALS AND METHODS

Between 2015 and 2019, 245 patients who underwent percutaneous nephrolithotomy or retrograde intrarenal surgery for kidney stones were included. The patients were divided into asymptomatic (n=124) and symptomatic (n=121) groups. All patients underwent blood and urine tests, preoperative non-contrast computed tomography, and postoperative stone composition analysis. We retrospectively analyzed and compared the characteristics of the patients and stones, operation time, stone-free rate, and postoperative complications between the two groups.

RESULTS

In the asymptomatic group, mean body mass index (BMI) was significantly higher (25.7±3.8 kg/m² vs. 24.3±2.8 kg/m², p=0.002) and urine pH was significantly lower (5.6±0.9 vs. 5.9±0.9, p=0.013). The ratio of calcium oxalate dihydrate stones was significantly higher in the symptomatic group (5.3% vs. 15.5%, p=0.023). No significant differences were observed in stone characteristics, postoperative outcomes, or complications. In the multivariate logistic regression analysis for predicting variables for asymptomatic renal stones, BMI (odds ratio [OR], 1.144; 95% confidence interval [CI], 1.038-1.260; p=0.007), and urine pH (OR, 0.608; 95% CI, 0.407-0.910; p=0.016) were independent predictive variables for asymptomatic renal stones.

CONCLUSIONS

This study demonstrated that thorough medical check-ups are needed for the early detection of renal stones in individuals with a high BMI or low urine pH.

Terahertz spectroscopy of citrate Salts: Effects of crystalline state and crystallization water

Citrate salts are widely used as food additives and medicines for health and treatment. Accurate and fast detection of citrate salts is most important in food industry and medicine health. In this work, terahertz (THz) time-domain spectroscopy was used to detect and analyze different citrate salts and differentiate their crystalline hydrates. Effects of the crystalline state, the crystallization water and the metal cation on the THz spectra of citrate salts were investigated. Results indicate the crystalline states of the citrate salt samples strongly influence their THz featuring absorption peaks and citrate salts with crystallization water have larger absorption coefficients at the same frequency and higher possibility of existing featuring absorption peaks in comparison with citrate salts without crystallization water. Size of the metal cation also influences the THz absorption peak of the citrate salt and a small cation radius results in a large absorption peak frequency. This work illustrates the terahertz spectroscopy can be well used as a new technique to detect the citrate salts and differentiate their crystalline hydrates.

Ethnomedicinal Plants Used for Treatment of Urolithiasis in India: A Review

Background:

The kidney stone is the most commonly observed and painful disease of the urinary tract in human being. Numerous intrinsic and extrinsic factors are responsible for the formation of kidney stone, for instance, age, sex, heredity (intrinsic factors) and climate, dietary, geography, mineral composition, and water intake (extrinsic factors). The kidney stones are categorized into calcium, struvite or magnesium ammonium phosphate, uric acid or urate, cystine and other types of stones based on chemical composition and pathogenesis. Due to the multifactorial nature of kidney stone disease, the patient may need to rely on complex synthetic medication. However, in ancient Indian history, there are several pieces of evidence where natural resources such as plants were used to remediation this lethal disease.

Objective:

The present review attempts to provide exhaustive information of ethnomedicinal and ethnopharmacological information of medicinal plants used for kidney stone in India.

Result:

Hitherto, there are a total of 258 ethnomedicinal plants from 90 different families reported using for kidney stone application. The majority of the plant species are associated with three important families: Asteraceae, Amaranthaceae, and Fabaceae. Most of the plants are from Andhra Pradesh (43 plants), followed by East Bengal (38), Jammu & Kashmir (36), Uttarakhand (31), Panjab (27), Mizoram (23), Karnataka (20), Maharashtra (20) and Assam (18). The commonly used plant parts for the herbal preparation are roots (21.22 %) followed by leaves/leaf (20.15 %), and sometimes complete plant (17.77 %) is used. The most commonly used method for the formulation is decoction (46.41 %) followed by powder (18.66 %) and then extracts (15.78 %) of different aerial and non-aerial parts of the plant. To date, the in-vitro and in-vivo activities against the kidney stone assessed for more than sixty ethnomedicinal plants.

Conclusion:

The present review epitomizes the ethnomedicinal information of medicinal plants used for kidney stone and pharmacological evidence for anti-urolithiasis activity. Most reported medicinal plants are not yet scientifically explored and need immediate attention before we lose some important species due to excessive deforestation for farming and industrial needs.

Quantitative phase analysis and microstructural characterization of urinary tract calculi with X-ray diffraction Rietveld analysis on a Caribbean island

In the twin-island state of Trinidad and Tobago, urinary stone analysis is not routinely performed. This study investigates, via powder X-ray diffraction, 52 urinary tract calculi collected from hospitals in Trinidad. Of these, 46 stones were analysed with Rietveld refinement for quantitative analysis and materials characterization. Refined unit-cell, microstructural and weight fraction parameters were obtained, with the last being used for stone classification. The results revealed seven distinct mineralogical phases of varying frequency: calcium oxalate monohydrate (COM, 58%), calcium oxalate dihydrate (COD, 23%), carbonated apatite (APA, 48%), brushite (BRU, 6%), struvite (STR, 42%), uric acid (UA, 23%) and ammonium acid urate (AAU, 19%). The average refined crystallite sizes were 1352 ± 90 Å (COM), 1921 ± 285 Å (COD), 83 ± 5 Å (APA), 1172 ± 9 Å (BRU), 1843 ± 138 Å (STR), 981 ± 87 Å (UA) and 292 ± 83 Å (AAU). Subsequently, 36.5% of stones were categorized as phosphates, 34.6% as oxalates, 13.5% as uric acid/urates and 15.4% as mixed compositions. The study findings highlight the importance of stone analysis as a necessary step towards disease management of local patients, and endorse the application of Rietveld refinement as a natural extension to diffraction-based kidney stone investigations.

Influence of Age and Geography on Chemical Composition of 98043 Urinary Stones from the USA

Background

Urolithiasis is a growing issue globally, but it is heterogeneous, with a different epidemiology and pathophysiology for each different stone composition.

Objective

The purpose of this study is to describe the incidence of urinary stones in the USA from 2016 to 2019 by chemical composition and to investigate the influence of age and geography on these stone types.

Design, setting, and participants

We obtained compositional analyses for all urinary stones submitted to a national laboratory over an approximately 3-yr period.

Outcome measurements and statistical analysis

Data collected included the chemical constituents of a stone, patient age, and geographical origin. We describe the incidence of each stone type by frequency. Statistical testing was performed to determine the influence of age and geographical region on overall incidence of each stone composition.

Results and limitations

In total, 99 908 specimens were analyzed. When pure stones were ordered by frequency, we found that the most common stone type was calcium oxalate (CaOx) (79.2%), followed by uric acid (UA; 14.3%), calcium phosphate (CaPO₄; 3.7%), cystine (0.51%), drug induced (0.12%), and magnesium ammonium phosphate (0.04%). CaOx, UA, and CaPO₄ were often mixed with one another. Among CaOx stones, the plurality (28.0%) was made of pure calcium oxalate monohydrate (COM), and only 0.002% was pure calcium oxalate dihydrate. There was an overall association between stone composition and both geographical distribution and age (p < 0.001).

Conclusions

CaOx stones comprise the majority of urinary stones in the USA, of which almost 28% were pure COM. Additionally, age and geographical region are significantly associated with variations in stone composition.

Patient summary

We evaluated the incidence of urinary stones in the USA based on their chemical composition. The most common stone type was calcium oxalate, the majority of which was pure calcium oxalate monohydrate. We also found age and geographical region to be significantly associated with variations in stone composition.

Prevention and management of urinary stone

The prevalence of urolithiasis is increasing not only in South Korea but also around the world. Urolithiasis has a high recurrence rate, therefore, reducing it is very important in the quality of life for stone formers. For this purpose, dietary modifications and drug therapy can be performed through stone analysis and 24-hour urine collection. Stone analysis is recommended for all stone formers, and the 24-hour urine collection is usually recommended for recurrent stone formers or high-risk groups. A general dietary modification for all stone formers includes a sufficient fluid intake, low levels of sodium, sugar, and animal protein, a normal calcium diet, as well as a high amount of citrate intake. Drug therapy should be performed in cases such as the recurrence of stones or increase of the existing ones, even after the application of preservation therapy, such as dietary modification. The ideal drug therapy should prevent the occurrence of urolithiasis, have no side effects, and have a suitable patientsʼ compliance. Follow-up should be performed periodically, through 24-hour urine collections and imaging studies. For follow-up imaging studies, a lowdose non-enhanced computed tomography is recommended, and it can be performed once a year if the patient is in a stable state. To control various and complex metabolic abnormalities in recurrent stone formers, multiple approaches may be required through diet modifications, drug therapy, treatment of the metabolic syndrome, and lifestyle modifications.

Giant bladder uric acid stone with a history of prolonged sun exposure and high protein diet in North Moluccas: Case series

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Giant bladder uric acid stone cases are rare.

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Open suprapubic cystolithotomy is the best method to extract giant bladder stones.

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The most important factors were the climate and dietary habits.

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Benign prostatic hyperplasia was not found.

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Uric acid stone is common in Southeast Asia, with a multifactorial pathogenesis.

Introduction

Giant bladder uric acid stone cases that have more than 4 cm in diameters and weighing more than 100 g are considered rare.

Presentation of cases

At the end of 2019, two men presented with chronic lower abdominal pain since five years ago. Abdominal radiography found a giant opaque mass inside the bladder. Open suprapubic cystolithotomy was performed by a general surgeon. Both giant bladder stones were extracted and measured approximately 11 × 7 × 6 cm and 500 g in weight. More than 80 % of stone composition was uric acid. Neither of the patients developed severe complications after the procedure.

Discussion

Our patients had a history of prolonged sun exposure related to occupation and high protein intake. Benign prostatic hyperplasia as a major underlying cause for stone formation was not found in the digital rectal examination. Prostatectomy was not performed. Uric acid stone is common in Southeast Asia, with a multifactorial pathogenesis.

Conclusions

Open suprapubic cystolithotomy is the best method to extract giant bladder stones in limited settings in the rural areas of Indonesia. It was likely that the most important factors associated with the stone formation were the climate and dietary habits. The findings showed that pathogenesis of bladder stone formation and particularly, uric acid bladder stone is still not clearly understood.

Preliminary analysis of serum electrolytes and body mass index in patients with and without urolithiasis

OBJECTIVES

To compare body mass index (BMI); serum parameters; and urine parameters between patients with and without urolithiasis.

METHODS

Data from 1164 patients admitted to our Department of Urology from January 2011 to July 2013 were retrospectively reviewed; 714 patients (age, 5-87 years; male:female ratio, 1.8:1) exhibited urolithiasis, and 450 patients (age, 12-94 years; male:female ratio, 3.8:1) did not. Blood and urine were collected from patients the morning after hospital admission. Serum and urine parameters were checked by an automatic biochemistry analyzer. Statistical analysis included the Mann-Whitney U test and binary logistic regression.

RESULTS

Serum sodium, potassium, chloride, calcium, phosphorus, and carbon dioxide combining power significantly differed between groups. In male patients, serum sodium, calcium, and phosphorus levels were higher in the urolithiasis group, whereas serum potassium and urine pH levels were lower. In female patients, serum sodium was higher in the urolithiasis group. BMI was higher in the urolithiasis group in all patients, male and female. Respective β-values of serum sodium and BMI in male patients were 0.077 and 0.084; in female patients, these values were 0.119 and 0.102.

CONCLUSIONS

Changes in serum sodium and BMI may be involved in the pathogenesis and treatment of urolithiasis.

Decreased Associated Risk of Gout in Diabetes Patients with Uric Acid Urolithiasis

Uric acid urolithiasis constitutes approximately 7–10% of all urinary stones. Previous studies have revealed that patients with gout do not equally have uric acid stones. Instead, the risk of gout in patients with uric acid stones remains controversial. This study aimed to investigate whether there is different associated risk of gout for diabetes mellitus (DM) and non-diabetes patients with uric acid urolithiasis. Therefore, we examined all baseline chemistries to determine any risk factors or protective factors related to developing gout in patients with uric acid stones. Ninety-nine patients from a single medical center, who had a uric acid component in their stone specimen were enrolled and their medical records were reviewed retrospectively between January 2010 and December 2016. All patients were divided into gout and non-gout groups. Gout was confirmed in 24 patients in this study (24.2%). The proportion of DM was significantly higher in the non-gout group (34.7%) than in the gout group (4.3%, p < 0.05). Renal function was decreased and serum triglyceride was higher in patients with gout. Uric acid urolithiasis patients with DM had a lower risk for gout (adjusted odds ratio: 0.08; 95% confidence interval (CI) = 0.01–0.61, p = 0.015). In 89 patients with predominant uric acid stones (>50% uric acid composition), the risk for gout was still lower in patients with diabetes than non-diabetes (adjusted odds ratio: 0.08; 95% confidence interval (CI) = 0.01–0.61, p = 0.015). These findings suggest that decreased risk of gout is found in uric acid urolithiasis patients with diabetes. Our results imply that patients with uric acid stones should have complete diabetes evaluation before the administration of uric acid controlling medication.

Long-term Recurrence Rates in Uric Acid Stone Formers With or Without Medical Management

OBJECTIVE

To determine if medical therapy affects long-term clinical outcomes in uric acid stone formers (UASF).

METHODS

We identified 53 UASF who had complete stone clearance following stone procedure by computed tomography (CT) and had ≥1 postoperative 24-hour urine collection and a clinical follow-up ≥6 months with a surveillance CT scan. Patients were divided into "adherent to medical therapy" (compliance with potassium citrate ± allopurinol verified by computerized pharmacy data) or nonadherent groups. Primary outcomes were CT stone recurrence rate and need for surgical stone intervention.

RESULTS

We found 28 of 53 (53%) adherent and 25 of 53 (47%) nonadherent individuals (14 declined medication, 11 intolerant). With median follow-up of 24 months, no significant differences were noted between groups in regards to stone recurrence (32%; P = .99) or in 24-hour urine pH compared to baseline or follow-up (range 5.46-5.62; P = 0.06). Adherent patients, however, had smaller CT stone recurrence sizes (6.3 ± 3.8 vs 11.8 ± 6.2 mm, P = .02), were 28% less likely to require stone surgery compared to those without therapy (P <.01), and trended toward longer time intervals without recurrence (23.1 ± 18.8 vs 10.5 ± 7.5 months, P = .10) compared to nonadherents. Study confounders included a variety of medication dosages and adherences, limited nonadherent follow-up, and small study number.

CONCLUSION

UASF adherent to medical therapy had smaller recurrence sizes and fewer surgical interventions vs nonadherent, highlighting the protective role of potassium citrate in UA stone disease. The comparable urine pH and stone recurrence rates between groups, however, underscore areas for improvement in future UA stone prevention strategies.

High Serum Uric Acid Is Associated with Tubular Damage and Kidney Inflammation in Patients with Type 2 Diabetes

Background

Uric acid presents different roles in an organism. High serum uric acid concentrations may induce inflammatory pathways and promote kidney damage through different mechanisms. Therefore, this study investigated the association among high serum uric acid concentrations, renal tubular damage, and renal inflammation assessed via estimation of urinary kidney injury molecule-1 (KIM-1) and inflammatory cytokines in patients with type 2 diabetes (T2D).

Methods

Urinary concentrations of KIM-1, IL-1, IL-6, IL-10, and TNF-alpha, as well as other biochemical parameters, were assessed in 125 patients with T2D who were grouped into two groups based on the serum uric acid levels (<6.0 mg/dL and ≥6.0 mg/dL). Patients were also stratified according to the tertiles of serum uric acid concentrations.

Results

Urinary KIM-1, IL-1, IL-6, and TNF-alpha were higher in patients with serum uric acid concentrations ≥ 6.0 mg/dL. However, the differences between the groups were not statistically significant when the urinary values of KIM-1 and cytokines were normalized by the urinary creatinine concentration. Serum uric acid concentrations were significantly associated with urinary KIM-1 (values normalized by urinary creatinine concentration) and urinary TNF-alpha (absolute values and values normalized by urinary creatinine concentration), independent of the body mass index (BMI) and estimated glomerular filtration rate (eGFR).

Conclusions

High serum uric acid concentrations were associated with high urinary KIM-1 levels accompanied by the increase of urinary proinflammatory cytokines in patients with T2D. However, normalization of urinary markers by urine creatinine concentration seems to influence the profile of the results.

Pharmacological basis for use of madecassoside in gouty arthritis: anti-inflammatory, anti-hyperuricemic, and NLRP3 inhibition

Objectives: Gouty arthritis is caused by the deposition of monosodium urate (MSU) crystals in joints, which is associated with the rise of serum urate content. This study aims to investigate the therapeutic effect of Madecassoside on gouty arthritis and hyperuricemia. Methods: DBA/1 mice were intradermally injected with MSU to stimulate joint inflammation or intraperitoneally injected with MSU to trigger peritonitis. Moreover, ICR mice were exposed to potassium oxonate to stimulate hyperuricemia. Results: Madecassoside repressed MSU-triggered pad swelling, joint 99mTc uptake, and joint inflammation in DBA/1 mice with gouty arthritis. Neutrophil infiltration and IL-1β & IL-6 & MCP-1 secretion was also alleviated in lavage fluids from DBA/1 mice with peritonitis due to Madecassoside treatment. Furthermore, Madecassoside decreased MSU-induced neutrophil cytosolic factor 1, caspase-1 and NLRP3 expression in mice with peritoneal inflammation. In hyperuricemic mice, Madecassoside improved renal dysfunction. Serum uric acid, BUN, and creatinine were down-regulated by Madecassoside. Conclusion: These findings indicate that Madecassoside has potential to ameliorate inflammation in both acute gouty arthritis model and peritonitis model, probably via regulating IL-1β and NLRP3 expression. Practical point: Madecassoside also exhibited a urate-lowering effect and a renal protective effect in hyperuricemic mice.

Medical dissolution therapy for the treatment of uric acid nephrolithiasis

INTRODUCTION

Uric acid (UA) nephrolithiasis represents 10% of kidney stones in the US with low urine pH and high saturation of UA as the main risk factors for stone development. Dissolution therapy for UA kidney stones via urinary alkalization has been described as a treatment option. We present our experience in treating UA nephrolithiasis with medical dissolution therapy.

METHODS

A retrospective review was performed of UA stone patients referred for surgery but treated with dissolution therapy between July 2007 and July 2016. Patients were identified using ICD-9 codes. Patients were treated with potassium citrate alone or in combination with allopurinol. Serial imaging and urine pH were obtained at follow-up. Demographics, aggregate stone size, time to stone clearance, urine pH (office dip), and complications were recorded.

RESULTS OBTAINED

Twenty-four patients (14 men and 10 women) were identified that started medical dissolution therapy for UA nephrolithiasis after initial referral for surgical management. Three patients (13%) did not tolerate the initiation of dissolution therapy and discontinued this treatment. Of the 21 patients that were maintained on dissolution therapy, 14 patients (67%) showed complete resolution of nephrolithiasis and 7 patients (33%) showed partial reduction. Patients with partial response had a mean reduction in stone burden of 68%. There were 3 recorded complications (UTI, GI upset with therapy, and throat irritation) and 4 recorded stone recurrences among these 21 patients.

CONCLUSION

Based on our study population, medical dissolution therapy is a well-tolerated, non-invasive option for UA nephrolithiasis.

Proteomic analysis of a urinary stone with two layers composed of calcium oxalate monohydrate and uric acid

We examined the mechanism of urinary stone formation by analyzing the matrix proteins in a urinary stone with two layers composed of different crystals. Micro-area X-ray spectrometry and infrared spectroscopy revealed calcium oxalate monohydrate in the outside and uric acid in the inside. We also examined the interface. After the outside, inside, and interface parts were separated, proteomic analysis identified 48, 7, and 4 matrix proteins, respectively. Urinary stones with two layers are considered to have grown under different conditions. The matrix proteins in each part differed among the crystal components and may reveal the stone-generating process. The proteins in the interface likely function to enlarge the stone via the addition of different crystals.

The influence of serum uric acid on renal function in patients with calcium or uric acid stone: A population-based analysis

OBJECTIVES

To determine the influence of serum uric acid (UA) levels on renal impairment in patients with UA stone.

MATERIALS AND METHODS

We retrospectively analyzed 463 patients with calcium oxalate and/or calcium phosphate stones (CaOx/CaP), and 139 patients with UA stones. The subjects were divided into the serum UA-high (UA ≥ 7.0 mg/dL) or the UA-low group (UA < 7.0 mg/dL). The control group comprised 3082 community-dwelling individuals that were pair-matched according to age, sex, body mass index, comorbidities, hemoglobin, serum albumin, and serum UA using propensity score matching. We compared renal function between controls and patients with UA stone (analysis 1), and between patients with CaOx/CaP and with UA stone (analysis 2). Logistic regression analysis was used to evaluate the impact of the hyperuricemia on the development of stage 3 and 3B chronic kidney disease (CKD) (analysis 3).

RESULTS

The renal function was significantly associated with serum UA levels in the controls and patients with CaOx/CaP and UA stones. In pair-matched subgroups, patients with UA stone had significantly lower renal function than the control subjects (analysis 1) and patients with CaOx/CaP stones (analysis 2) regardless of hyperuricemia. Multivariate logistic regression analysis revealed that patients with UA stone, CaOx/CaP, hyperuricemia, presence of cardiovascular disease, higher body mass index, older age and lower hemoglobin had significantly higher risk of stage 3 and 3B CKD (analysis 3).

CONCLUSION

Patients with UA stones had significantly worse renal function than controls and CaOx/CaP patients regardless of hyperuricemia. Urolithiasis (CaOx/CaP and UA stone) and hyperuricemia had an association with impaired renal function. Our findings encourage clinicians to initiate intensive treatment and education approaches in patients with urolithiasis and/or hyperuricemia in order to prevent the progression of renal impairment.

Incidence of and risk factors for nephrolithiasis in patients with gout and the general population, a cohort study

BACKGROUND

Nephrolithiasis (NL) is known to be associated with gout, although there are few comparative studies on risk and risk factors for NL in gout compared to population cohorts. In this cohort study we investigated: (1) overall incidence of NL in gout (cases) and general population controls; (2) risk and risk factors (common comorbidities and medications) for first-time NL in cases and controls separately.

METHODS

Cases (n = 29,968) and age-matched and sex-matched controls (n = 138,678) were identified from the regional healthcare database in western Sweden (VEGA). The analyzed risk factors (comorbidities and current medication use) for first-time NL, and socioeconomic factors were retrieved from VEGA and other national Swedish registers. For cases, follow up began on 1 January 2006 or on the first diagnosis of gout if this occurred later, and for controls on their index patient's first diagnosis of gout. Follow up ended on death, emigration or 31 December 2012. Incidence rates (IR) per 1000 person-years and hazard ratios (HR) were calculated. The incidence calculations were performed for cases (regardless of prior NL) and their controls. HRs with first occurrence of NL as outcome were calculated only in those without previous NL.

RESULTS

In cases there were 678 NL events (IR: 6.16 events per 1000 person-years (95% CI: 5.70-6.64) and in controls 2125 NL events (IR 3.85 events per 1000 person-years (95% CI: 3.69-4.02), resulting in an age-sex-adjusted incidence rate ratio of 1.60 (95% CI:1.47-1.74). Point estimates for predictive factors were similar in cases and controls, except for a significant interaction for losartan which increased the risk of NL only in controls (HR = 1.49 (95% CI: 1.03-2.14). Loop diuretics significantly decreased the risk of NL by 30-34% in both cases and controls. Further significant predictors of NL in gout cases were male sex, diabetes and obesity and in controls male sex and kidney disease.

CONCLUSIONS

The risk (age and sex adjusted) of NL was increased by 60% in cases compared to controls. None of the commonly used medications increased the risk of NL in gout patients.

[S2k guidelines on diagnostics, therapy and metaphylaxis of urolithiasis (AWMF 043/025) : Compendium]

Every tenth German citizen will suffer from at least one urinary calculus during the lifetime. The diagnostics, treatment and follow-up treatment of urolithiasis are, therefore, part of the daily routine practice for all urologists in hospitals and private practices as well as in many other disciplines, such as general practitioners, internists, nephrologists and pediatricians. Although the diagnostics and therapy have experienced substantial alterations over the last 10 years, the possibilities of metabolic diagnostics and secondary prevention for patients at risk are, unfortunately and unjustly, in many places very poorly represented. The present S2k guidelines, which for the first time were established in an interdisciplinary consensus process, represent the current practical recommendations and, whenever possible, use tables and algorithms in order to facilitate easy reference in the routine daily work. Last but not least, this greatly simplifies the measures for metaphylaxis.

Rosehip inhibits xanthine oxidase activity and reduces serum urate levels in a mouse model of hyperuricemia

Rosehip, the fruit of Rosa canina L., has traditionally been used to treat urate metabolism disorders; however, its effects on such disorders have not been characterized in detail. Therefore, the present study investigated the effects of hot water, ethanol and ethyl acetate extracts of rosehip on xanthine oxidase (XO) activity in vitro. In addition, the serum urate lowering effects of the rosehip hot water extract in a mouse model of hyperuricemia (male ddY mice, which were intraperitoneally injected with potassium oxonate) were investigated. Furthermore, the influence of rosehip hot water extract on CYP3A4 activity, which is the most important drug-metabolizing enzyme from a herb-drug interaction perspective, was investigated. Rosehip extracts of hot water, ethanol and ethyl acetate inhibited XO activity [half maximal inhibitory concentration (IC50) values: 259.6±50.6, 242.5±46.2 and 1,462.8±544.2 µg/ml, respectively]. Furthermore, the administration of 1X rosehip hot water extract significantly reduced the levels of serum urate at 8 h, which was similar when compared with the administration of 1 mg/kg allopurinol. Rosehip hot water extract only marginally affected CYP3A4 activity (IC50 value, >1 mg/ml). These findings indicate that rosehip hot water extract may present as a functional food for individuals with a high urate level, and as a therapeutic reagent for hyperuricemic patients.

Epidemiology, pathophysiology, and management of uric acid urolithiasis: A narrative review

An in-depth comprehension of the epidemiology as well as pathophysiology of uric acid urolithiasis is important for the identification, treatment, and prophylaxis of calculi in these patients. Persistently low urinary pH, hyperuricosuria, and low urinary volume are the most important factors in pathogenesis of uric acid urolithiasis. Other various causes of calculus formation comprises of chronic diarrhea, renal hyperuricosuria, insulin resistance, primary gout, extra purine in the diet, neoplastic syndromes, and congenital hyperuricemia. Non-contrast-enhanced computed tomography is the radiologic modality of choice for early assessment of patients with renal colic. Excluding situations where there is acute obstruction, rising blood chemistry, severe infection, or unresolved pain, the initial management ought to be medical dissolution by oral chemolysis since this method has proved to be effective in most of the cases.

Difference in urinary stone composition between Uyghur and Han children with urolithiasis

The Objective of this study is to analyze the difference in renal stone composition between Uyghur and Han children with urolithiasis in China and possible reasons. From May 2011 to September 2013, we analyzed the stone compositions of 274 Chinese children with urolithiasis, including 151 Uyghur children from Xinjiang Province and 123 Han children from Guangdong Province. All the stone components were determined by Infrared spectroscopy and the main components were recorded. We also evaluated the data, including age, gender and geographic region of the patients. The mean age of Uyghur children was less than Han children (5.3 ± 4.2 vs 8.6 ± 5.7 years, p < 0.001). Calcium oxalate (CaOx) was the main stone composition in both Uyghur (35.1 %) and Han (64.2 %) children, but was more common in Han children (p < 0.0001). Cystine stone was also more abundant in Han children (8.9 % vs 0.7 %, p = 0.001). While, both uric acid (20.5 % vs 3.3 %, p < 0.0001) and magnesium ammonium phosphate (16.6 % vs 2.5 %, p < 0.0001) stones were more common in Uyghur. Interestingly, the significant differences in stone composition between the two groups were only observed in males. When the pediatric patients were further divided into three age groups which were 0-5, 6-12 and >12, the prevalence of calcium oxalate stones increased with age in both groups and was higher in Han children at each age level. The compositions of urinary stones were significantly different between Uyghur and Han children with urolithiasis, factors such as diet habit, life style, genetic diversity, environmental and medical conditions may all contribute to the variances.

Protein expression of urate transporters in renal tissue of patients with uric acid nephrolithiasis

URAT1 and GLUT9 are two primary urate transporters involved in the renal urate handling. Renal urate underexcretion was reported in uric acid stone formers (UASF) in previous clinical studies. The aim of this study was to investigate the clinical features and possible impact of protein expression of URAT1 and GLUT9 in renal tissues of patients with uric acid (UA) nephrolithiasis. 23 UASF, 27 patients with calcium oxalate (CaOx) stones, and 22 normal controls were enrolled in this study. Clinical data revealed that older age of onset, high plasma UA concentration, low urinary PH, and relative renal urate underexcretion were associated with UASF. By immunohistochemical or western blotting analysis, a significant increase in the relative expression quantity of URAT1 in renal tissue of UASF was found compared to patients with CaOx nephrolithiasis and normal controls. In conclusion, our results suggested that upregulated URAT1 protein expression might contribute to the relative urate underexcretion from the kidney of UASF.

Component analyses of urinary nanocrystallites of uric acid stone formers by combination of high-resolution transmission electron microscopy, fast Fourier transformation, energy dispersive X-ray spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy

This study aimed to analyse the components of nanocrystallites in urines of patients with uric acid (UA) stones. X-ray diffraction (XRD), Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy (HRTEM), fast Fourier transformation (FFT) of HRTEM, and energy dispersive X-ray spectroscopy (EDS) were performed to analyse the components of these nanocrystallites. XRD and FFT showed that the main component of urinary nanocrystallites was UA, which contains a small amount of calcium oxalate monohydrate and phosphates. EDS showed the characteristic absorption peaks of C, O, Ca and P. The formation of UA stones was closely related to a large number of UA nanocrystallites in urine. A combination of HRTEM, FFT, EDS and XRD analyses could be performed accurately to analyse the components of urinary nanocrystallites.

The association of metabolic syndrome and urolithiasis

There has been an increasing prevalence of kidney stones over the last 2 decades worldwide. Many studies have indicated a possible association between metabolic syndrome and kidney stone disease, particularly in overweight and obese patients. Many different definitions of metabolic syndrome have been suggested by various organizations, although the definition by the International Diabetes Federation (IDF) is universally considered as the most acceptable definition. The IDF definition revolves around 4 core components: obesity, dyslipidemia, hypertension, and diabetes mellitus. Several hypotheses have been proposed to explain the pathophysiology of urolithiasis resulting from metabolic syndrome, amongst which are the insulin resistance and Randall's plaque hypothesis. Similarly the pathophysiology of calcium and uric acid stone formation has been investigated to determine a connection between the two conditions. Studies have found many factors contributing to urolithiasis in patients suffering from metabolic syndrome, out of which obesity, overweight, and sedentary lifestyles have been identified as major etiological factors. Primary and secondary prevention methods therefore tend to revolve mainly around lifestyle improvements, including dietary and other preventive measures.

Use of the probability of stone formation (PSF) score to assess stone forming risk and treatment response in a cohort of Brazilian stone formers

INTRODUCTION

The aim was to confirm that PSF (probability of stone formation) changed appropriately following medical therapy on recurrent stone formers.

MATERIALS AND METHODS

Data were collected on 26 Brazilian stone-formers. A baseline 24-hour urine collection was performed prior to treatment. Details of the medical treatment initiated for stone-disease were recorded. A PSF calculation was performed on the 24 hour urine sample using the 7 urinary parameters required: voided volume, oxalate, calcium, urate, pH, citrate and magnesium. A repeat 24-hour urine sample was performed for PSF calculation after treatment. Comparison was made between the PSF scores before and during treatment.

RESULTS

At baseline, 20 of the 26 patients (77%) had a high PSF score (> 0.5). Of the 26 patients, 17 (65%) showed an overall reduction in their PSF profiles with a medical treatment regimen. Eleven patients (42%) changed from a high risk (PSF > 0.5) to a low risk (PSF < 0.5) and 6 patients reduced their risk score but did not change risk category. Six (23%) patients remained in a high risk category (> 0.5) during both assessments.

CONCLUSIONS

The PSF score reduced following medical treatment in the majority of patients in this cohort.

Characterisation of risk factors for stones in hyperuricosuric men attending a stone clinic

Hyperuricosuria is common among stone formers, but its significance is uncertain. To progress our understanding and target treatment, we need to identify and characterise patients with uniform underlying pathology. We aimed to identify hyperuricosuric patients with a primary defect in renal urate reabsorption (renal hyperuricosuria) and to look for associated risk factors for stones. We undertook a retrospective cross-sectional database study of 666 male stone formers attending the Southampton stone clinic. We estimated filtered urate from plasma urate and 24-h creatinine clearance, and the net percentage reabsorbed. 153 men had hyperuricosuria (urine urate >4.80 mmol/24 h); 513 had normouricosuria. Hyperuricosuric men filtered more urate (median 68.1 and 52.5 mmol/24 h) but the ranges overlapped. Thirty hyperuricosuric men with filtered urate below the median for normouricosuria were selected as the renal hyperuricosuria group. Their normal plasma urate and high urate clearance substantiated this classification. In comparison with 60 normouricosuric stone formers matched for filtration, they had a higher incidence of hypercalciuria (67 versus 40%), but similar, high, frequencies of hyperoxaluria (25 and 11%) and phosphaturia (40 and 27%).There were no differences in age at first stone, incidence of stone recurrence or positive family history (20 and 25%). The findings demonstrate multiple risk factors for stones in this subgroup. In comparison, the 30 hyperuricosuric men with the highest filtration had a higher incidence of hyperoxaluria (58%) but fewer (7%) had a positive family history. Creatinine clearance was raised in 73%. An excessive protein intake might be a major correctable factor underlying these abnormalities.

[Nephrolithiasis: metabolic defects and terapeutic implications]

Over the past 10 years, major progress has been made in the knowledge of urinary lithogenesis, including the potential pathogenetic role of Randall's plaques and renal tubular crystal retention. Urine supersaturation is the driving force of this process and can be induced by some risk factors, including low urine volume, high urinary excretion of calcium oxalate and uric acid and low urinary excretion of citrate. Primary hypercalciuria can be due to intestinal overabsorption renal leak and bone reabsorption of calcium. Prophilaxis is mainly conducted with thiazides and low calcium diet which is indicated only in the intestinal form. Primary hyperoxaluria is treated with pyridoxine and may require in the severe forms simultaneous renal and liver transplantation. Enteric hyperoxaluria is secondary to fatty acids malabsorption and requires diet, oral calcium and cholestiramine. Hyperuricosuria is caused by diet endogenous overproduction, mainly due to enzymatic defects or high renal excretion of uric acid. Urine alkalinization with K or K and Mg citrate can prevent stone formation even in idiopathic uric acid nephrolithiasis, in which a defect of urine acidification is supposed to be the main abnormality, and in hypocitraturic patients. Cystinuria is a rare inherited defect with an intense clinical impact. It can be classified in three forms and urinary stone formation is the role. Increased solubility and conversion of cystine in a more soluble form are the main goals of the prophylaxis which includes K citrate and thiol agents administration. Tiopronin is preferred to D-penicillamine due to its lower side effects.

Solubility of ammonium acid urate nephroliths from bottlenose dolphins (Tursiops truncatus)

Nephrolithiasis has been identified in managed populations of bottlenose dolphins (Tursiops truncatus); most of these nephroliths are composed of 100% ammonium acid urate (AAU). Several therapies are being investigated to treat and prevent nephrolithiasis in dolphins including the alkalization of urine for dissolution of nephroliths. This study evaluates the solubility of AAU nephroliths in a phosphate buffer, pH range 6.0-8.0, and in a carbonate-bicarbonate buffer, pH range 9.0-10.8. AAU nephroliths were obtained from six dolphins and solubility studies were conducted using reverse-phase high performance liquid chromatography with ultraviolet detection at 290 nm. AAU nephroliths were much more soluble in a carbonate-bicarbonate buffer, pH range 9.0-10.8 compared to phosphate buffer pH range 6.0-8.0. In the pH range 6.0-8.0, the solubility was 45% lower in potassium phosphate buffer compared to sodium phosphate buffer. When citrate was used along with phosphate in the same pH range, the solubility was improved by 13%. At pH 7 and pH 8, 150 mM ionic strength buffer was optimum for dissolution. In summary, adjustment of urinary pH alone does not appear to be a useful way to treat AAU stones in bottlenose dolphins. Better understanding of the pathophysiology of AAU nephrolithiasis in dolphins is needed to optimize kidney stone prevention and treatment.

Renal recoverability in infants with obstructive calcular anuria: is it better than in older children?

OBJECTIVE

Urolithiasis in infants can cause considerable morbidity. The literature regarding calcular anuria in this age group is very defective. Our aim was to evaluate impact of intervention on renal recoverability in these infants.

PATIENTS AND METHODS

A series of 24 patients presenting with obstructive calcular anuria were included in this study. Mean age was 16.5 ± 6.2 months. They were treated either by initial urinary diversion or definitive endoscopic (ureteroscopy or JJ stenting with medical alkalinization) or open surgical (ureterolithotomy or pyelolithotomy) treatment.

RESULTS

Mean serum creatinine was 5.8 ± 2.6 mg/dl. Initial peritoneal dialysis and/or urinary diversion was needed in 11 patients (45.8%). Open surgical treatment was applied in 5 (20.8%), endoscopic treatment was applied in 15 (62.5%), while combined treatment was applied in 4 (16.6%) patients. All patients had normal serum creatinine on discharge. Three (12.5%) had residual stones which were cleared by 2ry ureteroscopic intervention at 6 months. The overall complication rate in this study was 12.5% in the form of postoperative leakage (1) and postoperative fever (2). No mortality or development of chronic renal failure was reported at 6 months follow up. In comparison with these results, a previous study carried out in our centre on an older age group had a higher complication rate (28%) with higher mortalities and lower renal function recoverability rate (94%).

CONCLUSIONS

Appropriate and timely medical and surgical management of calcular anuria will mostly lead to full recovery of renal functions. In comparison with older children, renal prognosis in those less than 2 years seems more favorable.

Epidemiological gender-specific aspects in urolithiasis

PURPOSE

The incidence of urolithiasis is worldwide increasing and contributes to a rising economic and health care burden. The objective of this review is to identify gender differences in urolithiasis epidemiology in Europe and the USA as well as gender-specific risk factors for urolithiasis.

EVIDENCE ACQUISITION

A systematic review of the present literature was performed including English journals without a time limit. The MeSH terms used were as follows: ("Sex Characteristics"[Mesh]) AND "Urolithiasis"[Mesh] or ("Epidemiology"[Mesh]) AND "Urolithiasis"[Mesh]. Additionally, reference search of retrieved papers identified additional references. The MEDLINE database was searched.

EVIDENCE SYNTHESIS

The prevalence of urolithiasis is rising worldwide including both genders in different age groups. Especially women face an increase in prevalence in the USA. Overweight seems to be an important cause for this development. Additionally insulin resistance and hypertonia, conditions present in the metabolic syndrome complex, contribute to this phenomenon.

CONCLUSION

Stone prevalence across all age groups and both genders is increasing. Lifestyle changes along with increasing prevalence of obesity are key factors for this development. Female gender did significantly differ in the risk ratio of stone development in different variables including body mass index, hyperinsulinemia, and hypertension. It is important to inform the public on measures how to change lifestyle and dietary measures for preventing or lowering events of stone disease.