Uric acid nephrolithiasis: current concepts and controversies

Ceftriaxone-induced severe hemolytic anemia, renal calculi, and cholecystolithiasis in a 3-year-old child: a case report and literature review

Ceftriaxone is widely used in pediatric outpatient care for its efficacy against respiratory and digestive system infections, yet its increasing association with severe immune hemolytic reactions requires heightened vigilance from pediatricians. This report details a rare and severe case of ceftriaxone-induced severe immune hemolytic anemia (IHA), hemolytic crisis, myocardial injury, liver injury, renal calculi, and cholecystolithiasis in a previously healthy 3-year-old child. The child, treated for bronchitis, experienced sudden pallor, limb stiffness, and altered consciousness following the fifth day of ceftriaxone infusion, with hemoglobin (Hb) levels precipitously dropping to 21 g/L. Immediate cessation of ceftriaxone and the administration of oxygen therapy, blood transfusion, intravenous immunoglobulin (IVIG), and corticosteroids led to a gradual recovery. Despite initial improvements, the patient's condition necessitated extensive hospital care due to complications including myocardial injury, liver injury, renal calculi, and cholecystolithiasis. After a 12-day hospital stay and a 3-month follow-up, the child showed complete normalization of Hb and liver function and resolution of calculi. In children, ceftriaxone infusion may trigger severe, potentially fatal, hemolytic reactions. Pediatricians must promptly recognize symptoms such as pallor, limb stiffness, and unresponsiveness, indicative of ceftriaxone-induced severe IHA, and immediately discontinue the drug. Effective management includes timely blood transfusion, respiratory support, IVIG administration, and corticosteroids when necessary, along with rigorous vital signs monitoring. Continued vigilance is imperative, even after cessation of ceftriaxone, to promptly address any residual adverse effects.

Development and external validation of a machine learning-based model to classify uric acid stones in patients with kidney stones of Hounsfield units < 800

The correct diagnosis of uric acid (UA) stones has important clinical implications since patients with a high risk of perioperative morbidity may be spared surgical intervention and be offered alkalization therapy. We developed and validated a machine learning (ML)-based model to identify stones on computed tomography (CT) images and simultaneously classify UA stones from non-UA stones. An international, multicenter study was performed on 202 patients who received percutaneous nephrolithotomy for kidney stones with HU < 800. Data from 156 (77.2%) patients were used for model development, while data from 46 (22.8%) patients from a multinational institution were used for external validation. A total of 21,074 kidney and stone contour-annotated CT images were trained with the ResNet-18 Mask R-convolutional neural network algorithm. Finally, this model was concatenated with demographic and clinical data as a fully connected layer for stone classification. Our model was 100% sensitive in detecting kidney stones in each patient, and the delineation of kidney and stone contours was precise within clinically acceptable ranges. The development model provided an accuracy of 99.9%, with 100.0% sensitivity and 98.9% specificity, in distinguishing UA from non-UA stones. On external validation, the model performed with an accuracy of 97.1%, with 89.4% sensitivity and 98.6% specificity. SHAP plots revealed stone density, diabetes mellitus, and urinary pH as the most important features for classification. Our ML-based model accurately identified and delineated kidney stones and classified UA stones from non-UA stones with the highest predictive accuracy reported to date. Our model can be reliably used to select candidates for an earlier-directed alkalization therapy.

Association of urate-lowering drugs with the risk of future urolithiasis in patients with gout: A population-based nested case-control study

BACKGROUND

Patients with gout have an increased risk of urolithiasis and usually need urate-lowering therapy (ULT) for the prevention of disease progression. However, there is a paucity of clinical data regarding the risk of future urolithiasis in ULT users.

METHODS

This nested case-control study was performed using the Taiwan National Health Insurance Research Database. The aim of this study was to examine whether ULT (xanthine oxidase inhibitors [XOIs] or uricosuric agents) is associated with risk of future urolithiasis in patients with gout. Data were collected from January 2000 to December 2012.

RESULTS

This study included 2307 case patients and 2307 matched controls. Case patients had gout that developed into urolithiasis, and control patients had gout but were not diagnosed with urolithiasis during the study period. Patients had a mean age of 56.3 years at diagnosis of gout, and 83.2% were male patients. No association was detected between use of XOIs or uricosuric agents and risk of future urolithiasis. Furthermore, there was no significant difference in the risk of future urolithiasis in patients exposed to various cumulative days of XOI or uricosuric prescriptions.

CONCLUSION

The present study provides evidence that neither XOIs nor uricosuric agents are associated with risk of future urolithiasis in patients with gout. Before the availability of more clinical evidence, ensuring high fluid intake and prospective monitoring of urolithiasis development are still important for uricosuric agent users.

Recent advances on the mechanisms of kidney stone formation (Review)

Kidney stone disease is one of the oldest diseases known to medicine; however, the mechanisms of stone formation and development remain largely unclear. Over the past decades, a variety of theories and strategies have been developed and utilized in the surgical management of kidney stones, as a result of recent technological advances. Observations from the authors and other research groups suggest that there are five entirely different main mechanisms for kidney stone formation. Urinary supersaturation and crystallization are the driving force for intrarenal crystal precipitation. Randall's plaques are recognized as the origin of calcium oxalate stone formation. Sex hormones may be key players in the development of nephrolithiasis and may thus be potential targets for new drugs to suppress kidney stone formation. The microbiome, including urease-producing bacteria, nanobacteria and intestinal microbiota, is likely to have a profound effect on urological health, both positive and negative, owing to its metabolic output and other contributions. Lastly, the immune response, and particularly macrophage differentiation, play crucial roles in renal calcium oxalate crystal formation. In the present study, the current knowledge for each of these five aspects of kidney stone formation is reviewed. This knowledge may be used to explore novel research opportunities and improve the understanding of the initiation and development of kidney stones for urologists, nephrologists and primary care.

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.

The safety of ureteral stenting with the use of potassium citrate for management of renal uric acid stones

Objectives:

The objective is to evaluate the relative risks of ureteric stents application while managing uric acid stones with potassium citrate in terms of stone encrustations and urinary tract infection (UTI).

Patients and Methods:

We prospectively enrolled patients with renal uric acid stones who received K citrate from 2013 to 2018. Patient's demographics were collected. All patients were evaluated using noncontrast computed tomography (CT) scan to measure the stone size and density. JJ ureteric stent was inserted prior to the initiation of treatment. At follow-up, all patients underwent urine analysis for pH and to detect UTI. CT was repeated at 1 month and those patients who showed incomplete stone resolution underwent another course of treatment for another month. CT was repeated prior to stent removal. The presence of encrustations was inspected and collected.

Results:

We collected 59 patients with a median age of 36 years (18–73) and median stone burden of 26 mm³ (15–50). The median stone density was 310 HU (175–498). Twenty-one patients (35.6%) received K citrate treatment for 1-month, while the remaining patients had 2 months treatment. Sixteen patients (27.1%) had a complete stone dissolution, 41 patients (69.5%) had more than 50% decrease of stone burden while only 2 patients (3.4%) had stones with poor dissolution. Four patients (6.8%) experienced UTI while 2 patients (3.4%) had visible JJ encrustations. Most of these complications occurred when the treatment was offered for the 2^nd month.

Conclusion:

Short-term use of ureteral stents is safe during the management of uric acid stones with K citrate.

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.

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.

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.

[DRUG-INDUCED BILATERAL NEPHROLITHIASIS IN AN ULCERATIVE COLITIS PATIENT: A CASE REPORT]

A 59-year-old female experienced gross hematuria and right back pain, and she visited our hospital in March 2015. Abdominal computed tomography (CT) showed bilateral renal pelvic calculi; the right stone was 15 mm and the left stone was 18 mm in diameter. She had ulcerative colitis and had been taking salazosulfapyridine (SASP) for about 30 years. Urinalysis showed aciduria and deposition of urate crystals. An abdominal X-ray picture did not show a calculus shadow. We suspected uric acid calculus and started treatment with urinary alkalizer and uric acid production inhibitor.Three months later, abdominal CT showed enlargement of the bilateral renal pelvic calculi; the right stone was 25 mm and the left stone was 24 mm in diameter. She also complained of worse right back pain and underwent transurethral ureterolithotripsy for the right renal pelvic stone. The stone was orange, comparatively soft, and chipped down until it was approximately half of its original size. The stone analysis suggested suspected drug-induced urolithiasis, but not uric acid calculus. Thus, we investigated the stone and SASP using infrared spectroscopy, and the infrared absorption pattern was similar in both. The stone analysis demonstrated drug-induced urolithiasis induced by SASP.The patient's ulcerative colitis therapy was switched to mesalazine, and the amount of urinary alkalizer was increased. Abdominal CT 3 months thereafter showed dissipation of bilateral renal pelvic calculi. The patient did not take any preventative medication, and there was no recurrence of urolithiasis.

Diagnosis and management of non-calcium-containing stones in the pediatric population

Compared to adults, urolithiasis is less common in children, with a definite rise in incidence, especially among young adults (Tasian et al. in Clin J Am Soc Nephrol 11:488, 2016). In the last 25 years, the incidence in children has increased by approximately 6-10% annually, for reasons still unknown, with an associated significant increase in related health care-related expenditures (Hyams and Matlaga in Transl Androl Urol 3(3):278-83, 2014). It has been shown that there is twice as high a risk of chronic kidney disease (CKD) or end stage renal disease (ESRD) in stone formers compared to non-stone formers (Tasian et al. 2016). While calcium-containing stones are by far the most common category of stone encountered in both children and adults, non-calcium stones are more common in children than adults and have been shown in several studies to be associated with greater morbidity and lower renal function than calcium stones (Issler et al. in BMC Nephrol 18(1):136, 2017; Gambaro et al. in J Urol 198:268-273, 2017). This could be related to the challenges in the management of non-calcium-containing stones due to associated infection or metabolic derangements, further leading to recurrence and loss of renal function. There is currently a gap in our understanding of how to appropriately and effectively encounter and manage patients with non-calcium-containing stones, as such cases are encountered less frequently. Identification of stone composition and appropriate management is very important to reduce serious complications and recurrence, especially in non-calcium stones. We present a review of diagnosis and management of non-calcium-containing stones in the pediatric population, in hopes of providing more clarity to providers and promoting a consideration of non-calcium stone composition with all children presenting with urolithiasis.

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.

Stone Composition Among First-Time Symptomatic Kidney Stone Formers in the Community

OBJECTIVE

To determine the variation in kidney stone composition and its association with risk factors and recurrence among first-time stone formers in the general population.

PATIENTS AND METHODS

Medical records were manually reviewed and validated for symptomatic kidney stone episodes among Olmsted County, Minnesota, residents from January 1, 1984, through December 31, 2012. Clinical and laboratory characteristics and the risk of symptomatic recurrence were compared between stone compositions.

RESULTS

There were 2961 validated first-time symptomatic kidney stone formers. Stone composition analysis was obtained in 1508 (51%) at the first episode. Stone formers were divided into the following mutually exclusive groups: any brushite (0.9%), any struvite (0.9%), any uric acid (4.8%), and majority calcium oxalate (76%) or majority hydroxyapatite (18%). Stone composition varied with clinical characteristics. A multivariable model had a 69% probability of correctly estimating stone composition but assuming calcium oxalate monohydrate stone was correct 65% of the time. Symptomatic recurrence at 10 years was approximately 50% for brushite, struvite, and uric acid but approximately 30% for calcium oxalate and hydroxyapatite stones (P<.001). Recurrence was similar across different proportions of calcium oxalate and hydroxyapatite (P for trend=.10). However, among calcium oxalate stones, 10-year recurrence rate ranged from 38% for 100% calcium oxalate dihydrate to 26% for 100% calcium oxalate monohydrate (P for trend=.007).

CONCLUSION

Calcium stones are more common (93.5% of stone formers) than has been previously reported. Although clinical and laboratory factors associate with the stone composition, they are of limited utility for estimating stone composition. Rarer stone compositions are more likely to recur.

Endoscopic and histologic findings in a cohort of uric acid and calcium oxalate stone formers

OBJECTIVE

To characterize the endoscopic and histologic renal papillary lesions in a cohort of uric acid (UA) stone formers (SF).

METHODS

Data were prospectively obtained during percutaneous nephrolithotomy between 2009 and 2013. Renal papillae were endoscopically analyzed to quantitate surface area occupied by plaque or plug, and biopsies were obtained. UA SF were compared with non-SF controls and patients with >50% calcium oxalate (CaOx) in the absence of UA.

RESULTS

There were 23 UA SF; of which 19 stones (83%) were admixed with CaOx and 4 (17%) were pure. Compared with CaOx SF and controls, UA SF had a higher prevalence of diabetes and obesity, greater serum creatinine and UA levels, lower estimated glomerular filtration rate and urine pH, and elevated UA supersaturation. Characteristics of UA SF were compared with 95 CaOx SF and 19 controls. Overall, 23 (100%) UA SF had endoscopic plaque and 13 (57%) plugs. Endoscopically, UA SF displayed a greater incidence of plugging (57% vs 45% vs 11%; P = .006) relative to CaOx SF and controls. Likewise, UA SF had a greater percentage surface area of plugging (0.1 vs 0.0; P = .002) and plaque (2.0 vs 0.9; P = .006) than controls but similar amounts to CaOx SF. Histologic plugs were similar in UA and CaOx SF, although CaOx SF demonstrated greater interstitial inflammation on endoscopic biopsy.

CONCLUSION

UA and CaOx SF have similar amounts of plaque, whereas UA SF have more endoscopic but not histologic collecting duct plugs. These data suggest an overlap between the pathogenesis of UA and CaOx stones. The anchoring site for UA stones remains uncertain.

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.

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.

FT-IR analysis of urinary stones: a helpful tool for clinician comparison with the chemical spot test

Background. Kidney stones are a common illness with multifactorial etiopathogenesis. The determination of crystalline and molecular composition and the quantification of all stone components are important to establish the etiology of stones disease but it is often laborious to obtain using the chemical method. The aim of this paper is to compare chemical spot test with FT-IR spectroscopy, for a possible introduction in our laboratory. Methods. We analyzed 48 calculi using Urinary Calculi Analysis kit in accordance with the manufacturer's instructions. The same samples were analyzed by FT-IR using the Perkin Elmer Spectrum One FT-IR Spectrometer. All FT-IR spectra of kidney stones were then computer matched against a library of spectra to generate a report on the various components. Results. On the basis of FT-IR analysis, the 48 calculi were divided into three groups: pure stone, mixed stone, and pure stone with substances in trace. Results of each group were compared with those obtained with chemical spot test. A general disagreement between methods was observed. Conclusions. According to our data, the introduction of the FT-IR technique in clinical chemistry laboratory may be more responsive to clinician expectations.

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.

Kidney stones: an update on current pharmacological management and future directions

INTRODUCTION

Kidney stones are a common problem worldwide with substantial morbidities and economic costs. Medical therapy reduces stone recurrence significantly. Much progress has been made in the last several decades in improving therapy of stone disease.

AREAS COVERED

This review discusses i) the effect of medical expulsive therapy on spontaneous stone passage, ii) pharmacotherapy in the prevention of stone recurrence and iii) future directions in the treatment of kidney stone disease.

EXPERT OPINION

Fluid intake to promote urine volume of at least 2.5 L each day is essential to prevent stone formation. Dietary recommendations should be adjusted based on individual metabolic abnormalities. Properly dosed thiazide treatment is the standard therapy for calcium stone formers with idiopathic hypercalciuria. Potassium alkali therapy is considered for hypocitraturia, but caution should be taken to prevent potential risk of calcium phosphate stone formation. For absorptive hyperoxaluria, low oxalate diet and increased dietary calcium intake are recommended. Pyridoxine has been shown effective in some cases of primary hyperoxaluria type I. Allopurinol is used in calcium oxalate stone formers with hyperuricosuria. Treatment of cystine stones remains challenging. Tiopronin can be used if urinary alkalinization and adequate fluid intake are insufficient. For struvite stones, complete surgical removal coupled with appropriate antibiotic therapy is necessary.

Magnetic rotations of uric acid crystals and uratic crystals by static magnetic fields of up to 500 mT

In recent years, the disease concerning ureteral calculus is increasing possibly due to the changing lifestyles. For example, it is well known that the urinary calculi have a large impact to gout. As eating habitual diseases, gout and the hyper-uricemia are related to the formation of urinary calculus. In the previous studies, therapeutic agents were developed to enhance the uric acid excretion. From the viewpoint of side effects induction by the chemical agents, we are motivated to explore an alternative method to control the formation of ureteral crystals stimulator by physical stimulations. Therefore in the present study, we focused on the behaviors of uric acid crystals under magnetic fields of several hundreds of mT (Tesla). The uric acid crystals were re-crystallized from a suspension of uric acid powder, and the micro-crystals were prepared to be floating in the solution. We generated horizontal magnetic fields of maximum 500 mT by an electromagnet which contained a CCD microscope. A permanent magnet with magnetic fields of 200∼400 mT was also utilized. During the magnetic fields were applied to the uric acid crystals, we observed that the uric acid crystals were oriented by the magnetic fields down to 200 mT at the room temperature. It was speculated that the dimagnetic anisotropy in the uric acid crystals exhibited the rotational responses. The results indicate the possible remote control of the uric acid crystals in living body by the magnetic fields of 200 mT to 500 mT.

[Recurrence prevention of kidney stone disease]

In each urolithiasis patient the individual risk for recurrence determines the need for specific medical treatment. Therefore, a brief evaluation of the risk status after stone passage is mandatory to define patients at high risk for recurrence. Only one quarter of all urolithiasis patients are at high risk or suffer from severe metabolic disorders, which both demand further metabolic work-up prior to medical therapy. However, the other three quarters benefit sufficiently from general preventive measures, such as high fluid intake, well-balanced mixed diet and lifestyle changes. This article summarizes the recent recommendations for stone-specific recurrence prevention, discusses the different pharmacological treatment options and sketches the follow-up concept for high risk patients with ongoing medication.

Overweight, insulin resistance and blood pressure (parameters of the metabolic syndrome) in uric acid urolithiasis

Overweight, arterial hypertension and disturbances of the carbohydrate metabolism are important parameters of the metabolic syndrome (MS). The most important factor regarding renal pathophysiology is insulin resistance resulting in alterations of urine acidification and low urine pH. Since low urine pH is the main risk factor for uric acid urolithiasis (UAU), UAU may be regarded as a renal manifestation of the MS. So far, there are only few data on the prevalence of parameters of the MS in UAU patients especially with regard to the severity of the disease and recurrence rate, respectively. The objective of this study was to know more about the prevalence of different parameters of the MS and their importance for the natural history of this type of renal stone disease using a total number of 167 consecutive patients with pure UA stones. Stone analysis was performed by polarization microscopy and X-ray diffraction. The following parameters were measured: age, sex, systolic and diastolic arterial blood pressure (RRs and RRd), number of stone episodes, diabetes mellitus (DM); serum: creatinine, calcium, sodium, potassium, uric acid, glucose; urine: pH-profiles, citrate, calcium, uric acid, ammonia, urea, and creatinine. The following results were obtained (means ± standard deviations): age 61 ± 13 years, BMI 30 ± 6 kg/m(2), BP 147/84 ± 22/13 mmHg, number of stone episodes 1.8 ± 1.2, DM 32%; serum: creatinine 1.3 ± 0.6 mg/dl, glucose 136 ± 52 mg/dl, UA 6.3 ± 1.8 mg/dl, calcium 2.4 ± 1.3 mmol/l, sodium 134 ± 18 mmol/l, potassium 4.1 ± 0.4 mmol/l; urine: pH 5.87 ± 0.27, volume 2.4 ± 1.1 l/d, calcium 3.5 ± 2.5 mmol/d, UA 3.9 ± 2.4 mmol/d, citrate 1.3 ± 1.1 mmol/d, ammonia 41 ± 26 mmol/d, urea 390 ± 176 mmol/d. A significant positive correlation could be found for BMI and urea excretion, BMI correlated negatively with RRs and RRd. There was no significant correlation between BMI, urine pH, citrate, ammonia and UA in serum and urine. Undue acidity and hyperuricosuria were found in two-thirds of the UAU patients, increased urea excretion and decreased excretion of ammonia in less than 25%, Hyperuricemia in 37%. There was no significant correlation between the number of stone episodes and any other parameter studied. Overweight, arterial hypertension and DM as parameters of the MS are frequent in many patients with UAU. However, these parameters do explain the pathogenesis in two-thirds of the patients. The severity of the disease and the recurrence are not influenced by the presence of these metabolic parameters. Therefore, MS is no prognostic factor in UAU.

Melamine-induced infant urinary calculi: a report on 24 cases and a 1-year follow-up

Melamine has been the main factor leading to infant urinary calculi occurring on a rather wide scale in China in 2008, which were the results of a rapid aggradation of metabolites such as cyanuric acid diamide, cyanuric acid, etc., causing uric acid stone to accumulate. Here, we present a report on 24 infants who were admitted to our department, their ages ranging from 3 to 10 months. All of these infants had a confirmed history of having been fed with the "Sanlu" brand milk powder, which contained excessive levels of melamine, with the highest being 2,563 mg/kg. The diagnosis, medical treatment and follow-up by ultrasonography at 1, 3, 6, 12 months were reported. 22 cases of these infants were rehabilitated after medical treatment and 1 infant underwent pyelolithotomy for relieving an obvious ureter obstruction. No recurrence was found in these babies thereafter. Another infant died from rapidly worsening renal failure. Therefore, this series of cases have demonstrated that melamine contained in the "Sanlu" milk powder was the main cause of these urinary stones. Urine alkalinization and stone liberalization were the most effective treatments. Fast diagnosis and treatment of acute obstructive urolithiasis may prevent the development of acute renal failure, which is associated with high morbidity and mortality rates.

Gout--current diagnosis and treatment

BACKGROUND

Because of the changing dietary habits of an aging population, hyperuricemia is frequently found in combination with other metabolic disorders. Longstanding elevation of the serum uric acid level can lead to the deposition of monosodium urate crystals, causing gout (arthritis, urate nephropathy, tophi). In Germany, the prevalence of gouty arthritis is estimated at 1.4%, higher than that of rheumatoid arthritis. There are no German guidelines to date for the treatment of gout. Its current treatment is based largely on expert opinion.

METHODS

Selective literature review on the diagnosis and treatment of gout.

RESULTS AND CONCLUSIONS

Asymptomatic hyperuricemia is generally not an indication for pharmacological intervention to lower the uric acid level. When gout is clinically manifest, however, acute treatment of gouty arthritis should be followed by determination of the cause of hyperuricemia, and long-term treatment to lower the uric acid level is usually necessary. The goal of treatment is to diminish the body's stores of uric acid crystal deposits (the intrinsic uric acid pool) and thereby to prevent the inflammatory processes that they cause, which lead to structural alterations. In the long term, serum uric acid levels should be kept below 360 micromol/L (6 mg/dL). The available medications for this purpose are allopurinol and various uricosuric agents, e.g., benzbromarone. There is good evidence to support the treatment of gouty attacks by the timely, short-term use of non-steroidal anti-inflammatory drugs (NSAID), colchicine, and glucocorticosteroids.

[Evidence-based pharmacological metaphylaxis of stone disease]

Approximately one-fourth of urolithiasis patients are at high risk for recurrent stone formation or severe metabolic disturbances. These patients need specific metaphylaxis for effective stone prevention, adjusted to their individual metabolic risk. Recent recommendations for the pharmacological treatment of stone diseases are summarized in this article. For the different treatment options, evidence from the literature was assessed. In addition, a follow-up concept for pharmacologically treated high-risk stone formers is discussed.

Influence of body size on urinary stone composition in men and women

A larger body size has been shown to be associated with increased excretion of urinary lithogenic solutes, and an increased risk of nephrolithiasis has been reported in overweight patients. However, the type of stones produced in these subjects has not been ascertained. Based on a large series of calculi, we examined the relationship between body size and the composition of stones, in order to assess which type of stone is predominantly favoured by overweight. Among 18,845 consecutive calculi referred to our laboratory, 2,100 came from adults with recorded body height and weight. Excluding calculi from patients with diabetes mellitus, as well as struvite and cystine stones, the study material consisted of 1,931 calcium or uric acid calculi. All calculi were analysed by infrared spectroscopy and categorized according to their main component. Body mass index (BMI) values were stratified as normal BMI (< 25 kg/m2), overweight (BMI 25-29.9) or obese (BMI > or = 30). Overall, 27.1% of male and 19.6% of female stone formers were overweight, and 8.4 and 13.5% were obese, respectively. In males, the proportion of calcium stones was lower in overweight and obese groups than in normal BMI group, whereas the proportion of uric acid stones gradually increased with BMI, from 7.1% in normal BMI to 28.7% in obese subjects (P<0.0001). The same was true in females, with a proportion of uric acid stones rising from 6.1% in normal BMI to 17.1% in obese patients (P=0.003). In addition, the proportion of uric acid stones markedly rose with age in both genders (P<0.0001). The average BMI value was significantly higher in uric acid stone formers aged < 60 years than in all other groups, whereas it did not differ from other groups in those aged > or = 60 years. Stepwise regression analysis identified BMI and age as significant, independent covariates associated with the risk of uric acid stones. Our data provide evidence that overweight is associated with a high proportion of uric acid stones in patients less than 60 years of age, whereas beyond this limit, advancing age is the main risk factor.

Diagnosis and metaphylaxis of stone disease. Consensus concept of the National Working Committee on Stone Disease for the upcoming German Urolithiasis Guideline

This review draws the recent state of the art in metabolic diagnosis and metaphylaxis of stone disease. It is the basis for the consensus approval with the other medical societies and institutions in Germany involved in the guideline process of the new "Urolithiasis Guideline". The German Working Committee on Stone Disease reviewed critically the current literature in the field of urolithiasis-including the existing German and EAU-Guidelines as well as the Conference Book of the First International Consultation on Stone Disease. As far as possible the references were rated according to the EBM criteria. On this basis the expert group discussed all pathways and statements regarding the management of stone disease. The present review coincides with the consented guideline draft of the German Working Committee on Stone Disease. Occurrence of stone disease in the western world increases seriously. Modern lifestyle, dietary habits and overweight-problems of the affluent societies-emerge to be the important promoters of the "stone-boom" in the new millennium. This even affects children, whose stone prevalence is otherwise significantly less than that of adults. Criteria for the high risk group of stone formers were clearly defined. A diagnostic standard is formulated for the basic and the elaborate metabolic evaluation of a stone patient. Approximately 75% of all stone patients could anticipate stone recurrence with elementary reorientation of their lifestyle and dietary habits, summarized as general metaphylaxis. About 25% of the stone formers require additional pharmacological intervention to normalize their individual biochemical risk, precisely compiled for each stone type as specific metaphylaxis.

Methylated purines in urinary stones

BACKGROUND

The aim of the study was to measure the content of methylated purines that appear as admixtures in uric acid stones.

METHODS

We analyzed urinary calculi from 48 residents of Western Pomerania who underwent surgery at the urology ward in Szczecin. Stone samples were dissolved in 0.1 mol/L NaOH. Extracts were diluted in 50 mmol/L KH(2)PO(4) and analyzed by reversed-phase HPLC with ultraviolet detection and use of a gradient of methanol concentration and pH.

RESULTS

Uric acid was the main component of 9 stones. All 9 showed admixtures of 9 other purine derivatives: endogenous purine breakdown products (xanthine, hypoxanthine, and 2,8-dihydroxyadenine) and exogenous methyl derivatives of uric acid and xanthine (1-, 3-, and 7-methyluric acid; 1,3-dimethyluric acid; and 3- and 7-methylxanthine). Amounts of these purine derivatives ranged from the limit of detection to 12 mg/g of stone weight and showed a strong positive correlation (Spearman rank correlation coefficients, 0.63-0.94) with the uric acid content of the samples. The main methylated purine in the stones was 1-methyluric acid.

CONCLUSIONS

Urinary purines at concentrations below their saturation limits may coprecipitate in samples supersaturated with uric acid and appear as admixtures in urinary stones. The amount of each purine depends on its average urinary excretion, similarity to the chemical structure of uric acid, and concentration of the latter in the stone. These findings suggest that purines in stones represent a substitutional solid solution with uric acid as solvent. Methylxanthines, which are ubiquitous components of the diet, drugs, and uric acid calculi, may be involved in the pathogenesis of urolithiasis.

ACP Best Practice No 181: Chemical pathology clinical investigation and management of nephrolithiasis

Renal stones have afflicted humans for millennia but there is still no solution to this problem. This review discusses the laboratory and metabolic aspects of the clinical management of patients with renal stones, both primary and secondary in origin. First, non-pharmacological interventions such as increased fluid intake, decreased protein consumption, dietary changes in sodium, calcium, oxalate, potassium, purine, vitamins, and essential fatty acids are considered. Then specific pharmacological treatment to modify urine calcium, oxalate, urate, citrate, and acidity are considered. Finally, more unusual types of stone are examined.

Uric acid stones following hepatic transplantation

We report the case of a 52 year old man with a history of insulin-requiring diabetes and hepatitis B with cirrhosis who received an orthotopic liver transplant. One year later he developed renal colic and was found to have a 3 mm stone at the left ureterovesical junction. Numerous other stones formed and infrared spectroscopy analysis demonstrated all to be composed of 100% uric acid. Urine collections demonstrated a low urine pH of 5.1 without hyperuricosuria. His stones were effectively prevented with potassium citrate therapy. Few incidence data are available for uric acid stone occurrence in solid organ recipients. Calcineurin inhibitors are thought to often cause hyperuricemia on the basis of decreased urate excretion. However, this effect would not be expected to cause hyperuricosuria nor uric acid stones. This class of drugs may also be associated with low urine pH, perhaps on the basis of hypoaldosteronism, but the contribution of such a syndrome to uric acid stone formation is not established.