Temporal trends in the incidence of kidney stone disease. Kidney Int. 2013;83:146-152. [PMID: 22992468 DOI: 10.1038/ki.2012.320]

Polyfluoroalkyl chemicals and the risk of kidney stones in US adults: A population-based study

The potential nephrotoxicity of polyfluoroalkyl chemicals (PFCs) have received extensive attention. However, the relationship between PFCs and the risk of kidney stones remain unclear. This study aimed to examine the level of PFCs in the US population and its relationship with the risk of kidney stones. We investigated the serum levels of six PFCs in 8453 adult participants (≥20 years) from the National Health and Nutrition Examination Survey (NHANES) between 2007 and 2016, including perfluorodecanoic acid (PFDE), perfluorohexane sulfonic acid (PFHS), 2-(N-methyl-perfluorooctane sulfonamido) acetate (MPAH), perfluorononanoic acid (PFNA), perfluoroundecanoic acid (PFUA), and perfluorododecanoic acid (PFDO). Logistic regression model was used to evaluate the correlation between PFCs and kidney stones. Of the 8453 participants, 787 self-reported a history of kidney stones. After adjusting for gender, age, race, education, marital status, body mass index (BMI), hypertension, diabetes and estimated glomerular filtration rate (eGFR), we found that total PFCs and PFHS were positively correlated with the risk of kidney stones. Compared with the lowest tertile, the odds ratios with 95% confidence intervals (CI) with increasing tertiles were 1.30 (95% CI,1.08-1.59, p = 0.007) and 1.25 (95 CI%,1.00-1.52, p = 0.024) for total PFCs and 1.24 (95 CI%,1.03-1.51, p = 0.032), and 1.35 (95 CI,1.10-1.68, p = 0.005) for PFHS. Our study shows that total PFCs and PFHS were associated with an increased risk of kidney stones.

Microbiological Features and Clinical Factors Associated with Empirical Antibiotic Resistance in Febrile Patients with Upper Urinary Tract Calculi

BACKGROUND

To investigate the clinical and microbiological features of febrile patients with upper urinary tract calculi and factors that affect empirical antibiotic resistance.

METHODS

A retrospective analysis was performed on 203 febrile patients hospitalized between January 2011 and December 2016 with antibiotic treatment for urinary tract infections and upper urinary tract calculi at three institutions. We collected and analyzed data, including patients' age, sex, body mass index, underlying diseases, stone-related factors, and the results of urine and blood culture examinations and antibiotic sensitivity tests.

RESULTS

The male-to-female ratio was 1:2.3. Bacteria were identified in 152 of the 203 patients (74.9%). The most commonly cultured microorganisms included Escherichia coli (44.1%), followed by Enterococci spp. (11.8%), Proteus spp. (8.6%), Streptococcus agalactiae (6.6%), Klebsiella spp. (5.3%), Pseudomonas spp. (4.6%), coagulase-negative Staphylococcus (4.0%), Staphylococcus epidermidis (4.0%), Serratia spp. (2.6%), Enterobacter spp. (0.7%), Acinetobacter spp. (0.7%), and mixed infections (7.2%). Cultured bacterial species showed sex-specific differences. Multivariate analysis revealed that calculi's multiplicity was an independent predictive factor for quinolone resistance (P = 0.008). Recurrent infections were a significant predictor of cefotaxime resistance during multivariable analysis (P = 0.041).

CONCLUSION

Based on the present study results, quinolone was not recommended as the empirical treatment in febrile patients with upper urinary tract calculi. Combination antibiotic therapy is recommended in cases of recurrent infections due to the possible occurrence of cefotaxime resistance.

Relationship between urine specific gravity and the prevalence rate of kidney stone

Background

The purpose of this study was to evaluate the relationship between urine specific gravity (USG) and the prevalence rate of kidney stone.

Methods

We conducted a cross-sectional study of adult participants (≥20 years) of the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2008. The USG was divided into three groups: <1.008, 1.008-1.020 and >1.020. Univariate and multivariate logistic regression analysis was used to determine the effect of USG on the prevalence rate of kidney stone.

Results

A total of 4,791 patients were included in this study, of which 464 (9.7%) reported a history of kidney stone. Univariate logistic regression analysis showed that age, gender, race, hypertension, diabetes, body mass index (BMI), estimated glomerular filtration rate (eGFR), USG and urine creatinine were closely related to the prevalence of kidney stones. After adjusting for known confounding factors, multivariate logistic regression showed that the prevalence rate of kidney stone increased with the increase of USG (1.008-1.020 vs. <1.008, OR =1.31, 95% CI, 0.09-1.91, P=0.155; >1.020 vs. <1.008, OR =1.71, 95% CI, 1.16-2.54, P=0.007).

Conclusions

The increase of USG was significantly correlated with self-reported kidney stone. This finding helps to identify risk factors for kidney stones as early as possible in the United States.

Urolithiasis in second-generation immigrant children younger than 18 years of age in Sweden

AIM

To compare incidence of urolithiasis in second-generation immigrant children aged 0-17 years to children of Swedish-born parents.

METHODS

A nationwide study of individuals residing in Sweden. Urolithiasis was defined as having at least one registered diagnosis of urolithiasis in the Swedish National Patient Register between January 1, 1998 and December 31, 2015. Cox regression analysis was used to estimate the relative risk (hazard ratios (HR) with 95% confidence intervals (CI)) of incident urolithiasis compared to individuals with Swedish-born parents. The models were stratified by sex and adjusted for age, co-morbidities and sociodemographic status of parents.

RESULTS

Totally, 1653 incident cases of urolithiasis were registered, 658 boys and 995 girls, with a mean annual incidence per 100 000 person-years for children with Swedish-born parents of 4.0 (95% CI 3.7-4.3) in boys and 6.7 (95% CI 6.2-7.2) in girls, and for children with foreign-born parents of 5.3 (95% CI 5.1-5.4) in boys and 7.2 (95% CI 6.9-7.4) in girls. The fully adjusted HRs of urolithiasis in second-generation immigrants were non-significant, in boys (1.20, 95% CI 0.99-1.46) and girls (0.95, 95% CI 0.80-1.12).

CONCLUSION

The risk of urolithiasis in second-generation immigrants was not significantly different from that of children with Swedish-born parents.

Preliminary study of prevalence of urolithiasis in North-Eastern city of India

Introduction:

Urinary tract stone is one of the major urological problems globally and has changed significantly in the last few decades. The epidemiology differs according to geography, socioeconomic status, and diet. The primary care physicians are initially consulted rather than urologists because of increase in the prevalence of urolithiasis and saturation of health facilities.

Objectives:

To study the prevalence of urolithiasis in the urology department of a tertiary care centre, Manipur, India.

Methods:

A total 621 patients of urolithiasis were studied. After history and physical examination of each patient, urolithiasis was confirmed by X-ray Kidney Ureter Bladder (KUB) or Ultrasound (USG) KUB.

Results:

The male to female ratio was 1.01:1. 30.8% patients came from Imphal West district. 63.1% of studied population had single stone and commonly seen in the 31–40 years of age, whereas multiple stones (n = 59) were found most commonly in the 41–50 years of age group. The difference of number of stones according to age group was statistically significant (P = 0.000). The most common location of stones was in kidneys (67.4%) and stones in urethra were the least common (P = 0.000).

Conclusion:

In this preliminary study, we report the prevalence of urolithiasis in Manipur, India. The better understanding of the epidemiology of urolithiasis is important to plan the effective treatment and prevention strategies in general practice. There is a shift in gender distribution of urolithiasis. Aging demographics, number of stones, obesity; all were associated with increased prevalence of urolithiasis.

Development of a Portable Multi-Sensor Urine Test and Data Collection Platform for Risk Assessment of Kidney Stone Formation

In this paper, we present an Internet of things (IoT)-based data collection system for the risk assessment of urinary stone formation, or urolithiasis, by the measurement and storage of four parameters in urine: pH, concentrations of ionized calcium (Ca2+), uric acid and total dissolved solids. The measurements collected by the system from patients and healthy individuals grouped by age and gender will be stored in a cloud database. These will be used in the training phase of an artificial intelligence (AI) machine learning process utilizing the logistics regression model. The trained model provides a binary risk assessment, indicating if the end user is either a stone-former or not. For system validation, standard chemical solutions were used. Preliminary results indicated a sufficient measurement range, falling within the physiological range, and resolution for pH (2.0–10.0, +/−0.1), Ca2+(0.1–3.0 mmol/l, +/−0.05), uric acid (20–500 ppm, +/−1) and conductivity (1.0–40.0 mS/cm, +/−0.1), exhibiting high correlation with standard instruments. We intend to deploy this system in few hospitals in Taiwan to collect the data of patients’ urine, with analysis aided by urologist assessments for the risk of urolithiasis. The modularized design allows future modification and expansion to accommodate other sensing analytes.

Risk factors for urinary stone

Urolithiasis is one of the most common urologic diseases in Korea. The annual incidence of urolithiasis in Korea has increased over time. Understanding the epidemiology and risk factors for urolithiasis is essential for patient care and prevention. The purpose of this review was to summarize the recent literature regarding the risk factors for urolithiasis. The available Korean-population-based trials were enrolled in this study. The peak incidence age was the fifth to sixth decades in Korea. There has been a persistent male predominance in the prevalence and incidence of stone disease. The gender gap has continuously narrowed over the world. Climate and seasonal variations, such as temperature and humidity, have a profound effect on the development of urolithiasis. Various dietary factors, including calcium, sodium, animal protein, and oxalate, play an important role in the development of urolithiasis. Dehydration is a wellknown risk factor for stone disease. Many metabolic diseases can affect urolithiasis, including obesity, hypertension, diabetes, gout, and metabolic syndrome. The fast-moving super-aged society and global warming can increase stone disease burden in the near future. To prevent and reduce stone diseases, clinicians should understand the risk factors affecting stone formation.

Genetic polymorphisms in CLDN14 (rs219780) and ALP (rs1256328) genes are associated with risk of nephrolithiasis in Egyptian children

OBJECTIVE

Nephrolithiasis results from metabolic and anatomic abnormalities together with genetic factors. Claudin 14 (CLDN14) is a protein that regulates the passage of small solutes through the kidneys. Alkaline phosphatase (ALPL) hydrolyzes the pyrophosphate to free phosphate, proposing its enabling role in nephrolithiasis development. Solute carrier family 13 member 2 (SLC13A2) encodes Na+-Pi cotransporter 2a, which is responsible for the renal absorption of phosphate. We aimed to detect the association between CLDN14, ALPL, and SLC13A2 genetic variants and susceptibility to nephrolithiasis in the Egyptian pediatric population.

MATERIAL AND METHODS

We enrolled 204 consecutive pediatric patients with nephrolithiasis, and 126 normal individuals served as controls. Real-time polymerase chain reaction analysis of CLDN14 rs219780, ALPL rs1256328, and SLC34A1 rs11746443 single-nucleotide polymorphisms (SNPs) was performed.

RESULTS

We found that individuals carrying the T allele of CLDN14 rs219780 and ALPL rs1256328 SNPs had a significantly higher risk of nephrolithiasis than the controls (p=0.001 and 0.001, respectively). Genetic association analyses identified that CLDN14 rs219780 and ALPL rs1256328SNPs were significantly associated with the nephrolithiasis status (odds ratio [OR] =4.51; 95% confidence interval [CI]=2.758-7.374; p=0.001 and OR=6.088; 95% CI=3.651-10.152; p=0.001, respectively). The sequence variant ALPL rs1256328 T allele had a significant correlation with the increased serum alkaline phosphatase levels in children with nephrolithiasis (p=0.02). No significant association was found between SLC34A1 rs11746443 SNP and the risk of nephrolithiasis (p=0.5).

CONCLUSION

CLDN14 rs219780 and ALPL rs1256328 SNPs might raise the risk of nephrolithiasis in Egyptian children, and might be used as genetic markers in these patients.

Oxalobacter formigenes reduce the risk of kidney stones in patients exposed to oral antibiotics: a case-control study

This is the first prospective study to investigate the association between kidney stones, bone mineral density, serum testosterone, colon cancer and O. formigenes colonization. 40 kidney stone patients and 85 controls were enrolled. O. formigenes colonization was established. BMD was examined from T- and Z-scores using dual energy absorptiometry. O. formigenes was found in 28 of 40 cases and 80 of 85 controls. BMD was significantly reduced in patients (p < 0.05). The evaluation revealed a significant association between lowered O. formigenes colonization and low testosterone. Urinary calcium and oxalates levels were greater in patient. Serum testosterone and urinary citrate concentrations was reduced in patients with a significant difference. Also an association between O. formigenes and colon cancer was noted. Absence of O. formigenes might stand for a pathogenic factor in calcium oxalate stone, low bone mineral density, low testosterone levels and also colon cancer, when antibiotics are prescribed generously.

Lessons Learnt (Clinical Outcomes and Cost Savings) from Virtual Stone Clinic and Their Application in the Era Post-COVID-19: Prospective Outcomes over a 6-Year Period from a University Teaching Hospital

Introduction: We introduced a nurse-led telephone-based virtual stone clinic (VSC) follow-up for the surveillance of patients with asymptomatic renal calculi or those at a high risk of recurrent kidney stone disease (KSD). The aim of this study was to look at the outcomes of VSC and its role in the post-COVID era. Methods: Prospective outcomes audit was done for all patients referred to the VSC for a 6-year period (March 2014-April 2020). VSC is led by specialist stone nurses for on-going surveillance of KSD patients. Results: A total of 290 patients were seen (468 individual appointments; 1.6 ± 1.0 per patient), with a mean age of 57.0 ± 15.8 years (range: 17-92) and a men-women ratio of 3:2. The referral was for surveillance of asymptomatic small renal stones (230, 79.3%); history of recurrent stone disease (45, 15.5%); solitary kidneys (5, 1.7%); cystine stones; young age; and other conditions (10, 3.4%). The mean stone size was 5.0 ± 2.7 mm, followed up with kidney, ureter, and bladder radiograph (225, 77.6%) and ultrasound scan (USS) (65, 22.4%), for median duration of 12 months (range: 3-24 months). At the end, 132 patients (45.6%) remained in VSC, 106 (36.6%) were discharged, 47 (16.2%) returned to face-to-face clinic or treatment, and 5 (1.7%) had emergency admissions. Of 47 patients who returned, 23 (48.9%) developed new symptoms, 21 (44.6%) had stone growth, and 3 defaulted to face-to-face appointment. Thirty-five patients needed surgical intervention (URS-21, SWL-13, and PCNL-1) and 10 were managed conservatively. VSC reduced the cost per clinic appointment from £27.9 to £2 per patient (93% reduction), equating to a total saving of £12,006 for the study period. Conclusion: Nurse-led VSC not only provided a safe follow-up but also allowed to substantially reduce the cost of treatment by allowing patients to be either discharged or return to a face-to-face clinic or surgical intervention if needed. Post-COVID, this model using telemedicine will have a much wider uptake and further help to optimize health care resources.

Determining the true burden of kidney stone disease

The incidence and prevalence of kidney stones have increased over the past four decades. However, the diagnosis of 'kidney stone' can range from an incidental asymptomatic finding of limited clinical significance to multiple painful episodes of ureteral obstruction with eventual kidney failure. Some general strategies may be useful to prevent the recurrence of kidney stones. In particular, greater attention to kidney stone classification, approaches to assessing the risk of recurrence and individualized prevention strategies may improve the clinical care of stone formers. Although there have been some advances in approaches to predicting the recurrence of kidney stones, notable challenges remain. Studies of kidney stone prevalence, incidence and recurrence have reported inconsistent findings, in part because of the lack of a standardized stone classification system. A kidney stone classification system based on practical and clinically useful measures of stone disease may help to improve both the study and clinical care of stone formers. Any future kidney stone classification system should be aimed at distinguishing asymptomatic from symptomatic stones, clinically diagnosed symptomatic stone episodes from self-reported symptomatic stone episodes, symptomatic stone episodes that are confirmed from those that are suspected, symptomatic recurrence from radiographic recurrence (that is, with radiographic evidence of a new stone, stone growth or stone disappearance from presumed passage) and determine stone composition based on mutually exclusive categories.

Are upper urinary tract stones more common in more deprived populations?

Purpose:

To examine the relationship between deprivation and upper tract calculus formation, and provide a contemporary estimate of the incidence of upper urinary tract stone disease.

Methods:

A retrospective review of hospital episodes for patients presenting to our institution with upper urinary tract stone disease in a 3-year period between 2010 and 2014. Incidence of stone disease was calculated and stratified according to deprivation, as measured by the index of multiple deprivation (IMD) and its subdomains. Poisson regression was used to model the relationship between deprivation and stone disease.

Results:

The overall incidence of upper urinary tract stone disease was 115 patients/100,000 person-years (95% confidence interval (CI) 108–122 per 100,000 person-years). There is a link between the IMD (as well as a number of its subdomains) and stone disease. The rate of incident stone disease was 50.6% higher in the most deprived quintile of the IMD when compared to the least deprived ( p < 0.001). Multivariate Poisson regression found that education, skills and training deprivation was the subdomain that predicted stone disease most strongly, with the incidence rate ratio being 1.15 (95% CI 1.053–1.261) for each increase in quintile.

Conclusion:

This study provides a contemporary measure of the incidence of upper urinary tract stone disease derived from a population in the Midlands of England. It informs our understanding of the link between types of deprivation and stone occurrence.

Level of evidence:

2b

The Impact of Patient, Procedural, and Staffing Factors Upon Ureteroscopy Cost

Introduction: The purpose of this study was to evaluate factors during ureteroscopy that can potentially impact procedure cost. Materials and Methods: A retrospective review of 129 consecutive elective ureteroscopy cases was performed to determine direct procedure cost. Direct cost was defined as cost incurred because of operating room expenses, including operating room time, staffing expenses, equipment, and supply costs. Data regarding patient, procedural, and operating room staffing characteristics were compared between the most and least expensive cases. Univariate and logistic regression analysis were performed to identify factors predictive of higher costs. Results: The average direct ureteroscopy cost was $3298/case. On univariate analysis, ureteroscopies in the highest 50th cost percentile had larger stone burden (170.1 vs 146 mm²; p = 0.03) and longer operative times (95.3 vs 49.9 minutes; p < 0.01), were more likely performed for non-stone indications (21.4% vs 7.2%; p = 0.03), more likely to include a resident (65.5% vs 43.6%; p = 0.02), and less likely to have a dedicated urology scrub technician (38.2% vs 61.8%; p = 0.01) compared to cases in the lowest 50th percentile. The presence of a resident, larger stone burden, absence of a dedicated scrub technician, and longer operative time were associated with an average cost increase of $516, $700, $1122, and $1401, respectively. Logistic regression analysis showed that operating room time was the only factor predicting higher cost (OR [odds ratio] 12.8, 95% confidence interval [CI] 2.0-84.0). A post-hoc logistic regression analysis demonstrated that the presence of a resident during ureteroscopy (OR 2.9, 95% CI 1.1-8.0) and larger stone burden (OR 1.01, 95% CI 1.0-1.013) were significantly associated with longer operative times. Conclusion: Operating room time is the primary determinant of ureteroscopy case cost. All efforts should be made to decrease operative time, although balancing patient safety and maintaining a quality training environment.

Stone recurrence among childhood kidney stone formers: results of a nationwide study in Iceland

OBJECTIVES

To examine the stone recurrence rate among childhood kidney stone formers in the Icelandic population.

MATERIALS AND METHODS

We retrospectively examined kidney stone recurrence in a recently reported population-based sample of 190 individuals who experienced their first stone before 18 years of age in the period 1985-2013. Of these 190 individuals, 112 (59%) were females and the median (range) age at the incident stone diagnosis was 15.0 (0.2-17.9) years. Stone recurrence was defined as an acute symptomatic episode with imaging confirmation or self-reported stone passage, new stone detected by imaging in asymptomatic patients, and suspected clinical stone episode without verification. The Kaplan-Meier method was used to assess stone-free survival and the Chi-square, Fisher's exact, Wilcoxon rank-sum and the log-rank tests to compare groups.

RESULTS

A total of 68 (35%) individuals experienced a second stone event, 1.7 (0.9-18.9) years after the initial diagnosis. The recurrence rate was 26%, 35%, 41% and 46% after 5, 10, 15 and 20 years of follow-up, respectively. The 5-year recurrence rate increased with time and was 9%, 24% and 37% in the periods 1985-1994, 1995-2004 and 2005-2013, respectively (P = 0.005). No difference in stone recurrence was observed between the sexes (P = 0.23).

CONCLUSIONS

In our population-based sample of childhood kidney stone formers, the stone recurrence rate is similar to that reported for adults. The observed rise in stone recurrence with time may be related to closer patient follow-up in recent years or increased stone risk in general.

Upper urinary tract stone compositions: the role of age and gender

Objective:

To analyze the compositions of upper urinary tract stones and investigate their distributions in different gender and age groups.

Materials and Methods:

Patients diagnosed with upper urinary tract stone disease between December 2014 and March 2018 were retrospectively reviewed. Patient's age, gender, BMI, comorbidities, stone event characteristics, and compositions were collected, and proportions of stone components in different gender and age groups were analyzed.

Results:

A total of 1532 stone analyses were performed (992 from males and 540 from females). The mean age was younger in males (p <0.001). Males included more cases with larger BMI, hyperuricemia, and obesity, while females had more urinary tract infections. Multiple components were present in 61.8% of stones. Calcium oxalate (CaOx) (67.0%) was the most common component, followed by uric acid (UA) (11.8%), infection stone (11.4%), calcium phosphate (CaP) (8.0%), cystine (1.1%), brushite (0.4%), and 2, 8-dihydroxyadenine (0.2%). Men contributed with more CaOx stones than women at age 30-49 years (all p <0.01) and more UA stones at 30-59 years (all p <0.05). Women contributed with more infection stones than men in age groups 30-49 and 60-69 years (all p <0.05), and more CaP stones at 30-49 years. The prevalence peak was 50-59 years in men and 60-69 years in women. Both genders had the lowest prevalence in adolescence. Prevalence of UA stones increased while that of infection stones decreased with aging in both genders.

Conclusions:

Age and sex had a strong association with distribution of stone compositions in this Chinese cohort.

A prediction model of Nephrolithiasis Risk: A population-based cohort study in Korea

Purpose

Well-validated risk prediction models help to stratify individuals on the basis of their disease risks and to guide health care professionals in decision-making. The incidence of nephrolithiasis has been increasing in Korea. Racial differences in the distribution of and risk for nephrolithiasis have been reported in Asia but no population-specific nephrolithiasis models have been developed. We aimed to develop a simplified nephrolithiasis prediction model for the Korean population by using data from general medical practice.

Materials and Methods

This was a prospective, population-based cohort study in Korea. A total of 497,701 participants from the National Health Insurance Service–National Sample Cohort (NHIS-NSC) were enrolled from 2002 to 2010. A Cox proportional hazards model was used.

Results

During a median follow-up time of 8.5 years (range, 2.0–8.9 years) and among 497,701 participants, there were 15,783 cases (3.2%) of nephrolithiasis. The parsimonious model included age, sex, income grade, alcohol consumption, body mass index, total cholesterol, fasting blood glucose, and medical history of diseases. The Harrell's C-statistic was 0.806 (95% confidence interval [CI], 0.790–0.821) and 0.805 (95% CI, 0.782–0.827) in the derivation and validation cohorts, respectively.

Conclusions

The results of the present study imply that nephrolithiasis risk can be predicted by use of data from general medical practice and based on predictors that clinicians and individuals from the general population are likely to know. This model comprises modifiable risk factors and can be used to identify those at higher risk who can modify their lifestyle to lower their risk for nephrolithiasis. This study also offers an opportunity for external validation or updating of the model through the incorporation of other risk predictors in other settings.

Non-radiological assessment of kidney stones using the kidney injury test (KIT), a spot urine assay

OBJECTIVES

To evaluate the utility of kidney injury test (KIT) assay urinary biomarkers to detect kidney stones and quantify stone burden.

PATIENTS AND METHODS

A total of 136 spot urine samples from 98 individuals, with and without kidney stone disease, were processed in a predefined assay to measure six DNA and protein markers in order to generate a risk score for the non-invasive detection of nephrolithiasis. From this cohort, 56 individuals had spot, non-timed urine samples collected at the time of radiographically confirmed kidney stones, and 54 demographically matched, healthy controls without kidney stone disease also provided spot, non-timed urine samples. Sixteen individuals with persistent stone disease had more than one urine sample. Using a proprietary microwell-based KIT assay, we measured cell-free DNA (cfDNA), methylated cfDNA, clusterin, creatinine, protein and CXCL10. A KIT stone score was computed across all markers using the prior locked KIT algorithm. The KIT stone score, with a scale of 0 to 100, was then correlated with demographic variables, kidney stone burden, obstructive kidney stone disease, and urine solutes in 24-h urine collections.

RESULTS

The scaled KIT stone score, a composite of all six biomarkers, readily discriminated individuals with current or prior radiographically confirmed kidney stones from healthy controls without kidney stone disease (P < 0.001). In individuals with nephrolithiasis, KIT stone score also correlated with radiologically measured stone size (P = 0.017) and differentiated patients with a clinical radiological diagnosis of obstructive nephrolithiasis associated with upper renal tract dilatation (P = 0.001). Stone burden as assessed by KIT stone score, however, did not correlate with the any of the traditional measures of 24-h urine solutes or the 24-h urine supersaturation levels. In patients with persistent stone disease, where multiple urine samples were collected over time and after different interventions, the use of KIT stone score could non-invasively track stone burden over time through a spot urine, non-timed urine sample.

CONCLUSIONS

A random, spot urine-based assay, KIT stone score, can non-invasively detect, quantify and monitor current stone burden, and may thus minimize radiographic exposure for kidney stone detection. The KIT stone score assay may also help monitor stone recurrence risk for patients with nephrolithiasis, without the requirement for 24-h urine collections.

Does chronic hyperglycaemia increase the risk of kidney stone disease? results from a systematic review and meta-analysis

DESIGN

Systematic review and meta-analysis of observational studies was performed using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for studies reporting on diabetes mellitus (DM) or metabolic syndrome (MetS) and kidney stone disease (KSD).

OBJECTIVE

To examine the association between chronic hyperglycaemia, in the form of DM and impaired glucose tolerance (IGT) in the context of MetS and KSD.

SETTING

Population-based observational studies. Databases searched: Ovid MEDLINE without revisions (1996 to June 2018), Cochrane Library (2018), CINAHL (1990 to June 2018), ClinicalTrials.gov, Google Scholar and individual journals including the Journal of Urology, European Urology and Kidney International.

PARTICIPANTS

Patients with and without chronic hyperglycaemic states (DM and MetS).

MAIN OUTCOME MEASURES

English language articles from January 2001 to June 2018 reporting on observational studies.

EXCLUSIONS

No comparator group or fewer than 100 patients. Unadjusted values were used for meta-analysis, with further meta-regression presented as adjusted values. Bias was assessed using Newcastle-Ottawa scale.

RESULTS

2340 articles were screened with 13 studies included for meta-analysis, 7 DM (three cohort) and 6 MetS. Five of the MetS studies provided data on IGT alone. These included: DM, n=28 329; MetS, n=31 767; IGT, n=12 770.

CONTROLS

DM, n=5 89 791; MetS, n=1 78 050; IGT, n=2 93 852 patients. Adjusted risk for DM cohort studies, RR=1.23 (0.94 to 1.51) (p<0.001). Adjusted ORs for: DM cross-sectional/case-control studies, OR=1.32 (1.21 to 1.43) (p<0.001); IGT, OR=1.26 (0.92 to 1.58) (p<0.0001) and MetS, OR=1.35 (1.16 to 1.54) (p<0.0001). There was no significant difference between IGT and DM (cross-sectional/case-control), nor IGT and MetS. There was a moderate risk of publication bias. Statistical heterogeneity remained significant in adjusted DM cohort values and adjusted IGT (cross-sectional/case-control), but non-signficant for adjusted DM (cross-sectional/case-control).

CONCLUSION

Chronic hyperglycaemia increases the risk of developing kidney stone disease. In the context of the diabetes pandemic, this will increase the burden of stone related morbidity and mortality.

PROSPERO REGISTRATION NUMBER

CRD42018093382.

Handling and protecting your flexible ureteroscope: how to maximise scope usage

Flexible ureteroscopy is an important therapeutic and diagnostic procedure and has seen rapid rise in its utilisation in recent years. There have been numerous developments in flexible ureteroscope (fURS) technology but scope fragility, and the associated high maintenance costs, remains a concern. A comprehensive Medline search for related publications from the last 20 years was undertaken to identify common causes of fURS damage and ascertain practices to minimise this. Flexible ureteroscopy can be due to intraoperative causes (loss of the deflection mechanism, damage to the working channel due and fibreoptic bundle injury) and non-operative damage which occur during cleaning, sterilisation and handling of the fURS. The review summarises the available literature to help highlight common mechanisms of scope damage, and outlines evidence-based measures to reduce the risk of damage and maximise durability. Scope fragility remains a problem with significant associated cost implications. In a culture of rising fURS use and reducing re-imbursement for endourologists, prolonging the longevity of the fURS is imperative for maintaining profitability. There are simple and inexpensive practices which can be immediately adopted to maximise fURS use and reduce the need for repairs.

Utilizing da Vinci® surgical system to treat challenging urinary stones

Introduction:

A worldwide mounting in the incidence and prevalence of urolithiasis has been observed. The standard treatment of urologic stone disease (USD) has changed from open surgery to extracorporeal shock wave lithotripsy, percutaneous nephrolithotomy (PCNL), or ureteroscopy depending on the size and location of the stone. We are sharing our experience in utilizing Da Vinci^® robotic surgical system to treat patient with urolithiasis instead of open surgical approach.

Patients and Methods:

We reviewed prospectively collected data of 19 patients who underwent robotic-assisted stone surgery (RSS) between January 2010 and March 2018 at our institute for USD involving 22 nephroureteral units.

Results:

A total number of 22 RSS were accomplished with no conversion to open. Three patients had bilateral stone and needed to have RSS on each side separately. Eleven RSS were performed on the right. The indications for RSS included as follows: morbid obesity (n = 8, mean body mass index 56.4 kg/m²), need for concurrent renal surgery (n = 3) severe contractures limiting positioning for retrograde endoscopic surgery or PCNL (n = 2), symptomatic calyceal diverticular stone with failed endoscopic approach (n = 4), and after failed PCNL (n = 2). Twenty nephrouretral unit (91%) were rendered stone free on the first attempt with complication occurring after four cases (18%).

Conclusion:

RSS is viable options in the treatment of challenging urologic stone with high success rate and low risk of complication. The need for open stone surgery was eliminated by RSS at our center.

Nephrolithiasis in the Obese Patient

PURPOSE OF REVIEW

The link between metabolic syndrome (MetS)/obesity and kidney stone disease (KSD) has gained importance over recent years due to the increasing prevalence and healthcare burden worldwide. This review analyses the literature exploring the link between MetS/obesity and KSD and the impact that obesity has on KSD management.

RECENT FINDINGS

Metabolic syndrome has been shown to increase an individual's risk of developing kidney stone disease, with insulin resistance forming a core component of the pathophysiology. The body habitus of an individual also influences the type of intervention that is most appropriate, with flexible ureteroscopy increasingly being the preferred option in obese patients. It is important for urologists to consider the features of metabolic syndrome to effectively manage episodes of KSD in obese patients. In addition, better quality evidence is required to effectively compare different treatment options in this group of patients.

Peculiarities of course of the urolithiasis disease in patients with a solitary kidney and concomitant diabetes mellitus type II

Objective. To analyze the cases histories of urolithiasis disease and its course peculiarities in patients with a solitary kidney, unilateral urolithiasis and concomitant diabetes mellitus type II. Маterials and methods. Retrospective analysis of the cases histories was conducted in 109 patients, suffering urolithiasis disease with concomitant diabetes mellitus type II, of them in 31 patients a solitary kidney was present (Group I), in 78 - unilateral nephrolithiasis (Group II). Results. There was established, that even in adequately corrected hyperglycemia in the patients, having a solitary kidney, the risk for unfavorable course of urolithiasis disease and diabetes mellitus type II is higher, than in patients, having both functioning kidneys. The majority of patients, having a solitary kidney, owe the lowered velocity indices of glomerular filtration and glomerular hyperfiltration, proteinuria and arterial hypertension, what, even in presence of diabetes mellitus with the middle severity course, constitutes a high risk for rapid lowering of renal function. Conclusion. In the urolithiasis disease in the patients with a solitary kidney and concomitant diabetes mellitus type II there have an objectively proven risk for progressing of chronic renal disease. The necessity for the multidisciplinary approach realization of the urologists and endocrinologists activities in determination of personified schemes of treatment in these patients is substantiated.

A clinical prediction rule for uncomplicated ureteral stone: The STONE score; a prospective observational validation cohort study

Introduction

Renal colic is one of the most common complaints in patients admitted to Emergency Department (ED). Computed Tomography (CT) is the reference standard for the diagnosis of any stones in the kidneys or ureters. However, CT has classical disadvantages, such as radiation exposure, cost and availability. Recently, STONE clinical prediction criteria were suggested to identify uncomplicated ureteral stone cases among patiens admitted to the ED with abdominal pain. Primary objective of this study was the external validation of the STONE criteria.

Methods

This was a diagnostic accuracy study conducted on a prospective, observational cohort. All consecutive patients who underwent a non-enhanced abdominopelvic CT scan in the ED with an initial diagnosis of ureteral stone disease were enrolled. Using a pre-prepared checklist, all data and the final diagnosis according to the CT scan were recorded. STONE score was calculated for all patients. The area under the curve (AUC) of the STONE Score and the CT, the reference standard, were compared using the ROC curve analysis.

Results

Totally, 237 patients (59.9% male) with an average age of 41.54 years (SD: 13.37) were evaluated, and 156 cases (65.8%) were proved to have renal stone. The mean (SD) STONE scores in the groups of patients with renal stone and in the group of patients without renal stone group were 9.1 (2.6) and 6.0 ( 2.8), respectively (p < 0.001). The area under the curve (AUC) for the STONE score was 0.789 (95% confidence interval (CI) 0.725 to 0.852). The optimum threshold value of the STONE score for the diagnosis of a renal stone was 8 or more, which had a sensitivity of 75.0% and a specificity of 70.4%.

Conclusion

Despite the acceptable diagnostic accuracy, further modifications and enhancements of the STONE score are needed to differentiate patients with low risk prior to imaging.

The Urological Association of Asia clinical guideline for urinary stone disease

The Urological Association of Asia, consisting of 25 member associations and one affiliated member since its foundation in 1990, has planned to develop Asian guidelines for all urological fields. The field of stone diseases is the third of its guideline projects. Because of the different climates, and social, economic and ethnic environments, the clinical practice for urinary stone diseases widely varies among the Asian countries. The committee members of the Urological Association of Asia on the clinical guidelines for urinary stone disease carried out a surveillance study to better understand the diversity of the treatment strategy among different regions and subsequent systematic literature review through PubMed and MEDLINE database between 1966 and 2017. Levels of evidence and grades of recommendation for each management were decided according to the relevant strategy. Each clinical question and answer were thoroughly reviewed and discussed by all committee members and their colleagues, with suggestions from expert representatives of the American Urological Association and European Association of Urology. However, we focused on the pragmatic care of patients and our own evidence throughout Asia, which included recent surgical trends, such as miniaturized percutaneous nephrolithotomy and endoscopic combined intrarenal surgery. This guideline covers all fields of stone diseases, from etiology to recurrence prevention. Here, we present a short summary of the first version of the guideline - consisting 43 clinical questions - and overview its key practical issues.

A Retrospective Study of Kidney Stone Recurrence in Adults

Background

Nephrolithiasis or kidney stone disease (KSD) is a common disorder worldwide. Despite the availability of a variety of effective management strategies, KSD recurrence remains a problem. In the present study, we investigated the KSD recurrence after the treatment of the first stone episode.

Methods

Medical records of all patients who had KDS treated in our department from January 2012 to January 2016 were retrospectively reviewed. A total of 146 patients who had KDS recurrence were identified. The demographic information, biochemical data, treatment methods, report of hydronephrosis severity and stone chemical compositions were collected and analyzed.

Results

We reported that: 1) Sixty four (43.8%) out of 146 patients with stone recurrence were overweight or obese; 2) Of all 146 patients with stone recurrence, 86 (58.9%) had hyperlipidemia, 77 (52.4%) had hyperuricemia and 64 (43.8%) had hyperglycemia; 3) Mini-invasive methods were mostly used for the treatment of the first stone episode; 4) The most chief complaint differed during the first episode and recurrence; 5) The number of patients who had grades 3 and 4 hydronephrosis was significantly lower during recurrence compared with that in the first stone episode; 6) Seventy nine (54.1%) patients with recurrence had stone of calcium oxalate.

Conclusions

Majority of patients with KSD recurrence have overweight/obesity, hyperlipidemia, hyperuricemia and hyperglycemia, indicating a role of metabolic disorders in stone recurrence. Mini-invasive methods are the mainstay for the management of the first stone episode. The degree of hydronephrosis is significantly reduced during stone recurrence, possibly due to increased awareness of the disease and thereafter the change of lifestyle in patients. Over half of recurrent stones are of calcium oxalate.

ALLN-177, oral enzyme therapy for hyperoxaluria

Purpose

To evaluate the potential of ALLN-177, an orally administered, oxalate-specific enzyme therapy to reduce urine oxalate (UOx) excretion in patients with secondary hyperoxaluria.

Methods

Sixteen male and female subjects with both hyperoxaluria and a kidney stone history were enrolled in an open-label study. Subjects continued their usual diets and therapies. During a 3-day baseline period, two 24-h (24-h) urines were collected, followed by a 4-day treatment period with ALLN-177 (7,500 units/meal, 3 × day) when three 24-h urines were collected. The primary endpoint was the change in mean 24-h UOx from baseline. Safety assessments and 24-h dietary recalls were performed throughout.

Results

The study enrolled 5 subjects with enteric hyperoxaluria and 11 with idiopathic hyperoxaluria. ALLN-177 was well tolerated. Overall mean (SD) UOx decreased from 77.7 (55.9) at baseline to 63.7 (40.1) mg/24 h while on ALLN-177 therapy, with the mean reduction of 14 mg/24 h, (95% CI − 23.71, − 4.13). The calcium oxalate-relative urinary supersaturation ratio in the overall population decreased from a mean of 11.3 (5.7) to 8.8 (3.8) (− 2.8; 95% CI − 4.9, − 0.79). This difference was driven by oxalate reduction alone, but not any other urinary parameters. Mean daily dietary oxalate, calcium, and fluid intake recorded by frequent diet recall did not differ by study periods.

Conclusion

ALLN-177 reduced 24-h UOx excretion, and was well tolerated. The results of this pilot study provided justification for further investigation of ALLN-177 in patients with secondary hyperoxaluria.

Trial registration: Clinicaltrials.gov NCT02289755.

Baseline chronic kidney disease does not predict long-term renal functional decline after percutaneous nephrolithotomy

To compare renal functional outcomes in patients with and without chronic kidney disease (CKD) to identify predictors of change in renal function after percutaneous nephrolithotomy (PCNL). We reviewed patients who underwent PCNL by a single surgeon over 3.5 years. Patients' pre- and post-operative Glomerular Filtration Rate (GFR) was calculated. Baseline GFR < 60 ml/min/1.73 m² (stage ≥ 3 CKD) defined our CKD cohort. Patients' baseline renal function, comorbidities, stone parameters, and intra-operative variables were analyzed to determine the relationship with post-operative renal function after PCNL by multivariate analysis. 202 patients were analyzed. Mean follow-up time was 16 months. At baseline, 163 (80.7%) patients were free of CKD and 39 (19.3%) had CKD. Patients without CKD had an overall decrease in GFR from 105.6 to 103.3 ml/min/1.73 m² (p = 0.494). 14/163 (8.6%) non-CKD patients experienced a significant decline in renal function after PCNL; 7/163 (4.3%) developed de novo CKD and 7 had a ≥ 30% decline in GFR. Patients with CKD had an overall increase in mean GFR post-operatively, from 47.3 to 54.0 ml/min/m² (p = 0.067). Two in this cohort (5.1%) experienced a > 30% decline in renal function post-operatively. Age, gender, African American race, presence of comorbidities and pre-operative CKD were not significant predictors of renal function post-operatively on multivariate analysis. PCNL in this cohort appears GFR neutral in the setting of baseline CKD. CKD was not predictive of renal functional decline after PCNL. Given that stone disease carries a high recurrence rate and that CKD is associated with stone formers, further investigation into predictors of renal function change after PCNL is warranted.

Melamine promotes calcium crystal formation in three-dimensional microfluidic device

Melamine, which induces proximal tubular (PT) cell damage has a greater nephrotoxic effect when combined with cyanuric and uric acids; however, it is unknown whether such effect can stimulate calcium phosphate (CaP)/calcium oxalate (CaOx) stone formation. Here, we show that melamine acts as an inducer of CaP, CaOx and CaP + CaOx (mixed) crystal formations in a time and concentration-dependent manner by stabilizing those crystals and further co-aggregating with melamine. To explore the physiological relevance of such melamine-augmented calcium crystal formation, we used 2-dimensional (2D) and 3D microfluidic (MF) device, embedded with PT cells, which also resembled the effect of melamine-stimulated CaP, CaOx and mixed crystal formation. Significantly, addition of preformed CaP and/or CaOx crystal in the presence of melamine, further potentiated those crystal formations in 3D MFs, which helped the growth and aggregation of mixed crystals. Our data show that the mechanism of such predisposition of stone formation could be largely due to co-crystallization between melamine and CaP/CaOx and pronounced effect on induction of stone-forming pathway activation in 3D MF. Taken together, melamine-induced CaP and/or CaOx crystal formation ex-vivo will help us in understanding the larger role of melamine as an environmental toxicant in producing the pathology in similar cellular microenvironments.

In vitro analysis of urinary stone composition in dual-energy computed tomography

Purpose

Dual energy computed tomography (DECT) is a new method of computed tomography (CT) imaging, allowing the assessment of not only the object’s morphology, but also its composition. The aim of the study was to evaluate the potential of in vitro DECT evaluation of urinary stones’ chemical composition.

Material and methods

Six samples of surgically removed renal stones were scanned using DECT and analyzed by scanner vendor software. Uric acid stones were marked red and calcium stones white by the software. The real composition of the stones was finally verified using physicochemical laboratory analysis.

Results

In 5 out of 6 samples, the composition of stones in DECT (3 samples identified as uric acid and 2 samples as calcium) was consistent with the physicochemical analysis (3 samples identified as uric acid, 1 as calcium phosphate, 1 as calcium oxalate). In DECT it was not possible to determine more precisely the type of calcium compounds (calcium phosphate vs. calcium oxalate) as established in the physicochemical analysis.

In one stone identified in physicochemical analysis as uric acid, DECT detected a composite layered structure containing both uric acid and calcium compounds.

Conclusions

DECT allows uric acid to be distinguished from calcium urinary tract stones, which is crucial in the choice of appropriate therapy. Using the available hardware and software, it was not possible to more accurately distinguish types of calcified stones. Evaluation of the stone type in DECT may be limited in the case of mixed chemical composition.

Genetics of common complex kidney stone disease: insights from genome-wide association studies

Kidney stone disease is a common disorder in Western countries that is associated with significant suffering, morbidity, and cost for the healthcare system. Numerous studies have demonstrated familial aggregation of nephrolithiasis and a twin study estimated the heritability to be 56%. Over the past decade, genome-wide association studies have uncovered several sequence variants that confer increased risk of common complex kidney stone disease. The first reported variants were observed at the CLDN14 locus in the Icelandic population. This finding has since been replicated in other populations. The CLDN14 gene is expressed in tight junctions of the thick ascending limb of the loop of Henle, where the protein is believed to play a role in regulation of calcium transport. More recent studies have uncovered variants at the ALPL, SLC34A1, CASR, and TRPV5 loci, the first two genes playing a role in renal handling of phosphate, while the latter two are involved in calcium homeostasis. Although genetic data have provided insights into the molecular basis of kidney stone disease, much remains to be learned about the contribution of genetic factors to stone formation. Nevertheless, the progress made in recent years indicates that exciting times lie ahead in genetic research on kidney stone disease.

Body fatness, diabetes, physical activity and risk of kidney stones: a systematic review and meta-analysis of cohort studies

We conducted a systematic review and meta-analysis to clarify the association between adiposity, diabetes, and physical activity and the risk of kidney stones. PubMed and Embase were searched up to April 22nd 2018 for relevant studies. Summary relative risks (RRs) and 95% confidence intervals (CIs) were calculated using random effects models. Thirteen cohort studies were included. The summary relative risk was 1.21 (95% CI 1.12-1.30, I2 = 76%, n = 8) per 5 unit increment in BMI, 1.16 (95% CI 1.12-1.19, I2 = 0%, n = 5) per 10 cm increase in waist circumference, 1.06 (95% CI 1.04-1.08, I2 = 67%, n = 3) per 5 kg increase in weight and 1.12 (95% CI 1.06-1.18, I2 = 86%, n = 3) per 5 kg of weight gain. The summary RR was 1.16 (95% CI 1.03-1.31, I2 = 51%, n = 10) for participants with diabetes compared to participants without diabetes, and 0.93 (95% CI 0.78-1.10, I2 = 80%, n = 4) for high vs. low physical activity. These results suggest a positive association between adiposity and diabetes and the risk of kidney stones, but no association with physical activity.

SLC2A9 (GLUT9) mediates urate reabsorption in the mouse kidney

Uric acid (UA) is a metabolite of purine degradation and is involved in gout flairs and kidney stones formation. GLUT9 (SLC2A9) was previously shown to be a urate transporter in vitro. In vivo, humans carrying GLUT9 loss-of-function mutations have familial renal hypouricemia type 2, a condition characterized by hypouricemia, UA renal wasting associated with kidney stones, and an increased propensity to acute renal failure during strenuous exercise. Mice carrying a deletion of GLUT9 in the whole body are hyperuricemic and display a severe nephropathy due to intratubular uric acid precipitation. However, the precise role of GLUT9 in the kidney remains poorly characterized. We developed a mouse model in which GLUT9 was deleted specifically along the whole nephron in a tetracycline-inducible manner (subsequently called kidney-inducible KO or kiKO). The urate/creatinine ratio was increased as early as 4 days after induction of the KO and no GLUT9 protein was visible on kidney extracts. kiKO mice are morphologically identical to their wild-type littermates and had no spontaneous kidney stones. Twenty-four-hour urine collection revealed a major increase of urate urinary excretion rate and of the fractional excretion of urate, with no difference in urate concentration in the plasma. Polyuria was observed, but kiKO mice were still able to concentrate urine after water restriction. KiKO mice displayed lower blood pressure accompanied by an increased heart rate. Overall, these results indicate that GLUT9 is a crucial player in renal handling of urate in vivo and a putative target for uricosuric drugs.

Incidence of kidney stone disease in Icelandic children and adolescents from 1985 to 2013: results of a nationwide study

BACKGROUND

An increase in the incidence of kidney stone disease has been reported for all age groups worldwide. To examine this trend, we conducted a nationwide study of the epidemiology of kidney stones in Icelandic children and adolescents over a 30-year period.

METHODS

Computerized databases of all major hospitals and medical imaging centers in Iceland were searched for International Classification of Diseases and radiologic and surgical procedure codes indicative of kidney stones in patients aged < 18 years, followed by a thorough medical record review. Age-adjusted incidence was calculated for the time intervals 1985-1989, 1990-1994, 1995-1999, 2000-2004, 2005-2009, and 2010-2013. Time trends in stone incidence were assessed by Poisson regression. The prevalence of stone disease for the years 1999-2013 was also determined.

RESULTS

Almost all the 190 patients (97%) that we identified had symptomatic stones, and acute flank or abdominal pain and hematuria were the most common presenting features. The total annual incidence of kidney stones increased from 3.7/100,000 in the first 5-year interval to 11.0/100,000 during the years 1995-2004 (p < 0.001) and decreased thereafter to 8.7/100,000 in 2010-2013 (p = 0.63). The incidence rise was highest in girls aged 13-17 years, in whom it rose from 9.8/100,000 in 1985-1989 to 39.2/100,000 in 2010-2013 (p < 0.001), resulting in an overall female predominance in this age group. The mean annual prevalence of stone disease in 1999-2013 was 48/100,000 for boys and 52/100,000 for girls.

CONCLUSION

We found a significant increase in the incidence of childhood kidney stone disease, driven by a dramatic increase of stone frequency in teenage females which is poorly understood and warrants further study.

Worldwide Trends of Urinary Stone Disease Treatment Over the Last Two Decades: A Systematic Review

INTRODUCTION

Numerous studies have reported on regional or national trends of stone disease treatment. However, no article has yet examined the global trends of intervention for stone disease.

METHODS AND MATERIALS

A systematic review of articles from 1996 to September 2016 for all English language articles reporting on trends of surgical treatment of stone disease was performed. Authors were contacted in the case of data not being clear. If the authors did not reply, data were estimated from graphs or tables. Results were analyzed using SPSS version 21, and trends were analyzed using linear regression.

RESULTS

Our systematic review yielded 120 articles, of which 8 were included in the initial review. This reflected outcomes from six countries with available data: United Kingdom, United States, New Zealand, Australia, Canada, and Brazil. Overall ureteroscopy (URS) had a 251.8% increase in total number of treatments performed with the share of total treatments increasing by 17%. While the share of total treatments for percutaneous nephrolithotomy (PCNL) remained static, the share for extracorporeal shockwave lithotripsy and open surgery fell by 14.5% and 12%, respectively. There was significant linear regression between rising trends of total treatments year on year for URS (p < 0.001).

CONCLUSION

In the last two decades, the share of total treatment for urolithiasis across the published literature has increased for URS, stable for PCNL, and decreased for lithotripsy and open surgery.

Kidney Stone Disease: An Update on Current Concepts

Kidney stone disease is a crystal concretion formed usually within the kidneys. It is an increasing urological disorder of human health, affecting about 12% of the world population. It has been associated with an increased risk of end-stage renal failure. The etiology of kidney stone is multifactorial. The most common type of kidney stone is calcium oxalate formed at Randall's plaque on the renal papillary surfaces. The mechanism of stone formation is a complex process which results from several physicochemical events including supersaturation, nucleation, growth, aggregation, and retention of urinary stone constituents within tubular cells. These steps are modulated by an imbalance between factors that promote or inhibit urinary crystallization. It is also noted that cellular injury promotes retention of particles on renal papillary surfaces. The exposure of renal epithelial cells to oxalate causes a signaling cascade which leads to apoptosis by p38 mitogen-activated protein kinase pathways. Currently, there is no satisfactory drug to cure and/or prevent kidney stone recurrences. Thus, further understanding of the pathophysiology of kidney stone formation is a research area to manage urolithiasis using new drugs. Therefore, this review has intended to provide a compiled up-to-date information on kidney stone etiology, pathogenesis, and prevention approaches.

Total flavone of Desmodium styracifolium relieved apoptosis and autophagy of COM-induced HK-2 cells by regulating KIM-1 via p38/MAPK pathway

The purpose of the study was to investigate the mechanism of total flavone of Desmodium styracifolium (TFDS) in regulating the formation of urinary calculi. Protein levels of KIM-1, LC3-II, p-p38 were measured by Western blot. The effect of different COM concentrations, different TFDS concentrations, SB203580 (specific inhibitor of p38/MAPK), and overexpression of KIM-1 on cell viability were detected by WST-1 assay. The apoptotic cells and FITC positive cells were detected by flow cytometry. HK-2 cell viability decreased with the increase of COM concentration, and the protein levels of KIM-1, LC3-II, and p-p38 increased with the time. Blocking the p38/MAPK pathway or co-cultured with TFDS inhibited the effects of COM on apoptosis and autophagy of HK-2 cells. In addition, blocking the p38/MAPK pathway inhibited the expression of KIM-1. In COM-induced cells, after treated with SB203580, overexpression of KIM-1 could reverse the protection effect of SB203580 on COM-induced cell damage and the inhibition of SB203580 on COM-induced excessive autophagy, suggesting p38/MAPK regulated KIM-1 to regulate COM-induced cell apoptosis and autophagy. Finally, we proved that TFDS inhibited p38/MAPK pathway. And the protection effect of COM-induced cell injury increased with the increase of TFDS concentration, and the adhesion between COM and cells decreased with the increase of TFDS concentration. With the increase of the concentration of TFDS, p38/MAPK pathway was gradually inhibited, and KIM-1 and autophagy related proteins were decreased. TFDS inhibited HK-2 cell apoptosis and autophagy by regulating KIM-1 via p38/MAPK pathway.

Determining normal values of urinary phosphorus excretion in 3913 healthy children aged 2-18 to aid early diagnosis and treatment for urolithiasis

AIM

This study determined the specific reference values for urinary phosphorus excretion in healthy children and adolescents aged 2-18 years and evaluated whether they changed with age during growth and were gender dependent.

METHODS

We enrolled 3913 healthy children and adolescents aged 2-18 years to this study. The study population was divided into age groups, and the analysis was performed in one-year periods, separately for boys and girls. Urinary phosphorus excretion was analysed using four categories: P1 in mmol/24 hour units, P2 in mmol/kg/24 hours, P3 in mmol/1.73 m² /24 hours and P4 in mmol/mmol creatinine.

RESULTS

Clear differences in urinary exertion for girls and boys were observed as well as systematic changes with age. The boys presented with significantly higher daily urinary phosphorus excretion independent of its manner of expression (p < 0.001). The median urinary phosphorus (P1) rose with age (p < 0.001). Percentile tables of phosphorous exertion are presented.

CONCLUSION

This was the largest study of urinary phosphate excretion based on a randomly selected sample of girls and boys aged 2-18 years. It highlights the importance of determining phosphorus reference values for children of different ages to provide early diagnosis and treatment for urolithiasis.

Burden of Urolithiasis: Trends in Prevalence, Treatments, and Costs

CONTEXT

The recent evolution of management options for urolithiasis has presented a unique dilemma for the modern urologist. A comprehensive understanding of epidemiological trends along with current provider preferences in treating urinary stones would be beneficial.

OBJECTIVE

To review trends in the prevalence, treatments, and costs of urolithiasis worldwide.

EVIDENCE ACQUISITION

A literature review was performed using the MEDLINE database, the Cochrane Library Central search facility, Web of Science, and Google Scholar between 1986 and 2016. Keywords used for the search were "urolithiasis" and "prevalence; treatment; and cost".

EVIDENCE SYNTHESIS

The incidence and prevalence of urinary stones are rising around the world, including regions that have historically had low rates of urolithiasis. Common theories explaining this trend involve climate warming, dietary changes, and obesity. Shockwave lithotripsy (SWL) has been the preferred mode of treatment since its introduction in the 1980s. However, ureteroscopy (URS) has become increasingly popular for small stones regardless of location because of lower recurrence rates and costs. Developing countries have been slower to adopt URS technology and continue to use percutaneous nephrolithotomy at a steady rate.

CONCLUSIONS

URS has recently challenged SWL as the treatment modality preferred for small upper urinary tract stones. In some cases it is less expensive but still highly effective. As the burden of stone disease increases worldwide, appropriate selection of stone removal therapies will continue to play an important role and will thus require further investigation.

PATIENT SUMMARY

Urinary stones are becoming more prevalent. Recent advances in technology have improved the management of this disease and have decreased costs.

Effect of citrus-based products on urine profile: A systematic review and meta-analysis

Background. Urolithiasis is a disease with high recurrence rate, 30-50% within 5 years. The aim of the present study was to learn the effects of citrus-based products on the urine profile in healthy persons and people with urolithiasis compared to control diet and potassium citrate.  Methods. A systematic review was performed, which included interventional, prospective observational and retrospective studies, comparing citrus-based therapy with standard diet therapy, mineral water, or potassium citrate. A literature search was conducted using PUBMED, COCHRANE, and Google Scholar with "citrus or lemonade or orange or grapefruit or lime or juice" and "urolithiasis" as search terms. For statistical analysis, a fixed-effects model was conducted when p > 0.05, and random-effects model was conducted when p < 0.05.  Results. In total, 135 citations were found through database searching with 10 studies found to be consistent with our selection criteria. However, only 8 studies were included in quantitative analysis, due to data availability. The present study showed a higher increased in urine pH for citrus-based products (mean difference, 0.16; 95% CI 0.01-0.32) and urinary citrate (mean difference, 124.49; 95% CI 80.24-168.74) compared with a control group. However, no differences were found in urine volume, urinary calcium, urinary oxalate, and urinary uric acid. From subgroup analysis, we found that citrus-based products consistently increased urinary citrate level higher than controls in both healthy and urolithiasis populations. Furthermore, there was lower urinary calcium level among people with urolithiasis.  Conclusions. Citrus-based products could increase urinary citrate level significantly higher than control. These results should encourage further research to explore citrus-based products as a urolithiasis treatment.

Epidemiology of stone disease across the world

Nephrolithiasis is a highly prevalent disease worldwide with rates ranging from 7 to 13% in North America, 5-9% in Europe, and 1-5% in Asia. Due to high rates of new and recurrent stones, management of stones is expensive and the disease has a high level of acute and chronic morbidity. The goal of this study is to review the epidemiology of stone disease in order to improve patient care. A review of the literature was conducted through a search on Pubmed^®, Medline^®, and Google Scholar^®. This review was presented and peer-reviewed at the 3rd International Consultation on Stone Disease during the 2014 Société Internationale d'Urologie Congress in Glasgow. It represents an update of the 2008 consensus document based on expert opinion of the most relevant studies. There has been a rising incidence in stone disease throughout the world with a narrowing of the gender gap. Increased stone prevalence has been attributed to population growth and increases in obesity and diabetes. General dietary recommendations of increased fluid, decreased salt, and moderate intake of protein have not changed. However, specific recommended values have either changed or are more frequently reported. Geography and environment influenced the likelihood of stone disease and more information is needed regarding stone disease in a large portion of the world including Asia and Africa. Randomized controlled studies are lacking but are necessary to improve recommendations regarding diet and fluid intake. Understanding the impact of associated conditions that are rapidly increasing will improve the prevention of stone disease.

Progress in Understanding the Genetics of Calcium-Containing Nephrolithiasis

Renal stone disease is a frequent condition, causing a huge burden on health care systems globally. Calcium-based calculi account for around 75% of renal stone disease and the incidence of these calculi is increasing, suggesting environmental and dietary factors are acting upon a preexisting genetic background. The familial nature and significant heritability of stone disease is known, and recent genetic studies have successfully identified genes that may be involved in renal stone formation. The detection of monogenic causes of renal stone disease has been made more feasible by the use of high-throughput sequencing technologies and has also facilitated the discovery of novel monogenic causes of stone disease. However, the majority of calcium stone formers remain of undetermined genotype. Genome-wide association studies and candidate gene studies implicate a series of genes involved in renal tubular handling of lithogenic substrates, such as calcium, oxalate, and phosphate, and of inhibitors of crystallization, such as citrate and magnesium. Additionally, expression profiling of renal tissues from stone formers provides a novel way to explore disease pathways. New animal models to explore these recently-identified mechanisms and therapeutic interventions are being tested, which hopefully will provide translational insights to stop the growing incidence of nephrolithiasis.

Clinical relevance of seasonal changes in the prevalence of ureterolithiasis in the diagnosis of renal colic

Ureterolithiasis is one of the most frequently diagnosed urologic diseases worldwide. Its annual incidence in Japan increased three-fold from 1965 to 2005. Ureterolithiasis incidence is affected by numerous factors, including race, sex, body weight, fluid intake, and climate. Here, we aimed to address the latter by considering the effect of seasonal variation on stone incidence and incorporating this information into a predictive model for differential diagnosis of ureteral stone from other conditions with similar presentations. We retrospectively identified 491 patients in our emergency department computer database who complained of back, flank, or lower abdominal pain during 2007-2015. Among them, 358 had stones, as confirmed by computerized tomography or plain abdominal X-ray of kidney-ureter-bladder. We also charted the mean ambient temperatures in our city for a year. The cases of ureteral stones paralleled the ambient temperatures, peaking during the hottest weather. Univariate analysis identified 13 factors associated with ureteral stones. Multivariate analysis narrowed the number to eight: age <60 years, male sex, short duration of pain (<6 h), nausea/vomiting, hydronephrosis, hematuria, history of urinary stone(s), and summer (July-September in Japan). Pain appearing during summer was nine times more likely to be due to a ureteral stone than was pain appearing during other seasons. We incorporated the eight variables identified into a predictive logistic regression model, which yielded good prediction of ureteral stones. Awareness that hot weather is associated with increased incidence of ureterolithiasis could facilitate differential diagnosis, and our prediction model could be useful for screening for ureterolithiasis.

Trends in urological stone disease: a 5-year update of hospital episode statistics

OBJECTIVE

To provide a 5-year follow-on update on the changes in prevalence and treatment of upper urinary tract (UUT) stone disease in England.

METHODS

Data from the Hospital Episode Statistics (HES) website (http://www.hesonline.nhs.uk) were extracted, summarised, analysed, and presented.

RESULTS

The total number of UUT stone hospital episodes increased slightly from 83 050 in 2009-2010 to 86 742 in 2014-2015 (4.4% increase). The use of shockwave lithotripsy (SWL) for treating all UUT stones remained stable over the 5-year study period following a significant increase in previous years. There was a 49.6% increase in the number of ureteroscopic stone treatments from 12 062 in 2009-2010 to 18 055 in 2014-2015. Increase in ureterorenoscopy (flexible ureteroscopy) showed the most rapid increase from 3 267 to 6 631 cases in the 5-year study period (103% increase). The gap between the total number of ureteroscopies and SWL treatments continues to narrow. Open stone surgery continued to decline with only 30 reported cases in 2014-2015. Due to the continued rapid increase in the number of ureteroscopies performed, treatment for stone disease has continued to increase significantly in comparison to other urological activity.

CONCLUSION

This study provides an update on the changing landscape of the management of UUT stones in England. It shows a sustained high prevalence of stone disease commensurate with levels in other developed countries. This study reveals a trend in the last 5 years to surgically intervene on a higher proportion of patients with stones. As in other countries, there is a significant increase in the use of ureteroscopy (particularly intrarenal flexible ureteroscopy) in England. These data have important implications for work-force planning, training, service delivery, and research in the field of urolithiasis.

Prospective Outcomes of Ultra Mini Percutaneous Nephrolithotomy: A Consecutive Cohort Study

PURPOSE

Ultra mini percutaneous nephrolithotomy is a less invasive technique of percutaneous nephrolithotomy to treat small to medium sized calculi.

MATERIALS AND METHODS

We prospectively evaluated the outcomes of ultra mini percutaneous nephrolithotomy in a single surgeon, consecutive cohort study. Data on 94 patients who underwent ultra mini percutaneous nephrolithotomy were collected.

RESULTS

Mean ± SD calculus size was 15.9 ± 4.5 mm and mean density was 1,106 ± 167 HU. Access was achieved via the upper pole in 8 cases, interpolar in 33 and lower pole in 54. Mean operative time was 54 minutes (range 28 to 120). Mean hemoglobin loss was 0.81 gm/dl and the mean creatinine increase was 0.05 mg/dl. There were no transfusions or kidney injuries. Grade I and IIIb complications were observed in 4 and 1 patients, respectively. The most serious complication was a perinephric collection. Postoperatively oral analgesia was sufficient in 86 patients (91%). Mean length of stay was 38.2 ± 15.9 hours. Nephrostomy drainage was used in 13 patients while 7 (7%) required a stent for 1 week. Intraoperatively 99% of renal units were stone free (absence of detectable calculi) on fluoroscopy, and 74% and 81% were stone free on day 1 postoperative ultrasound and 1-month computerized tomography, respectively. The 10 to 20 mm stones showed less bleeding, shorter operative time and a significantly lower requirement for nephrostomy or a Double-J(®) stent.

CONCLUSIONS

Ultra mini percutaneous nephrolithotomy appears to be effective and safe with a short length of stay. It may be a valuable addition to the armamentarium to treat 10 to 20 mm calculi in patients who wish to avoid routine nephrostomy or stents. Randomized, controlled trials are required.