Renal stone epidemiology in Rochester, Minnesota: an update

Clinical and demographic predictors of repeat stone surgery

OBJECTIVE

To identify the clinical and demographic predictors of repeat stone surgery.

MATERIALS AND METHODS

We retrospectively analysed 1496 consecutive patients, aged > 18 years, who underwent stone surgery at our institution in the period from January 2009 to May 2017 and who had at least 12 months of postoperative follow-up. We defined surgical recurrence as repeat surgery on the same renal unit or on the opposite renal unit if the original imaging did not demonstrate significant stones on that side. Characteristics associated with the risk of surgical recurrence in univariate Cox regression analysis were entered into a multivariate model.

RESULTS

Most patients underwent ureteroscopy and laser lithotripsy (83.0%). Approximately 60% of the patients had a personal history of stone disease and 50% were obese. Over a mean (median; interquartile range) follow-up of 4.1  (3.9; 2.4-5.9) years, 24.5% of patients had surgical recurrence, with 82% of repeat surgeries performed for symptomatic nephrolithiasis. The factors associated with increased risk of surgical recurrence in the multivariate model were: age <60 years, female gender, malabsorptive gastrointestinal disease, diabetes, recurrent urinary tract infections, personal history of nephrolithiasis, renal stones and bilateral nephrolithiasis. The hazard ratios for these variables ranged within an interval of <0.5 (from 1.30 to 1.71).

CONCLUSION

We identified eight demographic and clinical factors associated with increased risk of repeat renal stone surgery. These factors could be combined as a numerical count that allows stratification of patients into low-, intermediate- and high-risk subgroups.

The impact of urinary stone disease and their treatment on patients' quality of life: a qualitative study

Urinary stone disease is a common, often recurrent disease, that can have a negative impact on patients’ health-related quality of life (HRQoL), often effecting working, productive members of society. The literature lacks data from structured, qualitative research which could give unique insight into patients’ HRQoL. The objective is to understand the impact of urinary stone disease and treatments on patients’ HRQoL, from patients’ and their relatives’ perspective using qualitative and quantitative methodologies. Semi-structured interviews and a focus group were used to understand the HRQoL issues of patients with urinary stones disease, covering the American Urology Association index stone categories. Thematic analysis was performed (using qualitative data analysis software). Familial impact was assessed using the family-related outcome measure (FROM-16©). 62 patients with stone disease and interventions (mean age 51, range 19–92) participated. Data collection stopped when data saturation was achieved. Analysis revealed negative impact of stone disease and interventions on the patients’ HRQoL, affecting domains of pain, physical symptoms, outlook on life, work/career, change in lifestyle/diet, social life, difficulties of daily living, travel/holiday problems, relationships and family member impact (106 themes grouped under ten broad headings). Sub-group analyses revealed similar impact in either sex, ureteric and renal stone groups. Recurrent stones were associated with work/financial concerns and treatment preferences varied accordingly. Our qualitative study presents detailed insights into the multidimensional impact of urinary calculi and their treatments on various domains of the HRQoL, confirming previous findings and adding new observations. The findings are expected to help in the development of patient-centric measures and communication tools.

Modeling the Incidence of Secondary Malignancy Related to Ionizing Radiation Use in the Management of Nephrolithiasis

OBJECTIVE

To model the risk of secondary malignancy and associated mortality due to ionizing radiation from the evaluation and management of nephrolithiasis.

METHODS

A PUBMED-based literature search was performed to identify model inputs, specifically annual incidence of nephrolithiasis sub-stratified by age and gender and radiation exposure associated with nephrolithiasis episodes. Estimates of age and gender specific radiation-induced malignancy and mortality rates were obtained from the BEIR VII Phase 2 report with dose extrapolation using the linear no-threshold model.

RESULTS

Incidence of new diagnoses of nephrolithiasis ranged from 42/100,000 in males 20-30 years old to 248/100,000 in males 60-70 years old. Radiation exposure per nephrolithiasis episode was 37.3 mSv over a 2-year period. Data regarding average stone episodes per patient with nephrolithiasis was limited and conservatively estimated at 1.5. Modeled lifetime attributable risk of secondary malignancy and subsequent mortality in individual stone patients ranged from 0.096% and 0.085%, respectively, in males over the age of 70 to 0.59% and 0.39% in females 20-30 years old. In the USA, overall incidence of secondary malignancy and associated mortality related to nephrolithiasis management was calculated to be 862.7 and 545.3 cases/year, respectively.

CONCLUSION

This model suggests that ionizing radiation from the management of nephrolithiasis carries a small but significant risk of causing secondary malignancy. This knowledge must be considered when using modalities that involve radiation in the diagnosis and therapeutic management of nephrolithiasis.

External Validation of the Recurrence of Kidney Stone Nomogram in a Surgical Cohort

Objective: To assess the performance of recurrence of kidney stone (ROKS) nomogram in identifying first-time stone formers who will require future stone procedures. Materials and Methods: From January 2009 to February 2016, 2287 patients underwent surgical treatment for nephrolithiasis at our institution and 498 of them were eligible for this study. We defined recurrence as repeat surgery for symptomatic nephrolithiasis. We analyzed the performance of the nomogram with respect to discrimination, calibration, and the clinical net benefit. We also examined the performance of each individual variable from the nomogram. Results: Over a median follow-up of 4.8 years (mean 4.6, IQR 3.1-6.1), 88 patients (17.7%) had recurrent nephrolithiasis requiring surgical treatment. The ROKS nomogram demonstrated moderate discriminative ability (AUC 0.655 for 2 years and 0.605 for 5 years). Calibration of the ROKS nomogram-based predictions was poor and net clinical benefit was minimal. Three of 11 predictors from the nomogram were statistically significantly associated with the risk of repeat surgery, with two of them representing similar clinical scenarios, namely symptomatic and nonsymptomatic renal stones. Conclusion: ROKS nomogram demonstrated limited discrimination and calibration in predicting the risk of repeat surgery for symptomatic nephrolithiasis in our cohort of first-time stone formers. This may be caused by the differences between stone patients who do and do not require surgery and suggests the need for development of more precise prediction instruments.

A PSA for Radiologists: Pictorial Review of Incidentalomas on Prostate Magnetic Resonance Imaging

Multiparametric magnetic resonance imaging (MRI) of the prostate is a powerful and increasingly utilized imaging study for the diagnosis, staging, and surveillance of prostate cancer. With greater adoption by clinicians, it is becoming more common for incidental findings to be first detected on prostate MRI. Inadequate description of clinically significant findings may not prompt appropriate patient management, while over-reporting of indolent findings comes at increased patient anxiety, cost of workup, and iatrogenic risk. This review article aims to improve awareness, review pathophysiology, and present key imaging features of incidental findings seen on prostate MRI, ranging from common to rare and from benign to clinically significant.

The Demographic Diversity of Food Intake and Prevalence of Kidney Stone Diseases in the Indian Continent

Food intake plays a pivotal role in human growth, constituting 45% of the global economy and wellbeing in general. The consumption of a balanced diet is essential for overall good health, and a lack of equilibrium can lead to malnutrition, prenatal death, obesity, osteoporosis and bone fractures, coronary heart diseases (CHD), idiopathic hypercalciuria, diabetes, and many other conditions. CHD, osteoporosis, malnutrition, and obesity are extensively discussed in the literature, although there are fragmented findings in the realm of kidney stone diseases (KSD) and their correlation with food intake. KSD associated with hematuria and renal failure poses an increasing threat to healthcare infrastructures and the global economy, and its emergence in the Indian population is being linked to multi-factorial urological disorder resulting from several factors. In this realm, epidemiological, biochemical, and macroeconomic situations have been the focus of research, even though food intake is also of paramount importance. Hence, in this article, we review the corollary associations with the consumption of diverse foods and the role that these play in KSD in an Indian context.

Activation of liver X receptor suppresses osteopontin expression and ameliorates nephrolithiasis

Nephrolithiasis is a common disease of the urinary system, of which idiopathic calcium oxalate (CaOx) kidney stones, in particular, are one of the special types. In the initial stages of CaOx kidney stone formation, Randall's plaques (RPs) develop. Liver X receptors (LXRs) inhibit oxidative stress and inflammatory in other diseases; nevertheless, the role of LXRs in nephrolithiasis has yet to be elucidated. In this study, the role of LXRs in the progression of RP formation was investigated. Microarray analysis revealed that LXR/RXR levels were significantly greater in low-plaque tissues (<5%) than in high-plaque tissues (>5%), confirming the link between LXR activation and RP formation. Correspondingly, expression levels of two LXR target genes, LXRα and LXRβ, were lower in high-plaque tissues than in low-plaque tissues. In vitro, LXR agonist alleviated calcium oxalate monohydrate-induced cellular calcium deposits and apoptosis. LXR activation decreased reactive oxygen species production and gene expression of inflammatory mediators, including osteopontin that has recently been demonstrated to correlate with the development of RPs. Moreover, p38 MAPK and JNK signaling may mediate LXR-regulated expression in HK-2 cells. In an animal model, the deposition was reduced by activating LXR, and osteopontin expression was also inhibited. Our findings suggest a role for LXRs in the progression of idiopathic CaOx kidney stones; LXR agonists may have therapeutic potential for the treatment of nephrolithiasis.

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.

Stones in pregnancy and pediatrics

Urinary stone disease is a highly prevalent condition affecting approximately 10% of the population, and has increased in incidence significantly over the past 20 years. Along with this, the rate of stone disease among women and children is also on the rise. The management of stone disease in specific populations, such as in children and during pregnancy can present unique challenges to the urologist. In both populations, a multi-disciplinary approach is strongly recommended given the complexities of the patients. Prompt and accurate diagnosis requires a high degree of suspicion and judicious use of diagnostic imaging given the higher risks of radiation exposure. In general, management proceeds from conservative to more invasive approaches and must be individualized to the patient with careful consideration of the potential adverse effects. However, innovations in endourologic equipment and techniques have allowed for the wider application of surgical stone treatment in these patients, and significant advancement in the field. This review covers the history and current advances in the diagnosis and management of stone disease in pregnant and pediatric populations. It is paramount for the urologist to understand the complexities of properly managing stones in these patients in order to maximize treatment efficacy, while minimizing complications and morbidity.

Epidemiology of urolithiasis consultations in the Paraíba Valley

OBJECTIVE

to know the epidemiological profile of patients with urolithiasis in the Paraíba Valley region, identifying its prevalence and spatial distribution.

METHOD

we conducted a cross-sectional study, by residence location in the Paraíba Valley, on morbidity data due to urolithiasis obtained from the DATASUS, covering the period between 2010 and 2012. We aimed at identifying the general, male and female prevalence of urolithiasis, the distribution by age, type of visit, year season and spatial distribution.

RESULTS

there were 1,901 visits for urolithiasis in the 35 municipalities of the Paraíba Valley in the three years studied, 52.3% of them of female patients. Of the total, 70.1% of the visits were emergency ones. The feminine visits (67.2%) were mostly also urgent (p <0.01). The overall prevalence for urolithiasis was 31.7/100,000. Male prevalence was 30.7/100,000, and the female, 32.7/100,000 (p>0.05). The prevalence ratio was 0.9 men for every woman. The age group with the highest prevalence was between 30 and 39 years, with 23.1%. Warm seasons concentrated 51.6% of cases, while 48.8% occurred in the cold ones (p>0.05) .

CONCLUSION

women are more affected by urolithiasis than the male in the Paraíba Valley region, an unprecedented in the literature. There was no relationship between the year season and the disease. We identified municipalities where preventive actions of urinary lithogenesis are required.

The Changing Incidence and Presentation of Urinary Stones Over 3 Decades

OBJECTIVE

To evaluate trends in the incidence of kidney stones and characteristics associated with changes in the incidence rate over 3 decades.

PATIENTS AND METHODS

Adult stone formers in Olmsted County, Minnesota, from January 1, 1984, to December 31, 2012, were validated and characterized by age, sex, stone composition, and imaging modality. The incidence of kidney stones per 100,000 person-years was estimated. Characteristics associated with changes in the incidence rate over time were assessed using Poisson regression models.

RESULTS

There were 3224 confirmed symptomatic (stone seen), 606 suspected symptomatic (no stone seen), and 617 incidental asymptomatic kidney stone formers. The incidence of confirmed symptomatic kidney stones increased from the year 1984 to 2012 in both men (145 to 299/100,000 person-years; incidence rate ratio per 5 years, 1.14, P<.001) and women (51 to 217/100,000 person-years; incidence rate ratio per 5 years, 1.29, P<.001). Overall, the incidence of suspected symptomatic kidney stones did not change, but that of asymptomatic kidney stones increased. Utilization of computed tomography for confirmed symptomatic stones increased from 1.8% in 1984 to 77% in 2012; there was a corresponding higher increased incidence of symptomatic small stones (≤3 mm) than of larger stones (>3 mm). Confirmed symptomatic kidney stones with documented spontaneous passage also increased. The incidence of kidney stones with unknown composition increased more than that of stones with known composition.

CONCLUSION

The incidence of both symptomatic and asymptomatic kidney stones has increased dramatically. The increased utilization of computed tomography during this period may have improved stone detection and contributed to the increased kidney stone incidence.

Familial Risks Between Urolithiasis and Cancer

Urolithiasis (UL, urinary tract stone disease) has been reported to increase subsequent cancers in the urinary tract. Recently, we showed data that surveillance bias may be an important confounder in the reported associations. In the present approach we want to address the question of possible cancer risk posed by UL mechanistically. Both UL and cancer have strong genetic components and we hypothesize that familial association between UL and cancer may be plausible. We thus assess familial risks between UL and cancer, hoping to find an explanation why UL may pose a risk of cancer. UL patients were identified from hospital inpatient and outpatient records and they were organized in families based on the Multigeneration Register into which also national cancer data were linked. Standardized incidence ratios were calculated for cancer in the offspring generation when parents were diagnosed with UL, and conversely for UL when parents were diagnosed with cancer. Familial risks between UL and cancer were generally small and inconsistent providing no convincing support of genetic sharing between UL and cancer. However, bladder UL was associated weakly with prostate cancer, and ureter and bladder UL were associated with salivary gland cancer. Potential mechanisms for these findings are proposed.

Incidence and characteristics of kidney stones in patients with horseshoe kidney: A systematic review and meta-analysis

Introduction

The horseshoe kidney (HSK) is the most common type of renal fusion anomaly. The incidence and characteristics of kidney stones in patients with HSK are not well studied. The aim of this meta-analysis was to evaluate the incidence and types of kidney stones in patients with HSK.

Methods

A systematic literature search was performed using MEDLINE, EMBASE, and Cochrane Database of Systematic Reviews from the databases' inception through November 2016. Studies assessing the incidence and types of kidney stones in patients with HSK were included. We applied a random-effects model to estimate the incidence of kidney stones. The study protocol was registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42016052037).

Results

A total of 14 observational studies with 943 patients (522 adults and 421 pediatric) with HSK were enrolled. The estimated pooled incidence of kidney stones was 36% (95% confidence interval [CI], 15%-59%) in adults with the HSK. Kidney stones were less common in pediatric patients with HSK with an estimated pooled incidence of 3% (95% CI, 2%-5%). The mean age of adult stone formers with HSK was 44.9 ± 6.2 years, and 75% were males. Within reported studies, 89.2% of kidney stones were calcium-based stones (64.2% calcium oxalate [CaOx], 18.8% calcium phosphate [CaP], and 6.2% mixed CaOx/CaP), followed by struvite stones (4.2%), uric acid stones (3.8%), and others (2.8%).

Conclusions

Kidney stones are very common in adult patients with HSK with an estimated incidence of 36%. Calcium-based stones are the most prevalent kidney stones in adults with HSKs. These findings may impact the prevention and clinical management of kidney stones in patients with HSK.

Ultrasound-guided percutaneous nephrolithotomy for the treatment in patients with kidney stones

BACKGROUND

In this study, we aimed to explore the effect of ultrasound-guided percutaneous nephrolithotomy (UGPN) for the treatment in patients with kidney stones (KS).

METHODS

We randomly assigned 86 patients with KS to a UGPN group or a control group, each group comprising 43 patients. Patients from the UGPN group underwent UGPN whereas those from control group underwent fluoroscopic-guided percutaneous nephrolithotomy (FGPN). The primary outcome included the stone-free rate. Secondary outcomes included complication rates, operative time, and length of hospitalization.

RESULTS

UGPN did not show better efficacy than the FGPN procedure in decreasing stone-free rate (UGPN group 79.1% vs control group 69.8%, P = .45), operative time (UGPN group 108.4 ± 31.7 minute vs control group 113.2 ± 34.5 minute, P = .50), and length of hospitalization (UGPN group 2.7 ± 1.3 days vs control group 3.1 ± 1.5 days, P = .19). Additionally, no complications, except fever (UGPN group 4.7% vs control group 9.3%, P = .41) and hemoglobin slightly reduced (UGPN group 7.0% vs control group 11.6%, P = .46) were noted in patients from both groups in this study.

CONCLUSIONS

To summarize, we demonstrated that both UGPN and FGPN techniques showed similar efficacy and complications when used for the management of KS.

Nephrolithiasis and risk of hypertension: a meta-analysis of observational studies

Background

Observational studies have demonstrated an association between nephrolithiasis and hypertension. The aim of this meta-analysis was to summarize all available evidence.

Methods

PubMed, EMBASE, the Cochrane Central Register of Controlled Trials databases, and the reference lists of relevant articles were searched to identify observational studies that reported study-specific risk estimates comparing the risk of hypertension in patients with nephrolithiasis. We used a random-effect model to pool the study-specific risk estimates. We also assessed the potential heterogeneity by subgroup analyses, meta-regression analyses, and sensitivity analyses.

Results

A total of 7 articles including 9 studies (n = 313,222 participants) were eventually identified in this meta-analysis. In comparison with the patients who did not have nephrolithiasis, nephrolithiasis significantly increased the risk of hypertension (OR, 1.43; 95% CI, 1.30–1.56), with significant heterogeneity between these studies (I² = 83.5%, P <0.001). The heterogeneity reduced in subgroups of cohort studies, USA, large sample size trials, men, and adjustment for confounding factors ≥ 5. Sensitivity analysis further demonstrated the results to be robust.

Conclusions

Nephrolithiasis is associated with increased risk of hypertension. Future randomized, high-quality clinical trials are encouraged to definitively clarify the relationship between nephrolithiasis and hypertension, which may influence clinical management and primary prevention of hypertension in nephrolithiasis patients.

Electronic supplementary material

The online version of this article (10.1186/s12882-017-0762-8) contains supplementary material, which is available to authorized users.

Compositional analysis of various layers of upper urinary tract stones by infrared spectroscopy

The objective of the present study was to determine the composition of various layers of upper urinary stones and assess the mechanisms of stone nucleation and aggregation. A total of 40 integrated urinary tract stones with a diameter of >0.8 cm were removed from the patients. All of the stones were cut in half perpendicularly to the longitudinal axis. Samples were selected from nuclear, internal and external layers of each stone. Fourier transform infrared spectroscopy (FT-IR) was adopted for qualitative and quantitative analysis of all of the fragments and compositional differences among nuclear, internal and external layers of various types of stone were subsequently investigated. A total of 25 cases of calcium oxalate (CaOx) stones and 10 cases of calcium phosphate (CaP) stones were identified to be mixed stones, while 5 uric acid (UA) calculi were pure stones (purity, >95%). In addition, the contents of CaOx and carbapatite (CA.AP) crystals in various layers of the mixed stones were found to be variable. In CaOx stones, the content of CA.AP in nuclear layers was significantly higher than that of the outer layers (32.0 vs. 6.8%; P<0.05), while the content of CaOx was lower in the inner than in the outer layers (57.6 vs. 86.6%; P<0.05). In CaP stones, the content of CA.AP in the nuclear layers was higher than that in the outer layers (74.0 vs. 47.3%; P<0.05), while the content of CaOx was lower in the inner than in the outer layers (7.0 vs. 40.0%; P<0.05). The UA stones showed no significant differences in their composition among different layers. In conclusion, FT-IR analysis of various layers of human upper urinary tract stones revealed that CaOx and CaP stones showed differences in composition between their core and surface, while all of the UA calculi were pure stones. The composition showed a marked variation among different layers of the stones, indicating that metabolism has an important role in different phases of the evolution of stones. The present study provided novel insight into the pathogenesis of urinary tract stones and may contribute to their prevention and treatment.

Epidemiology and economics of nephrolithiasis

Nephrolithiasis is a disease common in both the Western and non-Western world. Several population based studies have demonstrated a rising prevalence and incidence of the disease over the last several decades. Recurrence occurs frequently after an initial stone event. The influence of diet on the risk of nephrolithiasis is important, particularly dietary calcium and fluid intake. An increasing intake of dietary calcium and fluid are consistently associated with a reduced risk of incident nephrolithiasis in both men and women. Increasing evidence suggests that nephrolithiasis is associated with systemic diseases like obesity, diabetes, and cardiovascular disease. Nephrolithiasis places a significant burden on the health care system, which is likely to increase with time.

Kidney stones may increase the risk of coronary heart disease and stroke: A PRISMA-Compliant meta-analysis

BACKGROUND

We aimed to quantitatively assess the potential relationship between kidney stones and coronary heart disease or stroke.

METHODS

A meta-analysis was conducted on eligibly studies published before 31 May 2016 in PubMed or Embase. The data were pooled, and the relationship was assessed by the random-effect model with inverse variance-weighted procedure. The results were expressed as relative risk (RR) with 95% confidence intervals (95%CI).

RESULTS

Eight studies of 11 cohorts (n = 11) were included in our analysis with 3,658,360 participants and 157,037 cases. We found that a history of kidney stones was associated with increased risk of coronary heart disease (CHD) (RR = 1.24; 95%CI: 1.14-1.36; I = 79.0%, n = 11); similar effect on myocardial infarction, a serious condition of CHD, was observed (RR = 1.24; 95%CI: 1.10-1.40; I = 80.4%, n = 8). We also found that a history of kidney stones may increase the risk of stroke (RR = 1.21, 95%CI: 1.06-1.38; I = 54.7%, n = 4). In subgroup analysis, the risk of coronary heart disease was higher in men (RR = 1.23, 95%CI: 1.02-1.49) while the risk for stroke was higher in women (RR = 1.12; 95%CI: 1.03-1.21). No obvious publications bias was detected (Egger test: P = .47).

CONCLUSION

Kidney stones are associated with increased risk of coronary heart disease and stroke, and the effect may differ by sex.

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.

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.

Prevalence of kidney stones in mainland China: A systematic review

The data on the prevalence of kidney stones in mainland China are still lacking. We performed the present meta-analysis to assess the stone prevalence in mainland China from 1990 through 2016. A total of 18 articles were included. The pooled overall prevalence was 7.54% (95% CI, 5.94-9.15). The prevalence in age groups of <20 years, 20-29 years, 30-39 years, 40-49 years, 50-59 years, and 60 years and older was 0.27%, 3.15%, 5.96%, 8.18%, 9.14%, and 9.68%, respectively, showing that it increased with age. Moreover, the prevalence was 10.34% in males and 6.62% in females, with an odds ratio (OR) of 1.63 [95% CI: 1.51-1.76], indicating that males are more likely to suffer from this disease than females. However, urban areas (6.03%, 95% CI: 3.39-8.68) and rural areas (7.48%, 95% CI: 3.39-11.57) did not differ in the stone prevalence rate (OR = 0.84, 95% CI: 0.42-1.68). The prevalence in the year groups of 1991-2000, 2001-2010, and 2011 to date was 5.95%, 8.86%, and 10.63%, respectively, which indicated an increasing trend. Further high-quality surveys throughout mainland China are needed to confirm these findings.

Kidney Stone Recurrence among Children and Adolescents

PURPOSE

Kidney stone disease has become increasingly common during childhood and adolescence. However, the rate of symptomatic kidney stone recurrence for pediatric patients is uncertain. We sought to determine the recurrence rate of symptomatic kidney stones in a cohort of children with incident symptomatic nephrolithiasis.

MATERIALS AND METHODS

We performed a retrospective cohort study of patients 3 to 18 years old without anatomical abnormalities or genetic causes of nephrolithiasis who presented with a first symptomatic kidney stone between 2008 and 2014. We determined recurrence rates of symptomatic nephrolithiasis, defined as a new kidney stone on ultrasound and/or computerized tomogram associated with pain and/or vomiting. We also estimated associations between completing 24-hour urinalysis and symptomatic kidney stone recurrence using Kaplan-Meier curves and multivariable Cox regression models.

RESULTS

A total of 285 children with a median age of 14.8 years (IQR 11.3-16.6) at nephrolithiasis diagnosis were followed for 492 person-years. A total of 86 symptomatic recurrent stones developed in 68 patients (24%) during the followup period. The probability of symptomatic stone recurrence was 50% at 3 years after the index kidney stone. Median time to stone recurrence was 3 years at the first recurrence and 5 years at the second. Adjusting for confounders including adherence to followup, completing a 24-hour urinalysis after a kidney stone episode was associated with a 60% decreased risk of recurrence (hazard ratio 0.40, 95% CI 0.18-0.91).

CONCLUSIONS

The risk of kidney stone recurrence is high during childhood, with approximately 50% of children presenting with symptomatic recurrence within 3 years of the first stone. The role and usefulness of analyzing 24-hour urine chemistries in decreasing kidney stone recurrence should be explored in future prospective studies.

Incidence of kidney stones in kidney transplant recipients: A systematic review and meta-analysis

AIM

To evaluate the incidence and characteristics of kidney stones in kidney transplant recipients.

METHODS

A literature search was performed using MEDLINE, EMBASE, and Cochrane Database of Systematic Reviews from the inception of the databases through March 2016. Studies assessing the incidence of kidney stones in kidney transplant recipients were included. We applied a random-effects model to estimate the incidence of kidney stones.

RESULTS

Twenty one studies with 64416 kidney transplant patients were included in the analyses to assess the incidence of kidney stones after kidney transplantation. The estimated incidence of kidney stones was 1.0% (95%CI: 0.6%-1.4%). The mean duration to diagnosis of kidney stones after kidney transplantation was 28 ± 22 mo. The mean age of patients with kidney stones was 42 ± 7 years. Within reported studies, approximately 50% of kidney transplant recipients with kidney stones were males. 67% of kidney stones were calcium-based stones (30% mixed CaOx/CaP, 27%CaOx and 10%CaP), followed by struvite stones (20%) and uric acid stones (13%).

CONCLUSION

The estimated incidence of kidney stones in patients after kidney transplantation is 1.0%. Although calcium based stones are the most common kidney stones after transplantation, struvite stones (also known as “infection stones”) are not uncommon in kidney transplant recipients. These findings may impact the prevention and clinical management of kidney stones after kidney transplantation.

Loss of MeCP2 Causes Urological Dysfunction and Contributes to Death by Kidney Failure in Mouse Models of Rett Syndrome

Rett Syndrome (RTT) is a neurodevelopmental disorder characterized by loss of acquired skills during development, autonomic dysfunction, and an increased risk for premature lethality. Clinical experience identified a subset of individuals with RTT that present with urological dysfunction including individuals with frequent urinary tract infections, kidney stones, and urine retention requiring frequent catheterization for bladder voiding. To determine if urologic dysfunction is a feature of RTT, we queried the Rett Syndrome Natural History Study, a repository of clinical data from over 1000 individuals with RTT and found multiple instances of urological dysfunction. We then evaluated urological function in a mouse model of RTT and found an abnormal pattern of micturition. Both male and female mice possessing Mecp2 mutations show a decrease in urine output per micturition event. Furthermore, we identified signs of kidney failure secondary to urethral obstruction. Although genetic strain background significantly affects both survival and penetrance of the urethral obstruction phenotype, survival and penetrance of urethral obstruction do not directly correlate. We have identified an additional phenotype caused by loss of MeCP2, urological dysfunction. Furthermore, we urge caution in the interpretation of survival data as an endpoint in preclinical studies, especially where causes of mortality are poorly characterized.

Ex Vivo Renal Stone Characterization with Single-Source Dual-Energy Computed Tomography: A Multiparametric Approach

RATIONALE AND OBJECTIVES

We aimed to investigate a multiparametric approach using single-source dual-energy computed tomography (ssDECT) for the characterization of renal stones.

MATERIALS AND METHODS

ssDECT scans were performed at 80 and 140 kVp on 32 ex vivo kidney stones of 3-10 mm in a phantom. True composition was determined by infrared spectroscopy to be uric acid (UA; n = 14), struvite (n = 7), cystine (n = 7), or calcium oxalate monohydrate (n = 4). Measurements were obtained for up to 52 variables, including mean density at 11 monochromatic keV levels, effective Z, and multiple material basis pairs. The data were analyzed with five multiparametric algorithms. After omitting 8 stones smaller than 5 mm, the remaining 24-stone dataset was similarly analyzed. Both stone datasets were also analyzed with a subset of 14 commonly used variables in the same fashion.

RESULTS

For the 32-stone dataset, the best method for distinguishing UA from non-UA stones was 97% accurate, and for distinguishing the non-UA subtypes was 72% accurate. For the 24-stone dataset, the best method for distinguishing UA from non-UA stones was 100% accurate, and for distinguishing the non-UA subtypes was 75% accurate.

CONCLUSION

Multiparametric ssDECT methods can distinguish UA from non-UA stones of 5 mm or larger with 100% accuracy. The best model to distinguish the non-UA renal stone subtypes was 75% accurate. Further refinement of this multiparametric approach may increase the diagnostic accuracy of separating non-UA subtypes and assist in the development of a clinical paradigm for in vivo use.

Multivariate Analyses of Urinary Calculi Composition: A 13-Year Single-Center Study

BACKGROUND

The incidence and prevalence of urinary stone are increasing throughout the world. Compared to the past, recent demographics of patient with urolithiasis compositions are strikingly different. Furthermore, recent clinical studies implied that seasonal cyclicity might influence the distribution of stone composition.

METHODS

We sought to determine the trends in pathogenesis of urolithiasis based on urinary stone analyses. Between 2002 and 2014, a total of 2,383 eligible urinary stone samples from different patients were collected in our center. Infrared spectroscopy was used for urinary calculi analysis. A logistic regression analysis was used to investigate the relationship between urinary calculi composition and calendar month (season), gender, and age in north China during the past 13 years.

RESULTS

Calcium-containing calculi were the most frequent with an overall incidence of 84.1%. Calcium phosphate (CaP) or magnesium ammonium phosphate (MAP) stones were more frequent in females, while monohydrate calcium oxalate (COM), dihydrate calcium oxalate (COD), or uric acid (UA) stones were more common in males. Older individuals were associated with an increased risk of UA stones and a decreased risk of COD, CaP, or cystine stones. Additionally, from 2002 to 2014, the frequency of COD and MAP stone increased, whereas the trend of CaP, UA and cystine stones decreased. However, calendar month (season) was not significantly associated with differences in composition.

CONCLUSION

This study provides the present distribution of urolithiasis compositions in China. From 2002 to 2014, age and gender were significantly associated with stone composition, whereas calendar month was not.

Kidney stones

Kidney stones are mineral deposits in the renal calyces and pelvis that are found free or attached to the renal papillae. They contain crystalline and organic components and are formed when the urine becomes supersaturated with respect to a mineral. Calcium oxalate is the main constituent of most stones, many of which form on a foundation of calcium phosphate called Randall's plaques, which are present on the renal papillary surface. Stone formation is highly prevalent, with rates of up to 14.8% and increasing, and a recurrence rate of up to 50% within the first 5 years of the initial stone episode. Obesity, diabetes, hypertension and metabolic syndrome are considered risk factors for stone formation, which, in turn, can lead to hypertension, chronic kidney disease and end-stage renal disease. Management of symptomatic kidney stones has evolved from open surgical lithotomy to minimally invasive endourological treatments leading to a reduction in patient morbidity, improved stone-free rates and better quality of life. Prevention of recurrence requires behavioural and nutritional interventions, as well as pharmacological treatments that are specific for the type of stone. There is a great need for recurrence prevention that requires a better understanding of the mechanisms involved in stone formation to facilitate the development of more-effective drugs.

Annual Incidence of Nephrolithiasis among Children and Adults in South Carolina from 1997 to 2012

BACKGROUND AND OBJECTIVES

The prevalence of nephrolithiasis in the United States has increased substantially, but recent changes in incidence with respect to age, sex, and race are not well characterized. This study examined temporal trends in the annual incidence and cumulative risk of nephrolithiasis among children and adults living in South Carolina over a 16-year period.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed a population-based, repeated cross-sectional study using the US Census and South Carolina Medical Encounter data, which capture all emergency department visits, surgeries, and admissions in the state. The annual incidence of nephrolithiasis in South Carolina from 1997 to 2012 was estimated, and linear mixed models were used to estimate incidence rate ratios for age, sex, and racial groups. The cumulative risk of nephrolithiasis during childhood and over the lifetime was estimated for males and females in 1997 and 2012.

RESULTS

Among an at-risk population of 4,625,364 people, 152,925 unique patients received emergency, inpatient, or surgical care for nephrolithiasis. Between 1997 and 2012, the mean annual incidence of nephrolithiasis increased 1% annually from 206 to 239 per 100,000 persons. Among age groups, the greatest increase was observed among 15-19 year olds, in whom incidence increased 26% per 5 years (incidence rate ratio, 1.26; 95% confidence interval, 1.22 to 1.29). Adjusting for age and race, incidence increased 15% per 5 years among females (incidence rate ratio, 1.15; 95% confidence interval, 1.14 to 1.16) but remained stable for males. The incidence among blacks increased 15% more per 5 years compared with whites (incidence rate ratio, 1.15; 95% confidence interval, 1.14 to 1.17). These changes in incidence resulted in doubling of the risk of nephrolithiasis during childhood and a 45% increase in the lifetime risk of nephrolithiasis for women over the study period.

CONCLUSIONS

The incidence of kidney stones has increased among young patients, particularly women, and blacks.

Short-Term Tolvaptan Increases Water Intake and Effectively Decreases Urinary Calcium Oxalate, Calcium Phosphate and Uric Acid Supersaturations

PURPOSE

Some patients cannot effectively increase water intake and urine volume to prevent urinary stones. Tolvaptan, a V2 receptor antagonist, blocks water reabsorption in the collecting duct and should decrease urinary supersaturation of stone forming solutes, although this action has never been proved.

MATERIALS AND METHODS

We conducted a double-blind, randomized, placebo controlled, crossover study of 21 calcium urinary stone formers stratified into majority calcium oxalate (10 patients) and calcium phosphate (11) groups. Patients received 45 mg tolvaptan per day or placebo for 1 week, followed by a washout week and crossover to tolvaptan or placebo for week 3. A 24-hour urine sample was collected at the end of weeks 1 and 3.

RESULTS

Tolvaptan vs placebo decreased urinary osmolality (mean ± SD 204 ± 96 vs 529 ± 213 mOsm/kg, p <0.001) and increased urinary volume (4.8 ± 2.9 vs 1.8 ± 0.9 L, p <0.001). The majority of urinary solute excretion rates, including sodium and calcium, did not change significantly, although oxalate secretion increased slightly (from mean ± SD 15 ± 8 to 23 ± 8 mg per 24 hours, p = 0.009). Mean ± SD urinary calcium oxalate supersaturation (-0.01 ± 1.14 vs 0.95 ± 0.87 dG, p <0.001), calcium phosphate supersaturation (-1.66 ± 1.17 vs -0.13 ± 1.02 dG, p <0.001) and uric acid supersaturation (-2.05 ± 4.05 vs -5.24 ± 3.12 dG, p = 0.04) all dramatically decreased. Effects did not differ between the calcium oxalate and calcium phosphate groups (p >0.05 for all interactions).

CONCLUSIONS

Tolvaptan increases urine volume and decreases urinary supersaturation in calcium stone formers. Further study is needed to determine if long-term use of V2 receptor antagonists results in fewer stone events.

The Interaction between Enterobacteriaceae and Calcium Oxalate Deposits

Background

The role of calcium oxalate crystals and deposits in UTI pathogenesis has not been established. The objectives of this study were to identify bacteria present in pediatric urolithiasis and, using in vitro and in vivo models, to determine the relevance of calcium oxalate deposits during experimental pyelonephritis.

Methods

Pediatric kidney stones and urine were collected and both cultured and sequenced for bacteria. Bacterial adhesion to calcium oxalate was compared. Murine kidney calcium oxalate deposits were induced by intraperitoneal glyoxalate injection and kidneys were transurethrally inoculated with uropathogenic Escherichia coli to induce pyelonephritis

Results

E. coli of the family Enterobacteriaceae was identified in patients by calcium oxalate stone culture. Additionally Enterobacteriaceae DNA was sequenced from multiple calcium oxalate kidney stones. E. coli selectively aggregated on and around calcium oxalate monohydrate crystals. Mice inoculated with glyoxalate and uropathogenic E. coli had higher bacterial burdens, increased kidney calcium oxalate deposits and an increased kidney innate immune response compared to mice with only calcium oxalate deposits or only pyelonephritis.

Conclusions

In a murine model, the presence of calcium oxalate deposits increases pyelonephritis risk, likely due to preferential aggregation of bacteria on and around calcium oxalate crystals. When both calcium oxalate deposits and uropathogenic bacteria were present, calcium oxalate deposit number increased along with renal gene transcription of inner stone core matrix proteins increased. Therefore renal calcium oxalate deposits may be a modifiable risk factor for infections of the kidney and urinary tract. Furthermore, bacteria may be present in calcium oxalate deposits and potentially contribute to calcium oxalate renal disease.

Altered Calcium and Vitamin D Homeostasis in First-Time Calcium Kidney Stone-Formers

Background

Elevated serum 1,25-dihydroxyvitamin D (1,25(OH)₂D) concentrations have been reported among cohorts of recurrent calcium (Ca) kidney stone-formers and implicated in the pathogenesis of hypercalciuria. Variations in Ca and vitamin D metabolism, and excretion of urinary solutes among first-time male and female Ca stone-formers in the community, however, have not been defined.

Methods

In a 4-year community-based study we measured serum Ca, phosphorus (P), 25-hydroxyvitamin D (25(OH)D), 1,25(OH)₂D, 24,25-dihydroxyvitamin D (24,25(OH)₂D), parathyroid hormone (PTH), and fibroblast growth factor-23 (FGF-23) concentrations in first-time Ca stone-formers and age- and gender frequency-matched controls.

Results

Serum Ca and 1,25(OH)₂D were increased in Ca stone-formers compared to controls (P = 0.01 and P = 0.001). Stone-formers had a lower serum 24,25(OH)₂D/25(OH)D ratio compared to controls (P = 0.008). Serum PTH and FGF-23 concentrations were similar in the groups. Urine Ca excretion was similar in the two groups (P = 0.82). In controls, positive associations between serum 25(OH)D and 24,25(OH)₂D, FGF-23 and fractional phosphate excretion, and negative associations between serum Ca and PTH, and FGF-23 and 1,25(OH)₂D were observed. In SF associations between FGF-23 and fractional phosphate excretion, and FGF-23 and 1,25(OH)₂D, were not observed. 1,25(OH)₂D concentrations associated more weakly with FGF-23 in SF compared with C (P <0.05).

Conclusions

Quantitative differences in serum Ca and 1,25(OH)₂D and reductions in 24-hydroxylation of vitamin D metabolites are present in first-time SF and might contribute to first-time stone risk.

Effect of Demographics on Excretion of Key Urinary Factors Related to Kidney Stone Risk

OBJECTIVE

To investigate the effect of demographics including age and sex on excretion of 4 key urinary factors (calcium [Ca], magnesium [Mg], oxalate and uric acid [UA]) related to kidney stone risk.

METHODS

Twenty-four-hour urine samples were collected from non-Hispanic white sibships in Rochester, MN. Height, weight, blood pressure, serum creatinine, and cystatin C were measured. Diet was assessed using the Viocare food frequency questionnaire. Effects of demographics and dietary elements on urinary excretions were evaluated in univariate, multivariate, and interaction models that included age, sex, and body mass index (BMI).

RESULTS

Samples were available from 709 individuals. In multivariate models, sex was a significant predictor of all 4 urinary factors, age was significant for all but UA excretion, and serum creatinine was significant only for Ca and Mg excretion (P <.05). BMI or weight positively correlated with Mg, oxalate, and UA excretion (P <.05). Use of a thiazide diuretic (lower) and dietary protein (higher) were associated with Ca excretion, whereas dietary Ca was associated with higher Mg excretion. Urinary UA excretion increased with animal protein intake and cystatin C estimated glomerular filtration rate (eGFR) and was lower with concurrent loop diuretic use. Significant interaction effects on urinary UA excretion were observed for loop diuretic use and sex, eGFR and sex, age and animal protein intake, and BMI and eGFR (P <.05).

CONCLUSION

Age and sex influence excretion of key urinary factors related to kidney stone risk and should be taken into account when evaluating kidney stone patients.

Do Hypertension, diabetes mellitus and obesity increase the risk of severity of nephrolithiasis?

Objective:

In this study we planned to investigate the relationship between presence of kidney stones and stone burden with hypertension (HT), diabetes mellitus (DM) and body mass index (BMI).

Methods:

A total of 574 patients were included in the study. None of the patients had a history of stones. The 121 patients with kidney stone identified on ultrasound evaluation and the 453 patients with no stones were compared in terms of HT, BMI and DM. The stone burden of 121 patients with diagnosed stones was compared in terms of the same variables.

Results:

Of the 121 patients with kidney stones 30 (24.7%) had HT, while 66 (14.5%) of the 453 patients without stones had HT (p=0.007). BMI values of those with and without stones were 27.2 ± 4.93 kg/m² and 25.29 ± 4.12 kg/m², respectively (p<0.001). Twenty-five (20.6%) of the patients with stones diagnosed by ultrasound had DM, while 49 (10.8%) of those without stones had DM (p=0.004). When comparing patients with and without kidney stones, logistic regression analysis revealed that DM (odds ratio [OR] 2.06, 95% confidence interval [CI] 1.17 to 3.63, p=0.013) and BMI (OR 1.08, CI 1.03 to 1.13, p=0.003) were independently associated with presence of stones. No significant relationship was found between the same variables and cumulative stone diameter (CSD) and stone surface area (SA) evaluated for stone burden.

Conclusions:

While diabetes mellitus, Hypertension and increased Body Mass Index may add to the possibility of stone formation, they did not affect stone burden.

The new epidemiology of nephrolithiasis

Historically nephrolithiasis was considered a disease of dehydration and abnormal urine composition. However, over the past several decades, much has been learned about the epidemiology of this disease and its relation to patient demographic characteristics and common systemic diseases. Here we review the latest epidemiologic studies in the field.

Self-Fluid Management in Prevention of Kidney Stones: A PRISMA-Compliant Systematic Review and Dose-Response Meta-Analysis of Observational Studies

Epidemiologic studies have suggested that daily fluid intake that achieves at least 2.5 L of urine output per day is protective against kidney stones. However, the precise quantitative nature of the association between fluid intake and kidney stone risk, as well as the effect of specific types of fluids on such risk, are not entirely clear.We conducted a systematic review and dose-response meta-analysis to quantitatively assess the association between fluid intake and kidney stone risk. Based on a literature search of the PubMed, Embase, and Cochrane Library databases, 15 relevant studies (10 cohort and 5 case-control studies) were selected for inclusion in the meta-analysis with 9601 cases and 351,081 total participants.In the dose-response meta-analysis, we found that each 500 mL increase in water intake was associated with a significantly reduced risk of kidney stone formation (relative risk (RR) = 0.93; 95% CI: 0.87, 0.98; P < 0.01). Protective associations were also found for an increasing intake of tea (RR = 0.96; 95% CI: 0.93, 0.99; P = 0.02) and alcohol (RR = 0.80, 95% CI: 0.75, 0.85; P < 0.01). A borderline reverse association were observed on coffee intake and risk of kidney stone (RR = 0.88; 95% CI: 0.76, 1.00; P = 0.05). The risk of kidney stones was not significantly related to intake of juice (RR = 1.02, 95% CI: 0.95, 1.10; P = 0.64), soda (RR = 1.03; 95% CI: 0.90, 1.17; P = 0.65), or milk (RR = 0.96; 95% CI: 0.88, 1.03; P = 0.21). Subgroup analysis and sensitivity analyses showed inconsistent results on coffee, alcohol, and milk intake.Increased water intake is associated with a reduced risk of kidney stones; increased consumption of tea and alcohol may reduce kidney stone risk. An average daily water intake was recommended for kidney stone prevention.