Decreased renal function among adults with a history of nephrolithiasis: A study of NHANES III

Label-free detection of kidney stones urine combined with SERS and multivariate statistical algorithm

Kidney stones are a common urological disease with an increasing incidence worldwide. Traditional diagnostic methods for kidney stones are relatively complex and time-consuming, thus necessitating the development of a quicker and simpler diagnostic approach. This study investigates the clinical screening of kidney stones using Surface-Enhanced Raman Scattering (SERS) technology combined with multivariate statistical algorithms, comparing the classification performance of three algorithms (PCA-LDA, PCA-LR, PCA-SVM). Urine samples from 32 kidney stone patients, 30 patients with other urinary stones, and 36 healthy individuals were analyzed. SERS spectra data were collected in the range of 450-1800 cm-1 and analyzed. The results showed that the PCA-SVM algorithm had the highest classification accuracy, with 92.9 % for distinguishing kidney stone patients from healthy individuals and 92 % for distinguishing kidney stone patients from those with other urinary stones. In comparison, the classification accuracy of PCA-LR and PCA-LDA was slightly lower. The findings indicate that SERS combined with PCA-SVM demonstrates excellent performance in the clinical screening of kidney stones and has potential for practical clinical application. Future research can further optimize SERS technology and algorithms to enhance their stability and accuracy, and expand the sample size to verify their applicability across different populations. Overall, this study provides a new method for the rapid diagnosis of kidney stones, which is expected to play an important role in clinical diagnostics.

Identifying effects of volatile organic compounds exposure on kidney stone prevalence in U.S. adults: a cross-sectional analysis of NHANES 2007-2020

OBJECTIVE

Our aim was to comprehensively investigate the relationship between blood volatile organic compounds (VOCs) and kidney stone prevalence for U.S. adults.

METHODS

In this cross-sectional study, 10,052 participants from the 2007-2020 National Health and Nutrition Examination Survey (NHANES) were included. Multivariate logistic regression model was employed to investigate the association between 9 blood VOCs and kidney stones. We explored the dose-response relationship between blood VOCs and kidney stones using restricted cubic spline (RCS) analysis. Additionally, weighted quantile sum (WQS) regression model was performed to assess the overall association of 9 blood VOCs with kidney stones. Finally, subgroup analyses were conducted to identify the findings in different populations at high prevalence.

RESULTS

Logistic regression analysis and dose-response risk curves revealed that blood benzene (aOR = 1.308, 95% CI: 1.118-1.530, P = 0.001), blood ethylbenzene (aOR = 1.280, 95% CI: 1.054-1.554, P = 0.013), blood m-/p-xylene (aOR = 1.187, 95% CI: 1.008-1.398, P = 0.040), blood 2,5-dimethylfuran (aOR = 1.319, 95% CI: 1.135-1.533, P < 0.001) and blood furan (aOR = 1.698, 95% CI: 1.305-2.209, P < 0.001) were positively associated with the prevalence of kidney stones. WQS regression analysis revealed that exposure to mixed blood VOCs was positively correlated with kidney stone prevalence (OR = 1.34, 95% CI: 1.14-1.57), with furans carrying the greatest weight. Subgroup analyses suggested that kidney stones were more susceptible to the effects of blood VOCs in young and middle-aged, female, overweight and obese, non-hypertensive, and non-diabetic populations.

CONCLUSIONS

In this study, the results indicated that high VOC exposure was positively and independently associated with kidney stones in U.S. adults. This finding highlighted the need for public health strategies to reduce VOC exposure and its role in kidney stone prevention and treatment.

Risk of incident chronic kidney disease among patients with urolithiasis: a nationwide longitudinal cohort study

Background

Urolithiasis has been infrequently implicated to have a causal association with chronic kidney disease (CKD). Recently, several studies have demonstrated the relationship between urolithiasis and CKD. However, the generalizability of their results is limited. This study aimed to investigate the association between urolithiasis and the risk of incident CKD.

Methods

This longitudinal cohort study used the National Health Insurance Service data, including 219 570 Korean adults with incident urolithiasis requiring procedural interventions and without prior kidney disease and 219 570 age- and sex-matched controls without urolithiasis between 1 January 2002 and 31 December 2020. Primary outcome was the development of CKD, defined by an estimated glomerular filtration rate <60 ml/min/1.73 m2 for at least two consecutive measurements at least 90 days apart. The risk for incident CKD was further examined using the outcome defined by newly occurring diagnostic codes indicating CKD.

Results

Over a mean follow-up of 6 years, 12 338 (2.8%) primary outcome events of CKD were observed (incidence rate 4.6/1000 person-years). Per multivariable Cox analysis, urolithiasis was associated with a higher risk of incident CKD [adjusted hazard ratio 1.41 (95% confidence interval 1.36-1.46)]. This association remained consistent across all clinically relevant subgroups and when the CKD outcome was defined based on the diagnostic codes in the sensitivity analysis.

Conclusions

In this large national cohort study, patients with urolithiasis were associated with a higher risk of incident CKD than those without urolithiasis. Further studies are warranted to establish the benefits of preventing urolithiasis in reducing CKD development.

Association of dietary carotenoid intake with the prevalence kidney stones among the general adult population

PURPOSE

This study was to examine whether higher dietary carotenoid intake levels were associated with a lower prevalence of kidney stones.

MATERIALS AND METHODS

This study analyzed data from 2007 to 2018 National Health and Nutrition Examination Survey (NHANES) project. Dietary carotenoid intake (α-carotene, β-carotene, β-cryptoxanthin, lycopene, and lutein/zeaxanthin) was assessed using two 24-h dietary recall interviews. Multiple logistic regression and weighted quantile sum (WQS) regression were applied to examine the associations between five dietary carotenoids alone, compounds, and the prevalence of kidney stones. The dose-response relationships were analyzed by restricted cubic spline regression.

RESULTS

A total of 30,444 adults (2909 participants with kidney stones) were included in the analysis. The mean age of the participants was 49.95 years and 49.2% of the participants were male. Compared with the first quartile, the fourth quartile of α-carotene (odds ratio [OR] = 0.82 [0.73-0.92]), β-carotene (OR = 0.79 [0.70-0.89]), β-cryptoxanthin (OR = 0.88 [0.79-0.99]), and lutein/zeaxanthin (OR = 0.80 [0.71-0.91]) were significantly and inversely associated with the prevalence of kidney stones after adjusting for confounders. The dose-response analysis showed a linear relationship between five dietary carotenoid intake levels and the prevalence of kidney stones. Further WQS analysis revealed that the combination of all five dietary carotenoids was negatively associated with and the prevalence of kidney stones, with the largest effect coming from β-carotene (weight = 0.538).

CONCLUSION

Our findings indicated that higher dietary carotenoid intake levels were associated with decreased prevalence of kidney stones, and increasing the intake of foods rich in β-carotene may prevent the development of kidney stones.

Association between N, N-diethyl-m-toluamide exposure and the odds of kidney stones in US adults: a population-based study

Background

Currently, there is limited research on the specific relationship between N, N-diethyl-m-toluamide (DEET) exposure and the odds of kidney stones. We aimed to investigate the relationship between DEET exposure and the prevalence of kidney stones.

Methods

We included 7,567 qualified participants in our research from the 2007-2016 NHANES survey. We carried out three logistic regression models to explore the potential association between DEET exposure and the odds of kidney stones. Spline smoothing with generalized additive models (GAM) was utilized to assess the non-linear relationship and restricted cubic spline (RCS) curves was to determine the dose-response association. Multivariate regression models were used to conduct stratified analysis and sensitivity analysis.

Results

Baseline characteristics of study participants presented the distribution of covariables. Regression analysis revealed that the odds of kidney stones were positively associated with the main metabolites of 3-diethyl-carbamoyl benzoic acid (DCBA) (log2) (OR = 1.05, 95% CI 1.02 to 1.08). The fourth quartile of urine DCBA showed a greater risk of kidney stones in the fully adjusted model (OR = 1.36, 95% CI 1.08 to 1.72). Another DEET metabolite of N, N-diethyl-3-hydroxymethylbenzamide (DHMB) was used to confirm the accuracy and stability of the results. The spline smoothing curve represented two main DEET metabolites had similar no-linear relationships and a positive trend with kidney stones proportion. RCS implied that the incidence of kidney stones rose with increasing levels of DEET exposure. High-risk groups on kidney stones were exhibited by stratified analysis under DEET exposure.

Conclusion

Our study suggests that DEET exposure is positively associated with odds of kidney stones. Further investigation into the underlying processes of this association is required to guide the prevention and treatment of kidney stones.

Hydration for Adult Patients with Nephrolithiasis: Specificities and Current Recommendations

Nephrolithiasis affects around 10% of the population and is frequently associated with impaired dietary factors. The first one is insufficient fluid intake inducing reduced urine volume, urine supersaturation, and subsequently urinary lithiasis. Kidneys regulate 24 h urine volume, which, under physiological conditions, approximately reflects daily fluid intake. The aim of this study is to synthesize and highlight the role of hydration in the treatment of nephrolithiasis. Increasing fluid intake has a preventive effect on the risk of developing a first kidney stone (primary prevention) and also decreases the risk of stone recurrence (secondary prevention). Current guidelines recommend increasing fluid intake to at least at 2.5 L/day to prevent stone formation, and even to 3.5-4 L in some severe forms of nephrolithiasis (primary or enteric hyperoxaluria or cystinuria). Fluid intake must also be balanced between day and night, to avoid urinary supersaturation during the night. Patients should be informed and supported in this difficult process of increasing urine dilution, with practical ways and daily routines to increase their fluid intake. The liquid of choice is water, which should be chosen depending on its composition (such as calcium, bicarbonate, or magnesium content). Finally, some additional advice has to be given to avoid certain beverages such as those containing fructose or phosphoric acid, which are susceptible to increase the risk of nephrolithiasis.

Association and interactions between mixed exposure to trace elements and the prevalence of kidney stones: a study of NHANES 2017-2018

Background

The association between exposure to trace elements mixture and the prevalence of kidney stones and the interactions between elements are unclear. The aim of this study was to explore the association between exposure to trace elements mixture and the prevalence of kidney stones and the interactions between the elements.

Methods

A total of 1,244 participants (139 kidney stone formers and 1,105 non-stone former participants) in NHANES 2017-2018 were included. The exposure to trace elements was evaluated by measuring their concentration in urine samples. Three methods, Logistic regression, quantile-based g computation (qgcomp), and Bayesian kernel machine regression (BKMR), were used for analysis.

Results

According to the results from qgcomp and BKMR, a negative association was found between exposure to the 13 trace elements and the prevalence of kidney stones [OR = 0.50 (0.32, 0.78)]. Subgroup analysis revealed that Co, As, and iodine in the whole population, Co, As, and Ni in males, and Cs, iodine, and Sb in females, were most strongly associated with kidney stones. Kidney stone was found to be positively correlated with Co and negatively correlated with the other elements. Besides, there were significant interactions between Ni and Pb in the whole population, Co and iodine in males, and Pb and iodine in females.

Conclusion

There was a negative association between exposure to the mixture of 13 trace elements and the prevalence of kidney stones.

Modified Supine Percutaneous Nephrolithotomy in the Elderly: Outcomes and Safety

With increases in the aging population, conditions affecting older people and relevant surgical techniques are becoming more pertinent. Modified supine percutaneous nephrolithotomy (PCNL) is increasingly being adopted. There are limited data on the safety of this position in the elderly patient population. We describe our experience of the modified supine position in patients aged 70 years and older. Between April 2011 and March 2021, patients aged 70 years and older undergoing a modified supine PCNL performed by a single surgeon were prospectively evaluated. Data including patient age, operative time, complications, stone clearance, and length of stay were collected and analysed. Sixty-nine procedures were performed on 67 patients with a mean age was 76.5 years. Median total operative time was 95 min with 20 (29%) patients having a combined procedure with ureterorenoscopy. Preoperative mean stone burden was 23.5 mm and complete stone clearance was achieved in 46 (66.7%) patients. Twelve (17.4%) patients had complications during their hospitalisation. Six were Clavien-Dindo class II or less and one Clavien-Dindo class V. The modified supine position for PCNL is safe in the elderly patient population and has advantages including reduced handling of patients and achieving adequate stone-free rates. These benefits are particularly important in the elderly population, which frequently has a reduced tolerance to adaptation.

Association of serum bicarbonate with the development of kidney stones in patients with chronic kidney disease: a retrospective cohort study

BACKGROUND

Epidemiological studies demonstrate an association between kidney stones and risk of chronic kidney disease (CKD) and CKD progression. Metabolic acidosis, as a consequence of CKD, results in a reduced urine pH which promotes the formation of some types of kidney stones and inhibits the formation of others. While metabolic acidosis is a risk factor for CKD progression, the association of serum bicarbonate with risk of incident kidney stones is not well understood.

METHODS

We used an Integrated Claims-Clinical dataset of US patients to generate a cohort of patients with non-dialysis-dependent CKD with two serum bicarbonate values of 12 to <22 mmol/L (metabolic acidosis) or 22 to <30 mmol/L (normal serum bicarbonate). Primary exposure variables were baseline serum bicarbonate and change in serum bicarbonate over time. Cox proportional hazards models evaluated time to first occurrence of kidney stones during a median 3.2-year follow-up.

RESULTS

A total of 142 884 patients qualified for the study cohort. Patients with metabolic acidosis experienced post-index date kidney stones at greater frequency than patients with normal serum bicarbonate at the index date (12.0% vs 9.5%, P < .0001). Both lower baseline serum bicarbonate [hazard ratio (HR) 1.047; 95% confidence interval (CI) 1.036-1.057] and decreasing serum bicarbonate over time (HR 1.034; 95% CI 1.026-1.043) were associated with increased risk of kidney stone development.

CONCLUSIONS

Metabolic acidosis was associated with a higher incidence of kidney stones and shorter time to incident stone formation in patients with CKD. Future studies may investigate the role of correcting metabolic acidosis to prevent stone formation.

Role of the kidneys in acid-base regulation and ammonia excretion in freshwater and seawater fish: implications for nephrocalcinosis

Maintaining normal pH levels in the body fluids is essential for homeostasis and represents one of the most tightly regulated physiological processes among vertebrates. Fish are generally ammoniotelic and inhabit diverse aquatic environments that present many respiratory, acidifying, alkalinizing, ionic and osmotic stressors to which they are able to adapt. They have evolved flexible strategies for the regulation of acid-base equivalents (H⁺, NH₄ ⁺, OH^- and HCO₃ ^-), ammonia and phosphate to cope with these stressors. The gills are the main regulatory organ, while the kidneys play an important, often overlooked accessory role in acid-base regulation. Here we outline the kidneys role in regulation of acid-base equivalents and two of the key 'urinary buffers', ammonia and phosphate, by integrating known aspects of renal physiology with recent advances in the molecular and cellular physiology of membrane transport systems in the teleost kidneys. The renal transporters (NHE3, NBC1, AE1, SLC26A6) and enzymes (V-type H⁺ATPase, CAc, CA IV, ammoniagenic enzymes) involved in H⁺ secretion, bicarbonate reabsorption, and the net excretion of acidic and basic equivalents, ammonia, and inorganic phosphate are addressed. The role of sodium-phosphate cotransporter (Slc34a2b) and rhesus (Rh) glycoproteins (ammonia channels) in conjunction with apical V-type H⁺ ATPase and NHE3 exchangers in these processes are also explored. Nephrocalcinosis is an inflammation-like disorder due to the precipitation of calcareous material in the kidneys, and is listed as one of the most prevalent pathologies in land-based production of salmonids in recirculating aquaculture systems. The causative links underlying the pathogenesis and etiology of nephrocalcinosis in teleosts is speculative at best, but acid-base perturbation is probably a central pathophysiological cause. Relevant risk factors associated with nephrocalcinosis are hypercapnia and hyperoxia in the culture water. These raise internal CO₂ levels in the fish, triggering complex branchial and renal acid-base compensations which may promote formation of kidney stones. However, increased salt loads through the rearing water and the feed may increase the prevalence of nephrocalcinosis. An increased understanding of the kidneys role in acid-base and ion regulation and how this relates to renal diseases such as nephrocalcinosis will have applied relevance for the biologist and aquaculturist alike.

The association between visceral adiposity index and decreased renal function: A population-based study

Aims

We aimed to investigate the association of visceral adiposity index (VAI) with decreased renal function in US adults.

Design and methods

Cross-sectional data were analyzed for 35,018 adults in the National Health and Nutrition Examination Survey (NHANES) 2005–2018. VAI was determined using waist circumference, body mass index (BMI), triglycerides (TGs) and high-density lipoprotein-cholesterol. Albuminuria was defined as urinary albumin-to-creatinine ratio (ACR) &gt;30 mg/g. A low estimated-glomerular filtration rate (eGFR) was defined as an eGFR lower than 60 ml/min/1.73 m2. Chronic kidney disease (CKD) was defined as either albuminuria or low-eGFR. A multivariable logistic regression analysis was utilized to explore the relationship of VAI with albuminuria, low-eGFR and CKD. Subgroup analysis and interaction tests were also conducted.

Results

A total of 35,018 participants were enrolled with albuminuria, low-eGFR, and CKD prevalence rates of 5.18, 6.42, and 10.62%, respectively, which increased with the higher VAI tertiles. After full adjustment, a positive association of VAI with albuminuria (OR = 1.03, 95% CI: 1.00, 1.06) and CKD (OR = 1.04, 95% CI: 1.02, 1.06) was observed. Participants in the highest VAI tertile had a significantly 30% increased risk for albuminuria (OR = 1.30, 95% CI: 1.07, 1.58) and a 27% increased risk for CKD (OR = 1.27, 95% CI: 1.08, 1.49) compared with those in the lowest VAI tertile. No statistically significant association between VAI and low-eGFR was detected. Subgroup analysis and the interaction term indicated that there was no significant difference among different stratifications.

Conclusion

Visceral adiposity accumulation evaluating by VAI was associated with increased likelihood of the decline in renal function.

Retrospective analysis of 131 feline uroliths from the Republic of Ireland and Northern Ireland (2010-2020)

BACKGROUND

The proportions of different urolith types have not been investigated in cats from the Republic of Ireland (ROI) and Northern Ireland (NI) previously. The objective of this study was to investigate the proportions of different feline urolith types submitted to Minnesota Urolith Center from the ROI and NI from 2010 to 2020. An additional aim of this study was to identify potential risk factors associated with each urolith type in cats in this geographic area.

RESULTS

One hundred and thirty-one uroliths were submitted for the studied period with 44.3% being struvite, 43.5% calcium oxalate and 7.6% compound. Only 11 uroliths were submitted in the first 4 years. The number of submissions increased after 2015, peaking in 2019 with 25 submissions. Due to low numbers no conclusions could be made about changes in incidence of urolith types over time. Cats ≤7 years of age were significantly more likely to be diagnosed with struvite uroliths (OR, 2.87 [1.37-6.06]; p = 0.007) while cats ≥7 years of age with calcium oxalate uroliths (OR, 2.67, [1.29-5.37], p = 0.004).

CONCLUSIONS

This is the first epidemiologic study of urolithiasis from cats in the ROI and NI. The most prevalent types of uroliths in our study population were struvite and calcium oxalate. Due to the low number of urolith submissions, changes in the incidence of different uroliths could not be accurately determined. Increasing age was associated with calcium oxalate formation while younger cats were more commonly diagnosed with struvite urolithiasis which can be medically dissolved. Therefore, urolith dissolution is more likely to be successful in young cats than older cats.

The effect of anesthesia type on the outcomes of percutaneous nephrolithotomy in elderly males

Objective: To compare the anaesthesia methods in percutaneous nephrolithotomy in terms of safety and effectiveness in elderly men.Methods: Elderly male patients who had undergone percutaneous nephrolithotomy were screened retrospectively and divided into 2 groups: percutaneous nephrolithotomy under combined spino-epidural anaesthesia (Group CSEA, n = 70) and percutaneous nephrolithotomy under general anaesthesia (Group GA, n = 114). Preoperative, perioperative and postoperative outcome measures were examined.Results: Between the two groups, there was no statistically significant difference in terms of stone burden, stone location, presence of the previous operation in the same kidney, presence of staghorn stones, mean American Society of Anesthesiologists scores and presence of abnormal kidney (p > 0.05). The mean duration time in the operation room and post-anaesthesia care unit (PACU) was statistically shorter in the Group CSEA (p < 0.01). There was no significant difference between the two groups in terms of Clavien Grade 1 and above complications (p > 0.05). Stone-free rates and success rates were similar in both groups (p = 0.133 and p = 0.273, respectively).Conclusion: The type of anaesthesia does not affect the success rate and complication rate of percutaneous nephrolithotomy in elderly male patients. Patients who underwent percutaneous nephrolithotomy under CSEA needed less analgesic injection during the postoperative period. CSEA can shorten the time a patient spends in the operating room and PACU, which provides more effective use of operation room working hours.

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

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

Trans-ethnic Mendelian-randomization study reveals causal relationships between cardiometabolic factors and chronic kidney disease

BACKGROUND

This study was to systematically test whether previously reported risk factors for chronic kidney disease (CKD) are causally related to CKD in European and East Asian ancestries using Mendelian randomization.

METHODS

A total of 45 risk factors with genetic data in European ancestry and 17 risk factors in East Asian participants were identified as exposures from PubMed. We defined the CKD by clinical diagnosis or by estimated glomerular filtration rate of <60 ml/min/1.73 m2. Ultimately, 51 672 CKD cases and 958 102 controls of European ancestry from CKDGen, UK Biobank and HUNT, and 13 093 CKD cases and 238 118 controls of East Asian ancestry from Biobank Japan, China Kadoorie Biobank and Japan-Kidney-Biobank/ToMMo were included.

RESULTS

Eight risk factors showed reliable evidence of causal effects on CKD in Europeans, including genetically predicted body mass index (BMI), hypertension, systolic blood pressure, high-density lipoprotein cholesterol, apolipoprotein A-I, lipoprotein(a), type 2 diabetes (T2D) and nephrolithiasis. In East Asians, BMI, T2D and nephrolithiasis showed evidence of causality on CKD. In two independent replication analyses, we observed that increased hypertension risk showed reliable evidence of a causal effect on increasing CKD risk in Europeans but in contrast showed a null effect in East Asians. Although liability to T2D showed consistent effects on CKD, the effects of glycaemic phenotypes on CKD were weak. Non-linear Mendelian randomization indicated a threshold relationship between genetically predicted BMI and CKD, with increased risk at BMI of >25 kg/m2.

CONCLUSIONS

Eight cardiometabolic risk factors showed causal effects on CKD in Europeans and three of them showed causality in East Asians, providing insights into the design of future interventions to reduce the burden of CKD.

THE FUNCTIONAL STATE OF THE RENAL PARENCHYMA AFTER VARIOUS VIDEO ENDOSURGICAL METHODS OF TREATMENT OF PATIENTS WITH LARGE AND COMPLEX KIDNEY STONES

The work is based on the analysis of literature data devoted to the problem of preserving the functional state of the kidneys with various video endoscopic methods of surgical treatment of large and complex kidney stones. The purpose of the review is to highlight the likelihood of deterioration in the functional state of the kidneys in the postoperative period. A detailed analysis of postoperative outcomes in various minimally invasive methods of treatment of patients with large and complex kidney stones was carried out, with an overview of the possibility of using dynamic nephroscintigraphy as a method of objectively assessing the functional state of the kidneys.

Chronic Kidney Disease: Strategies to Retard Progression

Chronic kidney disease (CKD), defined as the presence of irreversible structural or functional kidney damages, increases the risk of poor outcomes due to its association with multiple complications, including altered mineral metabolism, anemia, metabolic acidosis, and increased cardiovascular events. The mainstay of treatments for CKD lies in the prevention of the development and progression of CKD as well as its complications. Due to the heterogeneous origins and the uncertainty in the pathogenesis of CKD, efficacious therapies for CKD remain challenging. In this review, we focus on the following four themes: first, a summary of the known factors that contribute to CKD development and progression, with an emphasis on avoiding acute kidney injury (AKI); second, an etiology-based treatment strategy for retarding CKD, including the approaches for the common and under-recognized ones; and third, the recommended approaches for ameliorating CKD complications, and the final section discusses the novel agents for counteracting CKD progression.

Independent and interactive effects of kidney stone formation and conventional risk factors for chronic kidney disease: a follow-up study of Japanese men

PURPOSE

To assess the impact of interactions between kidney stone formation and conventional risk factors on incident chronic kidney disease (CKD).

METHODS

A total of 11,402 subjects (men 30-69 years of age, Japanese) without CKD at baseline were observed over an average period of 4 years. Cox proportional hazards regression models were used to calculate hazard ratios (HRs) with 95% confidence intervals (CIs) to determine the association between incident CKD, kidney stone formation, and conventional risk factors (diabetes mellitus, hypertension, overweight/obesity, dyslipidemia, and hyperuricemia/gout). We also examined the interactions of renal stones and the conventional risk factors for CKD.

RESULTS

In total, 2301 men (20.2%) developed incident CKD during the follow-up period. After multivariable adjustment, kidney stones were found to increase the risk of incident CKD (HR 1.16; 95% CI 1.03-1.32). Kidney stone formers with hypertension, dyslipidemia, or hyperuricemia/gout presented a greater risk for incident CKD than those who had either kidney stones or other risk factors. However, no significant interactions between kidney stones and other risk factors were found to increase CKD risk. On the other hand, a negative interactive effect between kidney stones and overweight/obesity was observed, leading to reversed risk of incident CKD in coexistence of both factors.

CONCLUSION

Kidney stones were linked to a higher risk for the development of CKD. However, no positive interactive effects were identified between renal stones and conventional risk factors on the risk of incident CKD.

Despite initial recovery of GFR, long-term renal functions deteriorate following short periods of unilateral ureteral obstruction

Following the release of short periods of unilateral ureteral obstruction (UUO), glomerular filtration rate (GFR) recovers by time. However, research in experimental animal models has demonstrated the presence of an ongoing element of renal interstitial fibrosis a few weeks following UUO reversal. Interstitial fibrosis can cause deterioration in GFR, and it is not known whether it leads to an ongoing slow deterioration in other renal functions despite the apparent initial recovery postreversal. To investigate this, rats underwent a 72-h reversible UUO. Renal functions of nonobstructed and previously obstructed kidneys were measured 1, 4, and 18 mo postreversal. GFR in nonobstructed and previously obstructed kidneys was similar up to 18 mo postreversal. However, there was ongoing tubulointerstitial fibrosis, and the degree of tubular atrophy and dilatation deteriorated by time. This was associated with an increase in urinary albumin leakage and alterations in renal injury markers, proinflammatory and profibrotic cytokines, and p53 from 4 mo onward despite the recovery in GFR. In conclusion, several aspects of renal functions continue to deteriorate following reversal of relatively short periods of UUO despite the initial recovery in GFR. This might stimulate further research in this area and might have clinical implications in terms of determining the best time for intervention following acute ureteral obstruction and long-term monitoring of these individuals.

Association of Chronic Kidney Disease Stage with 24-Hour Urine Values Among Patients with Nephrolithiasis

Introduction: Nephrolithiasis is a known risk factor for chronic kidney disease (CKD); however, it is unknown how CKD affects urinary parameters related to stone risk. The purpose of this study was to assess the relationship of diminishing glomerular filtration rate (GFR) and kidney stone-related 24-hour urine (24H urine) composition. Materials and Methods: A single-institution retrospective review of patients (n = 2057) who underwent 24H urine analysis was performed. The serum creatinine within 1 year of the first 24H urine was used to determine estimated GFR and stratify patients by CKD stage. We performed analysis of variance and multivariable linear regression to assess the relationship of GFR and urinary analytes. Results: Among all patients, there were 184 (8.9%), 1537 (74.7%), 245 (11.9%), 70 (3.4%), 17 (0.8%), and 4 (0.2%) in CKD stage I, II, IIIa, IIIb, IV, and V groups, respectively. On analysis of 24H urine composition, as CKD increased, changes in urinary parameters protective against crystallization included decreased calcium and uric acid (UA) (P < 0.001). In addition, parameters favoring crystallization included decreased citrate and magnesium (P = 0.002 and P < 0.001, respectively). The net effect with increasing GFR was decreasing supersaturation of calcium oxalate and phosphate. On linear regression, urinary excretion of calcium, oxalate, citrate, UA, phosphate, and ammonia all decreased with decreasing GFR (all P < 0.05). Conclusions: Higher CKD stage was associated with changes in urinary analytes that both promoted and inhibited stone formation, with the net effect of decreasing calcium oxalate and phosphate supersaturation. These patients may benefit from medical therapy that targets improving urinary citrate instead of lowering calcium or UA.

Chronic kidney disease and kidney stones

PURPOSE OF REVIEW

Both chronic kidney disease (CKD) and kidney stones are major public health problems, which are closely interrelated. Recurrent kidney stones predispose to CKD although CKD seems to decrease risk of further kidney stone formation. Herein, we review new information of this interrelationship.

RECENT FINDINGS

Several epidemiological studies in the past have shown an association between history of kidney stones and risk for CKD and CKD progression. Recent literature supports this concept and it is reviewed in this article. The issue of whether CKD protects against new kidney stone formation remains unsettled and there is no recent literature addressing it. In relation to stone risk factors in CKD, there are several interesting new articles that discuss mechanisms of hypocitraturia in early CKD before overt metabolic acidosis. Since hypocitraturia is an important risk factor for kidney stone formation we addressed these new data in detail. There are also new data supporting urinary oxalate excretion as a predictor of CKD progression.

SUMMARY

It seems clear that recurrent kidney stones should be avoided not only because of their immediate clinical manifestations but also because of their long-term predisposition to CKD progression. Mechanisms leading to hypocitraturia in early CKD still remain controversial.

Predicting Adverse Events beyond Stroke and Bleeding with the ABC-Stroke and ABC-Bleeding Scores in Patients with Atrial Fibrillation: The Murcia AF Project

Background The ABC (age, biomarkers, and clinical history)-stroke and ABC-bleeding are biomarker-based scores proposed to predict stroke and bleeding, but non-specificity of biomarkers is common, predicting different clinical events at the same time. We assessed the predictive performance of the ABC-stroke and ABC-bleeding scores, for outcomes beyond ischemic stroke and major bleeding, in a cohort of atrial fibrillation (AF) patients.

Methods We included AF patients stable on vitamin K antagonists for 6 months. The ABC-stroke and ABC-bleeding were calculated and the predictive values for myocardial infarction (MI), acute heart failure (HF), a composite of cardiovascular events, and all-cause deaths were compared.

Results We included 1,044 patients (49.2% male; median age 76 [71–81] years). During 6.5 (4.3–7.9) years, there were 58 (5.6%) MIs, 98 (9.4%) acute HFs, 167 (16%) cardiovascular events, and 418 (40%) all-cause deaths. There were no differences in mean ABC-stroke and ABC-bleeding scores in patients with/without MI (p = 0.367 and p = 0.286, respectively); both scores were higher in patients with acute HF, cardiovascular events, or death (all p < 0.05). Predictive performances for the ABC-stroke and ABC-bleeding scores were similar, ranging from “poor” for MI (c-indexes ∼0.54), “moderate” for acute HF and cardiovascular events (c-indexes ∼0.60 and ∼0.64, respectively), and “good” for all-cause mortality (c-indexes > 0.70). Clinical usefulness whether assessed by ABC-stroke or ABC-bleeding was similar for various primary endpoints.

Conclusion In AF patients, the ABC-stroke and ABC-bleeding scores demonstrated similar predictive ability for outcomes beyond stroke and bleeding, including MI, acute HF, a composite of cardiovascular events, and all-cause deaths. This is consistent with nonspecificity of biomarkers that predict “sick” patients or poor prognosis overall.

Evaluation of anti-urolithiatic potential of ethyl acetate extract of Pedalium murex L. on struvite crystal (kidney stone)

Pedalium murex (L.) is a traditional herb, commonly used for the treatment of kidney stone related problems. Struvite stone can swiftly grow and become 'staghorn calculi' in kidney and its associated areas, which is the most aching urological disorder. The present study investigated the anti-urolithiasis activities of ethyl acetate extract of P. murex L. (EAEP) against struvite crystal. The antibacterial activity of EAEP examined against several urease producing bacteria. It showed the minimum bactericidal concentration (MBC) against Escherichia coli and Staphylococcus aureus (>125). On the other hand, total mass, volume, number, growth rate and dissolution rate of synthesised struvite crystals were observed at different concentrations 0.5%, 0.75%, 1% of EAEP and without EAEP. In which, EAEP addition showed appreciably reduced struvite crystal. Alternatively, MgO (300 mg of EAEP/kg/body weight) induced urolithiasis of Wistar albino rat at the rate of 1 ml for 28 days. Various biochemical parameters in serum, urine and histological analysis of kidney were taken for evaluation. Significant results (p < 0.05) were observed in 1% EAEP (300 mg) treated group than cystone treated group. From the histological study, reduced renal damage and glomerular development were observed. Our experiment, P. murex L. enhances the reducing activity on struvite crystal and prevents the crystal formation both in-vitro and in-vivo. It can be suggesting that P. murex L. and its phyto-components could be used as remedy for the management of kidney stone by dissolving the struvite stone in kidney.

Protective Effects of Epigallocatechin-3-Gallate from Green Tea in Various Kidney Diseases

Kidney diseases are common health problems worldwide. Various etiologies (e.g., diabetes, hypertension, drug-induced nephrotoxicity, infection, cancers) can affect renal function and ultimately lead to development of chronic kidney disease (CKD) and end-stage renal disease (ESRD). The global rise in number of CKD/ESRD patients during recent years has led to tremendous concern to look for effective strategies to prevent or slow progression of CKD and ESRD. Natural compounds derived from herbs or medicinal plants have gained wide attention for scientific scrutiny to achieve such goals. One of such natural compounds that has been extensively investigated is epigallocatechin-3-gallate (EGCG), a major polyphenol found in the tea plant (Camellia sinensis). A growing body of recent evidence has shown that EGCG may be a promising therapeutic or protective agent in various kidney diseases. This article thus highlights recent progress in medical research on beneficial effects of EGCG against a broad spectrum of kidney diseases, including acute kidney injury, cisplatin-induced nephrotoxicity, kidney stone disease, glomerulonephritis, lupus nephritis, renal cell carcinoma, diabetic nephropathy, CKD, and renal fibrosis. The renoprotective mechanisms are also detailed. Finally, future perspectives of medical research on EGCG and its potential use in clinical practice for treatment and prevention of kidney diseases are discussed.

Composition of uroliths in a tertiary hospital in South East Nigeria

Background

Urolithiasis affects primarily the urinary tract and complications as debilitating as renal failure may develop. Determining the chemical composition of uroliths can aid management and prevention of recurrence in patients.

Objective

To determine the chemical composition and anatomical distribution of uroliths in Nigeria.

Methods

This descriptive cross-sectional study was conducted between March 2014 and February 2016, in a tertiary hospital in Nigeria. We reviewed the outcomes of uroliths of adult patients sent to our laboratory for chemical analyses. Samples were analyzed using simple qualitative tests.

Results

52 adult patients were included with a mean age (SD) of 46.6 (12.6) years. Males (76.9%) were more affected than females (23.1%). For both sexes, highest occurrence of stones was in bladder (85.7%). Calcium-containing stones had the highest occurrence (85.2%) and predominated in the renal, ureter and urethra, followed by struvite stones (59.5%). In the bladder, struvite stones were predominant (85.8%), with calcium-containing stones accounting for 71.4%.

Conclusion

This study showed that struvite and calcium phosphate-containing stones constitute majority of uroliths in our setting with low occurrence of calcium oxalate stones. This indicates that urinary tract infection most likely plays a substantial role in the formation of uroliths in Nigerians. Modern methods of stone analysis is advocated to further define management options.

Physiology of Hyperuricemia and Urate-Lowering Treatments

Gout is the most common form of inflammatory arthritis and is a multifactorial disease typically characterized by hyperuricemia and monosodium urate crystal deposition predominantly in, but not limited to, the joints and the urinary tract. The prevalence of gout and hyperuricemia has increased in developed countries over the past two decades and research into the area has become progressively more active. We review the current field of knowledge with emphasis on active areas of hyperuricemia research including the underlying physiology, genetics and epidemiology, with a focus on studies which suggest association of hyperuricemia with common comorbidities including cardiovascular disease, renal insufficiency, metabolic syndrome and diabetes. Finally, we discuss current therapies and emerging drug discovery efforts aimed at delivering an optimized clinical treatment strategy.

The risk of nephrolithiasis is causally related to inactive matrix Gla protein, a marker of vitamin K status: a Mendelian randomization study in a Flemish population

Background

Vitamin K (VK)-dependent γ-glutamate carboxylation and serine phosphorylation activate matrix Gla protein (MGP) to a potent locally acting inhibitor of calcification. Nephrolithiasis represents a process of unwanted calcification associated with substantial mortality and high recurrence rates. We hypothesized that the risk of nephrolithiasis increases with VK shortage, as exemplified by higher plasma levels of desphospho-uncarboxylated MGP (dp-ucMGP).

Methods

In 1748 randomly recruited Flemish individuals (51.1% women; mean age 46.8 years), we determined dp-ucMGP and the prevalence of nephrolithiasis at baseline (April 1996-February 2015) and its incidence during follow-up until March 2016. We estimated the multivariable-adjusted relative risk associated with the doubling of dp-ucMGP, using logistic or Cox regression. We did a Mendelian randomization analysis using four MGP genotypes as instrumental variables.

Results

With adjustments applied for sex, age and 24-h urinary volume and calcium excretion, the odds of having prevalent nephrolithiasis [n = 144 (8.2%)] associated with dp-ucMGP was 1.31 [95% confidence interval (CI) 1.04-1.64; P = 0.022]. dp-ucMGP levels were associated (P ≤ 0.001) with MGP variants rs2098435, rs4236 and rs2430692. In the Mendelian analysis, the causal odds ratio was 3.82 (95% CI 1.15-12.7; P = 0.029). The incidence of nephrolithiasis over 12.0 years (median) was 37 cases (0.2%). With similar adjustments as before, the hazard ratio in relation to dp-ucMGP was 2.48 (95% CI 1.71-3.61; P < 0.001). Additional adjustment for a nephrolithiasis propensity score produced consistent results.

Conclusion

Higher levels of inactive dp-ucMGP may be causally associated with the risk of nephrolithiasis. Whether or not VK deficiency plays a role in these observations remains to be firmly established.

The Risk of Chronic Kidney Disease Associated with Urolithiasis and its Urological Treatments: A Review

PURPOSE

Urolithiasis can impair kidney function. This literature review focuses on the risk of kidney impairment in stone formers, the specific conditions associated with this risk and the impact of urological surgery.

MATERIALS AND METHODS

The PubMed® and Embase® databases were searched for publications on urolithiasis, its treatment, and the risk of chronic kidney disease, end stage renal disease and nephrectomy in stone formers.

RESULTS

In general, renal stone formers have twice the risk of chronic kidney disease or end stage renal disease, and for female and overweight stone formers the risk is even higher. Patients with frequent urinary tract infections, struvite stones, urinary malformations and diversions, malabsorptive bowel conditions and some monogenic disorders are at high risk for chronic kidney disease/end stage renal disease. Shock wave lithotripsy or minimally invasive urological interventions for stones do not adversely affect renal function. Declines in renal function generally occur in patients with preexisting chronic kidney disease or a large stone burden requiring repeated and/or complex surgery.

CONCLUSIONS

Although the effect size is modest, urolithiasis may cause chronic kidney disease and, thus, it is mandatory to assess patients with renal stones for the risk of chronic kidney disease/end stage renal disease. We suggest that all guidelines dealing with renal stone disease should include assessment of this risk.

Metabolic diagnosis and medical prevention of calcium nephrolithiasis and its systemic manifestations: a consensus statement

BACKGROUND

Recently published guidelines on the medical management of renal stone disease did not address relevant topics in the field of idiopathic calcium nephrolithiasis, which are important also for clinical research.

DESIGN

A steering committee identified 27 questions, which were proposed to a faculty of 44 experts in nephrolithiasis and allied fields. A systematic review of the literature was conducted and 5216 potentially relevant articles were selected; from these, 407 articles were deemed to provide useful scientific information. The Faculty, divided into working groups, analysed the relevant literature. Preliminary statements developed by each group were exhaustively discussed in plenary sessions and approved.

RESULTS

Statements were developed to inform clinicians on the identification of secondary forms of calcium nephrolithiasis and systemic complications; on the definition of idiopathic calcium nephrolithiasis; on the use of urinary tests of crystallization and of surgical observations during stone treatment in the management of these patients; on the identification of patients warranting preventive measures; on the role of fluid and nutritional measures and of drugs to prevent recurrent episodes of stones; and finally, on the cooperation between the urologist and nephrologist in the renal stone patients.

CONCLUSIONS

This document has addressed idiopathic calcium nephrolithiasis from the perspective of a disease that can associate with systemic disorders, emphasizing the interplay needed between urologists and nephrologists. It is complementary to the American Urological Association and European Association of Urology guidelines. Future areas for research are identified.

Comparative risk of chronic kidney diseases in patients with urolithiasis and urological interventions: a longitudinal population-based study

Large cohort studies on whether any association existed between urological interventions for urolithiasis and the development of CKD are lacking. From claims data of the National Health Insurance (NHI) program of Taiwan, we identified 54,433 patients newly diagnosed with urolithiasis during 1998-2010. For each case, four individuals without urolithiasis were randomly selected and frequency matched by age, sex, and diagnosis year. Both groups were followed up until the end of 2010. Incident CKD events were identified by the International Classification of Diseases, Ninth Revision (ICD-9) code in the NHI registration database. The overall incidence of periodontal diseases was 1.85-fold greater in the urolithiasis group than in the comparison group (33.9 vs 18.3 per 10,000 person-years; 95 % confidence interval [CI] 1.81-1.90). Compared with the adjusted hazard ratios (aHRs) of nonurolithiasis patients, those of patients with urolithiasis increased with the number of medical visits (from 0.91 [95 % CI 0.83-1.00] to 10.6 [95 % CI 9.48-11.8]) and urological interventions (from 1.22 [95 % CI 1.10-1.35] to 86.4 [95 % CI 67.6-110.6]). The aHR was similar in different urological intervention methods, extracorporeal shock wave lithotripsy, ureteroscopy, percutaneous nephrostolithotomy, and open stone surgery. The urological intervention for urolithiasis is associated with an increased risk of CKD. We should be aware of the risk for CKD, especially in patients who have received multiple urological interventions and those elderly.

An update on the role of the inflammasomes in the pathogenesis of kidney diseases

Innate immune response pathways play a critical role as the first line of defense. Initiation of an immune response requires sensors that can detect noxious stimuli within the cellular microenvironment. Inflammasomes are signaling platforms that are assembled in response to both microbe-specific and nonmicrobial antigens. Upon activation, proinflammatory cytokines are released to engage immune defenses and to trigger an inflammatory cell death referred to as pyroptosis. The aim of this review is to provide an overview of the current knowledge of the role of the inflammasomes in the pathogenesis of kidney diseases. As crystal deposition in the kidney is a frequent cause of acute kidney injury and chronic kidney disease in children, recent insights into mechanisms of inflammasome activation by renal crystals are highlighted. This may be of particular interest to pediatric patients and nephrologists in need of new therapeutic approaches. Lastly, current data findings that inflammasomes are not only of major importance in host defense but are also a key regulator of the intestinal microbiota and the progression of systemic diseases are reviewed.

Clinical, demographic, and laboratory characteristics of children with nephrolithiasis

While the incidence of pediatric kidney stones appears to be increasing, little is known about the demographic, clinical, laboratory, imaging, and management variables in this patient population. We sought to describe various characteristics of our stone-forming pediatric population. To that end, we retrospectively reviewed the charts of pediatric patients with nephrolithiasis confirmed by imaging. Data were collected on multiple variables from each patient and analyzed for trends. For body mass index (BMI) controls, data from the general pediatrics population similar to our nephrolithiasis population were used. Data on 155 pediatric nephrolithiasis patients were analyzed. Of the 54 calculi available for analysis, 98 % were calcium based. Low urine volume, elevated supersaturation of calcium phosphate, elevated supersaturation of calcium oxalate, and hypercalciuria were the most commonly identified abnormalities on analysis of 24-h urine collections. Our stone-forming population did not have a higher BMI than our general pediatrics population, making it unlikely that obesity is a risk factor for nephrolithiasis in children. More girls presented with their first stone during adolescence, suggesting a role for reproductive hormones contributing to stone risk, while boys tended to present more commonly at a younger age, though this did not reach statistical significance. These intriguing findings warrant further investigation.

Do kidney stone formers have a kidney disease?

Nephrolithiasis is a highly prevalent disorder affecting approximately one in eleven people and is associated with multiple complications including hypertension, cardiovascular disease, and chronic kidney disease. Significant epidemiologic associations with chronic kidney disease and ESRD have been noted and are reviewed herein, but debate persists in the literature as to whether kidney stone formation is a pathogenic process contributing to kidney disease. Corroborating evidence supporting the presence of kidney disease in stone formers includes the variability of renal function by stone type, the positive association of stone size with renal dysfunction, the presence of markers of renal injury in the urine of even asymptomatic stone formers, and direct evidence of renal tissue injury on histopathology. Proposed pathogenic mechanisms include recurrent obstruction and comorbid conditions such as recurrent urinary tract infections and structural abnormalities. Recent work evaluating the renal histopathology of different groups of stone formers adds further granularity, suggesting variability in mechanisms of renal injury by stone type and confirming the pathogenic effects of crystal formation. Genetic abnormalities leading to stone formation including cystinuria and primary hyperoxaluria, among others, contribute to the burden of disease in the stone-forming population.

Nephrolithiasis as a Risk Factor for CKD: The Atherosclerosis Risk in Communities Study

BACKGROUND AND OBJECTIVES

Previous studies demonstrated a higher risk of CKD in persons with a history of kidney stones, but these studies examined mostly white populations and did not evaluate important potential interactions such as race and plasma uric acid.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In 10,678 Atherosclerosis Risk in Communities (ARIC) study participants free of CKD at baseline (ARIC visit 4 in 1996-1998), we assessed the association between a history of nephrolithiasis (a time-varying variable, defined by a combination of self-report and diagnostic codes) and incident CKD (defined by diagnostic codes from linkage to hospitalizations and US Centers for Medicare and Medicaid Services' records).

RESULTS

At baseline, 856 participants had a history of nephrolithiasis; 322 developed nephrolithiasis during follow-up. Over a mean follow-up of 12 years, there were 1037 incident CKD events. Nephrolithiasis history was associated with a 29% (hazard ratio [HR], 1.29; 95% confidence interval [95% CI], 1.07 to 1.54) higher risk of CKD in demographic-adjusted analyses, but the association was no longer statistically significant after multivariable adjustment (HR, 1.09; 95% CI, 0.90 to 1.32). The multivariable-adjusted association was stronger among participants with plasma uric acid levels ≤6 mg/dl (HR, 1.34; 95% CI, 1.05 to 1.72) compared with those with levels >6 mg/dl (HR, 0.94; 95% CI, 0.70 to 1.28; P(interaction) = 0.05). There was no interaction of stone disease and race with incident CKD.

CONCLUSIONS

In this community-based cohort, nephrolithiasis was not an independent risk factor for incident CKD overall. However, risk of CKD was unexpectedly elevated in participants with stone disease and lower plasma uric acid levels.

Impact of nephrolithiasis on kidney function

Background

Kidney stone disease has been associated with reduced kidney function and chronic kidney disease (CKD). The objective of the study was to examine kidney function, body mass index (BMI) and the prevalence of cardiovascular disease, hypertension and diabetes in recurrent kidney stone formers.

Methods

A cross-sectional, case-control study comparing measures of kidney function, BMI and comorbid conditions was conducted in 195 kidney stone patients aged 18 to 70 years with recurrent clinical stone events and 390 age- and gender-matched controls. Wilcoxon-Mann-Whitney, chi-square tests and analysis of covariance were used to compare serum creatinine (SCr) and estimated glomerular filtration rate (eGFR) between the groups.

Results

The median age of stone formers was 51 (range, 19–70) years and 108 (55 %) were males. Seventy patients (36 %) had experienced 2–4 clinical stone events, 41 (21 %) 5–10 episodes and 84 (43 %) more than 10. The median SCr was 75 (41–140) μmol/L in the stone formers and 64 (34–168) μmol/L in the control group (p < 0.001). The mean eGFR was 87 ± 20 and 104 ± 22 mL/min/1.73 m² in the stone formers and controls, respectively (p < 0.001). After adjustment for body size and comorbid conditions, the difference in SCr and eGFR between cases and controls remained highly significant (p < 0.001). The prevalence of CKD was 9.3 % among stone formers compared with 1.3 % in the control group (P < 0.001). Hypertension and diabetes were significantly more prevalent among the cases that also had higher BMI than controls.

Conclusions

Recurrent kidney stone formers have a significantly lower level of kidney function and a markedly higher prevalence of CKD than age- and gender-matched control subjects. The observed deleterious effect of kidney stones on kidney function appears to be independent of comorbid conditions.

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.

Trends in pediatric urolithiasis: patient characteristics, associated diagnoses, and financial burden

BACKGROUND

The goal of this study was to examine national trends in hospitalization, emergency department (ED) utilization, secondary diagnoses, and charges associated with pediatric urolithiasis.

METHODS

Data were evaluated from the Kids' Inpatient Database of the Healthcare Costs and Utilization Project (HCUP) database from 1997 to 2012 and the HCUP National ED Sample from 2006 to 2011.

RESULTS

Pediatric nephrolithiasis discharges increased by 18%, while ureterolithiasis discharges decreased by 17%. Hospital charges increased by 20% when accounting for inflation, despite an overall decrease in discharges by 2.5%. Female patients and those aged 15-17 years were more commonly affected. Pediatric ED visits increased by 9%. The most common secondary diagnoses during 2003-2009 were urinary tract infections (UTI) (13%), asthma (9%), epilepsy (4%), and paralysis (4%).

CONCLUSIONS

Decreased hospitalizations and increased ED visits indicate a shift to outpatient care. Inpatient health care charges associated with pediatric urolithiasis continue to rise. Comorbidities include UTI, asthma, epilepsy, attention deficit hyperactivity disorder (ADHD), and mood disorders. Because of the significant health care burden and the increased risk to children of developing long-term sequelae there is a strong need for increased research into the mechanism of this systemic inflammatory disease and improved therapeutic targets.

Contribution of stone size to chronic kidney disease in kidney stone formers

OBJECTIVES

To determine whether stone burden correlates with the degree of chronic kidney disease in kidney stone formers.

METHODS

A total of 97 extracorporeal shockwave lithotripsy candidates aged 18 years and older were included. Size, number and location of the kidney stones, along with cumulative stone size, defined as the sum of diameters of all stones) were determined. Estimated glomerular filtration rate was determined using the Chronic Kidney Disease Epidemiology Collaboration cystatin C/creatinine equation, and chronic kidney disease was defined as estimated glomerular filtration rate <60 mL/min/1.73 m(2).

RESULTS

In individuals with cumulative stone size <20 mm, estimated glomerular filtration rate significantly decreased when moving from the first (estimated glomerular filtration rate 75.5 ± 17.8 mL/min/1.73 m(2)) to the fourth (estimated glomerular filtration rate 56.4 ± 20.44 mL/min/1.73 m(2) ) quartile (P = 0.004). When patients with a cumulative stone size ≥ 20 mm were included, the observed association was rendered non-significant. In individuals with a cumulative stone size < 20 mm, each 1-mm increase in cumulative stone size was associated with a 20% increased risk of having chronic kidney disease. The relationship persisted even after adjustment for age, sex, body mass index, C-reactive protein, fasting plasma glucose, thyroid stimulating hormone, presence of microalbuminuria, history of renal calculi, history of extracorporeal shockwave lithotripsy, number and location of the stones (odds ratio 1.24, 95% confidence interval 1.02-1.52). The same was not observed for individuals with a cumulative stone size ≥ 20 mm.

CONCLUSIONS

In kidney stone formers with a cumulative stone size up to 20 mm, estimated glomerular filtration rate linearly declines with increasing cumulative stone size. Additionally, cumulative stone size is an independent predictor of chronic kidney disease in this group of patients.

Effect of renal insufficiency on stone recurrence in patients with urolithiasis

The study was designed to assess the relationship between glomerular filtration rate (GFR) and urinary stone-forming constituents, and to assess the effect of renal insufficiency on stone recurrence risk in first stone formers (SF). Baseline serum creatinine levels were obtained, and renal insufficiency was defined as creatinine clearance ≤60 mL/min (Cockroft-Gault). This retrospective case-control study consists of 342 first SF; 171 SF with normal renal function were selected with 1:1 propensity scores matched to 171 SF with renal insufficiency. Urinary metabolic evaluation was compared to renal function. GFR was positively correlated with urinary calcium, uric acid, and citrate excretion. Subjects with renal insufficiency had significantly lower urinary calcium, uric acid, and citrate excretion than those with normal renal function, but not urine volume. With regard to urinary metabolic abnormalities, similar results were obtained. SF with renal insufficiency had lower calcium oxalate supersaturation indexes and stone recurrence rates than SF with normal renal function. Kaplan-Meier curves showed similar results. In conclusion, GFR correlates positively with urinary excretion of stone-forming constituents in SF. This finding implies that renal insufficiency is not a risk factor for stone recurrence.

Risk of chronic and end stage kidney disease in patients with nephrolithiasis

PURPOSE

We examine kidney stone disease as a potential risk factor for chronic kidney disease, end stage kidney disease and treatment with dialysis.

MATERIALS AND METHODS

The NHANES (National Health and Nutrition Examination Survey) 2007-2010 database was interrogated for patients with a history of kidney stones. Demographics and comorbid conditions including age, gender, body mass index, diabetes, hemoglobin A1c, hypertension, gout and smoking were also assessed. Multivariate analysis adjusting for patient demographics and comorbidities was performed to assess differences in the prevalence of chronic kidney disease and treatment with dialysis between the 2 groups. History of nephrolithiasis was assessed with the question, "Have you ever had kidney stones?" Chronic kidney disease was defined as an estimated glomerular filtration rate of less than 60 ml/minute/1.73 m(2) and/or a urinary albumin-to-creatinine ratio greater than 30 mg/gm. Statistical calculations were performed using Stata® software with determinations of p values and 95% CI where appropriate.

RESULTS

The study included an analysis of 5,971 NHANES participants for whom data on chronic kidney disease and kidney stones were available, of whom 521 reported a history of kidney stones. On multivariate analysis a history of kidney stones was associated with chronic kidney disease and treatment with dialysis (OR 1.50, 1.10-2.04, p = 0.013 and OR 2.37, 1.13-4.96, p = 0.025, respectively). This difference appeared to be driven by women, where a history of kidney stones was associated with a higher prevalence of chronic kidney disease (OR 1.76, 1.13-2.763, p = 0.016) and treatment with dialysis (OR 3.26, 1.48-7.16, p = 0.004). There was not a significant association between kidney stone history and chronic kidney disease or treatment with dialysis in men.

CONCLUSIONS

Kidney stone history is associated with an increased risk of chronic kidney disease and treatment with dialysis among women even after adjusting for comorbid conditions. Large scale prospective studies are needed to further characterize the relationship between nephrolithiasis and chronic kidney disease.

Nephrolithiasis in free-ranging North American river otter (Lontra canadensis) in North Carolina, USA

The North American river otter (Lontra canadensis) serves as an indicator species for environmental monitoring, is prized as a valuable furbearer, and is a popular display animal in zoologic collections. Nephrolithiasis has been reported as a frequent problem in other free-ranging and captive otter species but is rarely reported in North American river otters. In this study, we compared the prevalence of nephrolithiasis diagnosed using routine gross pathologic examination techniques with the use of computed tomography (CT) of excised kidneys. We also evaluated whether otter nephroliths could be accurately classified by their CT densities, and we examined the renal tissue uric acid concentrations in free-ranging otters in North Carolina, USA. Kidneys were collected from carcasses of legally trapped, free-ranging animals. Nephroliths were observed in 16.2% of the individuals (n = 229). Associations were found between age and nephrolith status and between capture location and nephrolith status (P = 0.026 and < 0.001, respectively). Computed tomography Hounsfield unit density measurements were not useful in determining nephrolith chemical composition in this study. Renal tissue uric acid concentrations were similar across genders, age groups, and stone status. The chemical composition of the nephroliths was determined by scanning electron microscopy-energy dispersive X-ray spectroscopy to be calcium phosphate in the carbonate form.

Dietary interventions for preventing complications in idiopathic hypercalciuria

BACKGROUND

Idiopathic hypercalciuria is an inherited metabolic abnormality that is characterised by excessive amounts of calcium excreted in the urine by people whose calcium serum levels are normal. Morbidity associated with idiopathic hypercalciuria is chiefly related to kidney stone disease and bone demineralisation leading to osteopenia and osteoporosis. Idiopathic hypercalciuria contributes to kidney stone disease at all life stages; people with the condition are prone to developing oxalate and calcium phosphate kidney stones. In some cases, crystallised calcium can be deposited in the renal interstitium, causing increased calcium levels in the kidneys. In children, idiopathic hypercalciuria can cause a range of comorbidities including recurrent macroscopic or microscopic haematuria, frequency dysuria syndrome, urinary tract infections and abdominal and lumbar pain. Various dietary interventions have been described that aim to decrease urinary calcium levels or urinary crystallisation.

OBJECTIVES

Our objectives were to assess the efficacy, effectiveness and safety of dietary interventions for preventing complications in idiopathic hypercalciuria (urolithiasis and osteopenia) in adults and children, and to assess the benefits of dietary interventions in decreasing urological symptomatology in children with idiopathic hypercalciuria.

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register (23 April 2013) through contact with the Trials' Search Co-ordinator using search terms relevant to this review. Studies contained in the Specialised Register are identified through search strategies specifically designed for CENTRAL, MEDLINE and EMBASE.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) and quasi-RCTs that investigated dietary interventions aimed at preventing complications of idiopathic hypercalciuria, compared with placebo, no intervention, or other dietary interventions regardless of route of administration, dose or amount.

DATA COLLECTION AND ANALYSIS

Studies were assessed for inclusion and data extracted using a standardised data extraction form. We calculated risk ratios (RR) for dichotomous outcomes and mean differences (MD) for continuous outcomes, both with 95% confidence intervals (CI).

MAIN RESULTS

We included five studies (379 adult participants) that investigated a range of interventions. Lack of similarity among interventions investigated meant that data could not be pooled. Overall, study methodology was not adequately reported in any of the included studies. There was a high risk of bias associated with blinding (although it seems unlikely that outcomes measures were unduly influenced by lack of intervention blinding), random sequence generation and allocation methodologies were unclear in most studies, but selective reporting bias was assessed as low.One study (120 participants) compared a low calcium diet with a normal calcium, low protein, low salt diet for five years. There was a significant decrease in numbers of new stone recurrences in those treated with the normal calcium, low protein, low salt diet (RR 0.77, 95% CI 0.61 to 0.98). This diet also led to a significant decrease in oxaluria (MD 78.00 µmol/d, 95% CI 26.48 to 129.52) and the calcium oxalate relative supersaturation index (MD 1.20 95% CI 0.21 to 2.19).One study (210 participants) compared a low salt, normal calcium diet with a broad diet for three months. The low salt, normal calcium diet decreased urinary calcium (MD -45.00 mg/d, 95% CI -74.83 to -15.17) and oxalate excretion (MD -4.00 mg/d, 95% CI -6.44 to -1.56).A small study (17 participants) compared the effect of dietary fibre as part of a low calcium, low oxalate diet over three weeks, and found that although calciuria levels decreased, oxaluria increased. Phyllanthus niruri plant substrate intake was investigated in a small subgroup with hypercalciuria (20 participants); there was no significant effect on calciuria levels occurred after three months of treatment.A small cross-over study (12 participants) evaluating the changes in urinary supersaturation indices among patients who consumed calcium-fortified orange juice or milk for one month found no benefits for participants.None of the studies reported any significant adverse effects associated with the interventions.

AUTHORS' CONCLUSIONS

Long-term adherence (five years) to diets that feature normal levels of calcium, low protein and low salt may reduce numbers of stone recurrences, decrease oxaluria and calcium oxalate relative supersaturation indexes in people with idiopathic hypercalciuria who experience recurrent kidney stones. Adherence to a low salt, normal calcium level diet for some months can reduce calciuria and oxaluria. However, the other dietary interventions examined did not demonstrate evidence of significant beneficial effects.No studies were found investigating the effect of dietary recommendations on other clinical complications or asymptomatic idiopathic hypercalciuria.

Nephrolithiasis and loss of kidney function

PURPOSE OF REVIEW

The prevalence of nephrolithiasis has been on the rise over recent decades. There have also been extensive efforts to identify risk factors for chronic kidney disease (CKD). The purpose of this review is to highlight recent evidence on the association of nephrolithiasis with the development of CKD and end-stage renal disease (ESRD).

RECENT FINDINGS

Several epidemiologic studies over the past decade assessed the relationship between history of nephrolithiasis and CKD. Across several studies, patients with nephrolithiasis had about a two-fold higher risk for decreased renal function or need for renal replacement therapy. This risk appears to be independent of risk factors for CKD that are common in stone formers such as hypertension and diabetes mellitus. Specific risk factors for CKD in stone formers include recurrent urinary tract infections, struvite and possibly uric acid stone composition, symptomatic stones, solitary kidney, ileal conduit, neurogenic bladder, and hydronephrosis.

SUMMARY

Recent evidence has shown a consistent relationship between nephrolithiasis history and an increased risk of CKD and ESRD. Understanding the characteristics that predispose to CKD may better inform how to optimally manage patients with nephrolithiasis and prevent this complication.

The association of prevalent kidney stone disease with mortality in US adults: the National Health and Nutrition Examination Survey III, 1988-1994

BACKGROUND

Kidney stone disease is associated with hypertension, diabetes, metabolic syndrome, kidney function decline, and increased cardiovascular (CV) events. However, its association with all-cause and CV mortality is unclear.

METHODS

We used the Third National Health and Nutrition Examination Survey, a large US population-based study with mortality data through 2006 determined via linkage to the National Death Index to examine kidney stone disease in relation to all-cause and CV mortality risks.

RESULTS

Among 14,879 men and women over 18 years of age who were eligible for analysis, 683 participants reported a history of kidney stones. There was a total of 3,590 all-cause and 1,608 CV deaths during a median follow-up of 14.9 years. Stone formers had a significantly higher risk for all-cause mortality [hazard ratio (HR): 1.95, 95% CI: 1.64-2.33, p < 0.0001) and CV mortality (HR: 2.05, 95% CI: 1.60-2.62, p < 0.0001) in unadjusted analyses. However, after multivariate adjustment for age, gender, race, and poverty, stone formers no longer had increased risk for all-cause mortality (HR: 1.08, 95% CI: 0.93-1.26, p = 0.3) and CV mortality (HR: 1.07, 95% CI: 0.84-1.36, p = 0.6). Results remain unchanged after further adjustment for other clinical variables including history of hypertension, diabetes, and CV disease.

CONCLUSION

The increased risk of all-cause and CV mortality in kidney stone formers is likely a reflection of unique demographics and associated comorbidities. There is no independent association of prevalent kidney stone disease with all-cause and CV mortality.

Kidney stone formation is positively associated with conventional risk factors for coronary heart disease in Japanese men

PURPOSE

We investigated the association between kidney stones and coronary heart disease risk factors in Japanese men.

MATERIALS AND METHODS

This cross-sectional study included 13,418 Japanese men 30 to 69 years old who voluntarily underwent medical examination between April 1995 and March 2001. Participants were divided into controls, and past and current kidney stone formers based on ultrasound results and medical history. We evaluated conventional risk factors of coronary heart disease, including overweight/obesity, hypertension, diabetes mellitus, gout/hyperuricemia, dyslipidemia and chronic kidney disease. Associations between coronary heart disease risk factors and kidney stones were investigated.

RESULTS

Of the 13,418 participants 404 current kidney stone formers (3.0%) had kidney stones on ultrasound and 1,231 past kidney stone formers (9.2%) had a history of kidney stones but no kidney stones on medical examination. Body mass index, systolic and diastolic blood pressure, and serum uric acid were significantly higher in past and current kidney stone formers than in controls. Logistic regression analysis indicated that the multivariate adjusted OR for overweight/obesity, hypertension, gout/hyperuricemia and chronic kidney disease significantly increased in the order corresponding to controls, and past and current kidney stone formers.

CONCLUSIONS

Kidney stone formers, even past stone formers, are likely to have accumulated risk factors for coronary heart disease. They could be preferentially targeted for coronary heart disease prevention.