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Removal of small, asymptomatic kidney stones during surgery to remove ureteral or contralateral stones resulted in less relapse than nonremoval and in similar numbers of subsequent emergency department visits.

Background Fructose intake, mainly as table sugar or high fructose corn syrup, has increased in recent decades and is associated with increased risk for kidney stones. We hypothesized that fructose intake alters serum and urinary components involved in stone formation. Methods We analyzed a previously published randomized controlled study that included 33 healthy male adults (40–65 years of age) who ingested 200 g of fructose (supplied in a 2-L volume of 10% fructose in water) daily for 2 weeks. Participants were evaluated at the Unit of Nephrology of the Mateo Orfila Hospital in Menorca. Changes in serum levels of magnesium, calcium, uric acid, phosphorus, vitamin D, and intact PTH levels were evaluated. Urine magnesium, calcium, uric acid, phosphorus, citrate, oxalate, sodium, potassium, as well as urinary pH, were measured. Results Ingestion of fructose was associated with an increased serum level of uric acid ( p  < 0.001), a decrease in serum ionized calcium ( p  = 0.003) with a mild increase in PTH ( p  < 0.05) and a drop in urinary pH ( p  = 0.02), an increase in urine oxalate ( p  = 0.016) and decrease in urinary magnesium ( p  = 0.003). Conclusions Fructose appears to increase urinary stone formation in part via effects on urate metabolism and urinary pH, and also via effects on oxalate. Fructose may be a contributing factor for the development of kidney stones in subjects with metabolic syndrome and those suffering from heat stress. Trial registration ClinicalTrials.gov NCT00639756 March 20, 2008.

Objective Kidney stone disease seems to be associated with an increased risk of incident cardiovascular outcomes; the aim of this study is to identify differences in 24-h urine excretory profiles and stone composition among stone formers with and without cardiovascular disease (CVD). Methods Data from patients attending the Department of Renal Medicine’s metabolic stone clinic from 1995 to 2012 were reviewed. The sample was divided according to the presence or absence of CVD (myocardial infarction, angina, coronary revascularization, or surgery for calcified heart valves). Univariable and multivariable regression models, adjusted for age, sex, BMI, hypertension, diabetes, eGFR, plasma bicarbonate and potential renal acid load of foods were used to investigate differences across groups. Results 1826 patients had available data for 24-h urine analysis. Among these, 108 (5.9%) had a history of CVD. Those with CVD were older, have higher prevalence of hypertension and diabetes and lower eGFR. Univariable analysis showed that patients with CVD had significantly lower 24-h urinary excretions for citrate (2.4 vs 2.6 mmol/24 h, p = 0.04), magnesium (3.9 vs 4.2 mmol/24 h, p = 0.03) and urinary pH (6.1 vs 6.2, p = 0.02). After adjustment for confounders, differences in urinary citrate and magnesium excretions remained significant. No differences in the probability of stone formation or stone compositions were found. Conclusions Stone formers with CVD have lower renal alkali excretion, possibly suggesting higher acid retention in stone formers with cardiovascular comorbidities. Randomized clinical trials including medications and a controlled diet design are needed to confirm the results presented here. Graphic abstract

Effect of vitamin C supplements on urinary oxalate and pH in calcium stone-forming patients. The contribution of ascorbate to urinary oxalate is controversial. The present study aimed to determine whether urinary oxalate and pH may be affected by vitamin C supplementation in calcium stone-forming patients. Forty-seven adult calcium stone-forming patients received either 1 g (N = 23) or 2 g (N = 24) of vitamin C supplement for 3 days and 20 healthy subjects received 1 g. A 24-hour urine sample was obtained both before and after vitamin C for calcium, oxalate, magnesium, citrate, sodium, potassium, and creatinine determination. The Tiselius index was used as a calcium oxalate crystallization index. A spot fasting morning urine sample was also obtained to determine the urinary pH before and after vitamin C. Fasting urinary pH did not change after 1 g (5.8 ± 0.6 vs. 5.8 ± 0.7) or 2 g vitamin C (5.8 ± 0.8 vs. 5.8 ± 0.7). A significant increase in mean urinary oxalate was observed in calcium stone-forming patients receiving either 1 g (50 ± 16 vs. 31 ± 12 mg/24 hours) or 2 g (48 ± 21 vs. 34 ± 12 mg/24 hours) of vitamin C and in healthy subjects (25 ± 12 vs. 39 ± 13 mg/24 hours). A significant increase in mean Tiselius index was observed in calcium stone-forming patients after 1 g (1.43 ± 0.70 vs. 0.92 ± 0.65) or 2 g vitamin C (1.61 ± 1.05 vs. 0.99 ± 0.55) and in healthy subjects (1.50 ± 0.69 vs. 0.91 ± 0.46). Ancillary analyses of spot urine obtained after vitamin C were performed in 15 control subjects in vessels with or without ethylenediaminetetraacetic acid (EDTA) with no difference in urinary oxalate between them (28 ± 23 vs. 26 ± 21 mg/L), suggesting that the in vitro conversion of ascorbate to oxalate did not occur. These data suggest that vitamin C supplementation may increase urinary oxalate excretion and the risk of calcium oxalate crystallization in calcium stone-forming patients.

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

Background We examined the association between kidney stones and renal cell carcinoma (RCC) and upper tract urothelial carcinoma (UTUC) risk in the Netherlands Cohort Study on diet and cancer. Methods In total, 120,852 participants aged 55–69 completed a self-administered questionnaire on diet, medical conditions and other risk factors for cancer at baseline (1986). After 20.3 years of cancer follow-up 4352 subcohort members, 544 RCC cases and 140 UTUC cases were eligible for case-cohort analysis. Hazard ratios (HR) and 95% confidence intervals (CIs) were estimated by multivariable-adjusted proportional hazards models. Results Kidney stones were associated with an increased RCC risk (HR: 1.39, 95% CI 1.05–1.84), vs. no kidney stones. Kidney stones were associated with an increased risk of papillary RCC (HR: 3.08, 95% CI 1.55–6.11), but not clear-cell RCC (HR: 1.14, 95% CI 0.79–1.65). UTUC risk was increased for participants with kidney stones (HR: 1.66, 95% CI 1.03–2.68). No heterogeneity of associations was found for UTUC in the ureter and renal pelvis. An early kidney stone diagnosis (≤40 years) was associated with an increased RCC and UTUC risk, compared to later diagnosis. Conclusion Kidney stones were associated with increased papillary RCC risk, but not clear-cell RCC risk. No heterogeneity was found for UTUC subtypes.

Nephrolithiasis is a common medical condition influenced by multiple environmental factors, including diet. Since nutritional habits play a relevant role in the genesis and recurrence of kidney stones disease, dietary manipulation has become a fundamental tool for the medical management of nephrolithiasis. Dietary advice aims to reduce the majority of lithogenic risk factors, reducing the supersaturation of urine, mainly for calcium oxalate, calcium phosphate, and uric acid. For this purpose, current guidelines recommend increasing fluid intake, maintaining a balanced calcium intake, reducing dietary intake of sodium and animal proteins, and increasing intake of fruits and fibers. In this review, we analyzed the effects of each dietary factor on nephrolithiasis incidence and recurrence rate. Available scientific evidence agrees on the harmful effects of high meat/animal protein intake and low calcium diets, whereas high content of fruits and vegetables associated with a balanced intake of low-fat dairy products carries the lowest risk for incident kidney stones. Furthermore, a balanced vegetarian diet with dairy products seems to be the most protective diet for kidney stone patients. Since no study prospectively examined the effects of vegan diets on nephrolithiasis risk factors, more scientific work should be made to define the best diet for different kidney stone phenotypes.

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 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. Kidney stones form when the urine becomes supersaturated with respect to a mineral, leading to crystal formation, growth, aggregation and retention within the kidneys. In this Primer, Khan et al. describe the contributing pathways to stone formation and the available treatments, as well as highlight the emerging management strategies.

Kidney stone disease is associated with numerous cardiovascular risk factors. However, the findings across studies are non-uniformly consistent, and the control of confounding variables remains suboptimal. This study aimed to investigate the association between kidney stone and cardiovascular disease. We conducted an observational study using data from the National Health and Nutrition Examination Survey conducted between 2007 and 2010. Weighted multivariable-adjusted logistic regression was used to evaluate the association between kidney stones and cardiovascular event risk. Moreover, in observational studies, Mendelian randomization (MR) was applied to avoid reverse causality and reduce the influence of potential confounding factors. Inverse-variance weighted (IVW) was the main analytical method. After controlling for cardiovascular and kidney stone risk factors among 7210 US adults, along with other potential confounding variables, patients with kidney stones exhibited a significantly elevated risk of acute myocardial infarction (AMI) (odds ratio [OR], 1.88 [95% confidence interval [CI], 1.09-3.26], P < 0.05). However, a non-significant association was observed with heart failure, hypertension, or stroke. MR analyses further indicated that genetically predicted kidney stones were causally associated with an increased risk of coronary heart disease (OR, 1.07 [95% CI, 1.04-1.53], P = 0.028), myocardial infarction (OR, 1.08 [95% CI,1.02-1.15], P = 0.015), hypertension (OR 1.01 [95% CI, 1.00-1.02], P = 0.042) and ischemic stroke (OR, 0.86 [95% CI, 0.75-0.98], P = 0.022) in IVW models, with non-significant associations detected for heart failure. The occurrence of kidney stones has been associated with an elevated risk of myocardial infarction within the context of cardiovascular events. However, cross-sectional analyses yield results that are inconsistent with those obtained from Mendelian randomization analyses regarding outcomes such as heart failure, hypertension, and stroke.