Urolithiasis: evaluation, dietary factors, and medical management: an update of the 2014 SIU-ICUD international consultation on stone disease

Association between urinary cobalt exposure and kidney stones in U.S. adult population: results from the National Health and Nutrition Examination Survey

PURPOSE

Heavy metal exposure can cause impaired or reduced pathology in the kidneys, lungs, liver, and other vital organs. However, the relationship between heavy metal exposure and kidney stones has not been determined. The goal of this research was to determine the association between heavy metal exposure and kidney stones in a population of American adults in general.

MATERIALS AND METHODS

We evaluated 29,201 individuals (≥20 years) from the National Health and Nutrition Examination Survey (NHANES). The association between heavy metal exposure and kidney stones was verified by multiple logistic regression and restricted cubic spline (RCS) regression. Dose-response curves were generated to analyze the relationship between heavy metal concentrations and the occurrence of kidney stones. Moreover, we used propensity score matching (PSM) to exclude the effect of confounding variables.

RESULTS

After a rigorous enrollment screening process, we included 8518 participants. Logistic regression showed that urinary cadmium (U-Cd) and urinary cobalt (U-Co) concentrations were significantly different in the kidney stone group before PSM (p < 0.001). Dose-response curves revealed that the occurrence of kidney stones increased significantly with increasing U-Cd and U-Co concentrations. After adjustment for covariates, only biomarkers of U-Co were linked to the occurrence of kidney stones. When the lowest quartile was used as a reference, the 95% confidence intervals (95% CIs) for kidney stones across the other quartiles were 1.015 (0.767-1.344), 1.409 (1.059-1.875), and 2.013 (1.505-2.693) for U-Cos (p < 0.001).

CONCLUSION

In the U.S. population, high U-Co levels are positively correlated with the potential risk of kidney stones.

Knowledge, attitude, and practice regarding stone formation and recurrence among urolithiasis patients: a cross-sectional study

This study investigated the knowledge, attitude, and practice (KAP) concerning stone formation and recurrence among patients with urolithiasis treated at Ningbo Medical Centre Lihuili Hospital between August 19, 2023, and April 19, 2024. A total of 394 patients were included, among which 70.30% were males. The median scores for knowledge, attitude, and practice were 7 (6-8.25), 29 (26.75-31), and 21.5 (18-25), respectively, indicating good knowledge and attitude but suboptimal practice. Positive correlations were found between knowledge and attitude (r = 0.274, P < 0.001) and between attitude and practice (r = 0.126, P < 0.05). Logistic regression revealed that knowledge, education, and whether the patient experienced a new or recurrent stone were independent predictors of attitude. Attitude, education, body mass index (BMI), and daily water intake were independent predictors of practice. Structural equation modeling (SEM) showed that knowledge, family history, and education directly influenced attitude, while education also significantly impacted practice. Our findings highlight the need for targeted diet, hydration, and lifestyle education to enhance preventive practices among patients with urolithiasis.

Risk relationship between inflammatory bowel disease and urolithiasis: A two-sample Mendelian randomization study

BACKGROUND

The causal genetic relationship between common parenteral manifestations of inflammatory bowel disease (IBD) and urolithiasis remains unclear because their timing is difficult to determine. This study investigated the causal genetic association between IBD and urolithiasis using Mendelian randomization (MR) based on data from large population-based genome-wide association studies (GWASs).

METHODS

A two-sample MR analysis was performed to assess the potential relationship between IBD and urolithiasis. Specific single nucleotide polymorphism data were obtained from GWASs, including IBD (n = 59957) and its main subtypes, Crohn's disease (CD) (n = 40266) and ulcerative colitis (UC) (n = 45975). Summarized data on urolithiasis (n = 218792) were obtained from different GWAS studies. A random-effects model was analyzed using inverse-variance weighting, MR-Egger, and weighted medians.

RESULTS

Genetic predisposition to IBD and the risk of urolithiasis were significantly associated [odds ratio (OR), 1.04 (95% confidence interval [CI], 1.00-.08), P = 0.01]. Consistently, the weighted median method yielded similar results [OR, 1.06 (95% CI, 1.00-1.12), P = 0.02]. The MR-Egger method also demonstrated comparable findings [OR, 1.02 (95% CI, 0.96-1.08), P = 0.45]. Both funnel plots and MR-Egger intercepts indicated no directional pleiotropic effects between IBD and urolithiasis. CD was strongly associated with it in its subtype analysis [OR, 1.04 (95% CI, 1.01-1.07), P = 0.01], and UC was also causally associated with urolithiasis, although the association was not significant [OR, 0.99 (95% CI, 0.95-1.03), P = 0.71].

CONCLUSION

A unidirectional positive causal correlation was identified between IBD and urolithiasis, with varying degrees of association observed among the different subtypes of IBD. Recognizing the increased incidence of urolithiasis in patients with IBD is crucial in clinical practice. Early detection and surveillance of IBD, improved patient awareness, adoption of preventive strategies, and promotion of collaborative efforts among healthcare providers regarding treatment methodologies are vital for improving patient outcomes.

Dietary management of hypocitraturia in children with urolithiasis: results from a systematic review

PURPOSE

Hypocitraturia is a low urinary excretion of citrate and a well-known risk factor for kidney stone development in children. This systematic review aimed to evaluate the dietary management of hypocitraturia in children with urolithiasis.

METHODS

Literature search was performed on 30th September 2022 using Embase, PubMed, and Cochrane Central Controlled Register of Trials. Studies were included if children with stones and hypocitraturia were managed with diet supplements.

RESULTS

Six papers were included. Four studies evaluated the role of oral potassium citrate associated with high fluid intake on stone resolution and recurrence. Two studies assessed the impact of oral potassium citrate on long-term stone recurrence after percutaneous nephrolithotomy and shock wave lithotripsy. All studies demonstrated that the association of potassium citrate and high fluid intake was well tolerated with no side effects and restored normal urine citrate excretion, allowed a reduction in stone size, and, following definitive treatments, was associated with a lower rate of stone regrowth and recurrence compared with controls. These effects were demonstrated across all pediatric ages.

CONCLUSIONS

Our review infers that oral potassium citrate and high fluid assumption are safe and effective in restoring urine citrate excretion, treating and preventing stone recurrence with no serious adverse events, and should probably be the first-line treatment of pediatric patients with asymptomatic stones and hypocitraturia.

Analysis of potential risk factors associated with urolithiasis

OBJECTIVES

Eating habits, regular fluid intake, lifestyle and body composition are a primary point of research. The research focused on urolithiasis approaching potential danger, trying to interpret risk factors responsible for urolithiasis and disease recurrence.

METHODS

Research file contains 166 patients suffering from urolithiasis, 87 (52.4%) males and 79 (47.6%) females, and 172 healthy subjects from control group. All data was accessed using fully anonymous and confidential questionnaires, then evaluated in the statistical GNU PSPP 1.4 software.

RESULTS

More than 3/4 patients have a BMI higher than 24.9 and almost 40% of subjects have obesity class I, II, or III. Patients have higher BMI than subjects (d = 1.285; p < 0.001), and females have significantly higher BMI than males (d = 0.385; p = 0.007). Female patients have higher BMI than Slovak healthy females (p < 0.001; MD = 4.581; CI: 3.24-5.93). Patients have a lower daily water intake than subjects (φc = 0.157; p = 0.04) and more than ²/3 of patients have insufficient water intake. Sedentary employment prevails markedly in patients than in subjects. Patients are much less physically active than subjects (φc = 0.633; p < 0.001) and the difference is rising with increasing age of patients (ρ = - 0.232; p = 0.003). Low physical and working activity are characteristic for patients in this study. Patients smoke more often in comparison to subjects (φc = 0.261; p < 0.001). Patients consume more meats (red and white), cocoa and lentils. A lot of patients exceed recommended daily intake of pork and beef.

CONCLUSIONS

Many conditions are different for the healthy population and patients' group. High BMI, low fluid intake, exceeded red meat consumption, and low physical activity are the strongest factors for developing urolithiasis. Patients should consume more fluids daily, exercise frequently and vigorously, and lower amount of red meat consumed.

Association of meteorological factors and ambient air pollution on medical care utilization for urolithiasis: a population-based time-series study

BACKGROUND

To identify the association of meteorological factors/ambient air pollutants with medical care utilization for urolithiasis and estimate the effect size/time lags.

METHODS

This is a population-based time-series analysis of 300,000 urolithiasis cases from eight large metropolitan areas in Korea. Seventeen meteorological factors and ambient air pollutants were measured daily during 2002-2017 for each metropolis. Data on daily medical utilization owing to urolithiasis were collected. A generalized additive model was used while factoring in the nonlinear relationship between meteorological factors/ambient air pollutants and urolithiasis and a time lag of ≤10 days. A multivariate analysis was performed. Backward elimination with an Akaike information criterion was used for fitting the multivariate model.

RESULTS

Urolithiasis was significantly associated with average temperature, diurnal temperature range, sunshine duration, particulate matter (PM) ≤2.5 μm, and carbon monoxide (CO) levels. The incidence of ureteral stones was positively correlated with average temperature, PM ≤2.5 μm level, and CO level (time lags 0-9, 2-4, and 0-9 days, respectively). The incidence of renal stones was positively correlated with PM ≤2.5 μm and CO levels (time lags 2-4 and 0-9 days, respectively). PM ≤2.5 μm (0.05 and 0.07% per 10 μg/m³⁾ and CO (2.05 and 2.25% per 0.1 ppm) conferred the highest excess risk on ureteral and renal stones.

CONCLUSIONS

Urolithiasis is affected by various meteorological factors and ambient air pollutants, PM ≤2.5 μm, and CO levels may be novel potential risk factors for this condition.

Renal stone detection using a low kilo-voltage paediatric CT protocol - a porcine phantom study

INTRODUCTION

Reducing tube voltage is an effective dose saving method in computed tomography (CT) assuming tube current is not concurrently increased. Recent innovations in scanner technology now enable CT tube voltage reduction to 70 kV thereby increasing opportunities for dose reduction in paediatric patients, but it is unclear if the increased image noise associated with 70 kV impacts on ability to visualise renal stones accurately. The purpose was to assess detectability of nephrolithiasis using a bespoke paediatric phantom and low kV, non-contrast CT and to assess inter-observer agreement.

METHODS

Forty-two renal stones of different size and chemical composition were inserted into porcine kidneys and positioned in a bespoke, water-filled phantom mimicking a 9-year-old child weighing approximately 33kg. The phantom was scanned using 120 and 70 kV CT protocols, and the detectability of the stones was assessed by three radiologists. Absolute agreement and Fleiss' kappa regarding detectability were assessed.

RESULTS

The mean diameter of renal stones as measured physically was 4.24 mm ranging from 1 to 11 mm. Four stones were missed by at least one observer. One observer had a sensitivity of 93 and 95% at 70 and 120 kV, respectively, while the sensitivity for observers 2 and 3 was 98% at both kV levels. Specificity was 100% across readers and kV levels. Absolute agreement between the readers at 70 kV was 92% (kappa = 0.86) and 98% (kappa = 0.96) at 120 kV indicating a strong agreement at both kV levels.

CONCLUSIONS

The results suggest that lowering the kV does not affect the detection rate of renal stones and may be a useful dose reduction strategy for assessment of nephrolithiasis in children.

Associations of exposure to polycyclic aromatic hydrocarbons and kidney stones in U.S. general population: results from the National Health and Nutrition Examination Survey 2007-2016

PURPOSE

It has been reported that polycyclic aromatic hydrocarbons (PAHs) exposure was associated with the increasing risk of various diseases. Utilizing the data from the general population of the U.S., we tried to assess the association between PAHs exposure and KS.

METHODS

The dataset was extracted from National Health and Nutrition Examination Survey (NHANES) 2007-2016. The hydroxylated metabolites of polycyclic aromatic hydrocarbons (OH-PAHs) were detected as representative of urinary PAHs. Ranking-based PAHs score was used to evaluate the total PAHs exposure burden. Multivariable logistic regression analyses were performed to assess the association between PAHs exposure and KS after adjusting a series of confounding factors.

RESULTS

8975 eligible participants were included. In multivariable logistic regression analyses, after adjusting confounding variables, 2-hydroxynaphthalene (OR 1.38, 1.16-1.65; p = 0.038) and 9-hydroxyfluorene (OR 1.39, 1.06-1.84, p = 0.019) were still observed to have significant positive correlations with the prevalence of KS, respectively. The incidence of KS increased significantly with the increase of total PAHs burden (p for trend = 0.011). Significant interaction effects were observed in the subgroup of gender (p for interaction < 0.05). Among female participants, PAHs exposure was more significantly correlated with KS. Higher 2-hydroxynaphthalene (OR 1.94, 1.39-2.70; p < 0.001), 1-hydroxyphenanthrene (OR 1.57, 1.07-2.30; p = 0.022) and 2-hydroxyphenanthrene (OR 1.85, 1.11-3.06; p = 0.018) were significantly associated with the increased incidence of KS in women.

CONCLUSIONS

There is a significant association between a high level of PAHs exposure and increased prevalence of KS. In particular, in the female population, the relationship between PAHs exposure and KS is especially significant.

Complementary and Alternative Medicine Use in First-time and Recurrent Kidney Stone Formers

OBJECTIVE

To describe the patterns of complementary and alternative medicine (CAM) among patients with kidney stones and analyze the alkali content of commonly used CAM therapies.

METHODS

We prospectively conducted structured interviews with patients who presented to a specialty stone clinic for the management of kidney stones. Open-ended questions were used to elicit information regarding CAM knowledge, formulation/dosing, and patterns of use. Several common CAM therapies were then analyzed for their alkali, organic anion, and sugar content.

RESULTS

Of 103 subjects, 82 (80%) patients reported knowledge of CAM and 52 (50%) reported using CAM. Patients with recurrent kidney stones were more likely to report using CAM than patients with first-time episodes (56% vs 26%, P = 0.04). Some respondents reported their condition decreased in severity or frequency since starting CAM therapy (17%) and improvements in pain (12%). Total alkali content per serving of the tested supplements was 0 mEq (Stonebreaker), 1.5 mEq (Ocean Spray Cranberry Juice Cocktail), 4.7 mEq (Lakewood Pure Cranberry Juice), 0.6 mEq (Braggs Apple Cider Vinegar), 11.9 mEq (LithoBalance), 9.5 mEq (Simply Grapefruit Juice), 19.8 mEq (KSP-Key Lime), and 20.2 mEq (KSP-Very Berry).

CONCLUSION

Patients with kidney stones may use CAM to alleviate symptoms or prevent recurrence. Commercially available CAM therapies may contain comparable alkali content to commonly prescribed citrate therapy. These data suggest that providers should be prepared to discuss the role of CAM with their patients.

Relationship Between Body Mass Index and Kidney Stones Based on Dose-Response Analyses Using Restricted Cubic Splines Applied to NHANES 2011-2016 Data

OBJECTIVE

The objective of the study was to estimate the dose-response relationship between body mass index (BMI) and the self-reported prevalence of kidney stones based on a restricted cubic spline (RCS) method.

METHODS

This cross-sectional study analyzed 13,223 adults aged ≥20 years who had participated in the National Health and Nutrition Examination Survey performed during 2011-2016. Kidney stones were identified using a standard questionnaire, and physical examinations were used to determine BMI. Logistic regression was used to assess the relationship between BMI and the prevalence of kidney stones, with the dose-response relationship explored using RCSs.

RESULTS

The overall prevalence of kidney stones was 9.7%: 10.6% in males and 8.9% in females. After adjusting for potential confounders, compared with those with a BMI in quartile 1, the odds ratios of kidney stones among those with BMIs in quartiles 2, 3, and 4 were 1.45, 1.60, and 2.00, respectively (95% confidence interval = 1.21-1.75, 1.33-1.92, and 1.67-2.39; all P < .001). Multivariate RCS regression revealed that BMI was related to kidney stones in a nonlinear manner (P for nonlinearity <0.001). There was a significant positive relationship, with the curves being steeper when BMI was <28 kg/m2.

CONCLUSION

This analysis of National Health and Nutrition Examination Survey data has demonstrated that BMI is significantly associated with the prevalence of kidney stones.

Benign Prostatic Hyperplasia and Kidney Stone Disease Thermobalancing Therapy with Dr Allen’s Device: Key to Successful Ageing Without Medications, Surgery, and Risky Exposure to Coronavirus Infection

Background: The choice of treatment for benign prostatic hyperplasia (BPH) and kidney stone disease (KSD) impacts the attainment of successful ageing and the level of patient care required in the long-term. Medications and surgeries typically used for these conditions have serious side effects and can interfere with healthy aging. Objectives: This study assesses the impact of Dr Allen’s Therapeutic devices (DATD) and thermobalancing therapy® (TT) on the ageing process of people with BPH and KSD. Methods: This study evaluated the outcomes of a clinical trial investigating the dynamics of symptoms and parameters in 124 male patients with BPH who used DATD as a monotherapy for six months at home and compared the results with a control group comprising 124 BPH patients who did not receive treatment with DATD. Furthermore, five case studies were randomly selected for assessment from 10-year empirical observations of patients with KSD treated with DATD. Results: DATD with TT reduced prostate volume (PV) from 45 mL to 31 mL (P < 0.001) and reduced urinary symptoms score from 14.2 to 4.9 (P < 0.001). It also improved quality of life (QoL) as measured by the reduction in the International Prostate Symptom score (I-PSS) from 3.9 to 1.3 (P < 0.001), while the control group showed no positive changes. DATD with TT dissolved kidney stones without renal colic in all patients. No side effects were observed. Conclusions: Using DATD and TT to treat BPH and KSD demonstrated high efficacy, safety, and easy disease management at home. In contrast, medications and surgeries for BPH and KSD often lead to sexual dysfunction, depression, hypertension, chronic kidney failure, and other morbidities, requiring an increased care level in the long-term. Thus, DATD and TT generate high treatment efficacy with lower exposure to coronavirus, reduce long-term care needs, and are vital to attaining successful ageing and longevity.

Can Dual Energy CT with Fast kV-Switching Determine Renal Stone Composition Accurately?

RATIONALE AND OBJECTIVES

To determine whether a single source computed tomography (CT) system utilizing fast kV switching and low dose settings can characterize (diameter and chemical composition) renal stones accurately when compared infrared spectroscopy.

MATERIALS AND METHODS

The chemical composition of 15 renal stones was determined using Fourier transform infrared spectroscopy. The stones were inserted into a porcine kidney and placed within a water tank for CT scanning using both fast kV switching dual energy and standard protocols. Effective atomic number of each stone was measured using scanner software. Stone diameter measurements were repeated twice to determine intra-rater variation and compared to actual stone diameter as measured by micro CT.

RESULTS

The chemical composition of three stones (one calcium phosphate and two carbonite apatite) could not be determined using the scanner software. The composition of 10/12 remaining stones was correctly identified using dual energy computed tomography (83% absolute agreement; k = 0.69). No statistical difference (p = 0.051) was noted in the mean stone diameter as measured by clinical CT and micro CT.

CONCLUSION

Dual energy computed tomography using fast kV switching may potentially be developed as a low dose clinical tool for identifying and classifying renal stones in vivo supporting clinical decision-making.

The Impact of Diet on Urinary Risk Factors for Cystine Stone Formation

Despite the importance of dietary management of cystinuria, data on the contribution of diet to urinary risk factors for cystine stone formation are limited. Studies on the physiological effects of diet on urinary cystine and cysteine excretion are lacking. Accordingly, 10 healthy men received three standardized diets for a period of five days each and collected daily 24 h urine. The Western-type diet (WD; 95 g/day protein) corresponded to usual dietary habits, whereas the mixed diet (MD; 65 g/day protein) and lacto-ovo-vegetarian diet (VD; 65 g/day protein) were calculated according to dietary reference intakes. With intake of the VD, urinary cystine and cysteine excretion decreased by 22 and 15%, respectively, compared to the WD, although the differences were not statistically significant. Urine pH was significantly highest on the VD. Regression analysis showed that urinary phosphate was significantly associated with cystine excretion, while urinary sulfate was a predictor of cysteine excretion. Neither urinary cystine nor cysteine excretion was affected by dietary sodium intake. A lacto-ovo-vegetarian diet is particularly suitable for the dietary treatment of cystinuria, since the additional alkali load may reduce the amount of required alkalizing agents.

Pharmacotherapeutic approach toward urological medications and vaccination during COVID-19: a narrative review

One year after the prevalence of the novel coronavirus pandemic, some aspects of the physiopathology, treatment and progression of coronavirus 2019 disease (COVID-19) have remained unknown. Since no comprehensive study on the use of urological medications in patients with COVID-19 has been carried out, this narrative review aimed to focus on clinically important issues about the treatment of COVID-19 and urologic medications regarding efficacy, modifications, side effects and interactions in different urologic diseases. In this review, we provide information about the pharmacotherapeutic approach toward urologic medications in patients with COVID-19 infection. This study provides an overview of medications in benign prostatic hyperplasia, prostate cancer, impotence and sexual dysfunction, urolithiasis, kidney transplantation and hypertension as the most frequent diseases in which the patients are on long-term medications. Also, the effect of urologic drugs on the efficacy of vaccination is briefly discussed.

Modern imaging techniques in urinary stone disease

PURPOSE OF REVIEW

Radiological imaging techniques are a fast developing field in medicine. Therefore, the purpose of this review was to identify and discuss the latest changes of modern imaging techniques in the management of urinary stone disease.

RECENT FINDINGS

The introduction of iterative image reconstruction enables low-dose and ultra-low-dose (ULD) protocols. Although current guidelines recommend their utilization in nonobese patients recent studies indicate that low-dose imaging may be feasible in obese (<30 kg/m) but not in bariatric patients. Use of dual energy computed tomography (CT) technologies should balance between additional information and radiation dose aspects. If available on a dose neutral basis, dual energy imaging and analysis should be performed. Current guidelines recommend measuring the largest diameter for clinical decision making; however, recent studies suggest a benefit from measuring the volume based on multiplanar reformation. Quantitative imaging is still an experimental approach.

SUMMARY

The use of low-dose and even ULD CT protocols should be diagnostic standard, even in obese patients. If dual energy imaging is available, it should be limited to specific clinical questions. The stone volume should be reported in addition to the largest diameter for treatment decision and a more valid comparability of upcoming studies.

Nephrotoxic metals of cadmium, lead, mercury and arsenic and the odds of kidney stones in adults: An exposure-response analysis of NHANES 2007-2016

BACKGROUND

Nephrotoxic metals of arsenic, cadmium, lead and mercury exposures are common environmental pollutants. The associations between arsenic, cadmium, lead and mercury exposures and the risk of kidney stones are unclear.

OBJECTIVE

To explore the associations between biomarkers of arsenic, cadmium, lead and mercury exposures and the odds of kidney stones.

METHODS

Adult participants (≥20 years) from the 2007-2016 NHANES were included. Restricted cubic splines were adopted.

RESULTS

The odds ratio (95% confidence interval) of kidney stones increased with increasing blood cadmium and reached the maximum at 1.00 μg/L [1.38 (1.02-1.88) overall, 1.62 (1.11-2.32) for women and 1.53 (1.06-2.22) for non-Hispanic white]. The odds of kidney stones increased with increasing urinary cadmium and reached the maximum at 1.50 μg/L [2.56 (1.17-5.59) overall, 5.57 (1.88-16.49) for women, 4.31 (1.75-10.63) for obese individuals and 3.75 (1.60-8.78) for non-Hispanic white]. The odds of kidney stones increased with increasing total urinary arsenic and urinary dimethylarsinic acid in women, and reached the maximum of 1.69 (1.08-2.67) at 40 μg/L and 1.71 (1.07-2.72) at 10.00 μg/L, respectively. Inverse associations were found between the odds of kidney stones and blood lead within 5.00 μg/dL [0.64 (0.46-0.90) overall, 0.53 (0.33-0.84) for men and 0.58 (0.37-0.92) for non-Hispanic white], methyl mercury within 3.00 μg/L [non-obese individuals: 0.71 (0.51-0.99)] and urinary arsenous acid within 1.20 μg/L [individuals other than non-Hispanic white: 0.63 (0.41-0.95)]. No association was found with other biomarkers.

CONCLUSIONS

Several biomarkers of arsenic, cadmium, lead and mercury exposures were associated with the odds of kidney stones in adults.

Caffeine intake and the risk of recurrent kidney stones in adults, an analysis of 2007-2014 National Health and Nutrition Examination Surveys

PURPOSE

The association between caffeine intake and the risk of recurrent kidney stones is unknown. We examined the association between caffeine intake and the risk of recurrent kidney stones in adults.

METHODS

Individuals with history of passing at least one kidney stone were included from 2007 to 2014 National Health and Nutrition Examination Survey. Recurrent kidney stones were defined using a standard questionnaire and structured dietary recalls were used to determine caffeine intake. The weighted logistic regression was used to assess the association between caffeine intake and the risk of recurrent kidney stones, and the non-linear relationship was explored with restricted cubic splines. Caffeine and dietary confounders (minerals and vitamins) were adjusted for total energy intake with residual model.

RESULTS

The multivariate-adjusted odds ratios (95% confidence intervals) of recurrent kidney stones for per-quartile increment in caffeine intake were 1.15 (1.01-1.31) overall, 1.11 (0.96-1.29) for white race individuals, 1.33 (1.09-1.63) for non-white race individuals, 1.15 (0.97-1.36) for men, 1.24 (1.01-1.53) for women, 1.54 (1.08-2.19) for non-overweight individuals, 1.11 (0.97-1.28) for overweight/obese individuals, 1.13 (0.99-1.29) for caffeine from coffee, and 0.90 (0.79-1.03) for caffeine from non-coffee sources. A linear relationship was found between caffeine intake and the risk of recurrent kidney stones overall and in subgroup analyses.

CONCLUSION

Compared with those who reported passing only one kidney stone, caffeine intake was independently and linearly associated with a higher risk of recurrent kidney stones in adults, especially for women, individuals of non-white race and non-overweight subjects. The increased risk may arise from caffeine from coffee.

Combined Laparoscope and Flexible Ureteroscope Pyelolithotomy Dealing with Large-Burden Complex Renal Calculi in Children Less Than 1 Year Old

Objective: To evaluate the experience and result of combined laparoscope and flexible ureteroscope (f-URS) pyelolithotomy in dealing with large-burden complex renal calculi in children <1 year old. Methods: Eleven patients (7 males and 4 females) <1 year old were retrospectively reviewed between December 2015 and May 2017, who had been diagnosed with renal calculi and received combined laparoscope and f-URS pyelolithotomy. The operations were carried out under general anesthesia. Patient' characteristics, presenting symptoms, operative times, and blood loss, stone-free rate, and postoperative complications were all collected retrospectively. Results: All 11 patients received combined laparoscope and f-URS pyelolithotomy. All operations went smoothly without conversion record and blood transfusion. Average time consumed was 109 minutes (55-187 minutes), and blood loss reported was 16 mL (10-25 mL). Average hospital stay after operation was 7 days (5-11 days). On mean follow-up of 6-12 months, no symptomatic urinary tract infections and urinary calculi were detected. Conclusion: Laparoscope combined f-URS pyelolithotomy is considered safe in the treatment of large-burden multiple renal calculi in infant patients with a high stone clearance rate. It has certain advantages in the treatment of renal calculi in infants <1 year old, and it could be an alternative treatment when other treatments fail or are unavailable.

Hydroxycitric Acid Tripotassium Inhibits Calcium Oxalate Crystal Formation in the Drosophila Melanogaster Model of Hyperoxaluria

Background

Hydroxycitric acid is a potential lithontriptic agent for calcium oxalate (CaOx) stones in the kidneys. This study aimed to evaluate the safety and efficiency of hydroxycitric acid tripotassium (K-HCA) against CaOx crystal formation using Drosophila melanogaster hyperoxaluria models.

Material/Methods

Wild-type D. melanogaster were fed standard medium with ethylene glycol or sodium oxalate added to induce hyperoxaluria. Their Malpighian tubules were dissected and observed under a microscope every 3 days. Crystal deposit score of each Malpighian tubule were evaluated under a magnification of ×200. Using hyperoxaluria Drosophila models, we investigated the inhibitory efficiency of hydroxycitrate acid tripotassium and citric acid tripotassium (K-CA) against CaOx crystal formation. The survival rate of each group was also assessed.

Results

When fed with 0.05% NaOx, the CaOx formation in Malpighian tubules increased significantly, without reduction of life span. Therefore, we selected 0.05% NaOx-induced hyperoxaluria models for the further investigations. After treatment, the stone scores showed that K-CA and K-HCA both significantly inhibit the formation of CaOx crystals in a dose-dependent manner, and with smaller dosage (0.01%), K-HCA was more efficient than K-CA. Moreover, after treatment of K-CA or K-HCA, the life span in different groups did not change, reflecting the safety to life.

Conclusions

The hyperoxaluria Drosophila models fed on 0.05% NaOx diet might be a useful tool to screen novel agents for the management of CaOx stones. K-HCA may be a promising agent for the prevention CaOx stones, with satisfying efficiency and acceptable safety.

Twenty-four-hour urine osmolality as a representative index of adequate hydration and a predictor of recurrence in patients with urolithiasis

PURPOSE

To determine the value of 24-h urine osmolality (UOsm) as a representative index of adequate hydration and predictor of stone recurrence in patients with urolithiasis.

METHODS

Medical records of consecutive patients presenting with renal or ureteric stones between 1994 and 2017 were retrospectively reviewed. Patients were grouped according to the results of 24-h UOsm (low ≤ 564 mOsm/kg H₂O, high > 564 mOsm/kg H₂O). Metabolic parameters and risk of stone recurrence were compared between the two groups.

RESULTS

The low urine concentration group were more likely to be older, to be female, and to have a lower body mass index and higher glomerular filtration rate than the high concentration group (each P < 0.005). A positive correlation was seen between 24-h UOsm and urinary calcium, sodium, uric acid, and magnesium excretion and 24-h specific gravity; a negative correlation was seen with 24-h urine volume. Stone-forming constituents, such as calcium and uric acid, were significantly higher in the high urine concentration group. Kaplan-Meier estimates showed that the low urine concentration group had a significantly longer stone recurrence-free period than the high urine concentration group (log-rank test, P < 0.001). In multivariate Cox regression analyses, 24-h UOsm was seen to be an independent risk factor for stone recurrence.

CONCLUSIONS

UOsm is a promising approach to assessing hydration and predicting stone recurrence in patients with urolithiasis. Maintaining UOsm < 564 mOsm/kg H₂O may reduce the risk of stone recurrence.

24-h urine metabolic profile: is it necessary in all kidney stone formers?

PURPOSE

A 24-h urine metabolic profile (24-UMP) is an integral part of nephrolithiasis work-up. We aimed to explore whether it can be waived under certain circumstances.

MATERIALS AND METHODS

We reviewed our prospective registry database of patients seen at our outpatient clinic for nephrolithiasis between the years 2010 and 2017. Data included: gender, age at first stone, body mass index (BMI), self-reported comorbidities and family history of nephrolithiasis. A 24-UMP was obtained from each patient under random diet. The following were recorded: urine volume, urinary levels of sodium, calcium, uric acid, oxalate and citrate. Presence of at least one comorbidity (i.e., hypertension/diabetes/hyperlipidemia) was defined as "associated comorbidities" (AC). Their absence was defined as "no comorbidities" (NC). Subjects were divided into two subgroups: first-time and recurrent stone formers, which were further divided into two subgroups: 1st + AC; 1st + NC; recurrent + AC; recurrent + NC. 24-UMPs have been compared between the four groups.

RESULTS

Four hundred and fifty-seven patients were included in the study. In the AC groups, patients demonstrated higher BMI levels (p = 0.001), and were statistically significantly obese (BMI > 30, p = 0.001) and older at first stone event (p = 0.001). First formers, either with AC or NC were more likely to have low urine volume (LUV) compared with recurrent formers (72.5 vs. 59.5%, p = 0.005). In the remaining metabolic abnormalities, no such differences were observed.

CONCLUSIONS

First-time stone formers, either with or without AC are likely to demonstrate LUV as their primary metabolic abnormality in 24-UMP. Therefore, 24-UMP may be postponed until recurrent stone event.

Obesity and kidney stone disease: a systematic review

INTRODUCTION

Currently, abdominal obesity has reached an epidemic stage and obesity represents an important challenge for worldwide health authorities. Epidemiologic studies have demonstrated that the stone risk incidence increases with Body Mass Index, through multiple pathways. Metabolic syndrome and diabetes are associated with an increased renal stones disease incidence. The aim of this systematic review was to investigate the prevalence, morbidity, risk factors involved in the association between obesity and urolithiasis.

EVIDENCE ACQUISITION

The search involved finding relevant studies from MEDLINE, EMBASE, Ovid, the Cochrane Central Register of Controlled Trials, CINAHL, Google Scholar, and individual urological journals between January 2001 and May 2017. The inclusion criteria were for studies written in the English language, reporting on the association between obesity and urinary stones.

EVIDENCE SYNTHESIS

The underlying pathophysiology of stone formation in obese patients is thought to be related to insulin resistance, dietary factors, and a lithogenic urinary profile. Uric acid stones and calcium oxalate stones are observed frequently in these patients. Insulin resistance is thought to alter the renal acid-base metabolism, resulting in a lower urine pH, and increasing the risk of uric acid stone disease. Obesity is also associated with excess nutritional intake of lithogenic substances and with an increase in urinary tract infection incidence. Recent studies highlighted that renal stone disease increases the risk of myocardial infarction, progression of chronic kidney disease, and diabetes. Contemporary, bariatric surgery has been shown to be associated with hyperoxaluria and oxalate nephropathy. Certainly, the many health risks of obesity, including nephrolithiasis, will add more burden on urologists and nephrologists.

CONCLUSIONS

Obesity related nephrolithiasis seems to necessitate weight loss as primary treatment, but the recognition of the associated complications is necessary to prevent induction of new and equally severe medical problems. The optimal approach to obesity control that minimizes stone risk needs to be determined in order to manage obesity-induced renal stones disease.

Oxalate-Degrading Enzyme Recombined Lactic Acid Bacteria Strains Reduce Hyperoxaluria

OBJECTIVE

To develop recombinant lactic acid bacteria (LAB) strains that express oxalate-degrading enzymes through biotechnology-based approach for the treatment of hyperoxaluria by oral administration.

MATERIAL AND METHODS

The coding gene of oxalate decarboxylase (ODC) and oxalate oxidase (OxO) was transformed into Lactococcus lactis MG1363. The oxalate degradation ability in vitro was evaluated in media with high concentration of oxalate. Hyperoxaluria rat models through high oxalate diet were given recombinant LAB through oral administration. Twenty-four-hour urinary oxalate was measured, and kidney stone formation was investigated.

RESULTS

LAB recombined with the coding gene of ODC could effectively decrease the amount of oxalate in the media and in the urine of rats. Moreover, the formation of calcium oxalate crystals in kidneys was also inhibited. The acid-induced promoter p170 significantly enhanced the reduction of hyperoxaluria. However, recombinant LAB expressing heterologous OxO showed less efficiency in oxalate degradation even in the presence of p170.

CONCLUSION

LAB expressing ODC is more efficient in degradation of oxalate in vitro and in vivo than that expressing OxO. This present study provided novel recombinant probiotic strains as a potential treatment tool against oxalosis.

Increased dietary long-chain polyunsaturated fatty acids alter serum fatty acid concentrations and lower risk of urine stone formation in cats

The lifespan of cats with non-obstructive kidney stones is shortened compared with healthy cats indicating a need to reduce stone formation and minimize chronic kidney disease. The purpose of this study was to investigate the effects of increasing dietary polyunsaturated fatty acids (PUFA) on urine characteristics. Domestic-short-hair cats (n = 12; mean age 5.6 years) were randomized into two groups and fed one of two dry-cat foods in a cross-over study design. For one week before study initiation, all cats consumed control food that contained 0.07% arachidonic acid (AA), but no eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA). Group 1 continued eating control food for 56 days. Group 2 was fed test food for 56 days, which was control food plus fish oil and high-AA oil. Test food contained 0.17% AA, 0.09% EPA and 0.18% DHA. After 56 days, cats were fed the opposite food for another 56 days. At baseline and after each feeding period, serum was analyzed for fatty acid concentrations, and urine for specific gravity, calcium concentration, relative-super-saturation for struvite crystals, and a calcium-oxalate-titrimetric test was performed. After consuming test food, cats had increased (all P<0.001) serum concentrations of EPA (173%), DHA (61%), and AA (35%); decreased urine specific gravity (P = 0.02); decreased urine calcium concentration (P = 0.06); decreased relative-super-saturation for struvite crystals (P = 0.03); and increased resistance to oxalate crystal formation (P = 0.06) compared with cats consuming control food. Oxalate crystal formation was correlated with serum calcium concentration (r = 0.41; P<0.01). These data show benefits for reducing urine stone formation in cats by increasing dietary PUFA.