Metabolic evaluation of first-time and recurrent stone formers

Metabolic Evaluation and Recurrence Prevention for Urinary Stone Patients: An EAU Guidelines Update

BACKGROUND AND OBJECTIVE

The aim of this review was to define patients who are at high risk of recurrence of urolithiasis, to delineate diagnostic and therapeutic algorithms for each type of stone, and to clarify general guidelines and recommendations for prevention of recurrence.

METHODS

A professional research librarian carried out literature searches for all sections of the urolithiasis guidelines, covering the timeframe between 1976 and June 2023.

KEY FINDINGS AND LIMITATIONS

For every patient with urolithiasis, an attempt should be made to analyse the stone. Patients should be given general instructions on how to prevent recurrence, including adequate fluid and calcium intake, and low consumption of sodium and protein. Identifying and correcting the causative factors is a cornerstone in preventing the recurrence of urolithiasis. Diagnostic and therapeutic algorithms by stone composition are available. Every patient should undergo baseline metabolic screening, while patients with calcium stones, who are at high risk of relapse and complications, should undergo extensive metabolic screening with two 24-h urine collections and should receive targeted therapy. Patients with uric acid, infection, or cystine stones are at high risk of relapse. All patients at high risk of recurrence should be closely monitored, especially those not complying with therapy in the long term.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Metabolic stone evaluation and patient follow-up are highly recommended to prevent urolithiasis recurrence.

Medical management of urolithiasis: Great efforts and limited progress

Objective

To provide a comprehensive review on the existing literature on medical management of urolithiasis.

Methods

A thorough literature review was performed using Medline, PubMed/PMC, Embase, and the Cochrane Database of Systematic Reviews up to December 2022 to identify publications on the medical management of urolithiasis. Studies that assessed dietary and pharmacologic management of urolithiasis were reviewed; studies on medical expulsive therapy were not included in this review.

Results

Medical management of urolithiasis ranges from the prophylactic management of kidney stone disease to dissolution therapies. While most treatment concepts have been long established, large randomized controlled trials are scarce. Dietary modification and increased fluid intake remain cornerstones in the conservative management of urolithiasis. A major limitation for medical management of urolithiasis is poor patient compliance.

Conclusion

Medical management of urolithiasis is more important in patients with recurrent urolithiasis and patients with metabolic abnormalities putting them at higher risk of developing stones. Although medical management can be effective in limiting stone recurrence, medical interventions often fail due to poor compliance.

Outcomes and rates of dissolution therapy for uric acid stones

INTRODUCTION

To describe the outcomes and quantify the rate of uric acid stone medical dissolution therapy using automated, software-generated stone volume measurements.

METHODS

A sample of patients treated with oral dissolution therapy was reviewed from a single institution between 2008 and 2019. Baseline patient demographics, metabolic urine testing and stone characteristics were collected. Computed tomography (CT) scan images were evaluated using the quantitative Stone Analysis Software (qSAS) to obtain total stone volume (TSV), maximum diameter (MD) and stone number. Rate of dissolution using total stone volume was calculated over the treatment period.

RESULTS

Twenty-seven patients were started on oral dissolution therapy, corrected for renal function. After mean duration of 180 days (range 41-531), 16 patients failed treatment resulting in surgical therapy. Twenty stones in 11 patients showed complete or partial dissolution. Compared to those who failed treatment, patients with complete or partial dissolution had lower 24 h urinary uric acid and higher treatment urine pH. Thirteen (65%) stones showed complete dissolution after a mean 167.6 days. Rate of change for responders was 4.73 mm³ or 0.6% of total stone volume per day. Time to dissolution of one half of stone volume based on total stone volume was 86 days (12.30 weeks).

DISCUSSION/CONCLUSIONS

Software-calculated total stone volume may be an effective method of measuring uric acid stone response to oral alkalization therapy. Stone volume decreased by 50% after 12.3 weeks of treatment and could be an important benchmark for oral dissolution therapyoral dissolution therapy. Further studies with a larger sample and validation of the software are needed to confirm if this can be used to guide surveillance schedules for dissolution therapy.

Methods for the dietary assessment of adult kidney stone formers: a scoping review

BACKGROUND

Kidney stones are a frequent and potentially severe condition, affecting 5-10% of the European population. Causes are multifactorial, diet in particular plays a major role in the formation and management of kidney stones. The aim of this scoping review is to assess the methods used to study the diet of adult kidney stone formers.

METHODS

We conducted a systematic search in Medline Ovid SP, Embase, Cinahl, Cochrane (CENTRAL), Web of Sciences databases on June 10th, 2020. Self-report methods (such as food frequency questionnaires or 24-h dietary recalls), objective nutritional biomarkers and controlled diets were considered. We analyzed the selected publications based on the origin of participants, study design and dietary assessment methods used.

RESULTS

We screened 871 publications and included 162 of them. Most studies included participants from North America and Europe and were observational. Short and cost-effective tools such as food frequency questionnaires and other questionnaires were the most frequently used. Moreover, food diary was a frequently selected method to study the diet of kidney stone formers. New technologies (e.g. online questionnaires, phone applications, connected tools) were rarely used.

CONCLUSION

Accurate reporting of the methods used in nutritional studies is of key importance to interpret results and build evidence. Assessing long-term dietary intake is still a challenge for nutritional epidemiology. A combination of self-report methods with objective dietary biomarkers and new technologies probably represents the best way forward.

LITHORISK.COM: the novel version of a software for calculating and visualizing the risk of renal stone

Estimation of state of saturation with stone-forming salt represents a reliable tool to assess the overall risk. The available methods are based on computer-assisted ab initio calculations. Our earlier method URSUS was subsequently substituted by Lithorisk®, a software including visualization of risk profiles. Unfortunately, Lithorisk does not adapt to new versions of Windows® and Macintosh® Apple, neither runs on smartphones or tablets. We propose a novel version of the software which can be directly used online on any device equipped by different operating systems. Upon online connection and after registration, the software is ready for unlimited accesses, in either Italian, English or French. After digiting input variables (urea and creatinine also included) in a fixed dashboard, state of saturation is promptly given. In addition to state of saturation (ß) with calcium oxalate, brushite and uric acid, ß struvite and cystine are available. Both input variables and ß results are graphically depicted as green or red horizontal bars to indicate recommended values. The software was implemented with equations allowing to omit sulphate and ammonium excretion for users with difficult access to these measurements. This simplified version, tested for ßCaOx and ßBsh on 100 urine samples showed close correlation with the full version. The software gives a list of total and free concentrations and soluble complex species distribution. Results can be printed or saved as PDF. So, we propose an easily accessible software to estimate state of saturation usable on any operating system and personal device.

Preliminary analysis of serum electrolytes and body mass index in patients with and without urolithiasis

OBJECTIVES

To compare body mass index (BMI); serum parameters; and urine parameters between patients with and without urolithiasis.

METHODS

Data from 1164 patients admitted to our Department of Urology from January 2011 to July 2013 were retrospectively reviewed; 714 patients (age, 5-87 years; male:female ratio, 1.8:1) exhibited urolithiasis, and 450 patients (age, 12-94 years; male:female ratio, 3.8:1) did not. Blood and urine were collected from patients the morning after hospital admission. Serum and urine parameters were checked by an automatic biochemistry analyzer. Statistical analysis included the Mann-Whitney U test and binary logistic regression.

RESULTS

Serum sodium, potassium, chloride, calcium, phosphorus, and carbon dioxide combining power significantly differed between groups. In male patients, serum sodium, calcium, and phosphorus levels were higher in the urolithiasis group, whereas serum potassium and urine pH levels were lower. In female patients, serum sodium was higher in the urolithiasis group. BMI was higher in the urolithiasis group in all patients, male and female. Respective β-values of serum sodium and BMI in male patients were 0.077 and 0.084; in female patients, these values were 0.119 and 0.102.

CONCLUSIONS

Changes in serum sodium and BMI may be involved in the pathogenesis and treatment of urolithiasis.

Educational review: role of the pediatric nephrologists in the work-up and management of kidney stones

BACKGROUND

The incidence of nephrolithiasis in children and adolescents is increasing and appears to double every 10 years. The most important role of the pediatric nephrologist is to diagnose and modify various metabolic and non-metabolic risk factors, as well as prevent long-term complications especially in the case of recurrent nephrolithiasis.

OBJECTIVE

The purpose of this review is to summarize the existing literature on the etiology and management of pediatric nephrolithiasis.

RESULTS

The incidence of kidney stones is increasing; dietary and environmental factors are probably the main causes for this increased incidence. In most pediatric patients, the etiology for the kidney stones can be identified. Metabolic factors, such as hypercalciuria and hypocitraturia, urinary tract infection, and urinary stasis, constitute leading causes. Herein, we review the etiologies, diagnostic work-up, and treatment options for the most prevalent causes of kidney stones. The detrimental effects of excessive dietary sodium, reduced fluid intake, and the benefits of plant-based over animal-based protein consumption on urinary crystal formation are discussed. We also review the long-term complications.

CONCLUSIONS

Pediatric nephrologists have an important role in the diagnostic work-up and prevention of recurring nephrolithiasis.

Stone residual fragments: A thorny problem

Urolithiasis represents a widespread and common disorder among the world population, with a predicted increase in affected patients in the coming years. Treatment of renal and ureteral stones varies widely, and achieving true stone-free status in all patients is still difficult. Moreover, imaging used to assess residual fragments following procedure impacts the diagnosed stone-free rate percentage considerably. In particular, the use of computed tomography scans has led to a better evaluation of residual fragments as well as so-called clinically insignificant residual fragments, which in a considerable number of cases are, despite their definition, causes of adverse urological events, thus creating a thorny problem for both patients and urologists. Currently, there is no gold standard or validated protocol regarding the management, clearance and prevention of residual fragments. In this article, we review the current literature regarding residual fragments, clinically insignificant residual fragments and their natural history, reporting on diagnostic methods, incidence, complications and outcome with the use of less invasive procedures, taking into consideration viable treatment and management of patients affected.

A Retrospective Study of Kidney Stone Recurrence in Adults

Background

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

Methods

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

Results

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

Conclusions

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

Defining metabolic activity of nephrolithiasis - Appropriate evaluation and follow-up of stone formers

Considering the variation in metabolic evaluation and medical management of kidney stone disease, this consensus review was created to discuss the metabolic activity of nephrolithiasis, define the difference between single and recurrent stone formers, and develop a schema for metabolic and radiologic follow-up. A systematic review of the literature was performed to identify studies of metabolic evaluation and follow-up of patients with nephrolithiasis. Both single and recurrent stone formers share many similarities in metabolic profiles. The study group determined that based on an assessment of risk for stone recurrence and metabolic activity, single and recurrent stone formers should be evaluated comprehensively, including two 24 h urine studies on a random diet. Targeted medication and dietary recommendations are effective for many patients in reducing the risk of stone recurrence. Follow-up of those with stone disease should be obtained depending on the level of metabolic activity of the patient, the risk of chronic kidney disease and the risk of osteoporosis/osteopenia. A standard scheme includes a baseline metabolic profile, a repeat study 3-6 months after initiation of treatment, and then yearly when stable, with abdominal imaging obtained every 1-2 years.

Hyponatremia and the risk of kidney stones: A matched case-control study in a large U.S. health system

Kidney stones impose a large and increasing public health burden. Previous studies showed that hyponatremia is associated with an increased risk of osteoporosis and bone fractures, which are also known to be associated with kidney stones. However, the relation between hyponatremia and kidney stones is not known. To assess the relation between hyponatremia and kidney stones, we designed a matched case-control study by using the electronic health records of the MedStar Health system with more than 3.4 million unique patient records as of March 2016. Data were extracted for clinical factors of patients with kidney stones (cases) and those without kidney stones (controls). Cases (n = 20,199) and controls (n = 20,199) were matched at a 1:1 ratio for age, sex, race, and the duration of encounter window. Case and control exposures for each of the hyponatremia variables were defined by serum sodium laboratory measurements reported within the encounter windows, and divided into 3 categories: prior hyponatremia, recent hyponatremia, and persistent hyponatremia. In the final conditional logistic models adjusted for potential confounders, the risk of kidney stones significantly increased in both recent and persistent hyponatremia categories: prior hyponatremia odds ratio (OR) 0.93 (95% confidence interval [CI], 0.86–1.00); recent hyponatremia OR 2.02 (95% CI, 1.76–2.32); persistent hyponatremia OR 6.25 (95% CI, 3.27–11.96). In conclusion, chronic persistent hyponatremia is a significant and clinically important risk factor for kidney stones in patients in the U.S.

Updates in the Metabolic Management of Calcium Stones

PURPOSE OF REVIEW

Urinary risk factors, such as hypercalciuria, hypocitraturia, and hyperoxaluria, either in combination or alone, are associated with calcium stones. Dietary habits as well as underlying medical conditions can influence urinary risk factors. Evaluation of the conglomerate of patients' stone risks provides evidence for individualized medical management, an effective and patient-supported approach to prevention.

RECENT FINDINGS

Many patients with stones desire prevention to avoid repeated surgical interventions. Yet, recent practice pattern assessments and health care utilization data show that many patients are rarely referred for metabolic evaluation or management. Innovations in metabolic management over the past decade have improved its effectiveness in reducing risk and preventing calcium stones. Although no new pharmacologic agents for calcium stone prevention have recently become available, there is relatively new thinking about some diet-based approaches. This review will synthesize current evidence to support individualized metabolic management of calcium stones.

Epidemiology of stone disease across the world

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

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.

Medical management of urinary calculi: up to date 2016

Nephrolithiasis (NL) is one of the most prevalent nontransmissible diseases in western countries. It is being associated with other frequent diseases, including osteoporosis, cardiovascular disease, hypertension, diabetes mellitus, through a putative common link with metabolic syndrome and insulin resistance or altered mineral metabolism. This review will focus on classification, physicochemical basis, risk factors, laboratory and imaging investigations, medical management.Classification as to stone composition includes calcium, uric acid (UA), cystine (Cys), infected, 2-8 dihydroxyadenine and rare NL. According to pathophysiology, NL is classified as primary, secondary to systemic diseases or drugs, caused by renal or metabolic hereditary disorders.A stone can only form in supersaturated environment, and this is sufficient in UA, Cys and infected NL, but not in Ca-NL, which results from the imbalance between supersaturation and inhibition. All types are characterized by derangements of peculiar risk factors. Laboratory investigations aim at identifying type of NL, underlying risk factors and state of saturation, and pathophysiology. This justifies a rationale therapy able to dissolve some types of stones and/or produce reduction in recurrence rate in others.Medical management includes alkali and allopurinol for UA nephrolithiasis (UA-NL), thiols and alkali in Cys-NL, dietary and pharmacological intervention for Ca-NL. Thiazides and alkaline citrate salts are the most widely used drugs in Ca-NL, where they proved efficient to prevent new stones. Other drugs have only been used in particular subsets.Proper medical management and modern urological approaches have already notably improved clinical outcomes. Future studies will further clarify mechanisms of NL with expected new and targeted therapeutic options.

Quantification of asymptomatic kidney stone burden by computed tomography for predicting future symptomatic stone events

OBJECTIVE

To find the optimal characterization of asymptomatic radiographic stone burden on computed tomography (CT) scans.

METHODS

A survey was sent to stone formers who underwent a CT scan while asymptomatic during a stone clinic evaluation. Symptomatic stone passage events after CT scan were detected by survey and medical record review. Radiographic stone burden was quantified by number of stones, largest stone diameter, automated total stone volume (TSV), and bilateral stones and then compared as predictors of stone events.

RESULTS

There were 550 stone formers; 43% had a stone event for a median of 4.7 years after the CT scan. Stone burden by quartiles was 0-1, 2-3, 4-6, and ≥7 for number of stones; 0-2, 3-4, 5-7, and ≥8 mm for largest stone diameter; and 0-8, 9-78, 79-280, and ≥281 mm(3) for TSV; 48% had bilateral stones. The hazard ratios (HRs) for symptomatic event was 1.30 (P <.001) for the number of stones per quartile, 1.26 (P <.001) for largest stone diameter per quartile, 1.38 (P <.001) for TSV per quartile, and 1.80 (P <.001) for bilateral stones. On multivariate analysis, only TSV was an independent predictor of symptomatic events (HR, 1.35 per quartile; P = .01). This risk of events with TSV was also independent of demographics, urine chemistries, and stone composition. Among the 53 patients with interim events between CT scans, a rapid increase in TSV between CT scans (>570 mm(3) per year) predicted subsequent events (HR, 2.8; P = .05).

CONCLUSION

Automated TSV is more predictive of symptomatic events than manual methods for quantifying stone burden on CT scan.