Epidemiology of nephrolithiasis

The role of the general practictioner in the management of urinary calculi

BACKGROUND

The prevalence of kidney stones tends to increase worldwide due to dietary and climate changes. Disease management involves a high consumption of healthcare system resources which can be reduced with primary prevention measures and prophylaxis of recurrences. In this field, collaboration between general practitioners (GPs) and hospitals is crucial.

METHODS

a panel composed of general practitioners and academic and hospital clinicians expert in the treatment of urinary stones met with the aim of identifying the activities that require the participation of the GP in the management process of the kidney stone patient.

RESULTS

Collaboration between GP and hospital was found crucial in the treatment of renal colic and its infectious complications, expulsive treatment of ureteral stones, chemolysis of uric acid stones, long-term follow-up after active treatment of urinary stones, prevention of recurrence and primary prevention in the general population.

CONCLUSIONS

The role of the GP is crucial in the management and prevention of urinary stones. Community hospitals which are normally led by GPs in liaison with consultants and other health professional can have a role in assisting multidisciplinary working as extended primary care.

Medical Treatment and Prevention of Urinary Stone Disease

The pathophysiology underlying urinary stone formation remains an area of active investigation. There are many pharmacotherapies aimed at optimizing metabolic factors and reducing urinary supersaturation of stone components that play an important role in urinary stone prevention. In addition, medical expulsive therapy for ureteral stones and medical dissolution therapy for uric acid-based urinary stones are helpful treatment tools and are used alongside surgical treatments in the management of urinary stones.

Metabolic risk factors in children with kidney stone disease: an update

BACKGROUND

The prevalence of kidney stones in children has significantly increased in the past few decades, with concomitant increased morbidity and healthcare costs worldwide. Assessing metabolic risk factors is essential for diagnosis and specific treatment. The objective of this retrospective study is to identify the epidemiological and clinical characteristics of children under 17 years of age, as well as the metabolic risk factors of nephrolithiasis.

METHODS

A total of 300 children with kidney stone disease were included to undergo several clinical tests using a standardized protocol.

RESULTS

The mean age was 11.2 years, and the male:female ratio was 1.15:1.0. Biochemical abnormalities were found in 89.3% of all cases. A single urine metabolic risk factor was present in 52.6% (n = 141) of the patients, and multiple risk factors were present in 36.7% (n = 106). Idiopathic hypercalciuria (alone or in combination) and hypocitraturia (alone or in combination) were the most frequent risk factors identified in 47.0% and 39.6% of these patients, respectively. Renal colic and/or unspecified abdominal pain were the most frequent forms of presentation (76.9%), followed by hematuria in 64.4% with 97.5% of stones located in the upper urinary tract. A positive family history in first-degree and second-degree relatives was found in 64.8% of boys and 61.8% of girls.

CONCLUSIONS

We conclude that specific urinary metabolic risk factors can be found in most children with kidney stones, with hypercalciuria and hypocitraturia being the most common diagnoses. Graphical abstract .

Outcomes of percutaneous nephrolithotomy in elderly versus young patients under regional anesthesia: A comparative study

Introduction

Surgical management of elderly patients with renal calculi is inherently challenging. We compared the efficacy and safety of percutaneous nephrolithotomy (PCNL) performed under regional anesthesia between elderly patients (age >65 years) and patients aged <65 years.

Materials and Methods

Between July 2015 and June 2016, fifty patients aged >65 years with renal stones (size >1.5 cm) were treated with PCNL under regional anesthesia (elderly group). We retrospectively compared the outcomes with those obtained in an equal number of patients aged <65 years (younger group) who underwent PCNL under regional anesthesia. Patients with staghorn stones and pyonephrosis and falling under the American Society of Anesthesiologists (ASA) Grade IV were excluded. Data pertaining to demographic characteristics, body mass index, stone bulk, operative time, tract size, number of tracts required, blood loss, clearance rates, complications, and length of hospital stay were analyzed.

Results

The mean age at presentation in the elderly and younger groups was 66.8 ± 2.1 years and 38.7 ± 11 years, respectively; 56% of the patients in the elderly age group had ASA Grade II, whereas 58% in the younger age group had ASA Grade I. The mean stone size and the number of tracts were comparable in both the groups, whereas operative time was slightly longer in the elderly group (58.54 ± 18 vs. 51.98 ± 18 min; P < 0.05). Postoperative complications and stone-free rates (94% vs. 92%, respectively) were comparable in the two groups.

Conclusions

Age itself should not deter the treatment of elderly patients with renal stones as PCNL under regional anesthesia is safe and effective in elderly patients; outcomes in elderly and younger patients were comparable in this study.

Chemical compounds, antioxidant activity, and in vitro and in silico litholytic effects of Zizyphus lotus extracts

Background The aim of this study was to evaluate the antioxidant activity and to determine the chemical compounds of organic extracts of fruits and leaves of Zizyphus lotus. The litholytic effect was determined on the basis of the in vitro effect of the aqueous extracts on the formation of crystals of stones. Finally, chemical compounds were investigated to identify their target using an in silico approach. Methods The antioxidant activity was determined with the diphenylpicrylhydrazyl radical trapping method. An aliquot of 2 mL of urine and 100 μL of an infusion of fruit and leaf aqueous extract of Z. lotus at different concentrations were used. The induction of calcium oxalate (CaOx) crystals was done by the addition of oxalic acid at 0.1 mol/L. The effect of aqueous extracts was compared with two inhibitors (citrate and magnesium) used as references. In silico modelization was carried out using SwissTargetPrediction. Results The antioxidant activity test showed that the methanol extract was active with an IC50 of 5 mg/mL. The aqueous extracts of fruits and leaves inhibit the formation of crystals of CaOx. Then, the composition of the methanol extracts of the leaves and fruits in high-performance liquid chromatography showed majority compounds such as quercetin-3-galactoside and hyperin. In silico assays showed that the identified molecules exert their effect by targeting enzymes responsible for calcium regulation, urate regulation, and maintenance of acid-base balance, and that had anti-inflammatory properties. Conclusions The present study showed that Z. lotus may be considered as a functional or nutraceutical food. However, further studies should be carried out in order to extract and purify these compounds to test their effect on urinary lithiasis.

Water for preventing urinary stones

BACKGROUND

Urinary stone disease is a common condition characterised by increasing prevalence and high rates of recurrence. Observational studies have reported that increased water intake played a role in the prevention of urinary stone formation but with limited strength of evidence.

OBJECTIVES

To compare the effects of increased water intake with standard water intake for the prevention of urinary stone formation in participants with or without a history of urinary stones.

SEARCH METHODS

We performed a systematic search of PubMed (MEDLINE), EMBASE (Ovid) and the Cochrane Library to 15 October 2019. We handsearched review articles, clinical trial registries, and reference lists of retrieved articles. We did not apply any restrictions to publication language or publication status.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs looking at the benefits and harms of increased water intake versus standard water intake for the prevention of urinary stone formation in participants with or without a history of urinary stones.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Two review authors independently extracted data and assessed the risk of bias of included studies. We pooled dichotomous outcomes (e.g. incidence/recurrence rate of urinary stones; adverse events) using risk ratios (RRs) with 95% confidence intervals (CIs). We calculated hazard ratio (HRs) and corresponding 95% CIs to assess the intervention effect for time-to-event outcomes. We assessed the certainty of the evidence by using the GRADE criteria.

MAIN RESULTS

Our search identified no RCTs investigating the role of increased water intake for the prevention of urinary stone formation in participants with no history of urinary stones (primary prevention). We found one RCT assessing the effects of increased water intake versus standard water intake for the prevention of urinary stone formation in people with a history of urinary stones (secondary prevention). This trial randomised 220 participants (110 participants in the intervention group with increased water intake and 110 in the control group with standard water intake). Increased water intake was defined as achieving a urine volume of at least 2.0 L per day by drinking water. Based on this study, increased water intake may decrease stone recurrences (RR 0.45, 95% CI 0.24 to 0.84; 199 participants; low-certainty evidence); this corresponds to 149 fewer (43 fewer to 205 fewer) stone recurrences per 1000 participants with 270 stone recurrence per 1000 participants over five years in the control group. Increased water intake may also prolong the time to urinary stone recurrence compared to standard water intake (HR 0.40, 95% CI 0.20 to 0.79; 199 participants; low-certainty evidence); based on a stone recurrence rate of 270 per 1000 participants over five years, this corresponds to 152 fewer (209 fewer to 50 fewer) recurrences per 1000 participants. For both outcomes we downgraded the certainty of evidence for study limitations and imprecision. We found no evidence for the outcome of adverse events AUTHORS' CONCLUSIONS: We found no RCT evidence on the role of increased water intake for primary prevention of urinary stones. For secondary prevention, increased water intake achieving a urine volume of at least 2.0 L/day may reduce urinary stone recurrence and prolong time to recurrence for people with a history of urinary stone disease. However, our confidence in these findings is limited. We did not find evidence for adverse events.

Exploiting the aiming beam to increase the safety of laser lithotripsy: Experimental evaluation of light reflection and fluorescence

BACKGROUND AND OBJECTIVES

In Holmium laser lithotripsy, usually, the surgeon is guided by a visible beam superimposing the infrared (IR) treatment radiation. It has been shown that a green aiming beam excites stone autofluorescence. This fluorescence signal can be used for calculi detection to check the correct fiber position before triggering the IR laser, thus preventing damage to soft tissue and application devices. However, also the directly reflected green light from the fiber tip gives valuable information on fiber position and its surface condition.

MATERIALS AND METHODS

An external fiber-fiber-coupling-box (fiber core diameter 365 µm) for pulsed holmium laser radiation (2.1 µm) was set up containing a green diode laser module (520 nm, average power on the sample <0.5 mW) and optics and detectors for measuring the reflected light of this aiming beam as well as the fluorescence excited with it. Measurements were done via a lock-in technique with more than 20 human calculi samples and porcine calix in vitro. After the implementation of automatic data storage signals during ongoing in vitro lithotripsy procedures were recorded with the fiber positioned on tissue, stone, or in/on medical equipment (working channel of an endoscope, stone retrieval basket).

RESULTS

Stone fluorescence signals measured were a factor of 7 to >100 higher than those of tissue. Stone fluorescence was detectable in "non-contact mode" with a linear signal decrease over a distance up to ~1 mm in front of the fiber tip (core diameter 365 µm) and with severely damaged fibers (max. decrease: 75% with pinched off fiber). Reflection signals of the fiber tip surface in air and water surrounding decreased significantly when the fiber was damaged; measured ratios of intact to damaged fiber found in the air were (5-17):1 and in water (1.6-3.7):1. Surfaces in front of the fiber aggravated the evaluation of fiber condition due to reflections but enabled to detect, for example, the working channel of a flexible endoscope in combination with the (missing) fluorescence signal.

CONCLUSIONS

Autofluorescence induced by a green aiming beam can be exploited for stone detection in laser lithotripsy. A reflection measurement can give further information on fiber condition and position. Implementing this kind of safety features for an automatic block of IR laser emission in case of weak or missing fluorescence and un-normal reflections can assist the surgeon by avoiding tissue perforation, and damage to medical devices such as endoscopes. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

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

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

Retrograde intrarenal surgery: An expanding role in treatment of urolithiasis

During the past 3 decades, the surgical management of kidney stones has undergone many technological advances and one is the development of the flexible ureteroscopy. The development of this instrument as well as ancillary equipment such as baskets, graspers, and others, and improvements in lithotripsy with Holmium: YAG laser have led to expand its indications with diagnostic and therapeutic management of medical issues of the upper urinary tract such as urolithiasis and urothelial tumors. The objective of this review is to describe its indications and results in the different scenarios for the treatment of urinary stones.

Evaluation of Deceased Kidney Donors for Renal Stone Disease: Is Computed Tomography Needed?

Objective

To investigate the clinical consequences of neglected risk of urolithiasis in deceased kidney donors in routine clinical practice, this study focused on different management options for transplanted allograft stones, and tried to find new solutions for more accurate detection of urolithiasis in deceased kidney donors prior to renal transplantation.

Methods and Results

The overall prevalence of stone disease in endemic countries is between 7 and 29%. Because of the increased risk for stone disease in epidemic countries, screening renal grafts from deceased donors necessitates more sensitive imaging tests. Despite well established procedures on preoperative living related renal donor evaluation, there is no consensus on a preoperative imaging tool in cadaveric renal donor evaluation. The most commonly used imaging modality in deceased renal donors is ultrasonography. The overall sensitivity and specificity of ultrasonography for kidney stones are 45 and 88%, respectively. Use of a computed tomography scan for renal diseases, especially for urinary stones is now almost a routine test in clinical practice. Its sensitivity for renal stones < 3 mm is 85%, whereas for renal stones > 3 mm it is 100%.

Conclusion

The use of radiological modalities i.e. computed tomography with higher sensitivity in deceased donors prior to renal transplantation seems reasonable in urinary stone epidemic countries.

Prevalence and risk factors for kidney stones in fibrodysplasia ossificans progressiva

The worldwide prevalence and risk factors for kidney stones in patients with fibrodysplasia ossificans progressiva (FOP) are unknown. We conducted a survey of 383 patient-members of the International Fibrodysplasia Ossificans Progressiva Association, comprising the entire global membership of the international FOP community. Two hundred seven patients from 31 nations and 6 continents (54%) responded. Nineteen of 207 respondents had kidney stones, revealing a worldwide prevalence of 9.2%. In a confirmatory follow-up study of subjects participating in a longitudinal FOP natural history study, 9 of 114 individuals reported a history of kidney stones (7.9%). In both study populations patients with kidney stones were found to be more functionally impaired compared to those without nephrolithiasis. The prevalence of kidney stones in the adult FOP population of the Unites States was 15.8% (9/57 individuals) compared to a sex- and age-weighted prevalence of 4.5% (p=4×10^-5) in the general population. Although geographical variation exists, patients with FOP have an approximately three-fold greater prevalence of kidney stones than the general population. This unusually high prevalence may be due to high bone turnover from chronic immobilization, or to unknown mechanistic effects of the activating FOP mutation in activin A receptor, type I/activin-like kinase-2 (ACVR1/ALK2), increasing the disease burden and morbidity in this already disabling condition.

Evaluation of Guidelines for Surgical Management of Urolithiasis

PURPOSE

Many urological societies have provided evidence-based guidelines to help the urologist make therapeutic choices. However, the recommendations in these guidelines may be heterogeneous because they were developed using various methods. The objective of this study was to review key guidelines on the surgical management of urinary stones to provide practical guidance for clinical application.

MATERIALS AND METHODS

Guidelines on urolithiasis from all international urological societies were searched through the society websites. A search on PubMed® and Medline® restricted to publications in English was also performed for guidelines published between January 1, 2010 and July 1, 2017. Only the latest versions of guidelines containing an evaluation of the level of evidence and the grade of recommendation were included in the final analysis. All recommendations on surgical stone management and recommended techniques for each surgical modality were included. The AGREE II (Appraisal of Guidelines for Research and Evaluation II) instrument was used to assess the quality of the included guidelines.

RESULTS

Three international guidelines were included in analysis, including those of AUA (American Urological Association)/ES (Endourological Society), EAU (European Association of Urology) and SIU (Société Internationale d'Urologie)/ICUD (International Consultation on Urological Diseases). We highlighted the heterogeneity in the level of evidence and the grade of recommendation which arose due to the different methods of evaluations that had been adopted. Despite this our review highlighted the considerable similarities among the guidelines. In certain specific situations for which no good evidence was available the recommendations could only be based on expert opinion.

CONCLUSIONS

An option to provide clear guidance to the urologist might be to combine these international guidelines into one to reduce confusion about the surgical management of urolithiasis.

A Targeted Metabolomics Assay to Measure Eight Purines in the Diet of Common Bottlenose Dolphins, Tursiops truncatus

Bottlenose dolphins managed under human care, human beings and Dalmatian dogs are prone to forming urate uroliths. Limiting dietary purine intake limits urate urolith formation in people and dogs because purines are metabolized to uric acid, which is excreted in urine. Managed dolphins develop ammonium urate nephroliths, whereas free-ranging dolphins do not. Free-ranging dolphins consume live fish, whereas managed dolphins consume different species that have been stored frozen and thawed. Differences in the purine content of fish consumed by dolphins under human care versus in the wild may be responsible for the difference in urolith prevalence. Commercially available purine assays measure only four purines, but reported changes in purines during frozen storage suggest that a wider range of metabolites should be measured when comparing fresh and stored fish. A method using high performance liquid chromatography with tandem mass spectrometry was developed to quantify eight purine metabolites in whole fish and squid commonly consumed by dolphins. The coefficient of variation within and among days was sometimes high for purines present in small amounts but was acceptable (≤ 25%) for guanine, hypoxanthine, and inosine, which were present in high concentrations. This expanded assay identified a total purine content up to 2.5 times greater than the total that would be quantified if only four purines were measured. Assuming additional purines are absorbed, these results suggest that additional purine metabolites should be measured to better understand the associated risk when fish or other purine-rich foods are consumed by people or animals prone to developing uroliths.

A Targeted Metabolomics Assay to Measure Eight Purines in the Diet of Common Bottlenose Dolphins, Tursiops truncatus

Bottlenose dolphins managed under human care, human beings and Dalmatian dogs are prone to forming urate uroliths. Limiting dietary purine intake limits urate urolith formation in people and dogs because purines are metabolized to uric acid, which is excreted in urine. Managed dolphins develop ammonium urate nephroliths, whereas free-ranging dolphins do not. Free-ranging dolphins consume live fish, whereas managed dolphins consume different species that have been stored frozen and thawed. Differences in the purine content of fish consumed by dolphins under human care versus in the wild may be responsible for the difference in urolith prevalence. Commercially available purine assays measure only four purines, but reported changes in purines during frozen storage suggest that a wider range of metabolites should be measured when comparing fresh and stored fish. A method using high performance liquid chromatography with tandem mass spectrometry was developed to quantify eight purine metabolites in whole fish and squid commonly consumed by dolphins. The coefficient of variation within and among days was sometimes high for purines present in small amounts but was acceptable (≤ 25%) for guanine, hypoxanthine, and inosine, which were present in high concentrations. This expanded assay identified a total purine content up to 2.5 times greater than the total that would be quantified if only four purines were measured. Assuming additional purines are absorbed, these results suggest that additional purine metabolites should be measured to better understand the associated risk when fish or other purine-rich foods are consumed by people or animals prone to developing uroliths.

Postmenopausal osteoporosis

Osteoporosis is a metabolic bone disorder that is characterized by low bone mass and micro-architectural deterioration of bone tissue. Fractures of the proximal femur, the vertebrae and the distal radius are the most frequent osteoporotic fractures, although most fractures in the elderly are probably at least partly related to bone fragility. The incidence of fractures varies greatly by country, but on average up to 50% of women >50 years of age are at risk of fractures. Fractures severely affect the quality of life of an individual and are becoming a major public health problem owing to the ageing population. Postmenopausal osteoporosis, resulting from oestrogen deficiency, is the most common type of osteoporosis. Oestrogen deficiency results in an increase in bone turnover owing to effects on all types of bone cells. The imbalance in bone formation and resorption has effects on trabecular bone (loss of connectivity) and cortical bone (cortical thinning and porosity). Osteoporosis is diagnosed using bone density measurements of the lumbar spine and proximal femur. Preventive strategies to improve bone health include diet, exercise and abstaining from smoking. Fractures may be prevented by reducing falls in high-risk populations. Several drugs are licensed to reduce fracture risk by slowing down bone resorption (such as bisphosphonates and denosumab) or by stimulating bone formation (such as teriparatide). Improved understanding of the cellular basis for osteoporosis has resulted in new drugs targeted to key pathways, which are under development.

Ureteroscopy and stones: Current status and future expectations

Urolithaisis is becoming an ever increasing urological, nephrological and primary care problem. With a lifetime prevalence approaching 10% and increasing morbidity due to stone disease, the role of ureteroscopy and stone removal is becoming more important. We discuss the current status of stone disease and review the ever increasing role that ureteroscopy has to play in its management. We discuss technological advances that have been made in stone management and give you an overview of when, how and why ureteroscopy is the most common treatment option for stone management. We touch on the role of robotic ureteroscopy and the future of ureteroscopy in the next 10 years.

The -160C>a polymorphism in E-cadherin is associated with the risk of nephrolithiasis

Nephrolithiasis is a common disorder worldwide. E-cadherin (CDH1) is involved in epithelial cell-cell interactions and plays important roles in the etiology of nephrolithiasis. We hypothesized that variants in the CDH1 gene are associated with risk of nephrolithiasis. In a hospital-based case-control study of 127 nephrolithiasis patients and 152 controls frequency matched by age and sex, we genotyped the functional -160C>A (rs16260) polymorphism and assessed its associations with risk of nephrolithiasis in a Chinese population. We found that the CA/AA genotypes were associated with a significantly decreased risk of nephrolithiasis (OR = 0.53, 95%CI = 0.32-0.87), compared with the CC genotype, particularly among subgroups of BMI > 24 kg/m² (OR = 0.38, 95%CI = 0.17-0.85), age ≤ 57 years (OR = 0.47, 95%CI = 0.24-0.93), and men (OR = 0.56, 95%CI = 0.29-0.99). Our results suggest that the CDH1 polymorphism is involved in the etiology of nephrolithiasis and thus may be a marker for genetic susceptibility to nephrolithiasis.

Temporal trends in the incidence of kidney stone disease

Recent reports show an increased occurrence of kidney stone disease worldwide. To further evaluate and quantify this observation, we examined recent trends in the incidence of kidney stone disease in the adult population of Iceland over a 24-year period. Computerized databases of all major hospitals and medical imaging centers in Iceland were searched for International Classification of Diseases, radiologic and surgical procedure codes indicative of kidney stones in patients aged 18 years and older. The time trends in stone frequency of 5945 incident patients (63% men) were assessed by Poisson regression analysis. The majority of patients (90.5%) had symptomatic stone disease. The total incidence of kidney stones rose significantly from 108 per 100,000 in the first 5-year interval of the study to 138 per 100,000 in the last interval. The annual incidence of symptomatic stones did not increase significantly in either men or women. There was, however, a significant increase in the annual incidence of asymptomatic stones over time, from 7 to 24 per 100,000 for men and from 7 to 21 per 100,000 for women. The increase in the incidence of asymptomatic stones was only significant for women above 50 years of age and for men older than 40 years. Thus, we found a significant increase in the incidence of kidney stone disease resulting from increased detection of asymptomatic stones. This was largely due to a more frequent use of high-resolution imaging studies in older patients.

Changes in urinary stone composition in the Tunisian population: a retrospective study of 1,301 cases

BACKGROUND

Studies that evaluate the effect of age on stone composition are scarce. The aim of this study was to highlight the changes in epidemiological characteristics (stone composition and location) of urolithiasis according to patients' age.

METHODS

We studied 1,301 urolithiasis patients with age ranging from 6 months to 92 yr (781 males and 520 females). Stone analysis was performed using a stereomicroscope and infrared spectroscopy to determine the morphological type and molecular composition of each stone.

RESULTS

The annual average incidence of new stone formation was 31.7 per 100,000 persons. In 71.8% of cases, calculi were located in the upper urinary tract. Compared to other age groups, children and old men were more affected by bladder stones. Calcium oxalate monohydrate was the most frequent stone component, even though its frequency decreased with age (59.5% in young adults and 43.7% in the elderly, P<0.05) in favor of an increase in uric acid stones (11.5% in young adults and 36.4% in the elderly, P<0.05). Struvite stones were rare (3.8%) and more frequent in children than in adults.

CONCLUSIONS

The analysis of these data showed that urinary stones in Tunisian patients are tending to evolve in the same direction as the stones in patients from industrialized countries.

[Changes in kidney stones type according to sex and age in Tunisian patients]

BACKGROUND

Studies that evaluate the effect of age and gender on the stone composition are scarce. The aim of this study is to highlight the modification of epidemiological characteristics of this pathology according to patients' sex and age.

PATIENTS AND METHODS

We studied 1269 urolithiasic patients ranging from 6 months to 92 years old and known as having urinary stones (752 males and 517 females). Stone analysis was performed respectively using a stereomicroscope and infrared spectroscopy to determine, respectively, the morphological type and molecular composition of each.

RESULTS

The annual average incidence of new stone formation was 30.25 per 100,000 inhabitants. In 1041 patients (81%), calculi were located in the upper urinary tract. Children and old man were more affected by bladder stone. Calcium oxalate monohydrate remains the most frequent stone component even if its frequency fell according to age (63.2% in teenagers and 40.6% in elderly [p<0.05]) in favour of the increase of uric acid stones (3,5% in teenagers and 41.5% in elderly [p<0.05]). Struvite stones were rare (3.5%) and more frequent in children.

CONCLUSION

The analysis of these data shows that urinary stones in Tunisia are tending to evolve in the same direction as in industrialized countries.

Trends in urological stone disease

OBJECTIVE

To summarize the changes in prevalence and treatment of upper urinary tract stone disease in the UK over the last 10 years.

METHODS

Data from the Hospital Episode Statistics (HES) website (http://www.hesonline.nhs.uk) were extracted, summarized and presented.

RESULTS

The number of upper urinary tract stone hospital episodes increased by 63% to 83,050 in the 10-year period. The use of shock wave lithotripsy (SWL) for treating all upper tract stones increased from 14,491 cases in 2000-2001 to 22,402 cases in 2010 (a 55% increase) with a 69% increase in lithotripsy for renal stones. There was a 127% increase in the number of ureteroscopic stone treatments from 6,283 to 14,242 cases over the 10-year period with a 49% increase from 2007/2008 to 2009/2010. There was a decline in open surgery for upper tract stones from 278 cases in 2000/2001 to 47 cases in 2009/2010 (an 83% reduction). Treatment for stone disease has increased substantially in comparison with other urological activity. In 2009/2010, SWL was performed almost as frequently as transurethral resection of the prostate or transurethral resection of bladder tumour, ureteroscopy for stones was performed more frequently than nephrectomy, radical prostatectomy and cystectomy combined, and percutaneous nephrolithotomy was performed more frequently than cystectomy.

CONCLUSIONS

The present study highlights the increase in prevalence and treatment of stone disease in the UK over the last 10 years. If this trend continues it has important implications for workforce planning, training, service delivery and research in the field of urolithiasis.

Possible Relationship between Metabolic Syndrome Traits and Nephrolithiasis: Incidence for 15 Years According to Gender

PURPOSE

To analyze the independent effect of metabolic syndrome (MS) on nephrolithiasis (NL) despite differences in gender compared with the known lithogenic factors.

MATERIALS AND METHODS

From 1995 to 2009, 40,687 Koreans were enrolled in the study and observed for the development of NL at a health promotion center. The examination included anthropometric and biochemical measurements as well as kidney ultrasonography. A student's t-test or chi-square test was used to characterize the participants and a standard Cox proportional hazards model was used to calculate the adjusted odds ratio of lithogenic risk factors in the NL model.

RESULTS

The mean age of the study cohort was 44.9 years (range, 13-100 years), and 22,540 (55.4%) of the cohort was male. The incidence of NL was 1.5% (609 participants), with males exhibiting a higher incidence than females (1.9% vs 1.0%, p<0.01). Among the total cohort, MS as well as each trait of MS were risk factors for NL. In males, high body mass index (BMI), high blood pressure, and abnormal glucose metabolism were significant lithogenic factors, whereas in females, lithogenic factors included only high BMI and abnormal glucose metabolism.

CONCLUSIONS

MS is a significant lithogenic factor compared with other lithogenic factors. There was a correlated change in the prevalence of MS and NL and MS traits in Korea.

Epidemiology of pediatric urolithiasis

Pediatric urolithiasis has increased globally in the last few decades. There has been a change in the pattern of stone composition with an increase in the frequency of kidney stones and a decrease in bladder stones. The role of familial predisposition and environmental factors in pediatric urolithiasis is now better understood. Metabolic factors are more common in pediatric urolithiasis than in adult stone disease. This review updates on the epidemiology of pediatric urolithiasis with a focus on the changing trends in the stone disease, current spectrum of stone disease encountered in clinical practice, individual predisposition and the role of environmental factors in stone formation.

Urinary tract stone occurrence in the Women's Health Initiative (WHI) randomized clinical trial of calcium and vitamin D supplements

BACKGROUND

The Women's Health Initiative (WHI) randomized clinical trial (RCT) of calcium plus vitamin D (CaD) supplements found a 17% excess in urinary tract stone incidence in the supplemented group. This study evaluated whether this risk is modified by participant characteristics.

OBJECTIVE

We examined the correlates of urinary tract stone occurrence in the CaD arm of the WHI trial.

DESIGN

We analyzed an RCT involving 36,282 postmenopausal women aged 50-79 y from 40 WHI centers: 18,176 women received 500 mg calcium carbonate plus 200 IU vitamin D(3) twice daily (1000 mg and 400 IU daily, respectively), and 18,106 women received a matching placebo for an average of 7.0 y. The incidence of urinary tract stones was determined.

RESULTS

The incidence of self-reported clinically diagnosed urinary tract stones was more common in the active CaD medication group than in the placebo group (hazard ratio: 1.17; 95% CI: 1.02, 1.34): 449 women in the CaD group and 381 women in the placebo group reported a stone during the trial. The rates of self-reported stones did not differ between various demographic, anthropomorphic, dietary, and other hypothesized risk factors according to randomization assignment. Neither the total calcium intake nor the use of calcium supplements at baseline was associated with the risk of stones. In sensitivity analyses that censored participants who were below 80% adherence, the findings were similar.

CONCLUSIONS

Daily supplementation with CaD for 7 y was associated with an increase in the number of self-reported urinary tract stones. These findings have implications for CaD supplement use. This trial was registered with the WHI at clinicaltrials.gov as NCT00000611.

Ambient temperature as a contributor to kidney stone formation: implications of global warming

Nephrolithiasis is a common disease across the world that is becoming more prevalent. Although the underlying cause for most stones is not known, a body of literature suggests a role of heat and climate as significant risk factors for lithogenesis. Recently, estimates from computer models predicted up to a 10% increase in the prevalence rate in the next half century secondary to the effects of global warming, with a coinciding 25% increase in health-care expenditures. Our aim here is to critically review the medical literature relating stones to ambient temperature. We have categorized the body of evidence by methodology, consisting of comparisons between geographic regions, comparisons over time, and comparisons between people in specialized environments. Although most studies are confounded by other factors like sunlight exposure and regional variation in diet that share some contribution, it appears that heat does play a role in pathogenesis in certain populations. Notably, the role of heat is much greater in men than in women. We also hypothesize that the role of a significant human migration (from rural areas to warmer, urban locales beginning in the last century and projected to continue) may have a greater impact than global warming on the observed worldwide increasing prevalence rate of nephrolithiasis. At this time the limited data available cannot substantiate this proposed mechanism but further studies to investigate this effect are warranted.

[A new approach to urinary stone analysis according to the combination of the components: experience with 7949 cases]

OBJECTIVE

To evaluate a new approach to urinary stone analysis according to the combination of the components.

MATERIALS AND METHODS

A total of 7949 stones were analysed and their main components and combinations of components were classified according to gender and age. Statistical analysis was performed using the chi-square test.

RESULTS

Calcium oxalate monohydrate (COM) was the most frequent component in both males (39%) and females (37.4%), followed by calcium oxalate dihydrate (COD) (28%) and uric acid (URI) (14.6%) in males and by phosphate (PHO) (22.2%) and COD (19.6%) in females (p=0.0001). In young people, COD and PHO were the most frequent components in males and females respectively (p=0.0001). In older patients, COM and URI (in that order) were the most frequent components in both genders (p=0.0001). COM is oxalate dependent and is related to diets with a high oxalate content and low water intake. The progressive increase in URI with age is related mainly to overweight and metabolic syndrome. Regarding the combinations of components, the most frequent were COM (26.3%), COD+Apatite (APA) (15.5%), URI (10%) and COM+COD (7.5%) (p=0.0001).

CONCLUSIONS

This study reports not only the composition of stones but also the main combinations of components according to age and gender. The results prove that stone composition is related to the changes in dietary habits and life-style that occur over a lifetime, and the morphological structure of stones is indicative of the aetiopathogenic mechanisms.

Characteristic clinical and biochemical profile of recurrent calcium-oxalate nephrolithiasis in patients with metabolic syndrome

BACKGROUND

Metabolic syndrome is a risk factor for nephrolithiasis. This study was performed to evaluate the clinical and biochemical profile of calcium-oxalate nephrolithiasis in stone formers with metabolic syndrome.

METHODS

A total of 526 recurrent stone formers, 184 of them with metabolic syndrome, and 214 controls were examined on a free diet and after a sodium-restricted diet (sodium intake < 100 mmol/24 h).

RESULTS

On free diet, stone formers with metabolic syndrome showed higher sodium excretion [mean (95% confidence interval), 196 (176-218) vs 160 (150-168) mmol/24 h; P < 0.01] and lower citrate excretion [2.23 (1.99-2.58) vs 2.84 (2.51-3.17) mmol/24 h; P < 0.01] compared to controls, whereas stone formers without metabolic syndrome showed higher calcium and oxalate excretion [5.43 (5.01-5.82) vs 3.58 (2.84-4.19) and 0.34 (0.32-0.36) vs 0.26 (0.20-0.31)m mmol/24 h for calcium and oxalate, respectively; P < 0.01] and lower citrate excretion [2.18 (1.98-2.38) vs 2.84 (2.51-3.17) mmol/24 h; P < 0.01] compared to controls. The ion activity product of urinary calcium-oxalate salts was similar between stone formers with and without metabolic syndrome [1.41 (1.31-1.59) vs 1.40 (1.35-1.45); P > 0.05]. After the test diet, this index was lower in diet-compliant stone formers with metabolic syndrome compared to diet-compliant stone formers without metabolic syndrome [1.15 (1.10-1.21) vs 1.39 (1.31-1.45); P < 0.01].

CONCLUSIONS

The biochemical profiles and responses to the sodium-restricted diet were significantly different between stone formers with metabolic syndrome and those without. Dietary habits play a central role in the pathogenesis of nephrolithiasis in stone formers with metabolic syndrome.

Cushing's syndrome, glucocorticoids and the kidney

Glucocorticoids (GCs) affect renal development and function in fetal and mature kidneys both indirectly, by influencing the cardiovascular system, and directly, by their effects on glomerular and tubular function. Excess GCs due to endogenous GC overproduction in Cushing's syndrome or exogenous GC administration plays a pivotal role in hypertension and causes increased cardiac output, total peripheral resistance and renal blood flow. Glucocorticoids increase renal vascular resistance (RVR) in some species and experimental settings and decrease RVR in others. Short term administration of adrenocorticotrophic hormone or GCs causes an increased glomerular filtration rate (GFR) in humans, rats, sheep and dogs. Interestingly, chronic exposure may cause a decreased GFR in combination with a higher cardiovascular risk in human patients with Cushing's syndrome. Glomerular dysfunction leads to proteinuria and albuminuria in canine and human Cushing's patients, and some cases also show histological evidence of glomerulosclerosis. Tubular dysfunction is reflected by an impaired urinary concentrating ability and disturbed electrolyte handling, which can potentially result in increased sodium reabsorption, hypercalciuria and urolithiasis. Conversely, chronic kidney disease can also alter GC metabolism. More research needs to be performed to further evaluate the renal consequences of Cushing's syndrome because of its implications for therapeutic aspects as well as the general well-being of the patient. Because there is a high incidence of Cushing's syndrome in canines, which is similar to the syndrome in humans, dogs are an interesting animal model to investigate the link between hypercortisolism and renal function.

History, epidemiology and regional diversities of urolithiasis

Archeological findings give profound evidence that humans have suffered from kidney and bladder stones for centuries. Bladder stones were more prevalent during older ages, but kidney stones became more prevalent during the past 100 years, at least in the more developed countries. Also, treatment options and conservative measures, as well as 'surgical' interventions have also been known for a long time. Our current preventive measures are definitively comparable to those of our predecessors. Stone removal, first lithotomy for bladder stones, followed by transurethral methods, was definitively painful and had severe side effects. Then, as now, the incidence of urolithiasis in a given population was dependent on the geographic area, racial distribution, socio-economic status and dietary habits. Changes in the latter factors during the past decades have affected the incidence and also the site and chemical composition of calculi, with calcium oxalate stones being now the most prevalent. Major differences in frequency of other constituents, particularly uric acid and struvite, reflect eating habits and infection risk factors specific to certain populations. Extensive epidemiological observations have emphasized the importance of nutritional factors in the pathogenesis of urolithiasis, and specific dietary advice is, nowadays, often the most appropriate for prevention and treatment of urolithiasis.

Clinical and metabolic risk factor evaluation in young adults with kidney stones

INTRODUCTION

The most frequent urine metabolic risk factor in adults is idiopathic hypercalciuria while in children is hypocitraturia. If there is really a change of metabolic abnormalities with age it would be interesting to study risk factors in the intermediate population: young adults.

OBJECTIVE

We evaluated metabolic risk factors, clinical presentation and family history of stone formers between 17 and 27 years old.

METHODS

A total of 160 patients (87 males and 73 females) were studied with a standard protocol.

RESULTS

A single urine metabolic risk factor was present in 64% of the patients, and multiple risk factors were present in 27% of them. No metabolic abnormalities were found in the remaining 9%. The most common urine risk factor was idiopathic hypercalciuria (alone or in combination), which was identified in 42.5% followed by hypocitraturia (alone or in combination) found in 32.9% of the patients. In the subgroup of patients of 17-20 years (n = 75; mean age of 18.8 + or - 1.0 years), hypocitraturia (alone or in combination) was as frequent as idiopathic hypercalciuria (alone or in combination), which was identified in 38% (n = 30) and 36.7% (n = 29), respectively. The most frequent form of presentation was renal colic (72%). A positive family history of stone disease in first degree and second-degree relatives was found in 32.9 and 34.1%, respectively.

CONCLUSIONS

Metabolic abnormalities were found in 91% of young adults with renal lithiasis, similar to our adult series. Hypercalciuria was the most frequent metabolic abnormality found. Yet, hypocitraturia (alone or in combination) was very frequent, and in the subgroup of patients of 17-20 years, it was as frequent as idiopathic hypercalciuria, similar to what we found in children.

Regional and seasonal variation in the incidence of urolithiasis in Iran: a place for obsession in case finding and statistical approach

The objective of the study is to measure the incidence rate of urolithiasis in a nationwide population-based study by a new methodology. A multi-stage stratified "epsem scheme" sampling was designed among imaging centres in 12 ecologic regions (composed of 30 provinces) while the regions were assumed as independent epidemiologic units. Four temporal phases were determined for sampling to represent four seasons. Imaging-proven positive cases for urinary stones were included and questionnaire filled out by interview. 2,955 new cases of urinary stone were included and the overall pooled yearly incidence rate was 136/100,000 (95% CI, 103-168). The whole positive group had a mean age of 41.5 years (SD = 16.3 years) and composed of 57.9% male. The most common season for presentation of disease was autumn. Geographically, the west and north of Iran, and seasonally, autumn have shown the highest incidence rates for the urinary tract stones. To establish the real burden of urinary stone disease, our study adds a little piece of information to the worldwide epidemiology of urolithiasis.

Epidemiology of kidney stones in Iceland A population-based study

OBJECTIVE

The prevalence of kidney stones varies greatly between ethnic groups and geographic locations, ranging from 8% to 19% in males and from 3% to 5% in females in Western countries. The aim of this study was to examine the epidemiology of kidney stones in Iceland.

MATERIAL AND METHODS

Data were derived from the Reykjavik Study, a population-based cohort study carried out between 1967 and 1991. All subjects answered a thorough questionnaire concerning their medical history at each visit. The lifetime prevalence of kidney stones was calculated based on the answer to the question "Have you ever been diagnosed with a kidney stone?" at each person's first visit. Incidence was calculated based on answers from subjects who had made two or more visits. Prevalence and incidence were age-standardized to the truncated world population. Family history of kidney stones was also evaluated.

RESULTS

A total of 9039 men aged 33-80 years and 9619 women aged 33-81 years participated. Of these, 423 males and 307 females had a history of kidney stones (p=0.001). Prevalence increased significantly with age for both genders. Men aged 30-34 years had a prevalence of 2.9%, compared to 8.8% for those aged 65-69 years, whereas corresponding values for women were 2.5% and 5.0%. The age-standardized prevalence for the 30-79 years age group was 4.3% for men and 3.0% for women. No significant increase in prevalence was observed over time. The incidence was 562 per 100 000 per year among men and increased significantly with age. The incidence among women was 197 per 100 000 per year and did not differ between age groups. A family history of nephrolithiasis was present in 25% of subjects with a history of kidney stones, and in 4% of those without.

CONCLUSIONS

The incidence and prevalence of kidney stones in Icelandic women are similar to those that have been reported in other Western countries. The prevalence among men is lower that in neighboring countries but the incidence is similar. A strong family history of kidney stones suggests a genetic predisposition.

Hypercalciuria in pediatric patients with ureteropelvic junction obstruction is of genetic origin

OBJECTIVE

Genitourinary tract malformations are associated with urolithiasis. Hypercalciuria has been described in children with ureteropelvic junction obstruction (UPJO), although the etiology of this metabolic abnormality remains unknown. This study was conducted to find out whether children with UPJO have a higher prevalence of hypercalciuria and whether their family members are affected by hypercalciuria and/or urolithiasis.

MATERIAL AND METHODS

We studied the prevalence of hypercalciuria and urolithiasis in 27 children (14 males, 13 females) with UPJO and their parents.

RESULTS

One patient had a history of renal colic, whereas imaging studies showed macroscopic renal lithiasis in two patients and calyceal microlithiasis in four. Hypercalciuria was found in 17/27 children (63%), 15 of whom (88%) had a familial history of urolithiasis: seven families in first-degree relatives, six in second-degree relatives and two in other relatives. Concerning the 10 children without hypercalciuria, seven of them (70%) had a family history of urolithiasis: four in first-degree relatives and three in second-degree relatives. The prevalences of both urolithiasis and hypercalciuria were not influenced by gender.

CONCLUSIONS

Urolithiasis is associated with hypercalciuria in patients with UPJO. In accordance with previous data, our results show that the prevalence of hypercalciuria is greater in pediatric patients with UPJO than in the general population. Likewise, the prevalence of urolithiasis in the families of these children is also higher than that in the general population. Hypercalciuria was inherited as an autosomal dominant trait.

Asymptomatic nephrolithiasis detected by ultrasound

BACKGROUND AND OBJECTIVES

Data from several countries suggest a recent world-wide increase in the prevalence of stone disease. However, these studies have not analyzed the effect that increases in utilization of imaging modalities have had on detection of asymptomatic stones.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A retrospective chart review of all patients who had an abdominal or retroperitoneal ultrasound in 2005 at a Department of Veterans' Affairs Medical Center was conducted. The charts of patients who had ultrasounds demonstrating kidney stones were further reviewed. Patients were classified into symptomatic and asymptomatic groups on the basis of their clinical history. Age and sex for all patients were recorded. For those patients with stones, additional data were recorded. Of all patients in the study, the percentage of those with asymptomatic stones was calculated. Taking into account uncertainty about symptomaticity in some patients, a sensitivity analysis for the presence or absence of gross and microhematuria was performed to determine a range for the percent of asymptomatic stones. Appropriate statistical tests were used to determine significance.

RESULTS

The prevalence of all kidney stones in the study group was 8.6 %. Using the sensitivity analysis, 29.8 to 45.7% of all stones were asymptomatic. Of stones found on abdominal ultrasounds, 71.4% were asymptomatic, whereas 36.8% of stones found on retroperitoneal ultrasound were asymptomatic.

CONCLUSIONS

Asymptomatic stones have a relatively high prevalence on ultrasound. Epidemiologic estimates of prevalence of nephrolithiasis need to account for increases in utilization of imaging modalities and the resulting detection bias.

Obesity and urolithiasis

The current obesity epidemic in the United States has deleterious effects on the health of the population. Temporally related to the increase in obesity is an increase in the prevalence of urolithiasis. Epidemiologic studies have shown that the incident stone risk increases with body mass index. Obesity can increase stone risk in multiple ways. Excess nutritional intake increases traffic of lithogenic substances such as calcium, oxalate, and uric acid. Metabolic syndrome, commonly associated with obesity, alters renal acid-base metabolism, resulting in a lower urine pH and increased risk of uric acid stone disease. The low urine pH is caused by deficient ammonia production, which appears to be related to insulin resistance. Even weight-loss programs to combat obesity can influence stone risk. Contemporary bariatric surgery has been shown to frequently cause hyperoxaluria with associated stone formation and even oxalate nephropathy. Commonly used low-carbohydrate diets increase the risk of both calcium and uric acid stones. Certainly, the many health risks of obesity, including urolithiasis, necessitate weight loss, but recognition of the potential complications of such therapies is required to prevent induction of new and equally severe medical problems. The optimal approach to weight control that minimizes stone risk needs to be determined.

Genetic causes of hypercalciuric nephrolithiasis

Renal stone disease (nephrolithiasis) affects 3-5% of the population and is often associated with hypercalciuria. Hypercalciuric nephrolithiasis is a familial disorder in over 35% of patients and may occur as a monogenic disorder that is more likely to manifest itself in childhood. Studies of these monogenic forms of hypercalciuric nephrolithiasis in humans, e.g. Bartter syndrome, Dent's disease, autosomal dominant hypocalcemic hypercalciuria (ADHH), hypercalciuric nephrolithiasis with hypophosphatemia, and familial hypomagnesemia with hypercalciuria have helped to identify a number of transporters, channels and receptors that are involved in regulating the renal tubular reabsorption of calcium. Thus, Bartter syndrome, an autosomal disease, is caused by mutations of the bumetanide-sensitive Na-K-Cl (NKCC2) co-transporter, the renal outer-medullary potassium (ROMK) channel, the voltage-gated chloride channel, CLC-Kb, the CLC-Kb beta subunit, barttin, or the calcium-sensing receptor (CaSR). Dent's disease, an X-linked disorder characterized by low molecular weight proteinuria, hypercalciuria and nephrolithiasis, is due to mutations of the chloride/proton antiporter 5, CLC-5; ADHH is associated with activating mutations of the CaSR, which is a G-protein-coupled receptor; hypophosphatemic hypercalciuric nephrolithiasis associated with rickets is due to mutations in the type 2c sodium-phosphate co-transporter (NPT2c); and familial hypomagnesemia with hypercalciuria is due to mutations of paracellin-1, which is a member of the claudin family of membrane proteins that form the intercellular tight junction barrier in a variety of epithelia. These studies have provided valuable insights into the renal tubular pathways that regulate calcium reabsorption and predispose to hypercalciuria and nephrolithiasis.

Effect of skin-to-stone distance on shockwave lithotripsy success

PURPOSE

We evaluated the effect of increased body habitus on stone-free rates after shockwave lithotripsy (SWL), determined by three reproducible skin-to-stone distances (SSDs) on CT.

PATIENTS AND METHODS

We retrospectively reviewed the records of 85 patients with preoperative CT scans available on Stentor Radiology Imaging who underwent SWL with the unmodified Dornier HM3 lithotripter from 2002 to 2007. SSDs were measured at the following angles: 0 degrees (vertical), 30 degrees, and 90 degrees (horizontal). Successful therapy was defined as stone free (residual fragments <2 mm) on follow-up imaging. Data were analyzed using descriptive statistics, Student t test, and the Fisher exact test.

RESULTS

Four hundred and eighty patients underwent SWL at our institution from 2002 to 2007; 85 patients (50.6% men, mean age 50.8 +/- 15.7 years, mean body mass index [BMI] 28.8 +/- 6.6 kg/m2) had preoperative CT scans available for review. On follow-up imaging (142.7 +/- 217.2 days), 49.4% of patients were stone free. Mean SSDs (vertical, 30 degrees, horizontal) in patients who were stone-free v those with residual stone were 104.3 +/- 26.2 mm v 102.6 +/- 29.9 mm (P = 0.79), 103.9 +/- 28.2 mm v 101.0 +/- 31.5 mm (P = 0.66), and 106.6 +/- 25.3 mm v 107.1 +/- 29.3 mm (P = 0.94), respectively.

CONCLUSIONS

Multiple variables have been shown to be associated with SWL success. In our sample of patients with preoperative CT scans, SSD was found to have no effect on SWL success.

Metabolic syndrome and uric acid nephrolithiasis

The metabolic syndrome describes a cluster of metabolic features that increases the risk for type 2 diabetes mellitus and cardiovascular disease. The prevalence of uric acid nephrolithiasis is higher among stone-forming patients with features of the metabolic syndrome such as obesity and/or type 2 diabetes mellitus. The major determinant in the development of idiopathic uric acid stones is an abnormally low urinary pH. The unduly urinary acidity in uric acid stone formers increasingly is recognized to be one of the features observed in the metabolic syndrome. Two major abnormalities have been implicated to explain this overly acidic urine: (1) increased net acid excretion, and (2) impaired buffering caused by defective urinary ammonium excretion, with the combination resulting in abnormally acidic urine. New information is emerging linking these defects to changes in insulin signaling in the kidney. This article reviews the epidemiologic and metabolic studies linking uric acid nephrolithiasis with the metabolic syndrome, and examines the potential mechanisms underlying the unduly acidic urine in these conditions.

Management of renal stone disease in obese patients

Obesity represents an increasing burden to health care resources. Nephrolithiasis is associated with obesity and type 2 diabetes and the consumption of diets rich in protein, fat and carbohydrates; this article addresses some of the pathophysiological mechanisms associated with stone formation in these patients. Management of stone disease can be more difficult in obese patients; even diagnosis can be problematic because imaging techniques are less sensitive in these patients. Treatment with extracorporeal shockwave lithotripsy and surgery in obese patients can be challenging, and outcome data for the different treatments are discussed in this Review.

Epidemiology and risk factors in urolithiasis

Stone formation in the urinary tract affects about 5-10% of the population in industrialized countries, although it is very rare in other countries such as Greenland or Japan. The high incidence and recurrence rate contribute to making the urolithiasis a serious social problem. Nowadays, urolithiasis must be considered a 'disease in evolution' for several reasons, such as epidemiological changes, evolution of the methods used for diagnosis, and the treatment and prophylaxis of the population considered 'at risk' of stone disease. Some features of stone disease have changed over the last few years due to many social, economical and cultural factors that are described here. The increased prevalence of small urinary calculi has brought about a change in clinical symptoms, with frequent episodes of renal-ureteral colic, persistent pain and hydronephrosis. Similarly, the presence of residual fragments after extracorporeal shock wave lithotripsy has induced a radical change in the management of small calculi through the use of mini-invasive surgical techniques.

Clinical study on the effect of mineral waters containing bicarbonate on the risk of urinary stone formation in patients with multiple episodes of CaOx-urolithiasis

Investigations in healthy persons have shown that drinking mineral water containing HCO(3) has a positive effect on urine supersaturated with calcium oxalate (SS(CaOx)). The present study evaluates in a common setting whether these effects are also relevant in patients with multiepisodic urinary stone formation. A total of 34 patients with evident multiepisodic CaOx-urolithiasis were included in the study. Patients with hyperparathyroidism, renal tubular acidosis, Wilson's disease, Cushing disease, osteoporosis and malignant diseases were excluded. In a cross-over design and double-blinded the patients received 1.5 l of a mineral water with 2.673 mg HCO(3)/l (test water) or the same amount of water with a low mineral content (98 mg HCO(3)/l) (control water) daily for 3 days. During the study period the patients diet was recorded in a protocol, but not standardised. The main target parameter was SS(CaOx )in 24 h urine. In addition, urinary pH and the most important inhibiting and promoting factors were measured in 24 h urine (Ca, Ox, Mg, Cit). Both waters tested led to a highly significant increase in 24 h urine volume without a difference between each other. In the group, drinking the water containing HCO(3) the urinary pH increased significantly and was within a range relevant for metaphylaxis of calcium oxalate stone formation (x=6.73). This change was highly significant compared to the control group. In addition, significantly increased magnesium and citrate concentration were also observed. Supersaturation with calcium oxalate decreased significantly and to a relevant extent; however, there was no difference between the waters tested. As expected, the risk of uric acid precipitation also decreased significantly under bicarbonate water intake. However, an increase of the risk of calcium phosphate stone formation was observed. It is evident that both waters tested are able to lower significantly and to a relevant extent the risk of urinary stone formation in patients with multiepisodic CaOx-urolithiasis. In addition, the bicarbonate water increases the inhibitory factors citrate and magnesium due to its content of HCO(3) and Mg. Thus, it can be recommended for metaphylaxis of calcium oxalate and uric acid urinary stones.

Influence of body size on urinary stone composition in men and women

A larger body size has been shown to be associated with increased excretion of urinary lithogenic solutes, and an increased risk of nephrolithiasis has been reported in overweight patients. However, the type of stones produced in these subjects has not been ascertained. Based on a large series of calculi, we examined the relationship between body size and the composition of stones, in order to assess which type of stone is predominantly favoured by overweight. Among 18,845 consecutive calculi referred to our laboratory, 2,100 came from adults with recorded body height and weight. Excluding calculi from patients with diabetes mellitus, as well as struvite and cystine stones, the study material consisted of 1,931 calcium or uric acid calculi. All calculi were analysed by infrared spectroscopy and categorized according to their main component. Body mass index (BMI) values were stratified as normal BMI (< 25 kg/m2), overweight (BMI 25-29.9) or obese (BMI > or = 30). Overall, 27.1% of male and 19.6% of female stone formers were overweight, and 8.4 and 13.5% were obese, respectively. In males, the proportion of calcium stones was lower in overweight and obese groups than in normal BMI group, whereas the proportion of uric acid stones gradually increased with BMI, from 7.1% in normal BMI to 28.7% in obese subjects (P<0.0001). The same was true in females, with a proportion of uric acid stones rising from 6.1% in normal BMI to 17.1% in obese patients (P=0.003). In addition, the proportion of uric acid stones markedly rose with age in both genders (P<0.0001). The average BMI value was significantly higher in uric acid stone formers aged < 60 years than in all other groups, whereas it did not differ from other groups in those aged > or = 60 years. Stepwise regression analysis identified BMI and age as significant, independent covariates associated with the risk of uric acid stones. Our data provide evidence that overweight is associated with a high proportion of uric acid stones in patients less than 60 years of age, whereas beyond this limit, advancing age is the main risk factor.

Prevalence of urolithiasis in the autonomous city of Buenos Aires, Argentina

Urolithiasis is the third most common pathological disease afflicting the urinary tract, and usually occurs between the third and fourth decades of an individual's life. Epidemiological studies about this condition are lacking in our country. In 1998, we performed an epidemiological, cross-sectional study of the prevalence of urolithiasis in a sample of 1,086 subjects, which included men and women of all ages, selected from the general population of the city of Buenos Aires. The method used to gather basic information was an auto administered questionnaire about the present or past history of urolithiasis that was handled at the dwelling by a trained volunteer. We found a 3.96% lifetime prevalence of urolithiasis in the general population of Buenos Aires. The rate was slightly higher in men (4.35%) than in women (3.62%), with a male to female ratio of 1.19:1. No case of urolithiasis was found in subjects under the age of 20. In subjects over 19 years, the prevalence rate of the disease was 5.14%; 5.98% for men (CI 3.41-8.55%) and 4.49% for women (CI 2.61-6.37%). Prevalence increased with age, ranging from 2.75% in the 20-39 age group to 7.79% in those >or=60 years. The life time prevalence rate of urolithiasis observed in Buenos Aires is similar to that reported in a few other studies performed among males and females in the general population of USA and Europe. Prevalence of urolithiasis increases with age both in men and in women.