Pathophysiology and Management of Calcium Stones

Kidney stones and dietary intake in adults: a population-based study in southwest Iran

BACKGROUND

The prevalence of kidney stones is on the rise globally. Several risk factors, including lifestyle, contribute to the formation of kidney stones. Nevertheless, there is a contentious debate about the relationship between diet and kidney stones. Therefore, our study aimed to assess the relationship between macronutrients and micronutrients and the formation of kidney stones.

METHODS

This population-based cross-sectional study was conducted in the baseline phase of the Hoveyzeh Cohort Study, focusing on adults aged 35-70 in southwest Iran. The information on demographic characteristics, anthropometrics, kidney stone history, and food frequency was collected. Chi-square and t-tests were utilized to assess the relationship between categorical and numerical variables with kidney stones. The ANCOVA and logistic regression models were used to evaluate the relationships while controlling for confounding factors.

RESULTS

Among 10,009 participants, the overall prevalence of kidney stones was 18.77% (95% CI: 17.99-19.53). A higher intake of carbohydrates [OR = 1.02 (95% CI:1.002-1.03), p = 0.026] and copper [OR = 1.04 (95% CI:1.01-1.09), p = 0.025] were found to be associated with kidney stones. No associations were found between the other assessed macronutrients or micronutrients and kidney stones (p-tvalues > 0.05).

CONCLUSION

Our study's findings indicate a correlation between diet and the formation of kidney stones. However, the relationship between dietary factors and kidney stones is complex, and further research is needed.

End Point Considerations for Clinical Trials in Enteric Hyperoxaluria

Enteric hyperoxaluria is a medical condition characterized by elevated urinary oxalate excretion due to increased gastrointestinal oxalate absorption. Causative features include fat malabsorption and/or increased intestinal permeability to oxalate. Enteric hyperoxaluria has long been known to cause nephrolithiasis and nephrocalcinosis, and, more recently, an association with CKD and kidney failure has been shown. Currently, there are no US Food and Drug Administration-approved therapies for enteric hyperoxaluria, and it is unclear what end points should be used to evaluate the efficacy of new drugs and biologics for this condition. This study represents work of a multidisciplinary group convened by the Kidney Health Initiative to review the evidence supporting potential end points for clinical trials in enteric hyperoxaluria. A potential clinical outcome is symptomatic kidney stone events. Potential surrogate end points include ( 1 ) an irreversible loss of kidney function as a surrogate for progression to kidney failure, ( 2 ) asymptomatic kidney stone growth/new stone formation observed on imaging as a surrogate for symptomatic kidney stone events, ( 3 ) urinary oxalate and urinary calcium oxalate supersaturation as surrogates for the development of symptomatic kidney stone events, and ( 4) plasma oxalate as a surrogate for the development of the clinical manifestations of systemic oxalosis. Unfortunately, because of gaps in the data, this Kidney Health Initiative workgroup was unable to provide definitive recommendations. Work is underway to obtain robust information that can be used to inform trial design and medical product development in this space.

Underdiagnosis of Hyperparathyroidism in Patients With Nephrolithiasis in a Community Setting

Objective Untreated primary hyperparathyroidism (PHPT) has wide-ranging multisystemic effects. Recent studies based in the US have shown a less than 25% screening rate for PHPT. Our study aims to detect whether similar deficiencies exist in our community healthcare system while quantifying the prevalence of PHPT underdiagnosis and inadequate surgical referrals. Study design This retrospective quantitative study enrolled patients aged ≥18 years with imaged-confirmed nephrolithiasis at our healthcare facilities from 2017 to the present (n=2021). Patients with documented calcium levels and kidney/ureter stones were included. Descriptive and univariate analyses were performed. Results A total of 2021 subjects met the criteria to be enrolled in the study. 26.6% (n=537) of patients with nephrolithiasis had elevated calcium levels on record. 13.6% (n=73) of hypercalcemic patients were screened for PHPT with an intact parathyroid hormone (PTH). A majority (63%, n=46) of patients with intact PTH had PHPT defined as PTH levels >55 pg/mL. Ultimately, only 19.6% (n=9) of patients with PHPT were referred for surgical intervention, and there was no significant difference in referral rate between patients with PHPT and those without (p=0.913). Conclusions PHPT is underdiagnosed in our community, leading to a significantly low rate of surgical referral and delay in management. Implementation of hospital protocols to aid in improving diagnosis and interventions could improve outcomes for PHPT patients.

Oxalate (dys)Metabolism: Person-to-Person Variability, Kidney and Cardiometabolic Toxicity

Oxalate is a metabolic end-product whose systemic concentrations are highly variable among individuals. Genetic (primary hyperoxaluria) and non-genetic (e.g., diet, microbiota, renal and metabolic disease) reasons underlie elevated plasma concentrations and tissue accumulation of oxalate, which is toxic to the body. A classic example is the triad of primary hyperoxaluria, nephrolithiasis, and kidney injury. Lessons learned from this example suggest further investigation of other putative factors associated with oxalate dysmetabolism, namely the identification of precursors (glyoxylate, aromatic amino acids, glyoxal and vitamin C), the regulation of the endogenous pathways that produce oxalate, or the microbiota's contribution to oxalate systemic availability. The association between secondary nephrolithiasis and cardiovascular and metabolic diseases (hypertension, type 2 diabetes, and obesity) inspired the authors to perform this comprehensive review about oxalate dysmetabolism and its relation to cardiometabolic toxicity. This perspective may offer something substantial that helps advance understanding of effective management and draws attention to the novel class of treatments available in clinical practice.

Dietary supplements and medicinal plants in urolithiasis: diet, prevention, and cure

BACKGROUND

Urolithiasis has been a major health concern for centuries, primarily owing to the limited treatment options in the physician's armamentarium. However, various studies have underscored a lesser incidence of urolithiasis in cohorts predominantly consuming fruits and vegetables. This article aims to review various dietary plants, medicinal herbs and phytochemicals in the prevention and management of urolithiasis.

METHODS

To provide context and evidence, relevant publications were identified on Google Scholar, PubMed and Science-Direct using keywords such as urolithiasis, nephrolithiasis, urolithiasis, renal stones, phytochemicals and dietary plants.

RESULTS

Growing bodies of evidence suggest the incorporation of plant-based foods, medicinal and herbal supplements, and crude drugs containing phytochemicals into the staple diet of people. The anti-urolithiatic activity of these plant bioactives can be attributed to their antioxidant, antispasmodic, diuretic, and inhibitory effect on the crystallization, nucleation and crystal aggregation effects. These mechanisms would help alleviate the events and symptoms that aid in the development and progression of renal calculi. In addition, it will also avoid the exacerbation of secondary disorders like inflammation and injury, which can initiate a vicious circle in turn worsening the disease progression.

CONCLUSION

In conclusion, the results presented in the review demonstrate the promising role of various dietary plants, medicinal and herbal supplements, and phytochemicals in preventing and managing the precipitation of uroliths. However, more conclusive and cogent evidence from preclinical and clinical studies is required to substantiate their safety, efficacy and toxicity profiles in humans.

A case-based review of dietary management of calcium oxalate stones

PURPOSE

The purpose of this paper is to help patients with calcium oxalate stones to access prevention and treatment options with dietary management.

METHODS

Typical cases in our hospital and other hospitals were selected for case review; combined with literature review through PubMed search, comprehensive analysis and suggestions were put forward.

RESULTS

By retrieving the literature with sufficient evidence, selecting, and summarizing, analysis of dietary liquid, oxalate and oxalate precursors, calcium, protein, fruits and vegetables, salt, high dietary fiber, and other content with high evidence index was carried out, respectively.

CONCLUSION

Through the retrospective analysis of typical cases and literature review, the importance of diet management in the prevention and treatment of calcium oxalate stones was emphasized again, and suggestions were put forward to promote the prevention and treatment of calcium oxalate stones.

In-vivo or in-vitro stone attenuation: what is more valuable for the prediction of renal stone composition in non-contrast-enhanced abdominal computed tomography?

OBJECTIVES

To compare the efficacy of in-vivo and in-vitro stone attenuation in the prediction of stone composition using non-contrast-enhanced abdominal computed tomography (NCCT).

METHODS

This study included a total of 104 patients with renal stones who received percutaneous nephrolithotomy treatment for renal stones between December 2016 and December 2019 and underwent NCCT before the procedure. Preoperative (in-vivo) and postoperative (in-vitro) kidney stone attenuations were compared using the NCCT images of the patients. Renal stone fragments were analysed with the infrared spectrophotometer method.

RESULTS

The mean age of the 104 patients was 49.5 (interquartile range: 37-61) years. According to the receiver operating characteristics analysis, the cut-off values for the prediction of uric acid stones were determined to be 556 HU for the in-vivo and 774 HU for the in-vitro attenuation measurement. Sensitivity and specificity were 100% and 96.6%, respectively, for the in-vivo and 90.9 and 91%, respectively, for the in-vitro images. The cut-off values for the prediction of calcium stones were determined to be 824 HU and 1065 HU for the in-vivo and in-vitro attenuation measurements, respectively. Sensitivity and specificity were 97.3 and 96% for the in-vivo and 96 and 96% for the in-vitro images.

CONCLUSIONS

In-vivo stone attenuation measurement in NCCT was slightly superior to in-vitro measurement due to the reduction in the composition and size of the stone. Our findings show that NCCT in-vivo stone attenuation might differentiate uric acid and calcium stones from the other stone types.

Skeletal and extraskeletal disorders of biomineralization

The physiological process of biomineralization is complex and deviation from it leads to a variety of diseases. Progress in the past 10 years has enhanced understanding of the genetic, molecular and cellular pathophysiology underlying these disorders; sometimes, this knowledge has both facilitated restoration of health and clarified the very nature of biomineralization as it occurs in humans. In this Review, we consider the principal regulators of mineralization and crystallization, and how dysregulation of these processes can lead to human disease. The knowledge acquired to date and gaps still to be filled are highlighted. The disorders of mineralization discussed comprise a broad spectrum of conditions that encompass bone disorders associated with alterations of mineral quantity and quality, as well as disorders of extraskeletal mineralization (hyperphosphataemic familial tumoural calcinosis). Included are disorders of alkaline phosphatase (hypophosphatasia) and phosphate homeostasis (X-linked hypophosphataemic rickets, fluorosis, rickets and osteomalacia). Furthermore, crystallopathies are covered as well as arterial and renal calcification. This Review discusses the current knowledge of biomineralization derived from basic and clinical research and points to future studies that will lead to new therapeutic approaches for biomineralization disorders.

Randomized Placebo-Controlled Trial of Reloxaliase in Enteric Hyperoxaluria

BACKGROUND: Enteric hyperoxaluria is caused by increased intestinal oxalate absorption and can lead to kidney stones, chronic kidney disease, and kidney failure. Reloxaliase is an orally administered recombinant enzyme that degrades oxalate along the gastrointestinal tract, thereby preventing its absorption. METHODS: We randomly assigned participants with enteric hyperoxaluria to reloxaliase or placebo, three to five times per day with food for 4 weeks. The primary end point was percent change from baseline in 24-hour urinary oxalate (UOx) excretion during weeks 1 to 4. Secondary end points included the proportion of participants with more than a 20% reduction in 24-hour UOx and an efficacy assessment in the bariatric surgery subgroup. RESULTS: A total of 115 patients underwent randomization. The 24-hour UOx decreased from a baseline geometric mean of 83.2 to 67.4 mg/24 hr during weeks 1 to 4 in reloxaliase-treated participants. Corresponding data for placebo-treated participants were 84.2 to 78.1 mg/24 hr. Estimates from the mixed-effect model repeated-measures (MMRM) analysis showed a 22.6% reduction in geometric mean UOx during weeks 1 to 4 for reloxaliase and 9.7% for placebo, a difference of 14.3 percentage points (95% confidence interval [CI], 4.9 to 22.8; P=0.004). A 20% or greater reduction in 24-hour UOx was observed in 48.3% of reloxaliase-treated participants and 31.6% of placebo-treated participants (P=0.06). In the bariatric surgery subgroup, MMRM analysis showed a 21.2% reduction in geometric mean UOx for reloxaliase and a 6.0% reduction for placebo, for a difference of 16.2 percentage points (95% CI, 4.2% to 26.7%). Adverse events occurred in 69% of reloxaliase-treated participants versus 53% of individuals taking placebo and were most commonly gastrointestinal. All but one of the adverse events were grade 1 or 2 in severity; no reloxaliase-treated participants discontinued the study. CONCLUSIONS: Reloxaliase treatment for 4 weeks reduced UOx excretion in patients with enteric hyperoxaluria; adverse events were relatively common, but not dose-limiting. These data establish the foundation for a clinical trial to determine the impact of reloxaliase on nephrolithiasis in patients with enteric hyperoxaluria. (Funded by Allena Pharmaceuticals; ClinicalTrials.gov number, NCT03456830.)

The association between single nucleotide polymorphism in vitamin D receptor and calcium oxalate urolithiasis in dogs

Background

Polymorphisms of the vitamin D receptor (VDR) are associated with calcium oxalate (CaOx) nephrolithiasis in humans.

Objectives

To investigate the association between VDR polymorphisms and susceptibility to CaOx urolithiasis in dogs.

Animals

Thirty‐five dogs with CaOx urolithiasis were compared with 40 stone‐free dogs.

Methods

This was a case‐control study. Two VDR gene polymorphisms (rs851998024 and rs852900542) were detected by specific TaqMan real‐time polymerase chain reaction assay, and their relationship with serum 1,25‐dihydroxyvitamin D, serum and urinary electrolyte concentrations was evaluated.

Results

The distribution of the rs852900542 polymorphism was significantly different between the case and the control dogs (x² = 6.369, P = .04). Dogs with a CC or CT genotype had an increased risk of CaOx stones than those with the TT genotype (odds ratio = 3.82, 95% confidence interval 1.04‐13.98). The CaOx dogs with the TT genotype had a significantly lower urinary calcium‐to‐creatinine ratio than the CT+CC genotypes. 1,25‐(OH)2D concentrations did not differ between the cases and the controls (308.7 ± 217.4 vs 286.7 ± 185.1 pg/mL, P = .45).

Conclusions and Clinical Importance

This finding suggests that vitamin D metabolism might play a role in CaOx stone formation in dogs.

Prospective Randomized Evaluation of Idiopathic Hyperoxaluria Treatments

PURPOSE

Calcium oxalate(CaOx) stone formation is influenced by urinary oxalate excretion. Stone formers with elevated urinary oxalate are commonly prescribed a low-oxalate diet or oral supplementation with Vitamin B6 and magnesium to reduce urinary oxalate. This study aims to compare the effects of dietary modification versus supplementation versus a combination of both on urinary oxalate.

MATERIALS AND METHODS

We enrolled patients with a documented history of CaOx stones and newly diagnosed idiopathic hyperoxaluria. Patients were randomized into three treatment groups: low oxalate diet(D), supplementation with 25mg vitamin B6 and 400mg magnesium oxide(S), or both low oxalate diet and B6/magnesium supplementation(DS). Baseline and 3-month post-intervention 24-hour urine tests were obtained. The primary endpoint was change in 24-hour urinary oxalate(Ox24) at 12-weeks. Secondary endpoints included changes in other 24-hour urine parameters, compliance rates, and adverse effect rates.

RESULTS

In total, 164 patients were recruited and 62, 47, and 55 were enrolled into the D, S, and DS groups, respectively. Of these, 99 patients completed the study (56.5% of the D, 72.3% of the S, and 54.6% of the DS groups, respectively). Significant differences were noted in median percent reduction in Ox24 values(-31.1% vs.-16.0% vs.-23.9%,p=0.007) in the D, S, and DS groups, respectively. Furthermore, the percentages of patients within each treatment arm who realized a decrease in Ox24 were also significantly different: D=91.4% vs. S=67.6% vs. DS=86.7%, p=0.027. No significant adverse events were observed in any of the study arms.

CONCLUSION

Low oxalate diet is more effective than B6/magnesium supplementation at lowering urinary oxalate in idiopathic hyperoxaluric stone formers. Combination therapy did not produce greater reductions in urinary oxalate than either of the monotherapy arms suggesting it is of little clinical utility. Further study with long-term longitudinal follow-up is required to determine if these treatment strategies reduce recurrent stone events in this population.

Improving Compliance with 24-H Urine Collections: Understanding Inadequacies in the Collection Process and Risk Factors for Poor Compliance

PURPOSE OF REVIEW

The purpose of this review paper is to describe the 24-h urine collection in terms of its utility, collection process, and common problems with its acquisition.

RECENT FINDINGS

Although 24-h urine collections are standard of care for high-risk stone formers, several nuances in test acquisition including inaccurate urine collections 50% of the time and poor patient compliance limit its potential utility. Compliance in obtaining 24-h urine collections has been shown to be improved in patients who have not undergone surgical treatment of urinary calculi, patients with metabolic stone disease or family history of stone disease, Caucasian ethnicity, and in those with more sedentary occupations. Studies show conflicting data of compliance regarding patient age and gender. Physicians must understand the difficulties regarding 24-h urine collections including patient compliance, variability between collections, and complexities with interpretation to best utilize this tool in guiding clinical management for the treatment of nephrolithiasis.

Pharmacological Evaluation of Safoof-e-Pathar Phori- A Polyherbal Unani Formulation for Urolithiasis

Safoof-e-Pathar phori (SPP) is an Unani poly-herbomineral formulation, which has for a long time been used as a medicine due to its antiurolithiatic activity, as per the Unani Pharmacopoeia. This powder formulation is prepared using six different plant/mineral constituents. In this study, we explored the antiurolithiatic and antioxidant potentials of SPP (at 700 and 1,000 mg/kg) in albino Wistar rats with urolithiasis induced by 0.75% ethylene glycol (EG) and 1% ammonium chloride (AC). Long-term oral toxicity studies were performed according to the Organization for Economic Co-operation and Development (OECD) guidelines for 90 days at an oral dose of 700 mg/kg of SPP. The EG urolithiatic toxicant group had significantly higher levels of urinary calcium, serum creatinine, blood urea, and tissue lipid peroxidation and significantly (p < 0.001 vs control) lower levels of urinary sodium and potassium than the normal control group. Histopathological examination revealed the presence of refractile crystals in the tubular epithelial cell and damage to proximal tubular epithelium in the toxicant group but not in the SPP treatment groups. Treatment of SPP at 700 and 1,000 mg/kg significantly (p < 0.001 vs toxicant) lowered urinary calcium, serum creatinine, blood urea, and lipid peroxidation in urolithiatic rats, 21 days after induction of urolithiasis compared to the toxicant group. A long-term oral toxicity study revealed the normal growth of animals without any significant change in hematological, hepatic, and renal parameters; there was no evidence of abnormal histology of the heart, kidney, liver, spleen, or stomach tissues. These results suggest the usefulness of SPP as an antiurolithiatic and an antioxidant agent, and long-term daily oral consumption of SPP was found to be safe in albino Wistar rats for up to 3 months. Thus, SPP may be safe for clinical use as an antiurolithiatic formulation.

Phytotherapy and Herbal Medicines for Kidney Stones

BACKGROUND

Kidney stones are one of the longest known and most common diseases in the urinary tract, with a prevalence that ranges from 1% to 20%. Many phytotherapeutic and herbal medicines have been described for the treatment and prevention of kidney stones.

OBJECTIVE

The aim of this study was to perform a comprehensive review of publications on various phytotherapeutic and herbal medicines, including both clinical and animal studies.

RESULTS

Phytotherapy may influence the risk of recurrence of calcium oxalate and uric acid stones. The most solid evidence relates to Phyllanthus niruri, one of the most studied phytotherapeutics; findings suggest that it interferes with calcium oxalate crystallization, reduces hyperoxaluria and hyperuricosuria, and increases the efficacy of shock wave lithotripsy due to reduced crystallization, without significant adverse effects. Theobromine has been shown to reduce the crystallization of uric acid in patients and appears to be a promising supplement to treat such stones.

CONCLUSION

Many phytotherapeutic and herbal agents have been studied for the treatment of urolithiasis, most of them only in a small number of patients or in animal models. Further randomized clinical trials are needed to evaluate the effects of these agents on kidney stones.

Animal models of naturally occurring stone disease

The prevalence of urolithiasis in humans is increasing worldwide; however, non-surgical treatment and prevention options remain limited despite decades of investigation. Most existing laboratory animal models for urolithiasis rely on highly artificial methods of stone induction and, as a result, might not be fully applicable to the study of natural stone initiation and growth. Animal models that naturally and spontaneously form uroliths are an underused resource in the study of human stone disease and offer many potential opportunities for improving insight into stone pathogenesis. These models include domestic dogs and cats, as well as a variety of other captive and wild species, such as otters, dolphins and ferrets, that form calcium oxalate, struvite, uric acid, cystine and other stone types. Improved collaboration between urologists, basic scientists and veterinarians is warranted to further our understanding of how stones form and to consider possible new preventive and therapeutic treatment options.

Idiopathic calcium nephrolithiasis with pure calcium oxalate composition: clinical correlates of the calcium oxalate dihydrate/monohydrate (COD/COM) stone ratio

Pure calcium oxalate is the most frequent type of idiopathic kidney stone composition. Fourier transform infrared spectroscopy (FT-IR) allows to detect the ratio of calcium oxalate dihydrate (COD) and monohydrate (COM) crystals in stones, but the clinical significance of this parameter remains uncertain. The objective of this observational study was to verify the association of clinical and laboratory parameters of kidney stone disease with COD/COM ratio in a group of 465 (322 M, age 46 ± 14) patients suffering from idiopathic calcium nephrolithiasis with pure calcium oxalate stones (≥ 97%). Each participant underwent a complete clinical examination, serum chemistry, 24-h urine collection for the determination of the profile of lithogenic risk, and had stones analyzed by FT-IR. Most (62%) of the stones had a COD/COM ratio ≤ 0.25, and the urine chemistry of the corresponding patients showed a low prevalence of urinary metabolic abnormalities. With increasing COD/COM ratio intervals (0-0.25, 0.26-0.50, 0.51-0.75, 0.76-1), a significant association was observed for the number of urological procedures, serum calcium, 24-h urinary calcium excretion, prevalence of hypercalciuria and relative calcium oxalate supersaturation, and a negative trend was detected for the age of the first stone episode (all p values < 0.05). A linear regression model showed that the only parameters significantly associated with COD/COM ratio were 24-h urinary calcium excretion (standardized β = 0.464, p < 0.001) and urine pH (standardized β = 0.103, p = 0.013). In pure calcium oxalate idiopathic stones, COD/COM ratio may reflect the presence of urinary metabolic risk factors, and represent a guide for the prescription of urinary analyses.

Low Sodium Diet Decreases Stone Formation in Genetic Hypercalciuric Stone-Forming Rats

BACKGROUND

Urine (u) calcium (Ca) excretion is directly dependent on dietary sodium (Na) intake leading to the recommendation for Na restriction in hypercalciuric kidney stone formers. However, there is no direct evidence that limiting Na intake will reduce recurrent stone formation.

MATERIALS AND METHODS

We used genetic hypercalciuric stone-forming (GHS) rats, which universally form Ca phosphate (P) kidney stones, fed either a low Na (LNa, 0.05%) or normal Na (NNa, 0.4%) Na diet (D) for 18 weeks. Urine was collected at 6-week intervals. Radiographic analysis for stone formation and bone analyses were done at the conclusion of the study.

RESULTS

Mean uCa was lower with LNaD than NNaD as was uP and LNaD decreased mean uNa and uChloride. There were no differences in urine supersaturation (SS) with respect to calcium phosphate (CaP) or Ca oxalate (CaOx). However, stone formation was markedly decreased with LNaD by radiographic analysis. The LNaD group had significantly lower femoral anterior-posterior diameter and volumetric bone mineral density (vBMD), but no change in vertebral trabecular vBMD. There were no differences in the bone formation rate or osteoclastic bone resorption between groups. The LNaD group had significantly lower femoral stiffness; however, the ultimate load and energy to fail was not different.

CONCLUSION

Thus, a low Na diet reduced uCa and stone formation in GHS rats, even though SS with respect to CaP and CaOx was unchanged and effects on bone were modest. These data, if confirmed in humans, support dietary Na restriction to prevent recurrent Ca nephrolithiasis.

A Comparison between Silent and Symptomatic Renal Stones in Primary Hyperparathyroidism

BACKGROUND

Nephrolithiasis is a common complication of primary hyperparathyroidism (PHPT), and in a subgroup of patients stones are clinically silent. Patients with silent and symptomatic stones may differ biochemically. There is a scarcity of data available comparing patients with silent and symptomatic renal stones in PHPT.

AIMS

To characterize patients with PHPT with nephrolithiais and to compare patients with silent and symptomatic stones.

MATERIALS AND METHODS

We reviewed clinical data of 186 patients with PHPT managed at our center from January 1996 to December 2017. Silent renal stones were defined as ultrasonography finding of renal stones without symptoms. Symptomatic renal stones were defined as those with symptoms or a history of graveluria or any procedure for nephrolithiasis. A 5-mm diameter was set as the cut-off between micro- and macrolithiasis. We compared those with (n = 95) and without (n = 91) stones, and, among stone formers, those with symptoms (n = 66) and silent (n = 29) were compared.

RESULTS

There was no significant difference between stone formers and nonstone formers with respect to biochemical parameters. Patients with silent renal stones had significantly lower serum calcium and higher phosphate, than those with symptomatic stones. Most (75%) patients with silent renal stones had microlithiais, while only a fifth (22%) with symptomatic renal stones had microlithiasis.

CONCLUSION

Nephrolithiasis is a common complication of PHPT. Most patients with silent renal stones had microlithiasis and biochemical features of less severe disease. Patients with silent renal stones may represent early mild stage of PHPT.

Kidney Stone Disease: An Update on Current Concepts

Kidney stone disease is a crystal concretion formed usually within the kidneys. It is an increasing urological disorder of human health, affecting about 12% of the world population. It has been associated with an increased risk of end-stage renal failure. The etiology of kidney stone is multifactorial. The most common type of kidney stone is calcium oxalate formed at Randall's plaque on the renal papillary surfaces. The mechanism of stone formation is a complex process which results from several physicochemical events including supersaturation, nucleation, growth, aggregation, and retention of urinary stone constituents within tubular cells. These steps are modulated by an imbalance between factors that promote or inhibit urinary crystallization. It is also noted that cellular injury promotes retention of particles on renal papillary surfaces. The exposure of renal epithelial cells to oxalate causes a signaling cascade which leads to apoptosis by p38 mitogen-activated protein kinase pathways. Currently, there is no satisfactory drug to cure and/or prevent kidney stone recurrences. Thus, further understanding of the pathophysiology of kidney stone formation is a research area to manage urolithiasis using new drugs. Therefore, this review has intended to provide a compiled up-to-date information on kidney stone etiology, pathogenesis, and prevention approaches.

Risk factors for bladder calculi in patients with benign prostatic hyperplasia

We aim to find the risk factors that influence the formation of bladder calculi in patients with benign prostate hyperplasia (BPH) and to reduce the surgical intervention related to bladder calculi.Between January 2015 and October 2016, 332 patients with BPH underwent surgical therapy were retrospectively evaluated. Patients with BPH were categorized into 2 groups: 94 patients with bladder calculi in group 1 and 238 patients without bladder calculi in group 2. Medical history, age, body mass index (BMI), total prostate specific antigen, total prostate volume (TPV), International Prostate Symptom Score (IPSS), intravesical prostatic protrusion (IPP), urodynamic parameters, and urine culture were compared between groups.There was no significant difference in the age, BMI, peak flow rate, and total IPSS between groups. TPV, total prostate specific antigen, and duration of BPH were significantly lower in group 1 than those in group 2. In addition, IPP was significantly higher in group 1 than group 2 (P < .001). Besides, after exclusion of patients with urinary retention and indwelling catheter, group 1 associated with a significantly higher preoperative positive rate of urine culture than that of group 2 (P = .046). Multivariate analysis indicated that IPP was a significant independent risk factor for the presence of bladder calculi.The incidence of bladder calculi in patients with BPH was proved to be closely associated with preoperative positive urine culture and longer IPP in our study. Furthermore, the IPP was presented to be an independent risk factor for the formation of bladder calculi. And early antibacterial therapy of urinary tract infection (UTI) may help to prevent the presence of bladder calculi in patients with BPH.

Pathogenesis of calcium oxalate urinary stone disease: species comparison of humans, dogs, and cats

Idiopathic calcium oxalate nephrolithiasis is a highly recurrent disease that is increasing in prevalence. Decades of research have not identified effective methods to consistently prevent the formation of nephroliths or induce medical dissolution. Idiopathic calcium oxalate nephroliths form in association with renal papillary subepithelial calcium phosphate deposits called Randall's plaques (RPs). Rodent models are commonly used to experimentally induce calcium oxalate crystal and stone formation, but a rodent model that conclusively forms RPs has not been identified. Both dogs and cats form calcium oxalate uroliths that can be recurrent, but the etiopathologic mechanisms of stone formation, especially renal pathologic findings, are a relatively unexploited area of study. A large animal model that shares a similar environment to humans, along with a shorter lifespan and thus shorter time to recurrence, might provide an excellent means to study preventative and therapeutic measures, along with enhancing the concepts of the one health initiative. This review article summarizes and compares important known features of idiopathic calcium oxalate stone disease in humans, dogs, and cats, and emphasizes important knowledge gaps and areas for future study in the quest to discover a naturally occurring animal model of idiopathic calcium oxalate stone disease.

Effect of citrus-based products on urine profile: A systematic review and meta-analysis

Background. Urolithiasis is a disease with high recurrence rate, 30-50% within 5 years. The aim of the present study was to learn the effects of citrus-based products on the urine profile in healthy persons and people with urolithiasis compared to control diet and potassium citrate.  Methods. A systematic review was performed, which included interventional, prospective observational and retrospective studies, comparing citrus-based therapy with standard diet therapy, mineral water, or potassium citrate. A literature search was conducted using PUBMED, COCHRANE, and Google Scholar with "citrus or lemonade or orange or grapefruit or lime or juice" and "urolithiasis" as search terms. For statistical analysis, a fixed-effects model was conducted when p > 0.05, and random-effects model was conducted when p < 0.05.  Results. In total, 135 citations were found through database searching with 10 studies found to be consistent with our selection criteria. However, only 8 studies were included in quantitative analysis, due to data availability. The present study showed a higher increased in urine pH for citrus-based products (mean difference, 0.16; 95% CI 0.01-0.32) and urinary citrate (mean difference, 124.49; 95% CI 80.24-168.74) compared with a control group. However, no differences were found in urine volume, urinary calcium, urinary oxalate, and urinary uric acid. From subgroup analysis, we found that citrus-based products consistently increased urinary citrate level higher than controls in both healthy and urolithiasis populations. Furthermore, there was lower urinary calcium level among people with urolithiasis.  Conclusions. Citrus-based products could increase urinary citrate level significantly higher than control. These results should encourage further research to explore citrus-based products as a urolithiasis treatment.

Protective impact of resveratrol in experimental rat model of hyperoxaluria

PURPOSE

Resveratrol (RES) is a polyphenol with antioxidant, anti-inflammatory, and many other physiological effects on tissues. In the present study, the effect of resveratrol in hyperoxaluria driven nephrolithiasis/nephrocalcinosis is investigated.

METHODS

Wistar-Albino rats of 250-300 g (male, n = 24) were included in the present study. The rats were randomized into three groups: Group 1 consisted of the controls (n = 8), Group 2 of hyperoxaluria (1% ethylene glycol (EG), n = 8), and Group 3 of the treatment (1% EG + 10 mg/kg of RES, n = 8) group. At the beginning and fifth week of the study, two rats from each group were placed in metabolic cages for 24 h and their urine was collected. At the end of the study, the rats were killed and their blood was collected from the vena cava inferior. The right kidneys of the rats were used for biochemical and the left ones for immunohistochemical analyzes. Malondialdehyde (MDA), catalase, urea, calcium, oxalate, and creatinine clearance were studied in the blood, urine, and kidney tissues. Moreover, routine histological evaluation, and p38-MAPK and NFkB immunohistochemical analyses were conducted.

RESULTS

In the hyperoxaluria group, urinary oxalate levels were higher than the control group; yet, lower in the treatment group compared to hyperoxaluria group (p < 0.05). Serum MDA levels in the hyperoxaluria group were higher than the control group; but in the treatment group it is lower than the hyperoxaluria group (p < 0.05). P38 MAPK activity was higher in the hyperoxaluria group compared to the control (p < 0.05). However, in terms of p38 MAPK activity, there were no statistically significant difference between hyperoxaluria and the treatment group (p < 0.069). Whereas NFkB activity in the hyperoxaluria group is higher than the control (p < 0.001), no statistically significant difference was observed with the treatment group.

CONCLUSIONS

In the present study, resveratrol was seen to prevent hyperoxaluria. With preventing oxidative stress factors and Randall plaque formation caused by free oxygen radicals, resveratrol can be an alternative treatment option that can increase the success rate in preventing stone recurrence in the future.

Potassium citrate decreases urine calcium excretion in patients with hypocitraturic calcium oxalate nephrolithiasis

Two previous studies (<10 patients each) have demonstrated that alkali therapy may reduce urine calcium excretion in patients with calcium oxalate nephrolithiasis. The hypothesized mechanisms are (1) a decrease in bone turnover due to systemic alkalinization by the medications; (2) binding of calcium by citrate in the gastrointestinal tract; (3) direct effects on TRPV5 activity in the distal tubule. We performed a retrospective review of patients on potassium citrate therapy to evaluate the effects of this medication on urinary calcium excretion. A retrospective review was performed of a metabolic stone database at a tertiary care academic hospital. Patients were identified with a history of calcium oxalate nephrolithiasis and hypocitraturia who were on potassium citrate therapy for a minimum of 3 months. 24-h urine composition was assessed prior to the initiation of potassium citrate therapy and after 3 months of therapy. Patients received 30-60 mEq potassium citrate by mouth daily. Inclusion criterion was a change in urine potassium of 20 mEq/day or greater, which suggests compliance with potassium citrate therapy. Paired t test was used to compare therapeutic effect. Twenty-two patients were evaluated. Mean age was 58.8 years (SD 14.0), mean BMI was 29.6 kg/m(2) (SD 5.9), and gender prevalence was 36.4% female:63.6% male. Mean pre-treatment 24-h urine values were as follows: citrate 280.0 mg/day, potassium 58.7 mEq/day, calcium 216.0 mg/day, pH 5.87. Potassium citrate therapy was associated with statistically significant changes in each of these parameters-citrate increased to 548.4 mg/day (p < 0.0001), potassium increased to 94.1 mEq/day (p < 0.0001), calcium decreased to 156.5 mg/day (p = 0.04), pH increased to 6.47 (p = 0.001). Urine sodium excretion was not different pre- and post-therapy (175 mEq/day pre-therapy versus 201 mEq/day post-therapy, p = NS). Urinary calcium excretion decreased by a mean of 60 mg/day on potassium citrate therapy-a nearly 30 % decrease in urine calcium excretion. These data lend support to the hypothesis that alkali therapy reduces urine calcium excretion.

Metabolic abnormalities in patients treated with percutaneous nephrolithotomy

Objectives:

To assess metabolic abnormalities in patients with percutaneous nephrolithotomy (PCNL) that could pose a risk for stone recurrence.

Materials and methods:

The data was collected retrospectively on all patients who had PCNL and metabolic studies, between January 2000 and September 2012.

Results:

There were 144 patients; median age and follow up were 49.5 (15– 4) years and 80.2 (16–180) months, respectively. Nearly half of the patients had staghorn calculus. Metabolic abnormalities (MAs) were found in 55 (38.2%). The 31 (21.5%) of these had multiple metabolic abnormalities (MMA) while 24 (16.6%) had a single metabolic abnormality (SMA). Uricosuria was found in 24 (16.6%), hyperoxaluria in 22 (15.3%), hyperphosphaturia in 18 (12.5%), hypercalciuria in 10 (7%), hypomagnesuria in 6 (4.2%), cystinuria in 5 (3.5%) and hypocitraturia in 5 (3.5%). Hyperuricaemia was present in 10 (7%), hypercalcaemia in 5 (3.5%), hyperphosphataemia in 7 (5%) and renal tubular acidosis in 1 (0.7%). In non-staghorn, MAs were found in 25 (35.2%) and 16 (64%) of these had MMA. In patients with staghorn, MAs were present in 30 (41%) patients. Half of the patients 15 (50%) in this group had MMA. A high proportion of the first time stone formers requiring surgical treatment had MAs and 57% of these had MMA. Stone analysis was available for 69 (48%) and 37 (53.6%) of these had mixed composition. The highest proportion of patients with uric acid stones had MA 89% followed by cystine stones 80%, matrix stones 50%, calcium oxalate 36.6%, carbonate apatite 36.4% and triple phosphate 33.3% .

Conclusion:

A high proportion of first time stone formers, staghorn and non-staghorn stone formers with PCNL had MA. These findings suggest that the treatment of metabolic abnormalities can play an important role in reducing the risk of stone recurrences and management may include referral to dedicated metabolic stone clinics.

Effect of Potassium Citrate on Calcium Phosphate Stones in a Model of Hypercalciuria

Potassium citrate is prescribed to decrease stone recurrence in patients with calcium nephrolithiasis. Citrate binds intestinal and urine calcium and increases urine pH. Citrate, metabolized to bicarbonate, should decrease calcium excretion by reducing bone resorption and increasing renal calcium reabsorption. However, citrate binding to intestinal calcium may increase absorption and renal excretion of both phosphate and oxalate. Thus, the effect of potassium citrate on urine calcium oxalate and calcium phosphate supersaturation and stone formation is complex and difficult to predict. To study the effects of potassium citrate on urine supersaturation and stone formation, we utilized 95th-generation inbred genetic hypercalciuric stone-forming rats. Rats were fed a fixed amount of a normal calcium (1.2%) diet supplemented with potassium citrate or potassium chloride (each 4 mmol/d) for 18 weeks. Urine was collected at 6, 12, and 18 weeks. At 18 weeks, stone formation was visualized by radiography. Urine citrate, phosphate, oxalate, and pH levels were higher and urine calcium level was lower in rats fed potassium citrate. Furthermore, calcium oxalate and calcium phosphate supersaturation were higher with potassium citrate; however, uric acid supersaturation was lower. Both groups had similar numbers of exclusively calcium phosphate stones. Thus, potassium citrate effectively raises urine citrate levels and lowers urine calcium levels; however, the increases in urine pH, oxalate, and phosphate levels lead to increased calcium oxalate and calcium phosphate supersaturation. Potassium citrate induces complex changes in urine chemistries and resultant supersaturation, which may not be beneficial in preventing calcium phosphate stone formation.

Interstitial calcinosis in renal papillae of genetically engineered mouse models: relation to Randall's plaques

Genetically engineered mouse models (GEMMs) have been highly instrumental in elucidating gene functions and molecular pathogenesis of human diseases, although their use in studying kidney stone formation or nephrolithiasis remains relatively limited. This review intends to provide an overview of several knockout mouse models that develop interstitial calcinosis in the renal papillae. Included herein are mice deficient for Tamm-Horsfall protein (THP; also named uromodulin), osteopontin (OPN), both THP and OPN, Na(+)-phosphate cotransporter Type II (Npt2a) and Na(+)/H(+) exchanger regulatory factor (NHERF-1). The baseline information of each protein is summarized, along with key morphological features of the interstitial calcium deposits in mice lacking these proteins. Attempts are made to correlate the papillary interstitial deposits found in GEMMs with Randall's plaques, the latter considered precursors of idiopathic calcium stones in patients. The pathophysiology that underlies the renal calcinosis in the knockout mice is also discussed wherever information is available. Not all the knockout models are allocated equal space because some are more extensively characterized than others. Despite the inroads already made, the exact physiological underpinning, origin, evolution and fate of the papillary interstitial calcinosis in the GEMMs remain incompletely defined. Greater investigative efforts are warranted to pin down the precise role of the papillary interstitial calcinosis in nephrolithiasis using the existing models. Additionally, more sophisticated, second-generation GEMMs that allow gene inactivation in a time-controlled manner and "compound mice" that bear several genetic alterations are urgently needed, in light of mounting evidence that nephrolithiasis is a multifactorial, multi-stage and polygenic disease.

The inhibitory effect of an ethanol extract of the spores of Lygodium japonicum on ethylene glycol-induced kidney calculi in rats

We investigated the effect of an ethanol extract of Lygodii spora (LS) as a preventive and therapeutic agent for experimentally induced calcium oxalate nephrolithiasis with ethylene glycol (EG) in rats. Male Wistar rats were randomly divided into preventive (n = 18, for 28 days) and therapeutic (n = 24, for 42 days) groups. The preventive group was further subdivided into three groups of six rats each: preventive control, preventive lithiatic control (EG) and preventive lithiatic LS (EG + 400 mg/kg LS). Similarly, the therapeutic group was subdivided into four groups of six rats each: therapeutic control, therapeutic lithiatic control, therapeutic lithiatic untreated, and therapeutic lithiatic LS. Lithiasis was induced by adding 0.75% EG to the drinking water of all groups except the preventive and therapeutic control groups. Preventive and therapeutic subjects also received the LS ethanol extract in drinking water at a dose of 400 mg/kg, since day 0 or day 28, respectively. At the end of the each experimental period, various biochemical parameters were measured in urine and kidney homogenates. The kidneys were subjected to histopathological analysis. The results revealed that treatment with the LS preventive protocol significantly decreased the levels of urinary calcium, oxalate and uric acid, and increased the levels of urinary citrate as compared to those in the EG control. No significant changes in the urinary parameters except oxalate and citrate levels were observed in the rats in the therapeutic protocol. In both preventive and therapeutic protocols, the extract significantly decreased kidney peroxides, renal calcium, oxalate content, and the number of kidney oxalate deposits as compared to those in the EG group. We conclude that LS is useful as a preventive and therapeutic agent against the formation of oxalate kidney stones.

Human SLC26A1 gene variants: a pilot study

Kidney stones are a global health problem, incurring massive health costs annually. Why stones recur in many patients remains unknown but likely involves environmental, physiological, and genetic factors. The solute linked carrier (SLC) 26A1 gene has previously been linked to kidney stones in mice. SLC26A1 encodes the sulfate anion transporter 1 (SAT1) protein, and its loss in mice leads to hyperoxaluria and calcium oxalate renal stones. To investigate the possible involvement of SAT1 in human urolithiasis, we screened the SLC26A1 gene in a cohort of 13 individuals with recurrent calcium oxalate urolithiasis, which is the commonest type. DNA sequence analyses showed missense mutations in seven patients: one individual was heterozygous R372H; 4 individuals were heterozygous Q556R; one patient was homozygous Q556R; and one patient with severe nephrocalcinosis (requiring nephrectomy) was homozygous Q556R and heterozygous M132T. The M132 amino acid in human SAT1 is conserved with 15 other species and is located within the third transmembrane domain of the predicted SAT1 protein structure, suggesting that this amino acid may be important for SAT1 function. These initial findings demonstrate genetic variants in SLC26A1 of recurrent stone formers and warrant wider independent studies of SLC26A1 in humans with recurrent calcium oxalate stones.

Association of severe calcium lithogenic activity and bone remodeling markers

OBJECTIVE

To establish cutoff points for markers of bone remodeling that allow for screening of patients at risk for serious lithogenic activity.

MATERIALS AND METHODS

We conducted a cross-sectional study with 182 patients (aged between 25 and 60 years) divided into 3 groups: group 1, 56 patients without lithiasis; group 2, 67 patients with light calcium lithiasis; and group 3, 59 patients with severe calcium lithiasis. The criteria for inclusion in and exclusion from the study were established, and light and severe lithogenic activity were defined. Metabolic variables in blood and urine, along with bone densitometry, were studied for the groups. Statistical analysis of the results and preparation of receiver operating characteristic curves to establish optimal cutoff points were performed.

RESULTS

The patients in group 3 showed the greatest bone mineral density loss and the highest values for markers of bone remodeling, together with increased 24-hour calciuria. Using the receiver operating characteristic curves developed and based on statistical significance (P = .0001), the following cutoff points for severe lithogenic activity, with a sensitivity between 75% and 85%, were established: β-crosslaps >0.331 ng/mL; osteocalcin >13.2 ng/mL; β-crosslaps/osteocalcin >0.024; 24-hour calciuria >306.6 mg; and fasting urine calcium/creatinine >0.105.

CONCLUSION

Patients with calcium lithiasis and elevated values for osteocalcin, β-crosslaps, β-crosslaps/osteocalcin, 24-hour calciuria, and fasting urine calcium/creatinine may present a high risk of severe lithogenic activity.

Pathogenesis of bladder calculi in the presence of urinary stasis

PURPOSE

Although minimal evidence exists, bladder calculi in men with benign prostatic hyperplasia are thought to be secondary to bladder outlet obstruction induced urinary stasis. We performed a prospective, multi-institutional clinical trial to determine whether metabolic differences were present in men with and without bladder calculi undergoing surgical intervention for benign prostatic hyperplasia induced bladder outlet obstruction.

MATERIALS AND METHODS

Men who elected surgery for bladder outlet obstruction secondary to benign prostatic hyperplasia with and without bladder calculi were assessed prospectively and compared. Men without bladder calculi retained more than 150 ml urine post-void residual urine. Medical history, serum electrolytes and 24-hour urinary metabolic studies were compared.

RESULTS

Of the men 27 had bladder calculi and 30 did not. Bladder calculi were associated with previous renal stone disease in 36.7% of patients (11 of 30) vs 4% (2 of 27) and gout was associated in 13.3% (4 of 30) vs 0% (0 of 27) (p <0.01 and 0.05, respectively). There was no observed difference in the history of other medical conditions or in serum electrolytes. Bladder calculi were associated with lower 24-hour urinary pH (median 5.9 vs 6.4, p = 0.02), lower 24-hour urinary magnesium (median 106 vs 167 mmol, p = 0.01) and increased 24-hour urinary uric acid supersaturation (median 2.2 vs 0.6, p <0.01).

CONCLUSIONS

In this comparative prospective analysis patients with bladder outlet obstruction and benign prostatic hyperplasia with bladder calculi were more likely to have a renal stone disease history, low urinary pH, low urinary magnesium and increased urinary uric acid supersaturation. These findings suggest that, like the pathogenesis of nephrolithiasis, the pathogenesis of bladder calculi is likely complex with multiple contributing lithogenic factors, including metabolic abnormalities and not just urinary stasis.

Vanishing hypercalciuric kidney stones after treating underlying acromegaly

A 53-year-old male presented with recurrent calcium oxalate kidney stones as a first sign of underlying acromegaly, which vanished when his acromegaly was controlled. The exact mechanism behind hypercalciuria and urolithiasis in acromegaly is not yet clear. By discussing this case, a short overview of the pathophysiology of hypercalciuria in acromegaly and practical insights are given.

The preventive effect of N-butanol fraction of Nigella sativa on ethylene glycol-induced kidney calculi in rats

Background:

The current study was carried out to determine whether the aqueous-ethanolic extract or the butanolic fraction of Nigella sativa (NS) seeds could prevent or reduce calculi aggregation in experimental calcium oxalate nephrolithiasis in Wistar rats.

Materials and Methods:

Male Wistar rats were randomly divided into 5 groups: group A received tap drinking water for 28 days. Groups B, C, D and E received 1% ethylene glycol for induction of calcium oxalate (CaOx) calculus formation for 28 days. Rats in groups C, D and E also received aqueous-ethanolic extract of NS, N-butanol fraction and N-butanol phase remnant of NS, respectively, in drinking water at a dose of 250 mg/kg for 28 days. Urine concentration of oxalate, citrate, and calcium on days 0, 14, and 28, and also serum concentration of magnesium and calcium on days 0 and 28, were measured. On day 29, kidneys were removed for histopathologic study and examined for counting the calcium oxalate deposits in 10 microscopic fields.

Result:

Treatment of rats with N-butanol fraction and N-butanol phase remnant of NS significantly reduced the number and size of kidney calcium oxalate deposits compared with ethylene glycol group. Urinary concentration of oxalate in all experimental groups increased compared with control group on days 14 and 28, whereas the urine citrate concentration was lower in all experimental groups compared with control group on days 14 and 28.

Conclusion:

N-butanol fraction and N-butanol phase remnant of NS showed a beneficial effect on calcium oxalate deposition in the rat kidney. Therefore, the butanolic fraction of NS may be suggested for prevention of calcium oxalate calculi in humans.

Alcea rosea root extract as a preventive and curative agent in ethylene glycol-induced urolithiasis in rats

Introduction:

Alcea rosea L. is used in Asian folk medicine as a remedy for a wide range of ailments. The aim of the present study was to investigate the effect of hydroalcoholic extract of Alcea rosea roots on ethylene glycol-induced kidney calculi in rats.

Materials and Methods:

Male Wistar rats were randomly divided into control, ethylene glycol (EG), curative and preventive groups. Control group received tap drinking water for 28 days. Ethylene glycol (EG), curative and preventive groups received 1% ethylene glycol for induction of calcium oxalate (CaOx) calculus formation; preventive and curative subjects also received the hydroalcoholic extract of Alcea rosea roots in drinking water at dose of 170 mg/kg, since day 0 or day 14, respectively. Urinary oxalate concentration was measured by spectrophotometer on days 0, 14 and 28. On day 28, the kidneys were removed and examined histopathologically under light microscopy for counting the calcium oxalate deposits in 50 microscopic fields.

Results:

In both preventive and curative protocols, treatment of rats with hydroalcoholic extract of Alcea rosea roots significantly reduced the number of kidney calcium oxalate deposits compared to ethylene glycol group. Administration of Alcea rosea extract also reduced the elevated urinary oxalate due to ethylene glycol.

Conclusion:

Alcea rosea showed a beneficial effect in preventing and eliminating calcium oxalate deposition in the rat kidney. This effect is possibly due to diuretic and anti-inflammatory effects or presence of mucilaginous polysaccharides in the plant. It may also be related to lowering of urinary concentration of stone-forming constituents.

Renal stones and calcifications in patients with primary hyperparathyroidism: associations with biochemical variables

OBJECTIVE

To study the prevalence of renal stones and nephrocalcinosis in patients with primary hyperparathyroidism (PHPT) and to appraise biochemical variables as risk factors for developing renal calcifications.

DESIGN

Cross-sectional.

MATERIALS AND METHODS

All patients (n=177) undergoing diagnostic evaluation and surgery for PHPT at Aarhus University Hospital between 2007 and 2009. All patients underwent routine spiral CT scans of the abdomen to determine the presence or absence of renal calcifications.

RESULTS

A total of 45 patients (25.4%, 95% confidence intervals: 19.0-31.4%) had renal stones (15.3%) and/or renal calcifications (10.2%) on the CT scans. Compared with those without calcification (n=132), the group with calcification had a significantly lower plasma creatinine level (67.0±25.1 vs 74.6±17.5 μmol/l, 2P=0.03). Moreover, CaE was higher in PHPT patients with renal calcification than in PHPT patients without (0.91±0.28 vs 0.74±0.40 mmol/mmol, 2P=0.02). The other measured or derived biochemical variables were similar in the two groups. No biochemical variable was predictive for renal calcifications in a multiple regression analysis.

CONCLUSION

We found a high prevalence of renal calcifications among PHPT patients but no deterioration of renal function. The occurrence of calcifications was related to low plasma creatinine and a high urine calcium/creatinine ratio. However, biochemical markers in general were poor predictors for the risk of renal stones or nephrocalcinosis indicating that routine image diagnostics may be needed for the identification of these complications in order to establish indication for surgery and ensure proper treatment.

Fasting and postprandial spot urine calcium-to-creatinine ratios do not detect hypercalciuria

SUMMARY

Clinicians can diagnose high urine calcium by asking patients to collect urine for 24 h or to provide a random urine specimen. In this study, random urine calcium levels were not as accurate as those from the 24-h collection. Clinicians should only use 24-h collections to diagnose high urine calcium.

INTRODUCTION

Clinicians diagnose hypercalciuria using a 24-h urine calcium (24HUC) or a spot urine-calcium-to-creatinine ratio (SUCCR) specimen. The SUCCR is reportedly interchangeable with the 24HUC. However, studies to date show mixed results when comparing SUCCR and 24HUC values. We systematically compared fasting and postprandial SUCCR measurements to 24HUC measurements using Bland-Altman analysis.

METHODS

Twenty-one postmenopausal women aged 58 ± 7 years came to the research ward for three 24-h inpatient stays. At each study visit, research nurses collected fasting morning (n = 62) and postprandial (n = 62) spot urine specimens along with carefully timed and complete 24-h urine specimens (n = 63) from each woman.

RESULTS

Hypercalciuria was present in 13 24HUC samples (21%) using an upper limit of 250 mg/24-h. The fasting SUCCR underestimated the 24HUC (Bland-Altman bias -71 mg/24-h), with a sensitivity and specificity for diagnosing hypercalciuria of 0% and 98%, respectively. The postprandial SUCCR overestimated the 24HUC (Bland-Altman bias +61 mg/24-h), with a sensitivity and specificity of 77% and 61%, respectively. The average of fasting and postprandial SUCCR measurements had a lower Bland-Altman bias of -3 mg/24-h but demonstrated a sensitivity and specificity of only 42% and 78%, respectively.

CONCLUSIONS

The SUCCR is not interchangeable with the 24HUC. The fasting SUCCR systematically underestimates, and the postprandial SUCCR systematically overestimates, 24HUC. The average SUCCR demonstrates low sensitivity and specificity for hypercalciuria. Clinicians must use the 24HUC to diagnose hypercalciuria in postmenopausal women.