Calcium Oxalate Urinary Stones Research Articles

Establishment and application of a nomogram diagram for predicting calcium oxalate stones in patients with urinary tract stones

This retrospective study aims to examine the correlation between calcium oxalate (CaOx) stones and common clinical tests, as well as urine ionic composition. Additionally, we aim to develop and implement a personalized model to assess the accuracy and feasibility of using charts to predict calcium oxalate stones in patients with urinary tract stones. A retrospective analysis was conducted on data from 960 patients who underwent surgery for urinary stones at the First Affiliated Hospital of Soochow University from January 1, 2010, to December 31, 2022. Among these patients, 447 were selected for further analysis based on screening criteria. Multivariate logistic regression analysis was then performed to identify the best predictive features for calcium oxalate stones from the clinical data of the selected patients. A prediction model was developed using these features and presented in the form of a nomogram graph. The performance of the prediction model was assessed using the C-index, calibration curve, and decision curve, which evaluated its discriminative power, calibration, and clinical utility, respectively. The nomogram diagram prediction model developed in this study is effective in predicting calcium oxalate stones which is helpful in screening and early identification of high-risk patients with calcium oxalate urinary tract stones, and may be a guide for urologists in making clinical treatment decisions.

Investigation of the potential anti-urolithiatic activity of Alhagi maurorum (Boiss.) grown wild in Al-Ahsa (Eastern Province), Saudi Arabia.

The potential of Alhagi maurorum (Boiss.) aqueous extract (AME), used in traditional medicine for treatment or prevention of urolithiasis, to dissolve calcium oxalate stones in vitro was evaluated. In order to determine the litholytic potential of the extract, Calcium oxalate urinary stones were incubated during 12 weeks under continuous shaking in the presence of AME, Rowanix or NaCl 9 g/mL solution were used as controls. After the incubation period, the residual weight of the treated calculi was determined and the rate of dissolution was calculated. The medium pH variation was measured and changes in the calcium oxalate crystals at the stone surface were assessed using a scanning electron microscope (SEM). The results showed a significant dissolution effect for the extract on the kidney calculi during the experimentation period. At the end of the experiment, the percentages of calculi weight decrease were 41.23, 4.97 and 55.67% for the extract, NaCl solution and Rowanix, respectively. Gas Chromatography analysis revealed mainly the presence of the following phyto-compounds: Cyclopropenone, 2,3-diphenyl; 1-Nonadecanol; methyl-alpha-D-mannopyranoside; cis-9-Hexadecenal. These compounds unarguably play crucial roles in the health care system especially in cancer treatment and many other diseases including urolithiasis. The urinary stone dissolution, independent of medium pH, could be attributed to formation of complexes between the phytochemical compounds in the extract and the calculi.

In vivo base editing rescues primary hyperoxaluria type 1 in rats

Primary hyperoxaluria type 1 (PH1) is a childhood-onset autosomal recessive disease, characterized by nephrocalcinosis, multiple recurrent urinary calcium oxalate stones, and a high risk of progressive kidney damage. PH1 is caused by inherent genetic defects of the alanine glyoxylate aminotransferase (AGXT) gene. The invivo repair of disease-causing genes was exceedingly inefficient before the invention of base editors which can efficiently introduce precisely targeted base alterations without double-strand DNA breaks. Adenine base editor (ABE) can precisely convert A·T to G·C with the assistance of specific guide RNA. Here, we demonstrated that systemic delivery of dual adeno-associated virus encoding a split-ABE8e could artificially repair 13% of the pathogenic allele in AgxtQ84X rats, a model of PH1, alleviating the disease phenotype. Specifically, ABE treatment partially restored the expression of alanine-glyoxylate-aminotransferase (AGT), reduced endogenous oxalate synthesis and alleviated calcium oxalate crystal deposition. Western blot and immunohistochemistry confirmed that ABE8e treatment restored AGT protein expression in hepatocytes. Moreover, the precise editing efficiency in the liver remained stable six months after treatment. Thus, our findings provided a prospect of invivo base editing as a personalized and precise medicine for PH1 by directly correcting the mutant Agxt gene.

Effect of a low-calorie diet on 24-hour urinary parameters of obese adults with idiopathic calcium oxalate kidney stones.

ABSTRACTPurpose:to evaluate the effect of low-calorie diet on 24-hour urinary metabolic parameters of obese adults with idiopathic calcium oxalate kidney stones.Materials and Methods:Adult idiopathic calcium oxalate stone formers, with body mass index (BMI) ≥30kg/m2 and a known lithogenic metabolic abnormality, were submitted to low-calorie diet for twelve weeks. After enrolment, anthropometric measures, serum exams, 24-hour urinary metabolic parameters and body impedance were collected one month prior to dietary intervention and at the end of twelve weeks. Correlations between weight loss, waist circumference loss, fat loss and variation in 24-hour urinary lithogenic parameters and calcium oxalate urinary supersaturation (CaOx SS) as per Tiselius equation were analysed.Results:From January 2017 to January 2018, 39 patients were enrolled to participate in this study. Median (range) prescribed diet was 1300 (1100-2100) Kcal/day. Mean age was 51.7±11.0 (29-68) years old and 69.2% were female. 30.8% of the participants shifted from obesity to BMI <30kg/m2 and none to BMI <25kg/m2. A significant correlation was found between baseline 24-hour urinary oxalate and weight (p=0.018) and BMI (p=0.026). No correlation was found between variation of weight, waist circumference, fat mass and 24-h urinary stone risk factors or CaOx SS.Conclusions:Short-term modest weight loss induced by twelve weeks of low-calorie diet is not associated with a decrease of 24-hour urinary lithogenic parameters in idiopathic calcium oxalate stone formers. Calcium oxalate urinary stone formation is probably multifactorial and driven by other factors than weight.

Bisphosphonate Use May Reduce the Risk of Urolithiasis in Astronauts on Long-Term Spaceflights.

ABSTRACTLong‐duration spaceflight is associated with an increased risk of urolithiasis, and the pain caused by urinary calculi could result in loss of human performance and mission objectives. The present study investigated the risk of urolithiasis in astronauts during 6 months on the International Space Station, and evaluated whether the suppression of bone resorption by the bisphosphonate, alendronate (ALN), can reduce the risk. A total of 17 astronauts were included into the analysis: exercise using the advanced resistive exercise device (ARED) plus weekly oral 70 mg alendronate (ARED+ALN group, n = 7) was compared to resistive exercise alone (ARED group, n = 10). Urine volume decreased in both groups during spaceflight but recovered after return. The ARED group showed increased urinary calcium excretion from the 15th to 30th day of spaceflight, whereas urinary calcium was slightly decreased in the ARED+ALN group. Urinary N‐terminal telopeptide (NTX) and helical peptide (HP) of type I collagen, as bone resorption markers, were elevated in the ARED group during and until 0 days after spaceflight, while there was no elevation in these parameters in the ARED+ALN group. Urinary oxalate and uric acid excretion tended to be higher in the ARED group than in the ARED+ALN group during spaceflight. These results demonstrate that astronauts on long‐duration spaceflights may be at high risk for the formation of urinary calcium oxalate and calcium phosphate stones through increased urinary excretion of oxalate and uric acid, from degraded type I collagen, as well as of calcium from enhanced bone resorption. Our findings suggest that increased bone resorption during spaceflight, as a risk factor for urinary calculus formation, could be effectively prevented by an inhibitor of bone resorption. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

EDXRF, FTIR, and XRD characterization of low calcium oxalate urinary stones collected from arid area

Low calcium oxalate urinary stones from the kidney, bladder, and ureter have been collected from the arid area (Taif, Saudi Arabia). After careful washing and drying of the collected stones, the samples were converted into a contamination‐free homogenous fine powder with a particles' size smaller than 50 μm. The processed urinary stone powders were studied using attenuated total reflection Fourier transform infrared spectroscopy (ATR‐FTIR), laboratory setup and synchrotron radiation X‐ray diffraction (XRD), and energy‐dispersive X‐ray fluorescence (EDXRF). The activated function groups, quantitative phase analysis, and the semi‐quantitative elemental analysis of the present urinary stones were identified. Seventeen elements were measured in most of the urinary stone samples. The significant elements are Ca, P, S, Cl, Zn, K, Fe, and Cu, whereas other elements were found alternatively in a few number of urinary stone samples. It was recognized that Ca exists with low concentration, which indicates the presence of different calcium phases even with low percentages. In 33% of the urinary stones, the phosphorus (P) was not measured, but there were high concentrations of sulfur (S) and low concentrations of Ca up to 2.15 ± 0.05%. The ATR‐FTIR results indicate that the most compounds of the present urinary stones were urea and cystine combined with low ratios of calcium oxalate and calcium phosphate compounds. The quantitative phase analysis of the XRD of selected samples proves the presence of the cystine, urea, and calcium oxalate phases with different weight percent.

The Case | An unusual cause of tender skin lesion in an end-stage kidney disease patient

A 33-year-old woman initially presented with a calcium oxalate urinary stone at the age of 12, which required several urological procedures. Biochemical testing (increased urinary oxalate and glycolate excretion) suggested primary hyperoxaluria type 1 (PH1), which was confirmed by subsequent genetic testing (heterozygous alanine glyoxylate aminotransferase [AGXT] mutations: c.508G>A, p.G170R; c.33_34insC). She was medically managed with oral potassium citrate (10 mEq 3 times daily), pyridoxine (800 mg daily), and increased fluid intake.

Circadian clock gene BMAL1 reduces urinary calcium oxalate stones formation by regulating NRF2/HO-1 pathway

Calcium oxalate stones are closely related to oxalate metabolism and oxidative stress injury. Normal metabolism homeostasis and tissue repair are often affected by the biological rhythm, which plays an indispensable role in maintaining the homeostasis of the organism. Nuclear factor erythroid 2-related factor/heme oxygenase-1 (NRF2/HO-1) is one pathway related to oxidative stress injury in human body. Normal operation of this pathway is conducive to the resistance against oxidative stress-related injury. This study was mainly aimed to explore whether the rhythm gene “brain and muscle ARNT-like 1” (BMAL1) was involved in regulating oxidative stress-related NRF2/HO-1 pathway to reduce the formation of urinary calcium oxalate stones. In vitro experiment found that the activation of NRF2/HO-1 can significantly reduce the oxalate-induced oxidative damage and urinary calcium oxalate stone formation, and the relative expression of BMAL1 was increased. Then overexpression of circadian gene BMAL1 can activate the NRF2/HO-1 pathway and reduce the oxalate-induced oxidative damage. In the hyperoxaluria animal model, the BMAL1 expression level decreased obviously, and the production of calcium oxalate stones was significantly reduced after activating NRF2/HO-1. Finally, we further verified the BMAL1 expression in blood samples from the patients, and analysis of several single nucleotide polymorphisms showed BMAL1 was related to calcium oxalate stones. Therefore, maintaining normal biorhythms and appropriately intervening related rhythm genes and their downstream antioxidant pathways may play an important role in the prevention and postoperative recurrence of urinary calcium oxalate calculi, which may open up new directions for the treatment of urinary calculi.

Spectroscopic Characterization of Urinary Stones Richening with Calcium Oxalate.

Intact and non-intact urinary stones richening with calcium oxalate were collected and characterized. The elemental analysis, phase quantifications, and function groups were determined by different spectroscopic techniques, namely: energy-dispersive X-ray fluorescence (EDXRF), the synchrotron radiation X-ray diffraction (SR-XRD), and attenuated total reflection Fourier transform infrared (ATR-FTIR). The quantitative analysis of twenty elements was demonstrated in the most of the urinary stones and these elements are: Ca, Na, P, S, Mg, Cl, Zn, K, Ti, Sr, Ni, Co, Fe, Cu, Cd, Br, Pb, Se, I, and Mn. Using the Rietveld method, the diffraction phase quantification was illustrated. The main found phases are calcium oxalate (monohydrate and dihydrate) and hydroxyapatite phase. The FTIR outcomes reveal that the functional groups of O-H, N-H, C=O, and C-O indicate to the calcium oxalate whereas the P-O and O-P-O, and PO43- groups indicate to the calcium phosphates in the hydroxyapatite. A considerable correlations between the oxalate urinary stones and the group of elements were found. These elements are Zn, Sr, Ni, and Fe. These correlations could lead to new therapeutic approaches. Furthermore, the elements of sodium and chlorine have no vital role in the formation of calcium oxalate urinary stones.

Effect of Cucumis melo Seeds and Allopurinol on Litholytic and Renal Histological Profile in Male Rats

Introduction: Kidney stones are the 3rd major health problem affecting the urological system. Industrial chemical ethylene glycol can generate calcium oxalate crystals in kidneys. Allopurinol has been used to treat the hyperuricemia but can be effective against calcium oxalate kidney stones too. Seeds of Cucumis melo were traditionally utilized as antioxidant and diuretic, so can be studied as litholytic agent against stones as well. Aims &amp; Objectives: To assess and compare the litholytic effect of ethanolic extract of Cucumis melo seeds against ethylene glycol induced urolithiasis with allopurinol in rats. Place and Duration of study: This experimental study was conducted in Pharmacology Department of FPGMI, Lahore for the period of 2 months. Material &amp; Methods: Four groups of 10 rats in each group were made. Calcium oxalate urinary stones were induced by 0.75% ethylene glycol for 28 days in male rats. Groups 1&amp;2 served as negative and positive control while experimental groups 3&amp;4 received Allopurinol 50mg/kg and Cucumis melo seed’s ethanolic extract (EECMS) in dose of 400mg/kg from 15th day to 28th day respectively. At the end of study, kidney weight, urinary calcium, oxalate and phosphorus along with histological examination of kidneys were used as measuring criteria of litholytic effect of seeds of Cucumis melo and was compared to allopurinol. Data analysis was performed using SPSS 20.0 &amp; presented in mean±s.d .Post-hoc Tukey’s test and ANOVA were used for comparison between data groups Results: After 13 days of treatment experimental groups Groups 3 (Allopurinol 50mg/kg) and 4 (EECMS 400mg/kg) showed remarkable decreased mean urinary calcium, oxalate, phosphorus levels( mg/dl) and kidney weights(gm) of urinary calcium(10.55±1.53, 8.28±1.42), oxalate (18.3±0.78, 17.58±1.38), phosphorus (4.3±0.85, 3.59±1.49) and reduced kidney weights(1.43±0.22, 1.37±0.29) respectively(p value &lt;0.001) as compared to diseased control group 2. Thus exhibiting Cucumis melo seed’s ethanolic extract has better litholytic role than allopurinol which also proved to be efficacious. Histopathological examination of kidney also showed dissolution of calcium oxalate stones. Conclusion: Seeds of Cucumis melo extract have better litholytic effect on calcium oxalate kidney stones than allopurinol with improvement noted in the renal histological profile.

Serum antioxidant enzyme levels are decreased in patients with urinary calcium oxalate stones.

To compare the serum antioxidant enzyme levels between patients with urinary stone disease and healthy volunteers to determine the effect of cellular oxidative stress on urinary calcium oxalate stones formation.Materials &amp; Methods: A total of 51 patients with proven urinary calcium oxalate stones (female 35.3%, mean age: 49.3 years) and 37 healthy subjects (female 45.9%, mean age: 44.1 years) were included. The serum levels of antioxidant catalase, glutathione peroxidase, superoxide dismutase and lipid peroxidation were measured in serum samples taken from the peripheral venous circulation. Mean serum catalase level of patient group was insignificantly higher than healthy subjects (7.54 mmol- H2O2/mg/sec versus 6.16 mmolH2O2/mg/sec, respectively; P = .06) whereas mean superoxide dismutase level (1.56 U/ml versus 3.86 U/ml, P = .047), glutathione peroxidase level (6.70 U/ml versus 8.19 U/ml, P = .022) and lipid peroxidation level (2.35 nmol/ml versus 3.31 nmol/ml, P = .034) of patient group were significantly lower than healthy subjects. Patients with family history of urinary stone disease had significantly lower mean serumlevels of catalase (P = .037), superoxide dismutase (P = .047) and glutathione peroxidase (P = .01), compared with patients without family history. The findings of this study provide evidence regarding the role of oxidative stress in the development of urinary calcium oxalate stones. Future clinical trials are necessary to elucidate the actual mechanisms of the calcium oxalate stone formation in the environment with increased oxidative stress.

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.

Probiotics for prevention of urinary stones.

Urinary supersaturation is one key determinant of calcium oxalate (CaOx) urinary stone formation, and urinary excretions of oxalate and citrate are two key determinants. Each is influenced by gastrointestinal processes. Open label and randomized placebo studies have examined the effect of oral probiotic preparations on urinary supersaturation and oxalate excretion. Cross sectional studies in humans have studied the association of Oxalobacter formigenes colonization status and urinary oxalate excretion and prevalence of urinary stones. The intestinal microbiome of representative animals adapted to a high oxalate diet has been defined. The fecal content of O. formigenes, the best studied oxalate-degrader, varies depending on stone status. However, trials with probiotics designed to degrade oxalate including those containing O. formigenes, Lactobacillus, and/or Bifidobacterium spp., have been disappointing. Multiple intestinal segments of animals on a high oxalate diet contains diverse communities of microorganisms that can function together to degrade and detoxify a large oxalate load. Although the intestinal microbiome seems likely to play a role to modify gastrointestinal absorption of lithogenic substances and hence urinary stone risk, whether we can develop tools to manipulate it and decrease this kidney stone risk remains to be determined.

Elemental Content of Calcium Oxalate Stones from a Canine Model of Urinary Stone Disease.

One of the most common types of urinary stones formed in humans and some other mammals is composed of calcium oxalate in ordered hydrated crystals. Many studies have reported a range of metals other than calcium in human stones, but few have looked at stones from animal models such as the dog. Therefore, we determined the elemental profile of canine calcium oxalate urinary stones and compared it to reported values from human stones. The content of 19 elements spanning 7-orders of magnitude was quantified in calcium oxalate stones from 53 dogs. The elemental profile of the canine stones was highly overlapping with human stones, indicating similar inorganic composition. Correlation and cluster analysis was then performed on the elemental profile from canine stones to evaluate associations between the elements and test for potential subgrouping based on elemental content. No correlations were observed with the most abundant metal calcium. However, magnesium and sulfur content correlated with the mineral hydration form, while phosphorous and zinc content correlated with the neuter status of the dog. Inter-elemental correlation analysis indicated strong associations between barium, phosphorous, and zinc content. Additionally, cluster analysis revealed subgroups within the stones that were also based primarily on barium, phosphorous, and zinc. These data support the use of the dog as a model to study the effects of trace metal homeostasis in urinary stone disease.

E142 Application of thermogravimetric analysis (TGA) to the characterization of calcium oxalate and calcium phosphate urinary stones

E142 Application of thermogravimetric analysis (TGA) to the characterization of calcium oxalate and calcium phosphate urinary stones

Dielectric Behavior of Calcium Oxalate Monohydrate Urinary Stone

Calcium oxalate is the most significant component of urinary stones, usually in its monohydrate form. The mechanisms for the formation of calcium oxalate urinary stones are still not understood, though it is thought that organic macromolecules play a significant role. Calcium oxalate monohydrate (COM) urinary stone was subjected to dielectric studies in order to understand the formation and growth of the renal stones in vivo and use them to help in the treatment procedures for more effective stone fragmentation. The chemical composition and the crystalline nature were verified using Fourier Transform Infrared spectroscopy, X-ray diffraction and thermal analysis. The dielectric parameters for the COM renal stone namely, capacitance, dielectric loss coefficient, impedance, and resistance were measured at room temperature and hence the dielectric constant and the alternating current conductivity were calculated in the frequency range 200 Hz to 5 MHz. The measured values and the dielectric constant showed systematic variations up to 10 kHz. The alternating current conductivity was almost constant up to 2.0 kHz and then showed systematic increase at around 100 kHz and reaches a maximum value at around 5 MHz. The results may be used in further studies of renal stones about their formation and growth.

Effect of Costus igneus stem extract on calcium oxalate urolithiasis in albino rats

The effects of aqueous and ethanolic extracts of Costus igneus (stem) and isolated compounds lupeol and stigmasterol on calcium oxalate urolithiasis have been studied in male albino Wistar rats. Ethylene glycol feeding resulted in hyperoxaluria as well as increased renal excretion of calcium and oxalate. The increased deposition of stone-forming constituents in the urine, serum, and kidney homogenate of urolithic rats was significantly (p < 0.05) lowered by treatment using aqueous and ethanolic extracts of C. igneus (stem), and isolated compounds lupeol and stigmasterol. The calcium oxalate crystal deposition in the kidney was significantly greater in ethylene glycol-induced urolithic rats. After administration of aqueous and ethanolic extract of C. igneus, the deposition of calcium and oxalate was significantly lowered. Treatment with lupeol and stigmasterol significantly reduced the deposition of calcium and oxalate in the kidney, and also in the blood serum; the lipid profile serum total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL) and high-density lipoprotein (HDL) levels at 50 and 100 mg/kg were significantly (p < 0.05) lowered in urolithiatic rats. From this study, we conclude that both the treatments with aqueous and ethanolic extract of C. igneus (stem) and isolated compounds lupeol and stigmasterol had an inhibitory effect on calcium oxalate urinary stone. Lupeol and stigmasterol were identified from the stem of C. igneus by high-performance thin layer chromatography technique. The isolated compounds were confirmed by Fourier transform infrared (FTIR) and (13)C NMR spectra.

Antilithic effects of extracts from Urtica dentata hand on calcium oxalate urinary stones in rats

This study examined the potential antilithic effects of a traditional Chinese medicine Urtica dentata Hand (UDH) in experimental rats and screened the optimal extract of UDH as a possible therapeutic agent for kidney stones. The rat model of urinary calcium oxalate stones was induced by intragastric (i.g.) administration of 2 mL of 1.25% ethylene glycol (EG) and 1% ammonium chloride (AC) for 28 days and was confirmed by Color Doppler ultrasound imaging. The rats in different experimental groups were then intragastrically given petroleum ether extract (PEE), N-butanol extract (NBE), aqueous extract (AqE) of UDH, Jieshitong (positive control drug), and saline, respectively. Treatment with NBE significantly reduced the elevated levels of urinary calcium, uric acid, phosphate, as well as increased urinary output. Accordingly, the increased calcium, oxalate levels and the number of calcium oxalate crystals deposits were remarkably reverted in the renal tissue of NBE-treated rats. In addition, NBE also prevented the impairment of renal function to decrease the contents of blood urea nitrogen (BUN) and creatinine. Taken together, these data suggest that NBE of UDH has a beneficial effect on calcium oxalate urinary stones in rats by flushing the stones out and protecting renal function.

Assessment of Lithogenic Risk in Children Based on a Morning Spot Urine Sample

The Bonn Risk Index has been used to evaluate the risk of urinary calcium oxalate stone formation. According to the original method, risk should be determined based on 24-hour urine collection. We studied whether the Bonn Risk Index could be measured in spot urine samples and which part of the day is most suitable for this purpose. We collected total and fractionated 24-hour urine (in a 6-hour nocturnal portion and 9 consecutive 2-hour diurnal samples) in 42 children and adolescents with calcium oxalate urolithiasis and 46 controls. Bonn Risk Index values determined from each of the urine fractions were compared to those obtained from related 24-hour urine collections. Both groups exhibited similar circadian patterns of Bonn Risk Index values. Median Bonn Risk Index for the nighttime portion of urine in the stone group was 1.4 times higher than that obtained from the total 24-hour urine. The morning hours between 08:00 and 10:00 showed the peak lithogenic risk, and this fraction had the highest sensitivity and selectivity regarding discrimination between stone formers and healthy subjects. The afternoon hours demonstrated lower and less fluctuating crystallization risk. Despite diurnal fluctuations in Bonn Risk Index, there was still a well-defined cutoff between the groups. Bonn Risk Index determined from urine samples collected between 08:00 and 10:00 appears optimal in separating stone formers from healthy subjects, and appears as useful as the value determined from 24-hour urine collection. Investigation of this diurnal sample simplifies diagnosis in pediatric stone disease without loss of clinical information.

Bonn Risk Index Based Micromethod for Assessing Risk of Urinary Calcium Oxalate Stone Formation

The Bonn Risk Index has been used to evaluate the risk of urinary calcium oxalate stone formation. According to the original method, risk should be determined based on a 200 ml urine sample taken from a 24-hour collection. We evaluated whether the Bonn Risk Index can also be effectively determined in small urine samples. We studied 190 children and adolescents with nocturia and calcium oxalate urolithiasis. Initially Bonn Risk Index was determined according to the original method of Laube. Subsequently Bonn Risk Index was calculated using a computer program controlling a specially designed system to define the time point of induced crystallization based on consecutive urine samples of 1.5, 2.0 and 3.0 ml. No significant differences were found in Bonn Risk Index between values obtained from 200 ml samples and those based on the micromethod with urine samples of 2 and 3 ml. Assessment of risk of urinary calcium oxalate stone formation with Bonn Risk Index in small urine volumes, based on prototype equipment controlled by specialized computer software, is comparable to the original method. This finding facilitates the procedure and improves Bonn Risk Index determination in children.