Effect of antibiotic treatment on Oxalobacter formigenes colonization of the gut microbiome and urinary oxalate excretion.

The incidence of kidney stones is increasing in the US population. Oxalate, a major factor for stone formation, is degraded by gut bacteria reducing its intestinal absorption. Intestinal O. formigenes colonization has been associated with a lower risk for recurrent kidney stones in humans. In the current study, we used a clinical trial of the eradication of Helicobacter pylori to assess the effects of an antibiotic course on O. formigenes colonization, urine electrolytes, and the composition of the intestinal microbiome. Of 69 healthy adult subjects recruited, 19 received antibiotics for H. pylori eradication, while 46 were followed as controls. Serial fecal samples were examined for O. formigenes presence and microbiota characteristics. Urine, collected serially fasting and following a standard meal, was tested for oxalate and electrolyte concentrations. O. formigenes prevalence was 50%. Colonization was significantly and persistently suppressed in antibiotic-exposed subjects but remained stable in controls. Urinary pH increased after antibiotics, but urinary oxalate did not differ between the control and treatment groups. In subjects not on antibiotics, the O. formigenes-positive samples had higher alpha-diversity and significantly differed in Beta-diversity from the O. formigenes-negative samples. Specific taxa varied in abundance in relation to urinary oxalate levels. These studies identified significant antibiotic effects on O. formigenes colonization and urinary electrolytes and showed that overall microbiome structure differed in subjects according to O. formigenes presence. Identifying a consortium of bacterial taxa associated with urinary oxalate may provide clues for the primary prevention of kidney stones in healthy adults.

Study of risk factor of urinary calculi according to the association between stone composition with urine component.

Urolithiasis is a common urinary disease with high recurrence. The risk factor for the recurrence of calculi is not very clear. The object of the present study was to evaluate the association between calculi composition and urine component and analyse the risk factor for the recurrence of urolithiasis. In this study, a total of 223 patients with calculi and healthy control were enrolled, and the components of the calculi and urina sanguinis collected before surgery were analysed. Of the 223 patients, 157 were males and 66 were females. According to the stone composition, the case group was subdivided into three groups. 129 patients had single calcium oxalate stones, 72 had calcium oxalate stones mixed with other stones and 22 had other type of stones excluding calcium oxalate stones. Urine biochemicals were analysed and the associations were found between the chemicals in each group. Multivariate logistic analysis demonstrated that reduced urinary magnesium and uric oxalic acid were independent risk factors when comparing all cases with normal controls. Only decreased urinary magnesium was found to be a risk factor comparing the single calcium oxalate group with normal control group. Low level of urinary magnesium and uric oxalic acid were found to be risk factors comparing the mixed calcium oxalate group with normal control group. No risk factor was found comparing the other stone group with normal control group. In conclusion, there were clear relationships between stone components and urine chemicals. Urine chemicals might be risk factors to predicate the occurrence of urolithiasis.

End Points for Clinical Trials in Primary Hyperoxaluria.

Patients with primary hyperoxaluria experience kidney stones from a young age and can develop progressive oxalate nephropathy. Progression to kidney failure often develops over a number of years, and is associated with systemic oxalosis, intensive dialysis, and often combined kidney and liver transplantation. There are no therapies approved by the Food and Drug Association. Thus, the Kidney Health Initiative, in partnership with the Oxalosis and Hyperoxaluria Foundation, initiated a project to identify end points for clinical trials. A workgroup of physicians, scientists, patients with primary hyperoxaluria, industry, and United States regulators critically examined the published literature for clinical outcomes and potential surrogate end points that could be used to evaluate new treatments. Kidney stones, change in eGFR, urine oxalate, and plasma oxalate were the strongest candidate end points. Kidney stones affect how patients with primary hyperoxaluria feel and function, but standards for measurement and monitoring are lacking. Primary hyperoxaluria registry data suggest that eGFR decline in most patients is gradual, but can be unpredictable. Epidemiologic data show a strong relationship between urine oxalate and long-term kidney function loss. Urine oxalate is reasonably likely to predict clinical benefit, due to its causal role in stone formation and kidney damage in CKD stages 1-3a, and plasma oxalate is likely associated with risk of systemic oxalosis in CKD 3b-5. Change in slope of eGFR could be considered the equivalent of a clinically meaningful end point in support of traditional approval. A substantial change in urine oxalate as a surrogate end point could support traditional approval in patients with primary hyperoxaluria type 1 and CKD stages 1-3a. A substantial change in markedly elevated plasma oxalate could support accelerated approval in patients with primary hyperoxaluria and CKD stages 3b-5. Primary hyperoxaluria type 1 accounts for the preponderance of available data, thus heavily influences the conclusions. Addressing gaps in data will further facilitate testing of promising new treatments, accelerating improved outcomes for patients with primary hyperoxaluria.

Graphite/Ag/AgCl nanocomposite as a new and highly efficient electrocatalyst for selective electroxidation of oxalic acid and its assay in real samples.

Herein, graphite/Ag/AgCl nanocomposite is introduced as a new electrocatalyst material for the electrocatalytic oxidation of oxalic acid. Graphite/Ag/AgCl was synthesized by electroless deposition of nano-sized metallic silver and then silver chloride on graphite powder. The material obtained was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Energy-dispersive X-ray spectroscopy. The nanocomposite was mixed with n-eicosane as binder and used as carbon paste electrode for electrocatalytic oxidation of oxalic acid (OA). The graphite/Ag/AgCl nanocomposite electrode showed good catalytic activity for the electroxidation of oxalic acid in H3PO4 solution (0.05 mol L-1), leading to a distinct decrease in anodic overpotential (100 mV) and a substantial increase in anodic peak current (about 10 times), in comparison with the unmodified carbon paste electrode. Using the developed nanocomposite electrode and differential pulse voltammetry method, it became possible to determine oxalic acid in the concentration range of 0.01-0.75 mmol L-1 with detection limit of 3.7 × 10-6 mol L-1. The electrode showed very high sensitivity of 1341.3 µA mM-1 cm-2 which is remarkably better than the previously reported oxalic acid sensors. Thanks to high sensitivity and good selectivity of the electrode, the proposed method was successfully applied for the determination of OA in human urine and spinach samples. The satisfactory results obtained, confirmed the applicability of this sensor in the practical analysis.

Characterization of renal NaCl and oxalate transport in Slc26a6-/- mice.

The apical membrane Cl-/oxalate exchanger SLC26A6 has been demonstrated to play a role in proximal tubule NaCl transport based on studies in microperfused tubules. The present study is directed at characterizing the role of SLC26A6 in NaCl homeostasis in vivo under physiological conditions. Free-flow micropuncture studies revealed that volume and Cl- absorption were similar in surface proximal tubules of wild-type and Slc26a6-/- mice. Moreover, the increments in urine flow rate and sodium excretion following thiazide and furosemide infusion were identical in wild-type and Slc26a6-/- mice, indicating no difference in NaCl delivery out of the proximal tubule. The absence of an effect of deletion of SLC26A6 on NaCl homeostasis was further supported by the absence of lower blood pressure in Slc26a6-/- compared with wild-type mice on normal or low-salt diets. Moreover, raising plasma and urine oxalate by feeding mice a diet enriched in soluble oxalate did not affect mean blood pressure. In contrast to the lack of effect of SLC26A6 deletion on NaCl homeostasis, fractional excretion of oxalate was reduced from 1.6 in wild-type mice to 0.7 in Slc26a6-/- mice. We conclude that, although SLC26A6 is dispensable for renal NaCl homeostasis, it is required for net renal secretion of oxalate.

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

PURPOSE: A 24-h urine metabolic profile (24-UMP) is an integral part of nephrolithiasis work-up. We aimed to explore whether it can be waived under certain circumstances. MATERIALS AND METHODS: We reviewed our prospective registry database of patients seen at our outpatient clinic for nephrolithiasis between the years 2010 and 2017. Data included: gender, age at first stone, body mass index (BMI), self-reported comorbidities and family history of nephrolithiasis. A 24-UMP was obtained from each patient under random diet. The following were recorded: urine volume, urinary levels of sodium, calcium, uric acid, oxalate and citrate. Presence of at least one comorbidity (i.e., hypertension/diabetes/hyperlipidemia) was defined as "associated comorbidities" (AC). Their absence was defined as "no comorbidities" (NC). Subjects were divided into two subgroups: first-time and recurrent stone formers, which were further divided into two subgroups: 1st + AC; 1st + NC; recurrent + AC; recurrent + NC. 24-UMPs have been compared between the four groups. RESULTS: Four hundred and fifty-seven patients were included in the study. In the AC groups, patients demonstrated higher BMI levels (p = 0.001), and were statistically significantly obese (BMI > 30, p = 0.001) and older at first stone event (p = 0.001). First formers, either with AC or NC were more likely to have low urine volume (LUV) compared with recurrent formers (72.5 vs. 59.5%, p = 0.005). In the remaining metabolic abnormalities, no such differences were observed. CONCLUSIONS: First-time stone formers, either with or without AC are likely to demonstrate LUV as their primary metabolic abnormality in 24-UMP. Therefore, 24-UMP may be postponed until recurrent stone event.

Hydroxyproline Metabolism and Oxalate Synthesis in Primary Hyperoxaluria.

Background Endogenous oxalate synthesis contributes to calcium oxalate stone disease and is markedly increased in the inherited primary hyperoxaluria (PH) disorders. The incomplete knowledge regarding oxalate synthesis complicates discovery of new treatments. Hydroxyproline (Hyp) metabolism results in the formation of oxalate and glycolate. However, the relative contribution of Hyp metabolism to endogenous oxalate and glycolate synthesis is not known.Methods To define this contribution, we performed primed, continuous, intravenous infusions of the stable isotope [15N,13C5]-Hyp in nine healthy subjects and 19 individuals with PH and quantified the levels of urinary 13C2-oxalate and 13C2-glycolate formed using ion chromatography coupled to mass detection.Results The total urinary oxalate-to-creatinine ratio during the infusion was 73.1, 70.8, 47.0, and 10.6 mg oxalate/g creatinine in subjects with PH1, PH2, and PH3 and controls, respectively. Hyp metabolism accounted for 12.8, 32.9, and 14.8 mg oxalate/g creatinine in subjects with PH1, PH2, and PH3, respectively, compared with 1.6 mg oxalate/g creatinine in controls. The contribution of Hyp to urinary oxalate was 15% in controls and 18%, 47%, and 33% in subjects with PH1, PH2, and PH3, respectively. The contribution of Hyp to urinary glycolate was 57% in controls, 30% in subjects with PH1, and <13% in subjects with PH2 or PH3.Conclusions Hyp metabolism differs among PH types and is a major source of oxalate synthesis in individuals with PH2 and PH3. In patients with PH1, who have the highest urinary excretion of oxalate, the major sources of oxalate remain to be identified.

A combined liquid chromatography tandem mass spectrometry assay for the quantification of urinary oxalate and citrate in patients with nephrolithiasis.

Background Analysis of citrate and oxalate in a 24-h urine sample is important in the screening and monitoring of patients with nephrolithiasis. To streamline the analytical process, it was decided to combine oxalate and citrate and analyse them simultaneously in the same assay. Objective A highly sensitive and specific assay for analysis of urine citrate and oxalate was developed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with a simple weak anion exchange solid phase extraction (WAX SPE) clean-up procedure. Method Premixed calibrator/acidified urine (50 µL) was combined with mixed internal standard (13C2 oxalate/citrate-d4) and 5% v/v formic acid in water and passed through a Waters WAX SPE plate. After clean-up steps, the plate was eluted with 5% NH3 in methanol, the eluent was dried down and re-constituted with 100 µL distilled water. Separation was then performed on an HSS T3 2.1 × 50 mm column (Waters, Manchester, UK), flow rate of 0.5 mL/min using a gradient of aqueous and organic mobile phases. We detected multiple reaction monitoring transitions m/z citrate 191.1>110.9, citrate IS 195.1>112.9, oxalate 88.9>60.85, oxalate IS 90.9>61.9 using a Waters TQD in electrospray-negative mode. Results Oxalate and 13C2 oxalate were eluted at 0.29 min; citrate and citrate-d4 were eluted at 0.52 min. Mean recovery was 100% for oxalate and 103% for citrate; lower limit of quantification of oxalate was 60 µmol/L and 50 µmol/L for citrate. Oxalate was linear up to 1388 µmol/L; citrate was linear up to 4762.5 µmol/L. Oxalate was found to be affected by ion suppression (matrix effect: -23 to +65%) but was compensated for by the internal standard used in all cases. The coefficient of variation of the assay in urine for oxalate was <7% for oxalate and 5% for citrate. Discussion We have developed a rapid assay for LC-MS/MS measurement of urinary oxalate and citrate in a routine clinical laboratory. It is simple, reproducible and easy to perform.

Oxalic acid quantification in mouse urine and primary mouse hepatocyte cell culture samples by ion exclusion chromatography-mass spectrometry.

Due to medical relevance and a direct correlation with some diseases, accurate quantification of oxalic acid in different complex matrices is required. Effective chromatographic separation of this strong carboxylic acid was achieved by ion exclusion chromatography (IELC). Sensitive and selective detection was carried out by means of electrospray ionization-tandem mass spectrometry. Furthermore, it was shown that the isobaric interference of lactic acid is chromatographically resolved. Structurally similar compounds like glyoxylic acid and glycolic acid were baseline separated as well. The application of stable isotope dilution analysis with 13C2 oxalic acid facilitated precise quantification. The developed method was validated with a reference oxalate sample of human urine diluted to a range of 10-500µM. Finally, the applicability of this method was demonstrated on complex matrices, like mouse urine and supernatants of primary mouse hepatocyte cell cultures.

The safety and pharmacokinetics of high dose intravenous ascorbic acid synergy with modulated electrohyperthermia in Chinese patients with stage III-IV non-small cell lung cancer.

Ascorbic acid (AA) infusion and modulated electrohyperthermia (mEHT) are widely used by integrative cancer practitioners for many years. However, there are no safety and pharmacokinetics data in Chinese cancer patients. We carried out a clinical trial to evaluate the safety and pharmacokinetics of those methods in patients with stage III-IV non-small cell lung cancer (NSCLC). Blood ascorbic acid in the fasting state was obtained from 35 NSCLC patients; selecting from them 15 patients with stage III-IV entered the phase I study. They were randomized allocated into 3 groups, and received doses 1.0, 1.2, 1.5g/kg AA infusions. Participants in the first group received intravenous AA (IVAA) when mEHT was finished, in the second group IVAA was administered simultaneously with mEHT and in the third group IVAA was applied first, and followed with mEHT. Pharmacokinetic profiles were obtained when they received solely IVAA and when IVAA in combination with mEHT. The process was applied 3 times a week (every other day, weekend days off) for 4weeks. We found that fasting plasma AA levels were significantly correlated with stage of the disease. Peak concentration of AA was significantly higher in the simultaneous treatments than in other combinations with mEHT or in solely IVAA-managed groups. IVAA synergy with simultaneous mEHT is safe and the concomitant application significantly increases the plasma AA level for NSCLC patients.

Easy-to-use equations for the estimation of urine relative saturation in the assessment of risk of recurrence in urinary stones formers.

It is a fact that recurrence of urinary stones is a common medical problem. One of the key factors used in determining the risk of urinary stone-formation is the urine relative saturation in the major constituents of lithiasis. Nomograms were developed in the 1970's to estimate the relative saturation of urine. We present here easy-to-use mathematical equations derived from these nomograms. These equations can be integrated directly in the LIS of any laboratories, and can be used as a tool in the treatment and prevention of recurrent stone-formation.

A randomised Phase I/II trial to evaluate the efficacy and safety of orally administered Oxalobacter formigenes to treat primary hyperoxaluria.

BACKGROUND: Primary hyperoxaluria (PH) is a rare, genetic disorder which involves the overproduction of endogenous oxalate, leading to hyperoxaluria, recurrent urolithiasis and/or progressive nephrocalcinosis and eventually resulting in kidney failure and systemic oxalosis. The aim of this trial was to investigate whether treatment involving an oxalate-metabolising bacterium (Oxalobacter formigenes) could reduce urinary oxalate excretion in PH patients. METHODS: The efficacy and safety of O. formigenes (Oxabact® OC5; OxThera AB, Stockholm, Sweden) was evaluated in a randomised, placebo-controlled, double-blind study for 8 weeks. The primary objective was reduction in urinary oxalate excretion (Uox). Secondary objectives included faecal O. formigenes count and decrease in plasma oxalate concentration (Pox). RESULTS: Twenty-eight patients randomised 1:1 to the treatment group (OC5) or the placebo group completed the study. After 8 weeks of treatment, there was no significant difference in the change in Uox (mmol/24 h/1.73 m2) between the groups (OC5: +0.042, placebo: -0.140). Post-hoc analysis showed a statistically significant increase in Uox per urinary creatinine excretion in the OC5 group (OC5: +5.41, placebo: -15.96; p = 0.030). Change in Pox from baseline was not significantly different between groups (p = 0.438). The O. formigenes cell count was significantly increased in OC5-treated patients (p < 0.001) versus placebo. The treatment response to O. formigenes was related to individual stage of kidney deterioration, and Pox was directly correlated to kidney function, even for early-stage patients (chronic kidney disease stage 1). No safety issues were observed. CONCLUSIONS: Treatment with OC5 did not significantly reduce Uox or Pox over 8 weeks of treatment. The treatment was well tolerated and successfully delivered to the gastrointestinal tract.

Dietary Protein and Potassium, Diet-Dependent Net Acid Load, and Risk of Incident Kidney Stones.

BACKGROUND AND OBJECTIVES: Protein and potassium intake and the resulting diet-dependent net acid load may affect kidney stone formation. It is not known whether protein type or net acid load is associated with risk of kidney stones. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We prospectively examined intakes of protein (dairy, nondairy animal, and vegetable), potassium, and animal protein-to-potassium ratio (an estimate of net acid load) and risk of incident kidney stones in the Health Professionals Follow-Up Study (n=42,919), the Nurses' Health Study I (n=60,128), and the Nurses' Health Study II (n=90,629). Multivariable models were adjusted for age, body mass index, diet, and other factors. We also analyzed cross-sectional associations with 24-hour urine (n=6129). RESULTS: During 3,108,264 person-years of follow-up, there were 6308 incident kidney stones. Dairy protein was associated with lower risk in the Nurses' Health Study II (hazard ratio for highest versus lowest quintile, 0.84; 95% confidence interval, 0.73 to 0.96; P value for trend <0.01). The hazard ratios for nondairy animal protein were 1.15 (95% confidence interval, 0.97 to 1.36; P value for trend =0.04) in the Health Professionals Follow-Up Study and 1.20 (95% confidence interval, 0.99 to 1.46; P value for trend =0.06) in the Nurses' Health Study I. Potassium intake was associated with lower risk in all three cohorts (hazard ratios from 0.44 [95% confidence interval, 0.36 to 0.53] to 0.67 [95% confidence interval, 0.57 to 0.78]; P values for trend <0.001). Animal protein-to-potassium ratio was associated with higher risk (P value for trend =0.004), even after adjustment for animal protein and potassium. Higher dietary potassium was associated with higher urine citrate, pH, and volume (P values for trend <0.002). CONCLUSIONS: Kidney stone risk may vary by protein type. Diets high in potassium or with a relative abundance of potassium compared with animal protein could represent a means of stone prevention.

Bone remodeling markers as lithogenic risk factors in patients with osteopenia-osteoporosis.

PURPOSE: To analyze the presence of phosphocalcic metabolism disorders in patients with osteopenia-osteoporosis without nephrolithiasis with respect to a control group. METHODS: A cross-sectional study was conducted in patients with osteopenia-osteoporosis without nephrolithiasis (n = 67) in lumbar spine or femur and in a control group (n = 61) with no lithiasis or bone disorders. Blood bone markers, phosphocalcic metabolism, fasting urine, 24-h urine lithogenic risk factors, and densitometry were recorded in both groups. SPSS 20.0 was used for statistical analysis. RESULTS: In comparison with the controls, significantly higher blood calcium (9.27 ± 0.36 vs. 9.57 ± 0.38, p = 0.0001), intact parathormone (45.6 ± 14.9 vs. 53.8 ± 18.9, p = 0.008), and alkaline phosphatase (61.9 ± 20.9 vs. 70.74 ± 18.9, p = 0.014) levels were found in patients with osteopenia-osteoporosis. In the 24-h urine test, citrate (1010.7 ± 647.8 vs. 617.6 ± 315.8, p = 0.0001) and oxalate (28.21 ± 17.65 vs. 22.11 ± 16.49, p = 0.045) levels were significantly lower in osteopenia-osteoporosis patients than in controls, with no significant difference in calcium (187.3 ± 106.9 vs. 207.06 ± 98.12, p = 0.27) or uric acid (540.7 ± 186.2 vs. 511.9 ± 167.06, p = 0.35) levels. Patients with osteopenia-osteoporosis had significantly higher levels of lithogenic risk factors associated with bone remodeling, including significantly increased ß-crosslaps and osteocalcin values and higher ß-crosslaps/osteocalcin ratios. CONCLUSION: Patients with osteopenia-osteoporosis without nephrolithiasis showed phosphocalcic metabolism disorders as well as lower urinary citrate and higher ß-crosslaps/osteocalcin and fasting calcium/creatinine ratios, which would increase the risk of nephrolithiasis. Hence, prospective studies are warranted to evaluate the long-term risks.

Herbal medicines for urinary stone treatment. A systematic review.

OBJECTIVE: To analyze the clinical evidence on the efficacy of phytotherapy in the treatment of calculi in the urinary tract. METHODS: To be eligible, full-length articles should include the results of randomized controlled trials enrolling patients affected by urolithiasis, reporting any comparison between an experimental herbal agent versus placebo or any active comparator, aimed at preventing the formation or facilitating the dissolution of calculi in any portion of the urinary tract. Fifteen databases were searched for relevant references. The primary outcomes investigated were (i) the reduction of stone size and/or number and (ii) the urinary excretion rates of calcium, urate, or oxalate. The secondary outcome of the review was the adverse effects (AE) of treatment. Risk of bias (ROB) and quality of the evidence were assessed according to Cochrane and GRADE guidelines. We performed a random-effect meta-analysis. RESULTS: 541 articles were retrieved and 16 studies were finally confirmed as eligible. Multiple Cochrane ROB tool items were rated as having high risk of bias in each analyzed trial report. Pooled analysis of continuous data could be performed for three different comparisons: (i) phytotherapy versus citrate as single agent (ii) phytotherapy versus placebo, (iii) preparation of Didymocarpus pedicellata (DP)--combined with other herbal agents--versus placebo. Results showed that citrate is superior to phytotherapy in significantly decreasing both the size of urinary stones (mean difference: phytotherapy, 0.42 mm higher; 95% CI: 0.23 to 0.6; Z = 4.42, P < 0.0001; I2 = 30%) and the urinary excretion rate of urate (mean difference: 42.32 mg/24h higher, 95% CI: 19.44 to 65.19; Z = 3.63, P = 0.0003; I2 = 96%), assessed after 3 months on-therapy. No significant differences in the excretion rates of urinary calcium or oxalate were found. The DP preparation was superior to placebo in inducing total clearance (risk ratio: 6.19, 95% CI: 2.60 to 14.74; Z = 4.12, P < 0.0001; I2 = 0%) and size reduction (mean difference: DP preparation, 4.93 mm lower; 95% CI: -9.18 to -0.67; Z = 2.27, P = 0.02; I2 = 99%) of renal and ureteral stones after 3 months of therapy. No significant differences in the inter-arm variation of excretion rates of urinary calcium or urate were found as result of the pooled phytotherapy-placebo comparison. Herbal remedies were in general devoid of side effects and in few cases citrate appeared to induce GI disturbances in a higher fraction of patients. Most reports did not provide inferential data concerning AE, and meta-analysis was not feasible. CONCLUSIONS: Citrate is more effective than phytotherapy in decreasing the size of existing calculi in the urinary tract and in decreasing the urinary excretion rate of uric acid. A preparation containing Didymocarpus pedicellata combined with other herbal agents induces stone size reduction and clearance significantly better than placebo. Mayor limitations in the applicability of these results are the low quality of the evidence and the multiple sources of bias assessed in the studies included in the present review.

Use of urinary concentrations in mg/dl in relation to absolute values in 24-hour samples for the evaluation of lithogenic factors in stone forming patients. / Uso de las concentraciones urinarias en mg/dl en relación a los valores absolutos en 24 h para la evaluación de factores litogénicos en pacientes litiásicos.

OBJECTIVE: The aim of this study is to analyze urine concentrations (mg/dl) of different lithogenic factors in a sample of 24 h as a predictor of these changes rather than absolute values depend on the volume of diuresis. METHODS: A total of 131 patients from the North Almeria Health Management Area (Spain) with urinary calstone disease in whom a metabolic study was indicated were included from June 2014 to May 2015. The concentrations of calcium, oxalate, uric acid, citrate and magnesium were measured in the urine, and the calcium/citrate ratio was calculated. The classifications used were: hypercalciuria (>260mg/24h), hyperuricosuria (>750mg/24h), hyperoxaluria (>40mg/24h), hypocitraturia (<320mg/24h) and hypomagnesuria (<35mg/24h). The statistical analysis was performed using SPSS 17.0. RESULTS: A cut-off point of 12.55mg/dl, with a sensitivity of 90% and a specificity of 85% and a relative risk (RR) of 51.2 (13.9-188.4), was estimated for urinary calcium. For oxalate the cut-off point was 1.86mg/dl, with a sensitivity of 91% and a specificity of 84% with an estimated RR of 67.2 (8.3-540.6). As regards the uric acid concentration in urine, a cut-off point of 31.2mg/dl was estimated, with a sensitivity of 85% and a specificity of 70% and a RR of 12 (3.8-37.6). For citrate the cut-off point was 18.8mg/dl, with a sensitivity and specificity of 82% and 74%, respectively, with a RR of 13.7 (4.4- 42.6). The cut-off point for magnesium was 2.26mg/dl with a sensitivity of 95% and specificity of 78%, with a RR of 67.6 (11.4-398.3). CONCLUSION: The determination of urine concentrations, instead of absolute values, depends to a large extent on urine output, appears to be useful when estimating classic metabolic alterations and should be taken into account in the evaluation of patients with urinary stone disease.

Oxalate nephropathy in systemic sclerosis: Case series and review of the literature.

OBJECTIVE: To increase awareness of oxalate nephropathy as a cause of acute kidney injury (AKI) among systemic sclerosis patients with small intestinal dysmotility and malabsorption, and to prompt consideration of dietary modification and early treatment of predisposing causes of oxalate nephropathy in this population. METHODS: Two cases of biopsy-proven oxalate nephropathy were identified among systemic sclerosis patients in the course of direct clinical care. Subsequently, a retrospective search of the Johns Hopkins Pathology databases identified a third patient with systemic sclerosis who developed oxalate nephropathy. RESULTS: Among the three patients with qualifying biopsies, all three had systemic sclerosis with lower gastrointestinal involvement. All three presented with diarrhea, malabsorption, and AKI. In two of the three patients, diarrhea was present for at least 2 years before the development of AKI; in the third, incidental oxalate nephropathy was noted 3 years before she developed AKI and extensive oxalate nephropathy in the setting of a prolonged mycobacterium avium-intracellulare enteritis. In the first case, oxalate crystals were present by urinalysis months before diagnosis by biopsy; in the second, hyperoxaluria was diagnosed by urine collection immediately after; and in the third, oxalate crystals had been noted incidentally on post-transplant renal biopsy 3 years before the development of fulminant oxalate nephropathy. All three patients died within a year after diagnosis. CONCLUSIONS: Patients with systemic sclerosis and bowel dysmotility associated with chronic diarrhea and malabsorption may be at risk for an associated oxalate nephropathy. Regular screening of systemic sclerosis patients with small bowel malabsorption syndromes through routine urinalysis or 24-h urine oxalate collection, should be considered. Further studies defining the prevalence of this complication in systemic sclerosis, the benefit of dietary modification on hyperoxaluria, the effect of treating small intestinal bowel overgrowth with antibiotics, and the effectiveness of probiotics, calcium supplements, or magnesium supplements to prevent hyperoxaluria-associated renal disease in these patients, are warranted.

The importance of calciuria as lithogenic factors in patients with osteopenia/osteoporosis.

PURPOSE: Recurrent kidney stones are associated with bone mineral density loss, altered bone remodeling markers, hypercalciuria and increased in fasting calcium/creatinine ratio. The objective was to determine biochemical alterations in urine in patients with osteopenia/osteoporosis without calcium kidney stones compared with patients with calcium kidney stones. METHODS: This is a cross-sectional study including 142 patients who were divided in two groups: Group 1 (patients with recurrent calcium kidney stones) and Group 2 (patients with osteopenia/osteoporosis in the lumbar spine or hip). Analyses of bone mineral density, calcium-phosphorous and bone metabolism and lithogenic risk factors in fasting urine samples and 24-h urine samples were performed. Statistical analysis was carried out with SPSS 17.0. A p ≤ 0.05 was considered statistically significant. RESULTS: Patients in Group 2 presented greater loss of bone mineral density and more elevated alkaline phosphatase, iPTH, phosphorous and ß-crosslaps levels, as compared to patients in Group 1. However, Group 1 presented greater urine calcium, oxalate and uric acid and a higher proportion of hypocitraturia, hypercalciuria and hyperoxaluria, as compared to Group 2. Multivariate analysis revealed that advanced age and ß-crosslaps levels are risk factors for bone mineral density loss, while low urinary calcium excretion was protective against bone demineralization. CONCLUSION: Patients with osteopenia/osteoporosis without lithiasis present some urinary biochemical alterations. This would explain the lack of lithogenic activity, although low calcium excretion in 24-h urine samples is a protective factor against the loss of bone mineral density.

Electromembrane Extraction of Organic Acid Compounds in Biological Samples Followed by High-Performance Liquid Chromatography.

Electromembrane extraction (EME) coupled with high-performance liquid chromatography was developed for determination of organic compounds including citric, tartaric and oxalic acid in biological samples. Organic compounds moved from aqueous samples, through a thin layer of 1-octanol immobilized in the pores of a porous hand-made polypropylene tube, and into a basic aqueous acceptor solution present inside the lumen of the tube. This new set-up for EME has a future potential such as simple, cheap and fast sample preparation technique for extraction of organic compounds in various complicated matrices. The pH of acceptor phase, extraction time, voltage, ionic strength, temperature and stirring speed were studied and optimized. Optimum conditions were: the pH of acceptor phase, 7; extraction time, 30 min; voltage, 30 V and stirring speed, 500 rpm. At the optimum conditions, the preconcentration factors of 175-200, the limits of detection of 1.9-3.1 µg L(-1) were obtained for the analytes. The developed procedure was then applied to the extraction and determination of organic acid compounds from biological samples.