The utility of methylmalonic acid, methylcitrate acid, and homocysteine in dried blood spots for therapeutic monitoring of three inherited metabolic diseases.

Backgroud: Routine metabolic assessments for methylmalonic acidemia (MMA), propionic acidemia (PA), and homocysteinemia involve detecting metabolites in dried blood spots (DBS) and analyzing specific biomarkers in serum and urine. This study aimed to establish a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous detection of three specific biomarkers (methylmalonic acid, methylcitric acid, and homocysteine) in DBS, as well as to appraise the applicability of these three DBS metabolites in monitoring patients with MMA, PA, and homocysteinemia during follow-up. Methods: A total of 140 healthy controls and 228 participants were enrolled, including 205 patients with MMA, 17 patients with PA, and 6 patients with homocysteinemia. Clinical data and DBS samples were collected during follow-up visits. Results: The reference ranges (25th-95th percentile) for DBS methylmalonic acid, methylcitric acid, and homocysteine were estimated as 0.04-1.02 µmol/L, 0.02-0.27 µmol/L and 1.05-8.22 µmol/L, respectively. Following treatment, some patients achieved normal metabolite concentrations, but the majority still exhibited characteristic biochemical patterns. The concentrations of methylmalonic acid, methylcitric acid, and homocysteine in DBS showed positive correlations with urine methylmalonic acid (r = 0.849, p < 0.001), urine methylcitric acid (r = 0.693, p < 0.001), and serum homocysteine (r = 0.721, p < 0.001) concentrations, respectively. Additionally, higher levels of DBS methylmalonic acid and methylcitric acid may be associated with increased cumulative complication scores. Conclusion: The LC-MS/MS method established in this study reliably detects methylmalonic acid, methylcitric acid, and homocysteine in DBS. These three DBS metabolites can be valuable for monitoring patients with MMA, PA, and homocysteinemia during follow-up. Further investigation is required to determine the significance of these DBS biomarkers in assessing disease burden over time.

Valoración del impacto de la tasa libre de litiasis en los resultados de la evaluación metabólica / Is stone free status really necessary for metabolic evaluation following stone removal procedures?

Objetivo Evaluar si la tasa libre de litiasis afecta a los resultados del estudio metabólico en pacientes con alto riesgo de litiasis recidivante tras tratamiento completo mediante ureteroscopia. Pacientes y métodos Un total de 78 pacientes sometidos a cirugía retrógrada intrarrenal (CRIR) para el tratamiento de litiasis fueron incluidos en este estudio. Cuatro semanas después del tratamiento, los casos se dividieron en dos grupos en base a los resultados de la tomografía computarizada sin contraste (TCSC). Los casos del grupo 1 (n=54) presentaban una tasa libre de litiasis del 100% y los del grupo 2 (n=24) presentaban litiasis residuales en el riñón. Cuatro semanas después de la ureteroscopia flexible (URF) se realizó un análisis completo de orina de 24h a todos los pacientes de ambos grupos, para detectar los factores de riesgo implicados en la litogénesis. Los resultados del estudio metabólico (orina de 24h y suero) se compararon entre los dos grupos. Resultados La evaluación preoperatoria en orina y suero de los factores de riesgo asociados a la formación de cálculos no reveló diferencias estadísticas entre los dos grupos. El análisis comparativo de los factores de riesgo implicados en la formación de la litiasis mediante pruebas de orina de 24h tampoco reveló diferencias estadísticamente significativas entre los resultados preoperatorios y postoperatorios en los casos del grupo 2 con cálculos residuales. Tampoco se observaron diferencias significativas entre las medias de las variables séricas preoperatorias y postoperatorias de ambos grupos. Conclusiones Según nuestros resultados, y dada la similitud de los hallazgos obtenidos en los estudios metabólicos de los casos con y sin litiasis residual, la tasa libre de litiasis puede no constituir un factor imprescindible para la realización del estudio metabólico detallado (suero y orina de 24h) tras las intervenciones endourológicas para la extracción de los cálculos renales. (AU)

Objective To evaluate the impact of stone free status on the outcomes of metabolic evaluation in recurrent stone formers after ureteroscopic stone removal. Patients and methods A total of 78 patients undergoing retrograde intrarenal surgery (RIRS) for renal stones were included and cases were divided into two groups after 4 weeks based on the NCCT findings. While cases in the Group 1 (n=54) was completely stone free, cases in Group 2 (n=24) had residual fragments in the kidney. A full 24-hour urine analysis for relevant stone forming risk factors has been performed after 4 weeks following the fURS procedures in all patients of both groups. Outcomes of metabolic evaluation (24-hour urine and serum) have been comparatively evaluated in both groups. Results Evaluation of the preoperative serum and urine stone forming risk factors revelaed no statistical difference in both groups. Comparative evaluation of the 24-hour urinary stone forming risk factors also revealed no statistically significant difference between preoperative and postoperative findings in cases of Group 2 with residual stones. Last but not least, no significant difference was observed between the mean preoperative and postoperative serum variables between two groups. Conclusions Our results show that in the light of the similar metabolic evaluation outcomes obtained in cases with and without residual fragments, ‘stone free status’ may not be an essential factor to perform a detailed metabolic evaluation (24-hour urine analysis and serum parameters) after endourological stone removal procedures. (AU)

Patient compliance for metabolic evaluation and medical treatment (CoMET) in calcium-oxalate stone patients: prospective study by EULIS eCORE study group.

PURPOSE: In this study, we aimed to identify the compliance rates of calcium-oxalate stone patients for metabolic evaluation, diet and medical treatment and also determine the factors that are associated with poor compliance rates. METHODS: This study was conducted by the EULIS eCORE working group prospectively. In the initial visit, demographic and stone-related characteristics were recorded. Patients were suggested metabolic evaluation, dietary advices and medical treatment. Follow-up visit was performed after 3 months and compliance rates were recorded. Logistic regression analysis was performed to determine factors associated with poor compliance to metabolic evaluation, diet and medical treatment. RESULTS: Data of 346 patients from nine centers were analyzed. Compliance rates were 71.7%, 65.3%, and 63.7% for metabolic evaluation, diet, and medical treatment, respectively. In multivariate analysis, level of education (p = 0.003), history of emergency department visit (p = 0.04), number of stone surgeries (p = 0.03), patient care in dedicated stone clinic (p = 0.03), and history of shock wave lithotripsy (p = 0.005) were detected as independent predictors of compliance to metabolic analysis. Level of education (p < 0.001) and history of emergency department visit (p = 0.01) were detected as independent predictors of patient compliance to diet. Number of stone episodes (p = 0.03), family history of stones (p = 0.02), and polypharmacy (p < 0.001) were detected as independent predictors of patient compliance to medical treatment. CONCLUSIONS: Patient compliance to metabolic evaluation, diet, and medical therapy is important for successful management of urolithiasis. Dietary advices and medications should be personalized by taking in to account the factors associated with poor compliance.

Serum and 24-hour urinary tests cost-effectiveness in stone formers.

OBJECTIVE: To assess the routine serum and 24-hour urine tests proficiency in diagnosing the baseline metabolic abnormality of kidney stone formers. METHODS: This study analyzes the routine serum and 24-hour urine tests proficiency in diagnosing the baseline metabolic abnormality of kidney stone formers. The sensitivity and specificity, false positive, and negative results of the tests are extracted from diagnostic kits used in the laboratories of the target community. To accurately infer the results, a simulation based on 1000 people was used through 22 standard laboratory tests (Additional File 2), including calcium, oxalate, phosphate, uric acid, sulfate, potassium, sodium, citrate, and magnesium in 24-hour urine; and calcium, creatinine, Vit D, uric acid, and intact parathyroid hormone (PTH) in serum. The incremental cost-effectiveness ratio (ICER) was calculated and compared for each diagnostic test versus other diagnostic tests according to the incremental cost required for correct diagnoses of stone causes. RESULTS: Urinary uric acid, citrate, and serum potassium constitute the cost-effectiveness boundary curve in this study. This means that other diagnostic tests are not cost-effective compared to these three tests in terms of indexing at least one item of cost and effectiveness. The ICER index for each correct diagnosis with the urinary uric acid test was $ 1.25 per diagnosis, the most cost-effective test compared to serum potassium and urinary citrate. CONCLUSION: The simplified blood and 24-hour urine metabolic evaluation, including urinary uric acid, citrate, and serum potassium, constitute the cost-effectiveness boundary curve. The most cost-effective test was urinary uric acid measurement.

Is stone free status really necessary for metabolic evaluation following stone removal procedures?

OBJECTIVE: To evaluate the impact of stone free status on the outcomes of metabolic evaluation in recurrent stone formers after ureteroscopic stone removal. PATIENTS AND METHODS: A total of 78 patients undergoing retrograde intrarenal surgery (RIRS) for renal stones were included and cases were divided into two groups after 4 weeks based on the NCCT findings. While cases in the Group 1 (n = 54) was completely stone free, cases in Group 2 (n = 24) had residual fragments in the kidney. A full 24-h urine analysis for relevant stone forming risk factors has been performed after 4 weeks following the fURS procedures in all patients of both groups. Outcomes of metabolic evaluation (24-h urine and serum) have been comparatively evaluated in both groups. RESULTS: Evaluation of the preoperative serum and urine stone forming risk factors revelaed no statistical difference in both groups. Comparative evaluation of the 24-h urinary stone forming risk factors also revealed no statistically significant difference between preoperative and postoperative findings in cases of Group 2 with residual stones. Last but not least, no significant difference was observed between the mean preoperative and postoperative serum variables between two groups. CONCLUSIONS: Our results show that in the light of the similar metabolic evaluation outcomes obtained in cases with and without residual fragments, 'stone free status' may not be an essential factor to perform a detailed metabolic evaluation (24-h urine analysis and serum parameters) after endourological stone removal procedures.

Use of whole-exome sequencing to identify novel monogenic gene mutations and genotype-phenotype correlations in Chinese Han children with urolithiasis.

The incidence of urolithiasis (UL) in children has been increasing. Although the pathogenesis of pediatric UL is controversial and remains unclear, multiple monogenic causes of UL have been identified. We aim to investigate the prevalence of inherited UL causes and explore the genotype-phenotype correlation in a Chinese pediatric group. In this study, we analyzed the DNA of 82 pediatric UL patients using exome sequencing (ES). The data of metabolic evaluation and genomic sequencing were subsequently analyzed together. We detected 54 genetic mutations in 12 of 30 UL-related genes. A total of 15 detected variants were described as pathogenic mutations, and 12 mutations were considered likely pathogenic. Molecular diagnoses were made in 21 patients with pathogenic or likely pathogenic variants. Six novel mutations that were not previously reported were identified in this cohort. Calcium oxalate stones were detected in 88.9% cases (8/9) with hyperoxaluria-related mutations, while 80% of individuals (4/5) with cystinuria-causing defects were diagnosed with cystine stones. Our study highlights the significant genetic abnormalities in pediatric UL and demonstrates the diagnostic power of ES for screening patients with UL.

International Alliance of Urolithiasis (IAU) guidelines on the metabolic evaluation and medical management of urolithiasis.

The aim of this study was to construct the fourth in a series of guidelines on the treatment of urolithiasis by the International Alliance of Urolithiasis (IAU) that by providing a clinical framework for the metabolic evaluation, prevention, and follow-up of patients with urolithiasis based on the best available published literature. All recommendations were summarized following a systematic review and assessment of the literature in the PubMed database from January 1976 to June 2022. Each generated recommendation was graded using a modified GRADE methodology. Guideline recommendations were developed that addressed the following topics: initial evaluation, metabolic testing, dietary measures, medical management, and follow-up of recurrent stone formers. It was emphasized by the Panel that prevention of new stone formation is as important as the surgical removal of the stones. Although general preventive measures may be effective in reducing stone recurrence rates in some patients, specific medical and dietary management should be well considered and eventually applied in an individualized manner based on the outcomes of metabolic work-up, stone analysis and some certain patient related factors. A detailed follow-up of each case is essential depending on the metabolic activity of each individual patient.

Nephrolithiasis management and outcomes in pediatric patients with limited mobility.

INTRODUCTION AND OBJECTIVES: Pediatric patients with limited lower extremity mobility may be at increased risk of developing nephrolithiasis due to bone mineral metabolic derangements. This study sought to assess whether nephrolithiasis management and related outcomes differ between ambulatory versus non-ambulatory pediatric patients. METHODS: This was a retrospective review of ambulatory and non-ambulatory pediatric patients with nephrolithiasis from 2010 to 2021 from a single tertiary care center. Demographics, surgical history, stone compositions, and 24-h urine data were reviewed. Adjusted logistic and linear regression models were utilized to assess whether mobility status was associated with nephrolithiasis-related management and outcomes, including: age at first stone; requiring surgical intervention for stones; number of surgeries; stone compositions; urine culture results; and completion of 24-h urine studies. RESULTS: Among 339 pediatric patients with nephrolithiasis, 67 (19.8%) were non-ambulatory. In adjusted analyses, non-ambulatory patients had 3.24 times greater odds of requiring surgical intervention for stones (95% CI: 1.93-6.84; p < 0.0001); among those who required surgery, non-ambulatory patients required an average of 0.82 more surgical interventions (95% CI: 0.35-1.30; p = 0.0008) than ambulatory patients. Additionally, non-ambulatory patients had 5.28 times greater odds of having a positive urine culture at the time of surgery (95% CI: 2.35-14.08; p = 0.0001) and were significantly less likely to undergo 24-h urine studies (OR: 0.35; 95% CI: 0.15-0.83; p = 0.02). Stone composition significantly varied by mobility status, with non-ambulatory patients being significantly more likely to form calcium apatite (OR: 5.1; 95% CI: 2.18-11.93; p = 0.0002) or struvite (OR 3.72; 95% CI: 1.18-11.74; p = 0.03) stones, and significantly less likely to form calcium oxalate stones (OR: 0.19; 95 CI: 0.08-0.47; p = 0.0003). Among all patients, age at first stone occurred at a median age of 13.4 years (IQR: 8.2-16.4) and did not significantly differ by mobility status (p = 0.92). CONCLUSIONS: Patients with limited mobility required surgery for nephrolithiasis at significantly higher rates and had different stone compositions than ambulatory patients. Obtaining a 24-h urine study in patients with comorbidities affecting ambulation was uncommon, compared to ambulatory patients. Similarly to ambulatory patients, pediatric patients with limited mobility who develop nephrolithiasis tend to first present with stones in early adolescence.

Attitudes of urologists on metabolic evaluation for urolithiasis: outcomes of a global survey from 57 countries.

Although stone disease is an important health problem with high incidence and recurrence rates, it is a preventable disease. Attitudes and practices of urologists regarding the prevention of recurrence continue to be a subject of debate. In this context, an online survey study was conducted involving 305 urologists from 57 different countries. The first 7 questions collected demographic data about the urologists and the remaining 23 questions were about the recurrence and metabolic evaluation, medical treatment, and follow-up of urinary stone disease. Most urologists (85.2%) thought that metabolic examination was important. Approximately one-third of the participants (34.1%) performed 24-hour urine analysis and stone analysis was ordered by 87.5% of the urologists. Metabolic analysis was performed for all patients by 14.7% of the participants. For pediatric patients this rate was 68.5%, and for adults with recurrence the rate was 81.6%. Reasons cited by the urologists for not performing metabolic analysis included not feeling confident doing so (18.3%), having limited facilities in their hospital (26.5%), having an excessive daily workload (31.8%), patient-related factors (27.5%), and referring patients to other departments for metabolic evaluation (20.9%). Although majority of the responding urologists do consider the metabolic analysis as vital important, they seemed not to be willing to perform these tests with the same degree of enthusiasm in their daily practice. Our results show that urologists need support in performing and interpreting 24-hour urine analysis, improving their knowledge levels, and communicating with patients. Urology residency training should focus more on the prevention of urinary stone recurrence in addition to the surgical training.

Acidification of 24-hour urine in urolithiasis risk testing: An obsolete relic?

BACKGROUND: Recommendations on the optimal preservation of 24 h urine for the metabolic work-up in urolithiasis patients are very heterogeneous. In case two such tests with different storage condition recommendations are being analysed, multiple collections would be needed, challenging especially elderly and very young patients. We therefore aimed to evaluate the stability of urine constituents under different storage conditions. MATERIAL AND METHODS: We collected urine samples from ten healthy volunteers and prepared aliquots to be stored either at room temperature or 4 °C. Some aliquots were preserved using hydrochloric acid prior to storage, some thereafter, some using the BD Urine preservation tube and some were not preserved at all. Storage duration was 0, 24, 48 or 72 h. In all samples calcium, magnesium, phosphorus, creatinine, oxalate, citrate and uric acid were measured and compared to the according reference sample. RESULTS: We could not find any significant deviation for any of the analytes and preanalytical treatment conditions compared to the associated reference sample. CONCLUSION: Preservation of 24 h urine for the metabolic evaluation in stone formers might not be necessary for sample storage up to 72 h.

Urolitiasis en Atención Primaria: comparación de un seguimiento sistemático frente a la práctica habitual / Urolithiasis in Primary Care: Comparison of a systematic follow-up versus usual clinical practice

Objetivo: La implantación de acciones clínicas preventivas en Atención Primaria permitiría actuar sobre la alta incidencia de urolitiasis y sus factores de riesgo corregibles. Este estudio piloto comparó un seguimiento sistemático (SS) frente al seguimiento habitual (SH) en términos de viabilidad, seguridad y eficacia clínica. Materiales y métodos: Realizamos un estudio piloto multicéntrico y controlado en 30 pacientes, comparando el SS y el SH. Los pacientes fueron aleatorizados según una lista generada por ordenador. Se definió el «éxito del estudio» como la consecución de los objetivos de viabilidad: tasa de reclutamiento, adherencia, finalización del seguimiento y recursos humanos necesarios. Se recogieron variables clínicas (dolor y fiebre), analíticas (sangre y orina) y de imagen (ecografía y radiografía) a los 10, 45 y 90 días en el grupo de SS y a los 3 meses en el de SH. En el grupo de SS se entregaron recomendaciones dietéticas y analgésicas. Se hizo una comparación clínica preliminar y se registraron las complicaciones en cada grupo. Resultados: Los objetivos de viabilidad se consiguieron como sigue: 94,1% de tasa de reclutamiento, 5,9% de rechazo a la aleatorización, 10 pacientes reclutados al mes, adherencia del 93,1% y 90% de asistencia a la revisión final. Los resultados clínicos no favorecieron significativamente a ninguno de los dos grupos. En el grupo de SH hubo una recidiva. Conclusiones: Se cumplieron los objetivos de viabilidad estudiados excepto los relacionados con los recursos humanos. Los resultados clínicos no favorecieron a ningún grupo ni contraindicaron el desarrollo de un futuro ensayo clínico (AU)

Objective: The implementation of preventive clinical actions in Primary Care would allow to act on the high incidence of urolithiasis and the correctable risk factors. This pilot study compared a systematic follow-up (SFU) versus a regular follow-up (RFU) in terms of feasibility, safety and clinical outcomes. Materials and methods: We conducted a multicentric and controlled pilot study in 30 patients comparing SFU versus RFU. Patients followed allocation concealment by an independent blocked computer-generated list. We defined “success” if feasibility objectives were matched including recruitment rate, follow-up compliance, completion and staff resources. Clinic variables (pain and fever), analytics (blood and urine) and image techniques (echography and radiography) were recorded at 10, 45 and 90 days in SFU and at 3 months in RFU. The SFU group received nutritional and analgesic recommendations. Preliminary clinical outcomes were compared and complications were recorded in each group. Results: The feasibility objectives were matched as follows: 94.1% of recruitment rate, 5.9% refused to participate, 10 patients/month were recruited, 93.1% of follow-up compliance and 90% of completion. No clinical differences were found between groups. There was a recurrence in the RFU group. Conclusions: The feasibility objectives were matched except those related to human resources. Clinical outcomes did not favour any group or contraindicate the development of a future clinical trial (AU)

[Urolithiasis in Primary Care: Comparison of a systematic follow-up versus usual clinical practice]. / Urolitiasis en Atención Primaria: comparación de un seguimiento sistemático frente a la práctica habitual.

OBJECTIVE: The implementation of preventive clinical actions in Primary Care would allow to act on the high incidence of urolithiasis and the correctable risk factors. This pilot study compared a systematic follow-up (SFU) versus a regular follow-up (RFU) in terms of feasibility, safety and clinical outcomes. MATERIALS AND METHODS: We conducted a multicentric and controlled pilot study in 30 patients comparing SFU versus RFU. Patients followed allocation concealment by an independent blocked computer-generated list. We defined "success" if feasibility objectives were matched including recruitment rate, follow-up compliance, completion and staff resources. Clinic variables (pain and fever), analytics (blood and urine) and image techniques (echography and radiography) were recorded at 10, 45 and 90 days in SFU and at 3 months in RFU. The SFU group received nutritional and analgesic recommendations. Preliminary clinical outcomes were compared and complications were recorded in each group. RESULTS: The feasibility objectives were matched as follows: 94.1% of recruitment rate, 5.9% refused to participate, 10 patients/month were recruited, 93.1% of follow-up compliance and 90% of completion. No clinical differences were found between groups. There was a recurrence in the RFU group. CONCLUSIONS: The feasibility objectives were matched except those related to human resources. Clinical outcomes did not favour any group or contraindicate the development of a future clinical trial.

Do Infection-Associated Stone Subtypes Behave the Same Clinically? A Retrospective Bicenter Study.

Introduction and Objectives: Infection-associated renal stones are commonly composed of magnesium-ammonium-phosphate (MAP) and carbonate apatite (CA). The clinical implications of these two different, but closely related stone types, are unknown. We sought to compare the clinical, microbiologic, and metabolic characteristics of patients with MAP and CA stone types. Methods: We retrospectively reviewed the medical records of patients from two centers (one in the United States and one in Israel) who underwent ureteroscopy or percutaneous nephrolithotomy between 2012 and 2020 and identified patients with a predominant stone analysis component of CA or MAP and clinical data supporting an infection stone. We analyzed and compared demographic data, medical history, postoperative fever, stone and urinary microbiology, and 24-hour urine studies. Results: A total of 79 and 75 patients met the inclusion criteria for the MAP and CA cohorts, respectively. No significant difference was found in patient demographics or comorbidities between the MAP and CA cohort. Female predominance was noted in both. Although there were no significant differences in 24-hour urine parameters between the cohorts, hypercalciuria was common in both cohorts (38% and 32% of patients in the MAP and CA cohorts, respectively). Gram-negative bacteria were more common in the MAP stone cultures. Postoperative fever was significantly more common in the MAP cohort (14.7% vs 3.8%, p < 0.016). Conclusions: MAP and CA stone formers share similar demographic characteristics with a clear female predominance. MAP stones patients appear more likely to develop postoperative fever, possibly related to a higher occurrence of gram-negative bacteria in the stone cultures of the MAP cohort. Although there were no significant differences among metabolic parameters, hypercalciuria was noted in approximately a third of the cohort. The clinical significance of this finding is yet to be determined.

Three-channel ion chromatograph for improved metabolic evaluation of urolithiasis.

BACKGROUND: Urolithiasis is a multi-etiological disease resulting from a combination of environmental and genetic factors. One of the most challenging aspects of this disease is its high recurrence rate. For most patients, an in-depth metabolic evaluation may reveal the presence of urinary stones. The fact that different urinary stone-related compounds (USRCs) are measured by different methods renders the metabolic evaluation of urolithiasis quite tedious and complex. METHODS: A three-channel ion chromatograph (IC) that automatically measures the concentration of common metabolic indicators of urolithiasis in urine (i.e., oxalate, citrate, uric acid, calcium, and magnesium) was developed to improve the efficiency. To validate its precision and specificity, standard curves were prepared using working solution of these indicators. 100 standard solutions of these indicators were measured with our new IC and three other ICs as the control instruments; analyte concentrations in 100 24-h urine samples from volunteers and 135 calculi patients were also measured. RESULTS: All analytes had good linear relationships in concentration ranges of 0-10 mg/L. The precision experiments in the standard and urine samples showed that the measurement errors of the newly developed IC were all less than 5%. In urine, the recovery rate ranged from 99.6 to 100.4%, the coefficient of variation ranged from 1.39 to 2.99%, and the results matched between our newly developed IC and the control ICs. The results of the efficiency test showed that we can finish the analysis at the average number of 14 people per day with the new IC. While the average number in the control group is 3.85/day (p = 0.000). CONCLUSIONS: Overall, this multi-channel system significantly improves the efficiency of metabolic evaluation while retaining accuracy and precision.

Redox environment metabolomic evaluation (REME) of the heart after myocardial ischemia/reperfusion injury.

Myocardial ischemia/reperfusion injury (MIRI) is closely related to oxidative stress. However, the redox environment of the heart has not been evaluated thoroughly after MIRI, which limits precise redox intervention. In this study, we developed the redox environment metabolomic evaluation (REME) method to analyze the redox metabolites of the heart after MIRI. Based on the targeted metabolomics strategy, we established a detection panel for 22 redox-related molecules, including the major redox couples nicotinamide adenine dinucleotide (NADH/NAD+), nicotinamide adenine dinucleotide phosphate (NADPH/NADP+), and glutathione/glutathione disulfide (GSH/GSSG), reactive oxygen and nitrogen species-related molecules, and some lipid peroxidation products. The high sensitivity and specificity of the method make it suitable for evaluating the endogenous redox environment. The REME method showed that the heart tissue in a MIRI mouse model had a different redox profile from that in the control group. Different redox species changed in different ways. The ratios of GSSG/GSH and NADP+/NADPH increased, but the levels of both NAD+ and NADH decreased in the risk area of the infarcted heart after reperfusion. In addition, some reactive nitrogen species-related metabolites (tetrahydrobiopterin, arginine, and S-nitrosoglutathione) decreased and some lipid peroxides (4-hydroxy-2-nonenal, 4-hydroxy-2-hexenal, and benzaldehyde) increased. The redox metabolites GSH, GSSG, NADPH, NAD+, S-nitrosoglutathione, arginine, and tetrahydrobiopterin had a positive correlation with the ejection fraction and a negative correlation with the level of lactate dehydrogenase in plasma. In summary, we achieved a comprehensive, systemic understanding of the changes in the redox environment after MIRI. Our REME method could be used to evaluate the redox environment in other processes.

Investigating Fluid Intake in an Underserved Community: What Factors Are Associated with Low Urine Volume on 24-Hour Urine Collection?

Background: Stone prevention is dependent on high fluid intake, with evidence that low urine volume (LUV) can promote nephrolithiasis in the absence of other metabolic abnormalities. Herein, we investigate patient-related factors associated with LUV on initial 24-hour urine collection in an underserved population. Materials and Methods: A retrospective chart review was performed of patients treated by a single surgeon for nephrolithiasis from August 2014 to January 2019. Patients who submitted 24-hour urine samples were divided into two groups based on whether their initial collection was >2 L or not. Factors associated with 24-hour urine volume were analyzed using bivariate and multivariate analyses. As a secondary outcome, we investigated factors associated with corrected 24-hour urine volume on repeat 24-hour urine collection. Results: Two hundred eight patients (45.1%) submitted 24-hour urine collections, 63.9% (133/208) of which demonstrated a urine volume of <2 L. LUV was more common in female patients (77.1% vs 49.5%; p = 0.001) and patients with no insurance and Medicaid (no insurance [100%] vs Medicaid [74.1%] vs Medicare/private [58.6%]; p = 0.02). Female gender and insurance status were independent predictors of LUV in the multivariable analysis. Seventeen of 43 patients (39.5%) with LUV who provided a subsequent collection were able to correct their urine volume. Patients who improved their LUV were older (58.5 vs 45.9 years, p = 0.0149) and more likely to have surgical intervention for their kidney stones (94.1% vs 53.8%, p = 0.006). In our multivariable analysis, surgical intervention was associated with correcting urine volume. Conclusions: Female patients and those with no insurance or Medicaid were more likely to have LUV on an initial 24-hour urine collection. Further research into barriers to fluid intake is important for these two groups, along with directed patient education on strategies for increasing fluid intake.

[A comparison between 24h urine collection and overnight spot urines in evaluating the risk of stone disease].

Despite being recommended by most guidelines, the metabolic evaluation of patients with nephrolithiasis has limited diffusion due to difficulties relating both to the access to laboratory investigations and to urine collection modalities. Consequently, in addition to the classical 24-h collection, alternative and simplified collection modes have been proposed. We report here on the comparison between metabolic evaluation carried out on 24-h double collection (Lithotest) and overnight spot urines (RF test). Fifty-four patients with stone disease were enrolled, excluding patients with infection or cystine stones. For Lithotest, we measured all analytes necessary to calculate state of saturation (ß) with calcium oxalate, brushite and uric acid, by means of Lithorisk.com. For RF, we measured calcium, magnesium, oxalate, citrate, sulphate, phosphate, pH and creatinine. The comparison was made with creatinine ratios. An estimate of ßCaOx, ßbrushite and ßAU was obtained also on RF urines by using simplified algorithms. We found highly significant correlations between all parameters, despite quite different means. There was a nice correspondence between the two sets of measurements, assessed by the Bland-Altmann test, for calcium, oxalate, citrate, sulphate, urate and pH. Overnight urine had higher saturations compared to 24-h one owing to higher concentration of the former. In conclusion, RF test on overnight urine cannot completely replace Lithotest on 24-hr urine. However, it can represent a simplified tool for either preliminary evaluation or follow-up of patients with stone disease.

Metabolic Evaluation: Place of the Calcium Load Test: How, When, For Whom, and Why?

Most human urinary stones are calcium-based and are often associated with hypercalciuria. A simple test described in 1975 by Pak et al allows for pathogenic classification of hypercalciuria: the calcium load test (CLT). The CLT explores calcium homeostasis after a low-calcium diet and then a calcium load (typically oral administration of 1 g of elemental calcium). Only simple laboratory equipment is required. Inadequate calcium excretion after a calcium-free diet or a calcium load is suggestive of resorptive or absorptive hypercalciuria, respectively. The CLT is particularly valuable in diagnosing primary hyperparathyroidism, even in most early stages of this disease. PATIENT SUMMARY: Kidney stone formation can be linked to calcium metabolism. When high calcium levels are found in urine despite adequate diet changes, a calcium load test may help to understand the underlying mechanisms. Urine and blood levels are explored during a low-calcium diet phase, and after a calcium load phase in the test. The calcium load test is particularly advantageous for revealing abnormally high function of the parathyroid gland, which is called hyperparathyroidism.

Integration of exome sequencing and metabolic evaluation for the diagnosis of children with urolithiasis.

PURPOSE: To investigate the prevalence of inherited causes in an early onset urolithiasis cohort and each metabolic subgroup. METHODS: A retrospective analysis of both metabolic and genomic data was performed for the first 105 pediatric urolithiasis patients who underwent exome sequencing at our hospital from February 2016 to October 2018. Measurements included the diagnostic yield of exome sequencing in the entire cohort and each metabolic subgroup (hyperoxaluria, hypocitraturia, hypercalciuria, hyperuricosuria and cystine stone subgroups). The conformity between molecular diagnoses and metabolic evaluation was also evaluated. RESULTS: The present study involved a cohort of 105 pediatric patients with urolithiasis, from which diagnostic variants were identified in 38 patients (36%), including 27 primary hyperoxaluria and 11 cystinuria. In the metabolic subgroup analyses, 41% hyperoxaluria cases were primary hyperoxaluria caused by monogenic defects, and 100% of the causes of cystine stones could be explained by monogenic defects. However, no appropriate inherited causes were identified for hypocitraturia, hypercalciuria, or hyperuricosuria in the cohort. A high conformity (100%) was obtained between the molecular diagnoses and metabolic evaluation. CONCLUSION: Exome sequencing in a cohort of 105 pediatric patients with urolithiasis yielded a genetic diagnosis in 36% of cases and the molecular diagnostic yield varies substantially across different metabolic abnormalities.

[Establishment and primary clinical application of metabolic evaluation database of urolithiasis].

Objective: To establish the metabolic evaluation database of urolithiasis, perform metabolic evaluation, and provide instructions for treatment and prevention of urolithiasis. Methods: This metabolic evaluation database was developed by JAVA and was established by Oracle11g database and Browser/Server framework. We extracted the clinical data of all patients who had complete information, and analyzed their risk factors of stone formation, stone-related medical history, blood and urine tests results and 24-hour urine analysis. Results: A total of 360 patients diagnosed as urolithiasis were included in this research. Male to female ratio was 1.9∶1, and the urolithiasis was first diagnosed at (35.5±13.5) years old. Family history was positive in 39.7% of patients. Metabolic syndrome occurred in 35.0% of patients. Overweight or obesity occurred in 73.2% and 50.0% of male patients, respectively. Abdominal obesity in 62.3% and 56.1% of male and female patients, respectively. Among all patients, 67.5% had high urine sodium, 53.6% had hypercalciuria, 41.1% had hypocitraturia, 29.7% had hyperuricosuria, 22.5% had hypomagnesuria, 15.8% had hyperoxaluria, 11.7% had hyperphosphoraturia, and 36.4% had low urinary volume. Conclusions: The prevalence of overweight or obesity, abdominal obesity, hypertension, diabetes, and metabolic syndrome in stone patients were significantly higher than those in general population. The number of 24-hour urinary abnormalities was positively associated with body mass index. The interventions on high urinary sodium, low urinary volume, obesity and metabolic syndrome were important to the treatment of urolithiasis. This database would facilitate the metabolic evaluation, provide evidence for the treatment and prevention of urolithiasis, and lay foundation for finding important controllable risk factors of urinary stone.