Pathophysiology and Management of Hyperoxaluria and Oxalate Nephropathy: A Review

Pre-transplant residual diuresis and oxalic acid concentration influence kidney graft survival

BACKGROUND AND HYPOTHESIS

Oxalic acid, a toxic metabolic end product, accumulates when kidney function deteriorates. Apart from its direct tubulotoxicity, it crystallizes at concentrations above 30-40 µmol/L. High oxalic acid concentrations at transplantation might negatively influence kidney transplant function. The influence of the concentrations of oxalic acid and its precursors and residual diuresis on kidney transplant outcomes was studied.

METHODS

In this prospective cohort study, patients who received a kidney transplant between September 2018 and January 2022 participated. Concentrations of oxalic acid and precursors were determined in pre-transplant blood samples. Data on residual diuresis and other recipient, donor or transplant related variables were collected. Follow-up lasted until July 1st 2023.

RESULTS

496 patients were included, 154 were not on dialysis. Median residual diuresis was 1000 mL/day (IQR 200; 2000 mL/day). There were 230 living donor transplantations. Oxalic acid concentrations exceeded the upper normal concentration in 99% of patients, glyoxylic acid in all patients. There were 52 (10%) graft failures. As the influence of oxalic acid on the risk of graft failure censored for death was non-linear, it was categorized into two groups: ≤ 60 and > 60 μmol/L. In multivariable Cox analysis the graft failure censored for death risk was significantly influenced by residual diuresis, donor type (living versus deceased), donor age and oxalic acid. In 180 patients oxalic acid concentration shortly after transplantation was significantly lower than pre-transplant concentrations, suggesting excretion by the new graft. A better eGFR at day 7 was associated with lower oxalic acid concentration. Oxalic acid and residual diuresis did not influence patient survival.

CONCLUSION

Residual diuresis and oxalic acid concentration are important and independent predictors of graft survival censored for death. These results underline the importance of pre-emptive transplantation, or optimizing the pre-transplant patients' condition regarding waste product concentrations.

Single-Cell RNA Sequencing Analysis Reveals the Role of Macrophage-Mediated CD44-AKT-CCL2 Pathways in Renal Tubule Injury during Calcium Oxalate Crystal Formation

Oxalate-induced crystalline kidney injury is a common form of crystal nephropathy. The accumulation of calcium oxalate (CaOx) crystal could lead to renal epithelium injury and inflammation. The underlying cellular events in kidney after CaOx crystal formation are largely unknown. This study was aimed to gain a better understanding of mouse kidney function in the development of renal CaOx formation. The study utilized a mouse CaOx model to analyze the cellular response at 5 time points using single-cell RNA sequencing and investigate the interaction of different cells during renal CaOx crystal formation. Additionally, the study investigated the communication between these cells and macrophages, as well as the role of chemokines in recruiting infiltrating macrophages. RNA velocity analysis uncovered an alternative differentiation pathway for injured and S1 proximal tubule cells, which mainly communicate with macrophages through the SPP1-CD44 pair, along with the expression of proinflammatory factors and stone matrix genes during renal CaOx crystal formation. Furthermore, resident Fn1 macrophages were found to express chemokines, such as CCL2, which recruited infiltrating macrophages. The CCL2 secretion was mediated by the CD44-AKT pathway. Blocking CCL2 decreased the expression of injury markers in the kidney, including CLU, LCN2, and KIM-1, and inhibited CaOx crystal deposition. The study identified potential cell types and target genes involved in renal tubule injury in oxalate-related crystal nephropathy. The findings shed light on the cellular processes that contribute to the formation and damage caused by CaOx crystals within the kidney, which could lead to the development of potential cell types and target genes for treating this condition.

Optimizing Screening Performance for the Risk of Hyperoxaluria and Urolithiasis Using the Urinary Oxalate/Creatinine Ratio: A Retrospective Analysis

Background and objective

The risk of chronic kidney disease (CKD) and nephrolithiasis increases with higher levels of oxalate excretion in 24-h urine, warranting monitoring in specific populations, especially after malabsorptive bariatric surgery. However, implementation of systematic 24-h urine collection is challenging, so there is a need for alternative screening methods.

Methods

Using retrospective data from patients evaluated for the risk of urolithiasis, we assessed different thresholds for the urinary oxalate/creatinine (UOx/Creat) ratio to optimize the screening performance for hyperoxaluria diagnosis and urolithiasis risk using lithogenic risk surrogates.

Key findings and limitations

Among 1264 patients referred for urolithiasis, 38% were excluded because urine collection was considered incomplete. The remaining 786 individuals were included in our analysis, of whom 16% exhibited hyperoxaluria. A UOx/Creat screening threshold between 35 and 45 μmol/mmol demonstrated good performance, depending on the clinical weighting for false-negative versus true-positive results and the cost/benefit ratio.

Conclusions and clinical implications

The UOx/Creat ratio is a promising tool in screening for hyperoxaluria-related complications. However, future research is needed to validate its performance and address the limitations identified to confirm its clinical relevance and effectiveness.

Patient summary

Our study shows that a simple test to measure the ratio of oxalate to creatinine in urine can help in identifying people at risk of kidney stones, especially for patients who have had weight-loss surgery. The test showed good screening performance, but more research is needed to confirm our findings.

NINJ1-mediated macrophage plasma membrane rupture and neutrophil extracellular trap formation contribute to oxalate nephropathy

BACKGROUND

Oxalate nephropathy is characterized by calcium oxalate crystals deposition, which triggers necrosis of renal tubular epithelial cells and initiates an inflammatory cascade characterized by neutrophil and macrophage activation within the renal microenvironment. Despite the close association of immune cells with acute oxalate nephropathy, the underlying mechanisms still remain unclear. Nerve injury-induced protein 1 (NINJ1) plays an essential role in the induction of plasma membrane rupture (PMR), leading to damage-associated molecular patterns (DAMPs) release and triggering inflammation. We hypothesize that NINJ1-mediated high mobility group box 1 (HMGB1) release from macrophage PMR and neutrophil extracellular traps (NETs) formation synergistically contribute to the progression of acute oxalate nephropathy.

METHODS

Using a murine model of acute oxalate nephropathy, myeloid cell-specific deletion of Ninj1 mice (Ninj1fl/flvavcre) and their wild-type littermate control mice (Ninj1wt/wtvavcre) were administered intraperitoneal injection of 100 mg/kg sodium oxalate followed by drinking water with 3% sodium oxalate. Evaluation was conducted on tubular injury and inflammatory cell infiltration. In vitro studies involved isolation and culture of renal proximal tubular epithelial cells, bone marrow-derived macrophages and neutrophils to investigate NETs formation and HMGB1 release.

RESULTS

Targeted deletion of Ninj1 in myeloid cells significantly mitigated oxalate-induced acute kidney injury by suppressing both HMGB1 release and NETs formation in vivo. In vitro investigations demonstrated that HMGB1 release from macrophage PMR and NETs formation in neutrophils mediated by NINJ1 oligomerization, which consequently coordinated to enhance renal tubular epithelial cell death.

CONCLUSIONS

Our findings elucidate the pivotal role of NINJ1-dependent macrophage PMR and NETs formation in the progression of acute oxalate nephropathy, providing novel insights for its prevention and therapeutic targets.

Engineered Oxalate Decarboxylase Boosts Activity and Stability for Biological Applications

Oxalate decarboxylase (OxDC) from Bacillus subtilis is a Mn-dependent hexameric enzyme that converts oxalate to carbon dioxide and formate. Recently, OxDC has attracted the interest of the scientific community due to its biotechnological and medical applications for the treatment of hyperoxaluria, a group of pathologic conditions associated with excessive oxalate urinary excretion caused by either increased endogenous production or increased exogenous absorption. The fact that OxDC displays optimum pH in the acidic range represents a big limitation for most biotechnological applications involving processes occurring at neutral pH, where the activity and stability of the enzyme are remarkably reduced. Here, through bioinformatics-guided protein engineering followed by combinatorial mutagenesis and analyses of activity and thermal stability, we identified a double mutant of OxDC endowed with enhanced catalytic efficiency and stability under physiological conditions. The obtained engineered form of OxDC offers a potential tool for improved intestinal oxalate degradation in hyperoxaluria patients.

Acute oxalate nephropathy due to yellow rice wine: a case report

BACKGROUND

Acute oxalate nephropathy is a rare but potentially underrecognized cause of acute kidney injury (AKI). The reports of secondary oxalate nephropathy induced by high doses of vitamin C, portulaca oleracea, Peanut were described, but the cause as yellow wine consumption are rare. We report a 63-year-old man with acute kidney injury due to yellow rice wine. The patient has drunk yellow rice wine 500 mL/day for the past 10 years. He underwent an ultrasound-guided renal biopsy, which showed acute tubular injury and birefringent crystals were observed in the renal tubules under a polarizing microscope. The 24-hour urinary oxalate excretion established and the baseline serum creatinine of 407 µmol/L. Following 3 months therapy, subsequent laboratory evaluation demonstrated significant reduction in urinary oxalate excretion excretion and serum creatinine normal.

CONCLUSIONS

Acute secondary oxalate nephropathy due to excessive dietary intake of oxalate may lead to AKI. Kidney biopsies in unknown cause AKI patients is important and attention should be payed to food behaviors when reasons for AKI are explored.

Rutin ameliorates calcium oxalate crystal-induced kidney injury through anti-oxidative stress and modulation of intestinal flora

Kidney stones are a common urological disease. Although there are many ways to treat them, their high recurrence rate remains unresolved. Research has demonstrated that Lysimachia christinae Hance influences kidney stone development; however, the exact mechanism remains unclear. In this experiment, we investigated the protective effect of Lysimachia christinae Hance extract, rutin, on renal injury and its mechanism of action in a mouse model of glyoxalate-induced renal calculi. A kidney stone model was established in Balb/c mice by continuous intraperitoneal injection of glyoxalate (80 mg/kg) for 6 days. Simultaneous gavage of 30, and 60 mg/kg of rutin was administered for 6 days. Samples were collected for determination of index coefficients. Mouse kidney tissue was collected for RNA-seq, and segments of mouse colon were analyzed with 16 S RNA sequencing. We found that rutin significantly reduced renal calcium oxalate deposition and renal tissue injury in the glyoxylate-induced kidney stone model of mice. Rutin also significantly inhibited calcium oxalate deposition-induced apoptosis. In addition, rutin attenuates oxidative stress damage and inhibits the expression of signaling pathways associated with inflammation. 16 S RNA sequencing revealed that rutin regulated intestinal flora composition, significantly increasing the relative abundance of short-chain fatty acid-producing flora and promoting short-chain fatty acid production. In summary, rutin ameliorated renal tubular damage and apoptosis caused by renal stone deposition and reduced oxidative stress. It also regulates the intestinal flora, increases the enrichment of intestinal probiotics, and promotes the production of short-chain fatty acids, thereby inhibiting the formation of kidney stones.

Role of Z-DNA Binding Protein 1 Sensing Mitochondrial Z-DNA and Triggering Necroptosis in Oxalate-Induced Acute Kidney Injury

Key Points

Gene deletions of Zbp1 , Ripk3 , and Mlkl reduced severity of oxalate-induced AKI. Mice with mutation or deletion in the Z-nucleic acid sensing domain (Zα ) of Z-DNA binding protein 1 were protected from AKI. Z-DNA binding protein 1 sensed mitochondrial Z-DNA through its Zα domain, recruited receptor-interacting protein kinase 3 through receptor-interacting protein homotypic interaction motif, and activated mixed lineage kinase domain-like to induce necroptosis.

Background

Calcium oxalate–induced acute kidney injury is a severe condition in which the kidneys suffer rapid damage due to the deposition of oxalate crystals. Known factors contributing to cell death induced by calcium oxalate include receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL) protein–dependent necroptosis, as well as necrosis involving peptidylprolyl isomerase F–mediated mitochondrial permeability transition. However, the detailed molecular mechanisms linking mitochondrial dysfunction to RIPK3 activation are not fully understood.

Methods

Mice with gene knockout of Zbp1 , Ripk3 , or Mlkl and mice with mutations in the Z-nucleic acid sensing domain of Z-DNA binding protein 1 (ZBP1) or deletion of Zα 1 were used in an oxalate-induced AKI model. Proximal renal tubule cells were isolated and cultured for further investigation. Human oxalate nephropathy biopsy samples were analyzed.

Results

Specific gene deletions of Zbp1 , Ripk3 , or Mlkl in proximal renal tubules significantly reduced the severity of oxalate-induced AKI by preventing necroptosis and subsequent inflammation. Notably, mice with mutations in the Z-nucleic acid sensing domain of ZBP1 or deletion of Zα1 were protected from AKI. In cultured proximal tubular cells, calcium oxalate damaged mitochondria, accompanied by an increase in Bax and a decrease in BCL2 and transcription factor A, mitochondrial (TFAM), leading to the release of mitochondrial Z-DNA. ZBP1 sensed this mitochondrial Z-DNA and then recruited RIPK3 through the receptor-interacting protein homotypic interaction motifs, which in turn activated MLKL through RIPK3 phosphorylation, leading to necroptosis and contributing to AKI.

Conclusions

ZBP1 plays a critical role in sensing mitochondrial Z-DNA and initiating RIPK3/MLKL-mediated necroptosis, contributing to the development of oxalate-induced AKI.

Molecular insights into cell signaling pathways in kidney stone formation

Urolithiasis, or kidney stones, has emerged as a significant public health concern. Despite this, effective treatments targeting stone formation and recurrence are limited. This review delves into the molecular mechanisms underlying the condition. Investigating these molecular aspects can address existing gaps in treatment options. Future research can uncover new therapeutic strategies by targeting downstream pathways, and effector molecules. Cell signaling pathways offer potential targets, as they involve complex interactions that can be modulated to address multiple clinical symptoms. An imbalance in calcium and oxalate levels can lead to kidney stone formation which is characterized by oxidative stress, inflammation, and cell death. The interplay between key organelles like the endoplasmic reticulum and mitochondria triggers stress pathways, including oxidative stress and apoptosis. This review consolidates recent advances in understanding the pathophysiology and signaling events associated with kidney stones.

Empagliflozin reduces renal calcium oxalate deposition in hyperoxaluria rats induced with ethylene glycol-ammonium chloride

A retrospective study reported that empagliflozin reduced the risk of urinary stone events in patients with diabetes mellitus. To further investigate empagliflozin's potential, we conducted an animal experiment to determine whether empagliflozin can prevent renal stone formation in hyperoxaluria rats. Hyperoxaluria rat models were constructed by administrating 0.75 % ethylene glycol and 1 % ammonium chloride in water. The empagliflozin-treated rats were gauged with empagliflozin at different concentrations, and their body weight and blood sugar data were recorded. After 30 days of treatment, we obtained 24-h urine, kidney, and blood samples. The urine samples were subjected to component detection. Blood samples were prepared for component detection and cytokines detection. Renal samples were subjected to von Kossa staining, transmission electron microscopy, immunohistochemistry, and transcriptome sequencing analysis. Results showed that in empagliflozin-treated hyperoxaluria rats, renal crystal deposition and mitochondria injury, urinary concentration, and excretion of oxalate were significantly decreased. Additionally, plasma levels of VEGF, IL-2, IL-1β, and MCP-1 were decreased. Immunohistochemistry showed that renal expression of KIM-1, MCP-1 was significantly decreased in empagliflozin-treated hyperoxaluria rats. Transcriptome sequencing of renal tissue represented that 25 genes were down-regulated while 12 were up-regulated in empagliflozin-treated hyperoxaluria rats. These regulated genes were mainly enriched in fatty acid metabolism, insulin resistance, muscle contraction, bile secretion, and parathyroid metabolism. Our animal experiments found that empagliflozin could reduce urinary concentration and excretion of oxalate and inhibit renal inflammation, then abating renal calcium oxalate deposition in hyperoxaluria rats in a non-diabetic state.

Hot Hearts on Bone Scintigraphy Are Not All Amyloidosis: Hyperoxaluria-Associated Cardiomyopathy

ABSTRACT

A 54-year-old woman with a history of end-stage renal disease was found to have infiltrative cardiomyopathy by echocardiography. 99m Tc-pyrophosphate ( 99m Tc-PYP) scintigraphy was positive with a remarkable myocardial uptake. Gene test found a mutation of AGXT , confirming a final diagnosis of primary hyperoxaluria. Radiotracer uptake was due to high myocardial oxalate deposition. This case illustrates false positivity of the 99m Tc-PYP scan caused by hyperoxaluria-associated cardiomyopathy, which raises awareness for other conditions apart from amyloid cardiomyopathy.

Advances in Diagnosis and Treatment of Inherited Kidney Diseases in Children

Background

Inherited kidney diseases (IKDs) in children pose unique diagnostic and therapeutic challenges. IKD significantly impact patient quality of life, morbidity, mortality, and cost to the healthcare system. With over 150 genetic abnormalities, they account for approximately 30% of cases requiring renal replacement therapy. There is an urgent need to advance both diagnosis and treatment strategies. In this review, we present recent advances in diagnosis and treatment for facilitating personalized treatment approaches.

Summary

The diagnostic landscape for IKDs have evolved significantly, emphasizing precise genetic identification and classification of these disorders. Recent advancements include the refinement of genetic testing techniques, such as whole exome sequencing, which has improved the accuracy of diagnosing specific diseases and facilitated early intervention strategies. Additionally, this review categorizes IKDs based on genetic abnormalities and clinical manifestations, enhancing understanding and management approaches. Finally, it summarizes the corresponding treatment, and lists the application of emerging therapeutic options such as gene therapy and organoids, which show promise in transforming treatment outcomes.

Key Messages

This review summarizes the common types of IKDs in children, including their diagnosis and treatment advances, and provides an update on the status of gene therapy development for these disorders.

Determinants and impact of calcium oxalate crystal deposition on renal outcomes in acute kidney injury patients

OBJECTIVES

Calcium oxalate (CaOx) crystal deposition in acute kidney injury (AKI) patients is under recognized but impacts renal outcomes. This study investigates its determinants and effects.

METHODS

We studied 814 AKI patients with native kidney biopsies from 2011 to 2020, identifying CaOx crystal deposition severity (mild: <5, moderate: 5-10, severe: >10 crystals per section). We assessed factors like urinary oxalate, citrate, urate, electrolytes, pH, tubular calcification index, and SLC26A6 expression, comparing them with creatinine-matched AKI controls without oxalosis. We analyzed how these factors relate to CaOx severity and their impact on renal recovery (eGFR < 15 mL/min/1.73 m2 at 3-month follow-up).

RESULTS

CaOx crystal deposition was found in 3.9% of the AKI cohort (32 cases), with 72% due to nephrotoxic medication-induced tubulointerstitial nephritis. Diuretic use, higher urinary oxalate-to-citrate ratio induced by hypocitraturia, and tubular calcification index were significant contributors to moderate and/or severe CaOx deposition. Poor baseline renal function, low urinary chloride, high uric acid and urea nitrogen, tubular SLC26A6 overexpression, and glomerular sclerosis were also associated with moderate-to-severe CaOx deposition. Kidney recovery was delayed, with 43.8%, 31.2%, and 18.8% of patients having eGFR < 15 mL/min/1.73 m2 at 4, 12, and 24-week post-injury. Poor outcomes were linked to high urinary α1-microglobulin-to-creatinine (α1-MG/C) ratios and active tubular injury scores. Univariate analysis showed a strong link between this ratio and poor renal outcomes, independent of oxalosis severity.

CONCLUSIONS

In AKI, CaOx deposition is common despite declining GFR. Factors worsening tubular injury, not just oxalate-to-citrate ratios, are key to understanding impaired renal recovery.

Second transplantation after kidney graft loss in primary hyperoxaluria type 2: a pedigree study and mutation analysis

BACKGROUND

Primary hyperoxaluria type 2 (PH2) is a rare disorder caused by GRHPR mutations. Research on the mutation spectrum and pedigree of PH2 helps in comprehending its pathogenesis and clinical outcomes, guiding clinical diagnosis and treatment.

METHODS

We report a case of PH2 with a three-generational pedigree. The GRHPR genotypes of the family members were confirmed by Sanger sequencing. Urine and blood samples were collected for biochemical analysis. Computational analysis was performed to assess the pathogenicity of the mutations. Cellular experiments based on site-directed mutagenesis were conducted to confirm the effect of mutations on GRHPR expression, activity, and subcellular localization.

RESULTS

The proband underwent her first kidney transplantation in 2015, and experienced recurrent urinary tract infections and urolithiasis postoperatively. Graft failure occurred in 2018. Whole exome sequencing identified compound heterozygous GRHPR mutations p.G160E/p.P203Rfs*7. The patient underwent a second kidney transplantation in 2019 and maintained good graft function with urine dilution measures. Notably, her brother and sister carried the same mutations; however, only the proband progressed to renal failure. Computational analysis suggested that p.G160E reduced the affinity of GRHPR for coenzymes. Cellular experiments indicated that p.G160E reduced GRHPR activity (p < 0.001), whereas p.P203Rfs*7 not only suppressed expression (p < 0.001) and reduced activity (p < 0.001), but also facilitated protein aggregation. Based on our results, the variant p.G160E was classified as 'pathogenic' according to ACMG guidelines.

CONCLUSIONS

Our findings suggest that treatment strategies for the long-term prevention of oxalate nephropathy should be developed for patients with PH2 receiving isolated kidney transplantation. Moreover, the pathogenicity of the compound heterozygous GRHPR mutations p.G160E/p.P203Rfs*7 was also validated.

Single-Electrode Flow Cell for Electrochemiluminescent Flow Analysis

Flow injection analysis and liquid chromatography are frequently combined with electrochemiluminescence (ECL) for flow analysis. Almost all electrochemistry flow analyses employ traditional three-electrode electrochemical flow cells which have working electrode, counter electrode, and reference electrode; however, it is expensive and difficult to fabricate a traditional three-electrode electrochemical flow cell and inconvenient to renew the electrode. In this study, we have developed a single-electrode flow cell using commercially available conductive polyethylene film as the only electrode through potential differences induced by the electrode resistance for the first time. The single-electrode flow cell features a simple structure, easy renewal of the electrode, and low cost compared to the traditional three-electrode electrochemical flow cells. Taking the typical Ru(bpy)32+/oxalate ECL system as the analytical model, flow analysis of clinically important oxalate was achieved using single-electrode flow cell. A regression linear equation was obtained over the oxalate concentration ranges from 1 to 200 μM, with a detection limit of 0.92 μM. The single-electrode flow cell is promising for ECL flow analysis.

Discovery of l-Lysine Dioxalate (LH1513) as a Novel Inhibitor of Calcium Oxalate Crystallization for Hyperoxaluria

Hyperoxaluria is caused by increased urinary excretion of oxalate leading to the formation of calcium oxalate (CaOx) stones. The lack of effective management strategies for hyperoxaluria prompted us to investigate molecular mimics as stone inhibitors, a strategy that we previously used successfully to discover small molecule inhibitors of l-cystine crystallization for the prevention of l-cystine stone formation in cystinuria. Herein, we report the discovery of l-lysine dioxalate (LH1513), a novel dioxamate derivative, as a more potent inhibitor of CaOx crystallization than citrate and pyruvate. Such inhibition was corroborated by in situ atomic force microscopy (AFM) measurements of crystal growth rates at the microscopic length scale. A triester prodrug of LH1513 was found to have sufficient oral bioavailability for a preliminary in vivo study demonstrating efficacy in preventing urinary CaOx crystal formation in an Agxt-knockout mouse model for hyperoxaluria.

Diagnosis and management of primary hyperoxalurias: best practices

The primary hyperoxalurias (PH 1, 2, and 3) are rare autosomal recessive disorders of glyoxylate metabolism resulting in hepatic overproduction of oxalate. Clinical presentations that should prompt consideration of PH include kidney stones, nephrocalcinosis, and kidney failure of unknown etiology, especially with echogenic kidneys on ultrasound. PH1 is the most common and severe of the primary hyperoxalurias with a high incidence of kidney failure as early as infancy. Until the recent availability of a novel RNA interference (RNAi) agent, PH care was largely supportive of eventual need for kidney/liver transplantation in PH1 and PH2. Together with the Oxalosis and Hyperoxaluria Foundation, the authors developed a diagnostic algorithm for PH1 and in this report outline best clinical practices related to its early diagnosis, supportive treatment, and long-term management, including the use of the novel RNAi. PH1-focused approaches to dialysis and kidney/liver transplantation for PH patients with progression to chronic kidney disease/kidney failure and systemic oxalosis are suggested. Therapeutic advances for this devastating disease heighten the importance of early diagnosis and informed treatment.

The Altered Proteomic Landscape in Renal Tubular Epithelial Cells under High Oxalate Stimulation

Our study aimed to apply a proteomic approach to investigate the molecular mechanisms underlying the effects of oxalate on rat renal tubular epithelial cells. NRK-52E cells were treated with or without oxalate and subjected to quantitative proteomics to identify key proteins and key pathological changes under high oxalate stimulation. A total of 268 differentially expressed proteins (DEPs) between oxalate-treated and control groups were identified, with 132 up-regulated and 136 down-regulated proteins. Functional enrichment analysis revealed that DEPs are associated with oxidative stress, apoptosis, ferroptosis, pro-inflammatory cytokines, vitamin D, and biomineralization. SPP1, MFGE8, ANKS1A, and NAP1L1 were up-regulated in the oxalate-treated cells and the hyperoxaluric stone-forming rats, while SUB1, RNPS1, and DGLUCY were down-regulated in both cases. This altered proteomic landscape sheds light on the pathological processes involved in oxalate-induced renal damage and identifies potential biomarkers and therapeutic targets to mitigate the effects of hyperoxaluria and reduce the risk of CaOx stone formation.

Trigger Warning: How Modern Diet, Lifestyle, and Environment Pull the Trigger on Autosomal Dominant Polycystic Kidney Disease Progression

Understanding chronic kidney disease (CKD) through the lens of evolutionary biology highlights the mismatch between our Paleolithic-optimized genes and modern diets, which led to the dramatically increased prevalence of CKD in modern societies. In particular, the Standard American Diet (SAD), high in carbohydrates and ultra-processed foods, causes conditions like type 2 diabetes (T2D), chronic inflammation, and hypertension, leading to CKD. Autosomal dominant polycystic kidney disease (ADPKD), a genetic form of CKD, is characterized by progressive renal cystogenesis that leads to renal failure. This review challenges the fatalistic view of ADPKD as solely a genetic disease. We argue that, just like non-genetic CKD, modern dietary practices, lifestyle, and environmental exposures initiate and accelerate ADPKD progression. Evidence shows that carbohydrate overconsumption, hyperglycemia, and insulin resistance significantly impact renal health. Additionally, factors like dehydration, electrolyte imbalances, nephrotoxin exposure, gastrointestinal dysbiosis, and renal microcrystal formation exacerbate ADPKD. Conversely, carbohydrate restriction, ketogenic metabolic therapy (KMT), and antagonizing the lithogenic risk show promise in slowing ADPKD progression. Addressing disease triggers through dietary modifications and lifestyle changes offers a conservative, non-pharmacological strategy for disease modification in ADPKD. This comprehensive review underscores the urgency of integrating diet and lifestyle factors into the clinical management of ADPKD to mitigate disease progression, improve patient outcomes, and offer therapeutic choices that can be implemented worldwide at low or no cost to healthcare payers and patients.

Exploring the Impact of Gender-Specific Approaches inRetrograde Intrarenal Surgery: Effects on Operative Efficiency and Patient Recovery

Objective

Very limited data are available exploring the potential influence of gender on Retrograde Intrarenal Surgery outcomes. This study investigates the gender-specific influence of ShuoTongureteroscopy (ST-urs) and Flexible Ureteroscopy (F-urs) surgeries on operation efficacy and patient recovery in a sample of the Somali population.

Materials and Methods

We enrolled 390 participants. Participants were stratified into four gender-specific subgroups based on ureteroscopy operation type: 27.7% males in S-urs (group1), 44.4% females in S-urs (group2), 18.7% males in F-urs (group3), and 9.2% females in F-urs (group4). Primary outcomes included operation time, postoperative hospital stay duration, and VAS Pain Score. Multivariate logistic regression was used to assess associations.

Results

The mean age was 29.53 ± 7.61 years, 72.1% male and 27.9% female, with 46.4% of the patients undergoing ST-urs and 53.6% undergoing F-urs. Women had higher odds of prolonged hospital stays (OR = 2.62, 95% CI: 1.43-4.82, p < 0.001) and post-operation pain (OR = 5.06, 95% CI: 2.95-8.68, p = 0.002). Among men who underwent F-urs procedure, there was a significantly higher odds ratio (OR) of 6.14 (95% CI: 2.86-13.19, p < 0.001) for experiencing a long operation time. Conversely, for females, those who underwent S-urs surgery had a notably lower OR of 0.32 (95% CI: 0.13-0.79, p = 0.013) for long operation time, whereas those who underwent F-urs surgery exhibited a substantially elevated OR of 5.36 (95% CI: 1.85-15.53, p < 0.001). Both females undergoing F-urs surgery (OR: 5.16, 95% CI: 2.61-10.21, p < 0.001) and those undergoing F-urs surgery (OR: 5.25, 95% CI: 2.17-12.73, p < 0.001) experienced significantly higher post-operative pain.

Conclusion

Our research reveals gender disparities in retrograde intrarenal surgery outcomes. Women experience longer hospital stays and higher postoperative pain levels compared to men. F-urs procedures are associated with longer operation times and hospital stays, particularly affecting women. Contrarily, ST-urs offers shorter operation times for women but leads to prolonged hospital stays and heightened postoperative pain.

Mutation Characteristics of Primary Hyperoxaluria in the Chinese Population and Current International Diagnosis and Treatment Status

Background

Primary hyperoxaluria (PH) is a rare autosomal recessive disorder, mainly due to the increase in endogenous oxalate production, causing a series of clinical features such as kidney stones, nephrocalcinosis, progressive impairment of renal function, and systemic oxalosis. There are three common genetic causes of glycolate metabolism anomalies. Among them, PH type 1 is the most prevalent and severe type, and early end-stage renal failure often occurs.

Summary

This review summarizes PH through pathophysiology, genotype, clinical manifestation, diagnosis, and treatment options. And explore the characteristics of Chinese PH patients.

Key Messages

Diagnosis of this rare disease is based on clinical symptoms, urinary or blood oxalate concentrations, liver biopsy, and genetic testing. Currently, the main treatment is massive hydration, citrate inhibition of crystallization, dialysis, liver and kidney transplantation, and pyridoxine. Recently, RNA interference drugs have also been used. In addition, technologies such as gene editing and autologous liver cell transplantation are also being developed. C.815_816insGA and c.33_34insC mutation in the AGXT gene could be a common variant in Chinese PH1 population. Mutations at the end of exon 6 account for approximately 50% of all Chinese HOGA1 mutations. Currently, the treatment of PH in China still relies mainly on symptomatic and high-throughput dialysis, with poor prognosis (especially for PH1 patients).

From Smoothies to Dialysis: The Impact of Oxalate Nephropathy

Oxalate nephropathy is a rare cause of acute kidney injury that can lead to end-stage renal disease. This case report describes a 54-year-old male with type 2 diabetes mellitus and chronic kidney disease who presented for a routine clinic follow-up. Laboratory tests revealed significant deterioration in renal function with an unrevealing history and symptoms suggestive of the process. Initial investigations for worsening renal function were inconclusive, prompting a renal biopsy that confirmed acute tubular injury with abundant calcium oxalate deposits. Further investigation into dietary history revealed that the patient regularly consumed high-oxalate foods, such as spinach and kale smoothies, under the impression they were beneficial for his diabetes. Despite the initiation of hemodialysis, the patient did not recover renal function and remains dialysis-dependent. This case underscores the need for a high index of suspicion for oxalate nephropathy in chronic kidney disease patients presenting with unexplained acute kidney injury. Diagnosis is confirmed through renal biopsy and should be considered in patients with relevant dietary histories.

Delayed Graft Function After Kidney Transplantation: The Role of Residual Diuresis and Waste Products, as Oxalic Acid and Its Precursors

Delayed graft function (DGF) after kidney transplantation heralds a worse prognosis. In patients with hyperoxaluria, the incidence of DGF is high. Oxalic acid is a waste product that accumulates when kidney function decreases. We hypothesize that residual diuresis and accumulated waste products influence the DGF incidence. Patients transplanted between 2018-2022 participated in the prospective cohort study. Pre-transplant concentrations of oxalic acid and its precursors were determined. Data on residual diuresis and other recipient, donor or transplant related variables were collected. 496 patients were included, 154 were not on dialysis. Oxalic acid, and glyoxylic acid, were above upper normal concentrations in 98.8%, and 100% of patients. Residual diuresis was ≤150 mL/min in 24% of patients. DGF occurred in 157 patients. Multivariable binary logistic regression analysis demonstrated a significant influence of dialysis type, recipient BMI, donor type, age, and serum creatinine on the DGF risk. Residual diuresis and glycolic acid concentration were inversely proportionally related to this risk, glyoxylic acid directly proportionally. Results in the dialysis population showed the same results, but glyoxylic acid lacked significance. In conclusion, low residual diuresis is associated with increased DGF incidence. Possibly accumulated waste products also play a role. Pre-emptive transplantation may decrease the incidence of DGF.

Oxalate Metabolism: From Kidney Stones to Cardiovascular Disease

Oxalate kidney stones are common and exert a huge burden of morbidity worldwide. However, circulating or excreted concentrations of oxalate are rarely measured. We argue that oxalate and its metabolism are important above and beyond kidney stone formation. There is emerging evidence that increased concentrations of oxalate could be a driver of chronic kidney disease progression. Furthermore, oxalate has been implicated in cardiovascular disease. Thus, the reduction of elevated plasma oxalate concentrations may represent a novel cardioprotective and nephroprotective strategy.

Impact of low-oxalate diet on hyperoxaluria among patients suffering from nephrolithiasis

Low-oxalate diets are useful for treating hyperoxaluria in nephrolithiasis patients. This study was unique in examining how a low-oxalate diet in addition to a standard diet affected hyperoxaluria and renal function tests in nephrolithiasis patients. The effects of a low-oxalate diet were analyzed by different biochemical tests, that is, anthropometric measurements, blood oxalate test, renal function test, electrolyte profile test, and 24 h urine analysis. For this purpose, 112 patients were divided into 2 groups: Group T1 (Conventional diet) and Group T2 (Low-Oxalate diet) for 8 weeks. Each group was tested at the initiation and end of the study. Using SPSS, the obtained data from each parameter were statistically analyzed. The results showed that a low-oxalate diet had a positive effect on patients suffering from nephrolithiasis. Furthermore, after treatment, anthropometric measurement weight (kg) among the control group (T1) was 100.45 ± 5.65 and the treatment group (T2) was 79.71 ± 9.48 kg. The effect of low-oxalate diet on renal function test: creatinine (g/d) among T1 was 2.08 ± 0.86 and T2 was 1.17 ± 0.13, uric acid(mg/d) among T1 was 437.04 ± 24.20 and T2 was 364.61 ± 35.99, urinary oxalate (mg/d) among T1 was 76.84 ± 10.33 and T2 was 39.24 ± 1.51, respectively. Sodium (mEq/d) among T1 was 156.72 ± 6.37 and T2 was 159.84 ± 6.31, potassium (mEq/d) among T1 was 69.91 ± 15.37 and T2 was 89.21 ± 6.31, phosphorus (g/d) among T1 was 0.96 ± 0.07 and T2 was 0.34 ± 0.27, respectively. This study demonstrated that nephrolithiasis patients with hyperoxaluria benefit from low-oxalate diets. Hyperoxaluria patients should eat a low-oxalate diet to use oxalate without affecting metabolism and eliminate it from the kidney without stones.

Beneficial roles of gastrointestinal and urinary microbiomes in kidney stone prevention via their oxalate-degrading ability and beyond

Formation of calcium oxalate (CaOx) crystal, the most common composition in kidney stones, occurs following supersaturation of calcium and oxalate ions in the urine. In addition to endogenous source, another main source of calcium and oxalate ions is dietary intake. In the intestinal lumen, calcium can bind with oxalate to form precipitates to be eliminated with feces. High intake of oxalate-rich foods, inappropriate amount of daily calcium intake, defective intestinal transporters for oxalate secretion and absorption, and gastrointestinal (GI) malabsorption (i.e., from gastric bypass surgery) can enhance intestinal oxalate absorption, thereby increasing urinary oxalate level and risk of kidney stone disease (KSD). The GI microbiome rich with oxalate-degrading bacteria can reduce intestinal oxalate absorption and urinary oxalate level. In addition to the oxalate-degrading ability, the GI microbiome also affects expression of oxalate transporters and net intestinal oxalate transport, cholesterol level, and short-chain fatty acids (SCFAs) production, leading to lower KSD risk. Recent evidence also shows beneficial effects of urinary microbiome in KSD prevention. This review summarizes the current knowledge on the aforementioned aspects. Potential benefits of the GI and urinary microbiomes as probiotics for KSD prevention are emphasized. Finally, challenges and future perspectives of probiotic treatment in KSD are discussed.

Pathophysiology and management of enteric hyperoxaluria

Enteric hyperoxaluria is a metabolic disorder resulting from conditions associated with fatty acid malabsorption and characterized by an increased urinary output of oxalate. Oxalate is excessively absorbed in the gut and then excreted in urine where it forms calcium oxalate crystals, inducing kidney stones formation and crystalline nephropathies. Enteric hyperoxaluria is probably underdiagnosed and may silently damage kidney function of patients affected by bowel diseases. Moreover, the prevalence of enteric hyperoxaluria has increased because of the development of bariatric surgical procedures. Therapeutic options are based on the treatment of the underlying disease, limitation of oxalate intakes, increase in calcium salts intakes but also increase in urine volume and correction of hypocitraturia. There are few data regarding the natural evolution of kidney stone events and chronic kidney disease in these patients, and there is a need for new treatments limiting kidney injury by calcium oxalate crystallization.

Nedosiran Safety and Efficacy in PH1: Interim Analysis of PHYOX3

Introduction

Primary hyperoxaluria (PH) is a rare genetic disorder of hepatic glyoxylate metabolism. Nedosiran is an RNA interference (RNAi) therapeutic that the US Food and Drug Administration has approved for treatment of PH1. PHYOX3 is a trial evaluating monthly nedosiran in patients with PH.

Methods

In this PHYOX3 interim analysis, participants with PH1 who continued from a single-dose nedosiran trial (PHYOX1), with no previous kidney or liver transplantation, dialysis, or evidence of systemic oxalosis were eligible. The safety and efficacy of once-monthly nedosiran was assessed over 30 months.

Results

Thirteen participants completed PHYOX1 and continued into PHYOX3. At baseline, the mean (SD) and median (range) age was 24.2 (6.6) years and 23.0 (14-39) years, respectively; 53.8% were female and 61.5% were White. Mean estimated glomerular filtration rate (eGFR) remained stable (62-84.2 mL/min per 1.73 m2) to month 30. Mean 24-hour urinary oxalate (Uox) excretion showed a sustained reduction from baseline of ≥60% at every visit (months 2-30). From month 2, at least 10 of 13 (76.9%) participants achieved normal (<0.46 mmol/24h; upper limit of assay-normal [ULN]) or near-normal (≥0.46 to <0.60 mmol/24h; ≥ULN to <1.3 × ULN) 24-hour Uox excretion. All participants experienced ≥1 adverse event (AE), mostly mild or moderate in severity (primarily, injection site events). Three serious, not treatment-related AEs were reported; there were no deaths or study discontinuations due to AEs.

Conclusion

Nedosiran was well-tolerated in patients with PH1, and treatment resulted in a sustained, substantial reduction in Uox excretion for at least 30 months in this long-term study. No safety signals have been identified to date. The PHYOX3 study is ongoing.

Role of oxalic acid in fungal and bacterial metabolism and its biotechnological potential

Oxalic acid and oxalates are secondary metabolites secreted to the surrounding environment by fungi, bacteria, and plants. Oxalates are linked to a variety of processes in soil, e.g. nutrient availability, weathering of minerals, or precipitation of metal oxalates. Oxalates are also mentioned among low-molecular weight compounds involved indirectly in the degradation of the lignocellulose complex by fungi, which are considered to be the most effective degraders of wood. The active regulation of the oxalic acid concentration is linked with enzymatic activities; hence, the biochemistry of microbial biosynthesis and degradation of oxalic acid has also been presented. The potential of microorganisms for oxalotrophy and the ability of microbial enzymes to degrade oxalates are important factors that can be used in the prevention of kidney stone, as a diagnostic tool for determination of oxalic acid content, as an antifungal factor against plant pathogenic fungi, or even in efforts to improve the quality of edible plants. The potential role of fungi and their interaction with bacteria in the oxalate-carbonate pathway are regarded as an effective way for the transfer of atmospheric carbon dioxide into calcium carbonate as a carbon reservoir.

Oxalate nephropathy after pancreaticoduodenectomy: a case report

A 75-year-old male developed acute kidney injury KDIGO stage 3 a few weeks after Whipple surgery was performed for a distal cholangiocarcinoma. Kidney biopsy revealed oxalate nephropathy. This was attributed to post-Whipple malabsorption, poor compliance with pancreatic enzyme replacement therapy, and daily intake of vitamin C supplements. Pancreatic enzyme replacement therapy was resumed and calcium carbonate initiated, with an improvement in glomerular filtration rate. Unfortunately, due to oncological progression, best supportive care was initiated.We review the pathophysiology and conditions predisposing to secondary hyperoxaluria and oxalate nephropathy. This diagnosis should be considered among the main causes of acute kidney injury following pancreatectomy, with important therapeutic implications.

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 in vivo 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 in vivo base editing as a personalized and precise medicine for PH1 by directly correcting the mutant Agxt gene.

Management of de novo nephrolithiasis after kidney transplantation: a comprehensive review from the European Renal Association CKD-MBD working group

The lifetime incidence of kidney stones is 6%-12% in the general population. Nephrolithiasis is a known cause of acute and chronic kidney injury, mediated via obstructive uropathy or crystal-induced nephropathy, and several modifiable and non-modifiable genetic and lifestyle causes have been described. Evidence for epidemiology and management of nephrolithiasis after kidney transplantation is limited by a low number of publications, small study sizes and short observational periods. Denervation of the kidney and ureter graft greatly reduces symptomatology of kidney stones in transplant recipients, which may contribute to a considerable underdiagnosis. Thus, reported prevalence rates of 1%-2% after kidney transplantation and the lack of adverse effects on allograft function and survival should be interpreted with caution. In this narrative review we summarize current state-of-the-art knowledge regarding epidemiology, clinical presentation, diagnosis, prevention and therapy of nephrolithiasis after kidney transplantation, including management of asymptomatic stone disease in kidney donors. Our aim is to strengthen clinical nephrologists who treat kidney transplant recipients in informed decision-making regarding management of kidney stones. Available evidence, supporting both surgical and medical treatment and prevention of kidney stones, is presented and critically discussed. The specific anatomy of the transplanted kidney and urinary tract requires deviation from established interventional approaches for nephrolithiasis in native kidneys. Also, pharmacological and lifestyle changes may need adaptation to the specific situation of kidney transplant recipients. Finally, we point out current knowledge gaps and the need for additional evidence from future studies.

Association of metabolic syndrome and chronic kidney disease

The prevalence of kidney disease is increasing rapidly worldwide, reflecting rising rates of obesity, diabetes, and associated metabolic syndrome (MetS). Chronic kidney disease and related comorbidities such as obesity, diabetes, and hypertension place a significant financial burden on healthcare systems. Despite the widespread use of RAAS inhibitors, intensive blood pressure and glycemic control, and newer therapeutic options consisting of sodium/glucose cotransporter-2 (SGLT-2) inhibitors or glucagon-like peptide-1 (GLP-1) receptor agonists, a significant risk of progression to end-stage renal disease remains in the high-risk obese and diabetic population. The MetS is a cluster of cardiovascular risk factors that adversely affect the development and progression of chronic kidney failure. According to the criteria of the World Health Organization, it is defined by visceral adiposity, impaired glucose tolerance or insulin resistance, atherogenic dyslipidemia, raised blood pressure, and microalbuminuria with a albumin-to-creatinine ratio ≥30 mg/g. At molecular level MetS is marked by a proinflammatory state and increased oxidative stress leading to various pathophysiological changes causing endothelial dysfunction and a hypercoagulable state. Because the kidney is a highly vascularized organ, it is especially susceptible for those microvascular changes. Therefore, the MetS and its individual components are associated with the premature development, acceleration, and progression of chronic kidney disease. Therefore, it is becoming increasingly important to elucidate the underlying mechanisms of MetS-associated chronic kidney disease in order to develop new strategies for preventing and slowing the progression of renal disease. In this review, we will elucidate (i) the renal structural, hemodynamic, and metabolic changes that occur in obesity and obesity-related kidney injury; (ii) the clinicopathological characteristics of obesity-related kidney injury, primarily focusing on obesity-associated glomerulopathy; (iii) the potential additional factors or predisposing factors that may turn patients more susceptible to renal structural or functional compensatory failure and subsequent injury.

Oxalate Nephropathy: A Case Report of Acute Kidney Injury Due to Juice Diet

Oxalate nephropathy occurs due to the deposition of calcium oxalate crystals in kidney tubules and/or the interstitium as a part of primary or secondary hyperoxaluria. Secondary oxalate nephropathy can occur even with moderately high doses of ascorbic acid intake under yet unidentified clinical circumstances. Vitamin C, although traditionally considered an antioxidant, leads to the formation of superoxide and subsequent generation of reactive oxidant species at pharmacologic concentrations. Ascorbic acid is partly converted to oxalic acid, which is responsible for deposition and renal tubular injury. We report a case of a diabetic patient with normal kidney function who was put on a juice diet for a week due to upper gastrointestinal bleeding. He developed acute kidney injury due to biopsy-proven oxalate nephropathy requiring dialysis. Though he was lost to follow-up after two weeks on dialysis, he was expected to have only a slow recovery or become dependent on dialysis given his age, comorbidities, and extent of tubular involvement. Hence, caution should be exercised before supplementing vitamin C either in its natural form or as a drug. Risk factors for secondary oxalate nephropathy due to excessive intake of oxalate or its precursor are likely to be age, diabetes, dehydration, and underlying chronic kidney disease. Most of the patients do not have a complete recovery of kidney function, and many become dependent on dialysis.

Smart Stimulation Response of a Pyrene-Based Lanthanide(III) MOF: Fluorescence Enhancement to HX (F and Cl) or R-COOH and Artificial Applicable Film on HCl Vapor Sensing

Toxic acids produced by industries are major hazards to the environment and human health, and luminescent pyrene-based crystalline metal-organic frameworks (MOFs) demonstrate promising performance in the detection of toxic acids. Herein, two novel isostructural 3D porous lanthanide MOFs, H3O·[Ln3(TBAPy)2(μ2-H2O)2(OH)2]·2DMA·2Diox·6.5H2O (Ln = Pr (1) and Ce (2); H4TBAPy (1,3,6,8-tetrakis(p-benzoic acid)pyrene); and DMA: N,N-dimethylacetamide) were synthesized, which showed alb topology. Based on the protonation and hydrogen bond mechanism, complex 1 could be used as a fluorescence recognition sensor for HX (X = F, Cl, Br, and I) acid solutions with different luminescence behaviors. It is worth noting that complex 1 exhibited high sensitivity in the fluorescence enhancement sensing of hydrofluoric acid, oxalic acid, and trichloroacetic acid. In particular, complex 1 had a low limit of detection (LOD) for OA (0.1 μM) and was applied to real monitoring of orange fruit samples. In addition, the PVA@1 film could selectively, sensitively, and quantitatively respond to hydrochloric acid (HCl) vapor through fluorescent quenching; due to its protonation and adsorption capacity, the LOD was 0.18 ppm. Therefore, the portable optical device, the PVA@1 film, can detect HCl gas in trace amounts, achieving the ultimate goal of real-time and rapid detection, which has potential application value for industrial production safety.

Nutrition and Intestinal Rehabilitation of Children With Short Bowel Syndrome: A Position Paper of the ESPGHAN Committee on Nutrition. Part 1: From Intestinal Resection to Home Discharge

Short bowel syndrome (SBS) is the leading cause of intestinal failure (IF) in children. The mainstay of treatment for IF is parenteral nutrition (PN). The aim of this position paper is to review the available evidence on managing SBS and to provide practical guidance to clinicians dealing with this condition. All members of the Nutrition Committee of the European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) contributed to this position paper. Some renowned experts in the field joined the team to guide with their experience. A systematic literature search was performed from 2005 to May 2021 using PubMed, MEDLINE, and Cochrane Database of Systematic Reviews. In the absence of evidence, recommendations reflect the expert opinion of the authors. Literature on SBS mainly consists of retrospective single-center experience, thus most of the current papers and recommendations are based on expert opinion. All recommendations were voted on by the expert panel and reached >90% agreement. The first part of this position paper focuses on the physiological mechanism of intestinal adaptation after surgical resection. It subsequently provides some clinical practice recommendations for the primary management of children with SBS from surgical resection until discharged home on PN.

Primary hyperoxaluria type 1 in children: clinical and laboratory manifestations and outcome

BACKGROUND

Primary hyperoxaluria (PH) results from genetic mutations in different genes of glyoxylate metabolism, which cause significant increases in production of oxalate by the liver. This study aimed to report clinical and laboratory manifestations and outcome of PH type 1 in children in our center.

METHODS

A single-center observational cohort study was conducted at Children's University Hospital in Damascus, and included all patients admitted from 2018 to 2020, with a diagnosis of hyperoxaluria (urinary oxalate excretion > 45 mg/1.73 m2/day, or > 0.5 mmol/1.73 m2/day). PH type 1 (PH1) diagnosis was established by identification of biallelic pathogenic variants (compound heterozygous or homozygous mutations) in AGXT gene on molecular genetic testing.

RESULTS

The study included 100 patients with hyperoxaluria, with slight male dominance (57%), and median age 1.75 years (range, 1 month-14 years). Initial complaint was urolithiasis or nephrocalcinosis in 47%, kidney failure manifestations in 29%, and recurrent urinary tract infection in 24%. AGXT mutations were detected in 40 patients, and 72.5% of PH1 patients had kidney failure at presentation. Neither gender, age nor urinary oxalate excretion in 24 h had statistical significance in distinguishing PH1 from other forms of hyperoxaluria (P-Value > 0.05). Parental consanguinity, family history of kidney stones, bilateral nephrocalcinosis, presence of oxalate crystals in random urine sample, kidney failure and mortality were statistically significantly higher in PH1 (P-values < 0.05). Mortality was 32.5% among PH1 patients, with 4 PH1 patients (10%) on hemodialysis awaiting combined liver-kidney transplantation.

CONCLUSION

PH1 is still a grave disease with wide variety of clinical presentations which frequent results in delays in diagnosis, thus kidney failure is still a common presentation. In Syria, we face many challenges in diagnosis of PH, especially PH2 and PH3, and in management, with hopes that diagnosis tools and modern therapies will become available in our country. Graphical abstract A higher resolution version of the Graphical abstract is available as Supplementary information.

Purslane-induced oxalate nephropathy: case report and literature review

BACKGROUND

The kidney is particularly vulnerable to toxins due to its abundant blood supply, active tubular reabsorption, and medullary interstitial concentration. Currently, calcium phosphate-induced and calcium oxalate-induced nephropathies are the most common crystalline nephropathies. Hyperoxaluria may lead to kidney stones and progressive kidney disease due to calcium oxalate deposition leading to oxalate nephropathy. Hyperoxaluria can be primary or secondary. Primary hyperoxaluria is an autosomal recessive disease that usually develops in childhood, whereas secondary hyperoxaluria is observed following excessive oxalate intake or reduced excretion, with no difference in age of onset. Oxalate nephropathy may be overlooked, and the diagnosis is often delayed or missed owning to the physician's inadequate awareness of its etiology and pathogenesis. Herein, we discuss the pathogenesis of hyperoxaluria with two case reports, and our report may be helpful to make appropriate treatment plans in clinical settings in the future.

CASE PRESENTATION

We report two cases of acute kidney injury, which were considered to be due to oxalate nephropathy in the setting of purslane (portulaca oleracea) ingestion. The two patients were elderly and presented with oliguria, nausea, vomiting, and clinical manifestations of acute kidney injury requiring renal replacement therapy. One patient underwent an ultrasound-guided renal biopsy, which showed acute tubulointerstitial injury and partial tubular oxalate deposition. Both patients underwent hemodialysis and were discharged following improvement in creatinine levels.

CONCLUSIONS

Our report illustrates two cases of acute oxalate nephropathy in the setting of high dietary consumption of purslane. If a renal biopsy shows calcium oxalate crystals and acute tubular injury, oxalate nephropathy should be considered and the secondary causes of hyperoxaluria should be eliminated.

Idiopathic Oxalate Nephropathy Leading to End-Stage Kidney Disease: A Case Report

Oxalate nephropathy represents a frequently overlooked etiology of renal failure, characterized by the deposition of calcium oxalate crystals within the renal parenchyma. This progressive form of kidney disease is marked by a significant increase in serum creatinine (Cr) level accompanied by evidence of oxalate crystal deposition on renal biopsy causing tubular obstruction and tubular injury leading to fibrosis. In all instances of oxalate nephropathy, examination of stones consistently exhibits multiple birefringent calcium oxalate crystals under polarized light. This case report details the clinical course of a patient who initially presented with progressively worsening renal function and ultimately developed end-stage kidney disease (ESKD) as a consequence of idiopathic hyperoxaluria.

Acute Kidney Injury and Hair-Straightening Products: A Case Series

RATIONALE & OBJECTIVE

Keratin-based hair-straightening treatment is a popular hair-styling method. The majority of keratin-based hair-straightening products in Israel contain glycolic acid derivatives, which are considered safe when used topically. Systemic absorption of these products is possible, and anecdotal reports have described kidney toxicity associated with their use. We report a series of cases of severe acute kidney injury (AKI) following use of hair-straightening treatment in Israel during the past several years.

STUDY DESIGN

Case series.

SETTING & PARTICIPANTS

We retrospectively identified 26 patients from 14 medical centers in Israel who experienced severe AKI and reported prior treatment with hair-straightening products in 2019-2022.

FINDINGS

The 26 patients described had a median age of 28.5 (range, 14-58) years and experienced severe AKI following a hair-straightening procedure. The most common symptoms at presentation were nausea, vomiting, and abdominal pain. Scalp rash was noted in 10 (38%) patients. Two patients experienced a recurrent episode of AKI following a repeat hair-straightening treatment. Seven patients underwent kidney biopsies, which demonstrated intratubular calcium oxalate deposition in 6 and microcalcification in tubular cells in 1. In all biopsies, signs of acute tubular injury were present, and an interstitial infiltrate was noted in 4 cases. Three patients required temporary dialysis.

LIMITATIONS

Retrospective uncontrolled study, small number of kidney biopsies.

CONCLUSIONS

This series describes cases of AKI with prior exposure to hair-straightening treatments. Acute oxalate nephropathy was the dominant finding on kidney biopsies, which may be related to absorption of glycolic acid derivatives and their metabolism to oxalate. This case series suggests a potential underrecognized cause of AKI in the young healthy population. Further studies are needed to confirm this association and to assess the extent of this phenomenon as well as its pathogenesis.

Determinants on urinary excretion of oxalate and other key factors related to urolithiasis among patients with chronic kidney disease: a single center study

PURPOSE

Urolithiasis is a known risk factor for chronic kidney disease (CKD). However, how CKD might affect the risk of incidence of urolithiasis is not widely studied.

METHODS

Urinary excretion of oxalate as well as other key factors related to urolithiasis was analyzed in a single center study of 572 patients with biopsy-proven kidney disease.

RESULTS

The mean age of the cohort was 44.9 years and 60% were males. The mean eGFR was 65.9 ml/min/1.73 m2. Median urinary excretion of oxalate was 14.7 (10.4-19.1) mg/24-h and associated with current urolithiasis (OR 12.744, 95% CI: 1.564-103.873 per one logarithm transformed unit of urinary oxalate excretion). Oxalate excretion was not associated with eGFR and urinary protein excretion. Oxalate excretion was higher in patients with ischemia nephropathy as compared with patients with glomerular nephropathy and tubulointerstitial nephropathy (16.4 vs 14.8 vs 12.0 mg, p = 0.018). And ischemia nephropathy (p = 0.027) was associated with urinary oxalate excretion on adjusted linear regression analysis. Urinary excretion of calcium and uric acid was correlated with eGFR and urinary protein excretion (all p < 0.001), with ischemia nephropathy and tubulointerstitial nephropathy associated with uric acid excretion (both p < 0.01) as well. Citrate excretion was correlated with eGFR (p < 0.001) on adjusted linear regression.

CONCLUSION

Excretion of oxalate and other key factors related to urolithiasis was differentially associated with eGFR, urinary protein, and pathological changes in CKD patients. The influence of these intrinsic traits of the underlining kidney disease should be considered when evaluating urolithiasis risk in patients with CKD.

Oxalate Homeostasis in Non-Stone-Forming Chronic Kidney Disease: A Review of Key Findings and Perspectives

Chronic kidney disease (CKD) is a significant global public health concern associated with high morbidity and mortality rates. The maintenance of oxalate homeostasis plays a critical role in preserving kidney health, particularly in the context of CKD. Although the relationship between oxalate and kidney stone formation has been extensively investigated, our understanding of oxalate homeostasis in non-stone-forming CKD remains limited. This review aims to present an updated analysis of the existing literature, focusing on the intricate mechanisms involved in oxalate homeostasis in patients with CKD. Furthermore, it explores the key factors that influence oxalate accumulation and discusses the potential role of oxalate in CKD progression and prognosis. The review also emphasizes the significance of the gut-kidney axis in CKD oxalate homeostasis and provides an overview of current therapeutic strategies, as well as potential future approaches. By consolidating important findings and perspectives, this review offers a comprehensive understanding of the present knowledge in this field and identifies promising avenues for further research.

Oxalate as a potent promoter of kidney stone formation

Kidney stones are among the most prevalent urological diseases, with a high incidence and recurrence rate. Treating kidney stones has been greatly improved by the development of various minimally invasive techniques. Currently, stone treatment is relatively mature. However, most current treatment methods are limited to stones and cannot effectively reduce their incidence and recurrence. Therefore, preventing disease occurrence, development, and recurrence after treatment, has become an urgent issue. The etiology and pathogenesis of stone formation are key factors in resolving this issue. More than 80% of kidney stones are calcium oxalate stones. Several studies have studied the formation mechanism of stones from the metabolism of urinary calcium, but there are few studies on oxalate, which plays an equally important role in stone formation. Oxalate and calcium play equally important roles in calcium oxalate stones, whereas the metabolism and excretion disorders of oxalate play a crucial role in their occurrence. Therefore, starting from the relationship between renal calculi and oxalate metabolism, this work reviews the occurrence of renal calculi, oxalate absorption, metabolism, and excretion mechanisms, focusing on the key role of SLC26A6 in oxalate excretion and the regulatory mechanism of SLC26A6 in oxalate transport. This review provides some new clues for the mechanism of kidney stones from the perspective of oxalate to improve the understanding of the role of oxalate in the formation of kidney stones and to provide suggestions for reducing the incidence and recurrence rate of kidney stones.

Research progress on renal calculus associate with inborn error of metabolism

Renal calculus is a common disease with complex etiology and high recurrence rate. Recent studies have revealed that gene mutations may lead to metabolic defects which are associated with the formation of renal calculus, and single gene mutation is involved in relative high proportion of renal calculus. Gene mutations cause changes in enzyme function, metabolic pathway, ion transport, and receptor sensitivity, causing defects in oxalic acid metabolism, cystine metabolism, calcium ion metabolism, or purine metabolism, which may lead to the formation of renal calculus. The hereditary conditions associated with renal calculus include primary hyperoxaluria, cystinuria, Dent disease, familial hypomagnesemia with hypercalciuria and nephrocalcinosis, Bartter syndrome, primary distal renal tubular acidosis, infant hypercalcemia, hereditary hypophosphatemic rickets with hypercalciuria, adenine phosphoribosyltransferase deficiency, hypoxanthine-guanine phosphoribosyltransferase deficiency, and hereditary xanthinuria. This article reviews the research progress on renal calculus associated with inborn error of metabolism, to provide reference for early screening, diagnosis, treatment, prevention and recurrence of renal calculus.

Acetate attenuates hyperoxaluria-induced kidney injury by inhibiting macrophage infiltration via the miR-493-3p/MIF axis

Hyperoxaluria is well known to cause renal injury and end-stage kidney disease. Previous studies suggested that acetate treatment may improve the renal function in hyperoxaluria rat model. However, its underlying mechanisms remain largely unknown. Using an ethylene glycol (EG)-induced hyperoxaluria rat model, we find the oral administration of 5% acetate reduced the elevated serum creatinine, urea, and protected against hyperoxaluria-induced renal injury and fibrosis with less infiltrated macrophages in the kidney. Treatment of acetate in renal tubular epithelial cells in vitro decrease the macrophages recruitment which might have reduced the oxalate-induced renal tubular cells injury. Mechanism dissection suggests that acetate enhanced acetylation of Histone H3 in renal tubular cells and promoted expression of miR-493-3p by increasing H3K9 and H3K27 acetylation at its promoter region. The miR-493-3p can suppress the expression of macrophage migration inhibitory factor (MIF), thus inhibiting the macrophages recruitment and reduced oxalate-induced renal tubular cells injury. Importantly, results from the in vivo rat model also demonstrate that the effects of acetate against renal injury were weakened after blocking the miR-493-3p by antagomir treatment. Together, these results suggest that acetate treatment ameliorates the hyperoxaluria-induced renal injury via inhibiting macrophages infiltration with change of the miR-493-3p/MIF signals. Acetate could be a new therapeutic approach for the treatment of oxalate nephropathy.