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Introduction and Objective: Kidney stone growth and new stone formation are common clinical trial endpoints and are associated with future symptomatic events. To date, a manual review of CT scans has been required to assess stone growth and new stone formation, which is laborious. We validated the performance of a software algorithm that automatically identified, registered, and measured stones over longitudinal CT studies. Methods: We validated the performance of a pretrained machine learning algorithm to classify stone outcomes on longitudinal CT scan images at baseline and at the end of the 2-year follow-up period for 62 participants aged >18 years in the Prevention of Urinary Stones with Hydration (PUSH) randomized controlled trial. Stones were defined as an area of voxels with a minimum linear dimension of 2 mm that was higher in density than the mean plus 4 standard deviations of all nonnegative HU values within the kidney. The four outcomes assessed were: (1) growth of at least one existing stone by ≥2 mm, (2) formation of at least one new ≥2 mm stone, (3) no stone growth or new stone formation, and (4) loss of at least one stone. The accuracy of the algorithm was determined by comparing its outcomes to the gold standard of independent review of the CT images by at least two expert clinicians. Results: The algorithm correctly classified outcomes for 61 paired scans (98.4%). One pair that the algorithm incorrectly classified as stone growth was a new renal artery calcification on end-of-study CT. Conclusions: An automated image analysis method validated for the prospective PUSH trial was highly accurate for determining clinical outcomes of new stone formation, stone growth, stable stone size, and stone loss on longitudinal CT images. This method has the potential to improve the accuracy and efficiency of clinical care and endpoint determination for future clinical trials.

BACKGROUND: The performance of estimated glomerular filtration rate (eGFR) among patients with heart failure (HF) may be worse than in the general population due to a higher prevalence of confounding factors affecting creatinine and cystatin C. Studies in this area are scarce and not stratified by type of HF. We evaluated the performance of current creatinine and cystatin C equations (eGFRcr, eGFRcys, and eGFRcrcys) compared with measured GFR (mGFR) among patients with HF stratified by ejection fraction. METHODS: We pulled data on Mayo Clinic patients with an mGFR performed for clinical indications from 2011 to 2023, with serum creatinine and cystatin C measured within 7 days and an echocardiogram performed up to 1 year before the mGFR date. HF was identified by the presence of International Classification of Diseases codes within 1 year before the mGFR and subgrouped into ejection fraction (EF) ≥50% (HFEF≥50%, n=182) or <50% (HFEF<50%, n=115) and compared with no-HF controls (n=1871). CKD-EPI (and EKFC) eGFRcr, eGFRcys, and eGFRcrcys equations were calculated and compared for bias (mGFR minus eGFR) and accuracy (1-P30, proportion of people with ≥30% difference between eGFR and mGFR). CIs were generated by bootstrapping. RESULTS: The HF groups were characterized by older age, higher proportion of males, more diabetes, higher creatinine, and higher cystatin C than controls. In terms of bias, eGFRcr overestimated mGFR to a greater extent in both HF groups compared with controls, whereas eGFRcys and eGFRcrcys showed similar bias in both HF groups and controls. In the HF groups, cystatin C-based equations were more accurate than eGFRcr, particularly within HFEF<50% (1-P30 of 28% and 34% for CKD-EPI eGFRcys and eGFRcrcys, respectively, versus 60% for eGFRcr), whereas eGFRcrcys was more accurate in controls. The CKD-EPI and EKFC equations were overall convergent, showing similar results. CONCLUSIONS: Among patients with HF, eGFRcr demonstrates inferior performance (more bias and less accuracy) compared with cystatin C-based eGFRs, with this effect being more pronounced in those with HFEF<50%.

Key Points Genetic testing of individuals suspected of monogenic urinary stone disease resolved 34% of families with 22 different genes detected. Resolved individuals had a lower baseline and last visit eGFR and earlier age of stone presentation than the unresolved group. Specific phenotypes and younger diagnostic age were associated with a monogenic cause, allowing refinement of future screenings. Background Urinary stone disease with a clear genetic cause, monogenic stone disease (MSD), is increasingly recognized as a significant proportion of the total population. When MSD is suspected, genetic testing provides a firm diagnosis that can alter management and treatment. Here, we present testing results from a large cohort with suspected MSD. Methods Patients with features suggestive of MSD (early onset, family history, frequent stones, nephrocalcinosis [NC], and/or CKD) were recruited by the Rare Kidney Stone Consortium and genotyped for up to 160 known or candidate MSD genes via a targeted massively parallel sequencing panel. We compared clinical and biochemical features between genetically resolved MSD and unresolved individuals. Results Of 426 families (657 patients) enrolled, 145 (34%) were resolved with identified disease associated variants in 22 known MSD genes. Ninety-nine families were biallelic, 37 monoallelic, and two digenic. An additional 21 of the 231 screened family members were resolved. Genes identified in ten or more families include the following: AGXT , HOGA1 , SLC34A3 , CYP24A1 , SLC3A1 , and CLCN5 . Compared with the unresolved group, MSD probands had a lower baseline and last visit eGFR, earlier age of stone presentation, and more stone events and procedures/year of life. The resolve rate was higher in those <16 years, and NC was seen earlier in the MSD group. Overall, NC was a risk factor for lower eGFR. Among the specific disorders, patients with primary hyperoxaluria had the earliest age of stone and NC diagnosis, and as expected, the highest urinary oxalate level. Conclusions Our study emphasizes the value of selecting patients enriched for factors associated with MSD, and comprehensive genetic testing to achieve a high yield of genetic diagnoses. Significant clinical and biochemical characteristics of patients with MSD were defined. A definitive MSD diagnosis facilitates individualized management and strategies to delay disease progression in probands and affected family members.

Key Points Significant heterogeneity in patient characteristics, urine metabolic studies, and kidney outcomes exist among enteric hyperoxaluria patients from diverse etiologies. Structurally induced malabsorption and exocrine pancreatic insufficiency have the highest kidney stone event rates. Patients with structurally induced malabsorption have up to 18% ESKD incidence at 5 years. Background Enteric hyperoxaluria (EH) is a risk factor for calcium oxalate nephrolithiasis and kidney disease. The study compares patient characteristics and urine metabolic profiles at the time of EH diagnosis and kidney stones and ESKD events during follow-up in a cohort with diverse causes of EH. Methods Adult patients with newly documented elevated urinary oxalate excretion >40 mg/24 h between January 1, 2010, and October 10, 2023, and a known enteric diagnosis including inflammatory bowel disease, exocrine pancreatic insufficiency (EPI), celiac disease, structural intestinal malabsorption (SIM), or malabsorptive bariatric surgery (Bariatric) were identified. Event rates and cumulative incidence of kidney stones and ESKD were assessed. Results Among 814 identified patients, the most common enteric etiology was Bariatric ( n =524, 64%). Patients with ulcerative colitis had the highest prevalence of kidney stones at EH diagnosis (93.6%) compared with other enteric etiologies ( P = 0.002). Patients with SIM had the highest urinary oxalate, lower urinary citrate, and volume, compared with other enteric etiologies ( P < 0.05). Calcium oxalate supersaturation was similar among the enteric groups ( P = 0.67). Median stone event rate for the overall cohort was 0.70 stone events/year during a mean (SD) follow-up of 5.0 (3.9) years. The SIM and EPI groups experienced the highest stone events (median [IQR] 1.24 [0.28–2.40] and 1.20 [0.41–1.99] events/year, respectively) while the Bariatric group had the lowest event rates (median [IQR] 0.45 [0.00–1.66 events/year]; P < 0.001). The SIM group had the highest ESKD incidence (17.8% 5 years postdiagnosis; log-rank test P < 0.001). Conclusions We describe a large EH cohort from diverse enteric etiologies. Significant heterogeneity exists in patient characteristics, urine metabolic risk factors, and adverse kidney outcomes. Patients with SIM and EPI experienced the highest kidney stone events and patients with SIM had the highest ESKD incidence. This study highlights the urgent need for more granular information regarding the natural history and risk factors for kidney complications for patients with EH to support interventional trials to improve outcomes.

Key Points In individuals undergoing bariatric surgery, the magnitude of decline in GFR postbariatric surgery is directly associated with presurgery GFR. Reductions in GFR postsurgery were only weakly correlated with weight loss. In obese individuals, GFR-estimating equations performed best when deindexed and when applied in people with reduced kidney function. Background Important questions remain about how bariatric ( i.e ., weight loss) surgery affects measured GFR (mGFR) and eGFR as well as what factors influence change in mGFR postsurgery. Methods Data were pooled from all seven available studies (dates: 2004–2018) measuring GFR prebariatric and postbariatric surgery using gold standard methods. Change in postsurgery mGFR, factors that could influence change in mGFR, and effects on five GFR-estimating equations were analyzed using standard statistical methods. Results The cohort included 105 individuals from the United States and Europe. Sixty-eight percent were female, 97% were White, the mean age was 50 years (range, 24–70), and the mean body mass index was 46±8 kg/m 2 . The mean presurgery mGFR of 107 ml/min (range, 31–215) fell to 92 ml/min (−14%; 95% confidence interval, −21 to −10) postsurgery, with a strong linear relationship existing between presurgery mGFR and % change in GFR ( r =−0.51; −0.64 to −0.35). Individuals with presurgery mGFR ≥90, 60 to <90, and<60 ml/min had −25 (−32 to −19), 1 (−11 to 13), and 7 (0 to 14) ml/min mean postoperative changes in mGFR. Change in weight was significantly correlated with change in mGFR ( r =0.22; 0.03 to 0.40). After adjusting for sex, changes in mGFR postsurgery were associated with higher presurgical age (−0.6 ml/min per year; −1.1 to −0.2), mGFR (−0.5 ml/min per 1 ml/min; −0.6 to −0.4), and change in systolic BP (−0.3 ml/min per 1 mm Hg; −0.6 to 0.0). All GFR-estimating equations significantly underestimated postsurgical GFR reductions in people with preserved kidney function and had improved bias, precision, and accuracy when deindexed and applied to individuals with mGFR <90 ml/min. Conclusions In individuals with obesity undergoing bariatric surgery, the magnitude of postsurgical decline in mGFR was directly associated with presurgery GFR and weakly correlated with weight loss. In addition, GFR-estimating equations' performance improved when deindexed and used in people with reduced kidney function, with the combined creatinine/cystatin C equations having the best overall performance.

Abstract Nephrocalcinosis provides a nidus for stone formation and is strongly linked to renal injury and chronic kidney disease. Although the crucial role of macrophages in the formation and progression of calcium oxalate (CaOx) crystals has long been widely recognized, finding effective immunotherapies for nephrocalcinosis remains a challenge. In this study, we described an innovative macrophage‐based method that delivers interleukin‐10 (IL‐10) into the kidney, reduces the deposition of CaOx crystals, and alleviates renal injury in a mouse model of glyoxylate‐induced CaOx. Compared with recombinant IL‐10 direct injection, the macrophage‐based method has the advantages of biocompatibility and sustaining action. We found that the transplantation of engineered macrophages via the tail vein significantly reduced the volume of crystals in the kidney, thereby alleviating the kidney injury caused by crystal. In mechanistic studies, IL‐10‐secreting macrophages inhibited crystal formation and promoted crystal clearance by promoting macrophage M2 polarization, exerting a protective effect on renal tissue. Our data suggest that macrophage‐based delivery of IL‐10 to the kidney can be a potential treatment method for nephrocalcinosis.

ABSTRACT Background Primary hyperoxaluria (PH), a rare autosomal recessive disease of oxalate accumulation in the kidneys, is caused by biallelic pathogenic changes in three known genes: AGXT (PH1), GRHPR (PH2) and HOGA1 (PH3). Methods To better understand the overall risk of developing clinical PH, we manually curated and classified PH genetic variants and calculated the estimated genetic prevalence overall and in five ethnic subpopulations using allelic frequencies from the population Genome Aggregation Database (gnomAD version 2.1.1). Results Of the 651 identified PH variants, 273 were found in gnomAD 2.1.1 on the day of download and after reclassification, 208 were determined pathogenic (P) or likely pathogenic (LP) (AGXT, n = 94; GRHPR, n = 46; and HOGA1, n = 68) and a further 65 were classified as rare variants of uncertain significance (VUS). Using P and LP only, estimated carrier frequency was 1:229 for PH1, 1:465 for PH2 and 1:151 for PH3, while genetic prevalence was 1:209 357 for PH1, 1:863 028 for PH2 and 1:90 834 for PH3 (i.e. nearly 5, 1 and 11 per 1 million individuals, respectively). The highest carrier frequencies for AGXT pathogenic variants were in East Asians (1 in 146) and the European non-Finnish population (1 in 187); for GRHPR, South Asians (1 in 313) and the European non-Finnish population (1 in 413); and for HOGA1, Ashkenazi Jewish (1 in 38) and East Asians (1 in 100). The estimated risk of developing PH was ≈1:59 017. Conclusions This careful benchmarking exercise indicates that a significant number of individuals at risk for PH symptoms remain undiagnosed. Since these numbers exceed known diagnosed cases of PH, improved screening and diagnosis of this underestimated disease is necessary.

Key Points Circulating proteins independently associated with kidney stone diagnosis are related to kidney stone matrix. Lower circulating uromodulin and higher scavenger receptor cysteine-rich domain-containing group B protein levels were associated with higher kidney stone risk, whereas kidney stone presence elevates plasma matrix metalloproteinase 7 level. The protective effect of uromodulin against kidney stones was independent of kidney function. Background Kidney stones are increasingly recognized as a systemic disorder with a high global prevalence. However, large proteomics studies are lacking. Methods An individual-level proteomics study with rigorous adjustments was performed on 35,331 UK Biobank participants to uncover the independent associations between 2922 circulating proteins and prevalent kidney stone disease. Mendelian randomization analysis was used to assess causal relationships. Findings were validated using genomic data from the Mayo Clinic Biobank ( N =43,744), concentration-response analysis, transcriptomics analyses, and additional genome-wide association studies. Results Nine plasma proteins were independently associated with a kidney stone diagnosis, including reduced uromodulin (UMOD; β , −0.10; 95% confidence interval [CI], −0.15 to −0.05) and elevated scavenger receptor cysteine-rich domain-containing group B protein (SSC4D; β , 0.28; 95% CI, 0.17 to 0.38) and were enriched in extracellular matrix pathways. Mendelian randomization analysis revealed that the presence of kidney stone contributed to elevated levels of matrix metalloproteinase 7. Conversely, lower plasma UMOD (odds ratio [OR], 0.93; 95% CI, 0.90 to 0.97) and higher plasma SSC4D (OR, 1.10; 95% CI, 1.02 to 1.18) were associated with kidney stone risk. These associations were consistently replicated in the Mayo Clinic Biobank dataset (UMOD; OR, 0.92; 95% CI, 0.86 to 0.98; SSC4D; OR, 1.13; 95% CI, 1.01 to 1.27) and further validated by a concentration-response analysis. Single-nucleus RNA sequencing and quantitative trait loci analyses confirmed consistent associations between thick ascending limb UMOD expression and stone former status and with blood and urine UMOD concentrations. Genome-wide association study analysis, adjusted for eGFR, suggested that the protective role of UMOD against kidney stones was independent of kidney function. Conclusions This study highlights significant associations between concentrations of specific blood proteins and a history of kidney stones. Several implicated proteins are related to kidney stone matrix, with UMOD independently associated with lower risk and SSC4D with higher risk of kidney stones.

ABSTRACT Human alanine:glyoxylate aminotransferase (AGT) is a liver peroxisomal enzyme that metabolizes glyoxylate, the oxalate precursor, to glycine. AGT deficiency, due to recessive pathogenic changes in the AGXT gene, results in calcium oxalate accumulation and kidney stones, a condition known as primary hyperoxaluria type 1 (PH1). Most missense variants lead to PH1 by causing AGT misfolding, but their effects manifest differently based on the presence of two polymorphic variants, p.Pro11Leu (p.P11L) and p.Ile340Met (p.I340M), which are usually present in linkage disequilibrium and generate the minor haplotype. While the p.P11L substitution reduces AGT global stability and worsens the effects of pathogenic changes, the p.I340M exerts a stabilizing effect whose role on PH1 pathogenesis has never been elucidated. The p.Ile279Thr (p.I279T) variant is frequent in healthy populations (0.29%), mainly on the major allele, but we present data from six PH1 families (eight patients) suggesting p.I279T as a PH1 pathogenic allele. Interestingly, in these families, p.Thr279 is always associated with p.Leu11 and p.Ile340, thus with a split AGXT haplotype. Analysis of the effects of the p.I279T mutation by in silico predictions, biochemical analyses on purified proteins, and expression in two cellular models of disease ( AGXT1 ‐KO HepG2 and CHO cells) shows that it causes a folding defect that is exacerbated by p.P11L but mitigated by p.I340M, thus explaining why p.Thr279 is pathogenic just on the p.Leu11–p.Ile340 haplotype. These data indicate that genetic screenings for PH1 should document the AGXT haplotype, including its components, to obtain an accurate diagnosis and possible prognostic information.