Sarah Anne Howles

Kidney stones form as a result of the accumulation of mineral deposits on an organic matrix. They are more common in patients with metabolic and/or anatomical abnormalities that lead to urine supersaturation, have a prevalence of ~10% and recur in ~50% of patients at 5-10 years of follow-up. Known risk factors for kidney stones are obesity and metabolic syndrome, anatomical abnormalities leading to urinary stasis, dietary habits and genetic factors leading to potential dysregulation of urinary calcium, uric acid, oxalate and cystine concentrations. Kidney stones are diagnosed based on imaging, including ultrasonography, radiography and CT. Minimally invasive treatments, including shock wave lithotripsy, ureteroscopy and percutaneous nephrolithotripsy, have largely replaced open surgery in kidney stone management. These modalities can achieve stone clearance, while minimizing complication rates, improving health-related quality of life and enabling a quicker return to daily activities compared to open surgery. Technological advances, such as advanced laser fibres and devices and suction technology, which are used during minimally invasive treatments, are further improving clinical outcomes.

Objectives: To investigate the predictive accuracy of European Association of Urology (EAU) Urolithiasis guidelines risk stratification in predicting future stone events over 5 years following presentation. Patients and Methods: The EAU Urolithiasis guidelines recommend that follow up of individuals with kidney stone disease (KSD) is guided by whether they are at high‐ or low‐risk of future disease based on their published criteria. We developed a virtual stone clinic (VSC) from UK Biobank (UKB) and All of Us (AoU) data, using diagnostic and operative codes to identify individuals with clinically significant KSD, defined as renal colic or a KSD intervention, individuals were assigned to high‐ and low‐risk groups based on EAU criteria. We evaluated the risk of symptomatic events over the 5 years following presentation using time‐to‐event analyses, predictive accuracy statistics, and decision curve analysis (DCA). Results: The VSC included 8449 and 17 233 individuals with clinically significant KSD from the UKB and AoU, respectively. At first presentation, 34% and 28% of the UKB and AoU VSC patients, respectively, were classified as high risk of recurrence based on the EAU criteria. The EAU risk classification system demonstrated limited ability to predict KSD recurrence over a 5‐year period, with a time‐dependent area under curve (AUC) of 0.61. DCA showed no clinical benefit to risk‐stratified follow‐up. The only factor associated with prediction of future stone events was a prior history of two or more symptomatic episodes (time‐dependent AUC at 5 years = 0.62). Conclusion: The EAU Urolithiasis risk classification system has limited ability to predict future kidney stone events over 5‐years; our findings do not support its use to guide risk‐stratified follow‐up.

Background and objective: Kidney stone disease (KSD) is common and distinct monogenic forms with well-defined treatment pathways exist. However, it is unclear which patients should undergo genetic testing and the significance of monoallelic variants in SLC34A1, SLC34A3, CYP24A1, SLC7A9, and SLC3A1 . We aimed to define monogenic KSD inheritance patterns, determine the diagnostic yield of genetic testing in selected and unselected cohorts, and establish the utility of standard serum biochemistry in highlighting those at risk of monogenic KSD. Methods: We compared genetic and phenotypic data from individuals with and without KSD in the UK Biobank to determine inheritance patterns. We established the “number needed to test” (NNTT) to identify monogenic KSD in the UK Biobank and a specialist adult kidney stone nephrology clinic where patients had genetic testing based on age, recurrence, and family history. We examined the utility of standard serum biochemistry in identifying monogenic KSD in both settings. Key findings and limitations: Monogenic KSD associated with SLC34A3, SLC7A9, and SLC3A1 is inherited in an autosomal dominant manner and monogenic KSD associated with SLC34A1 and CYP24A1 in an autosomal recessive manner. A monogenic diagnosis was made in ∼1% of KSD in the UK Biobank (NNTT∼90) and 15% of KSD in a specialist nephrology clinic (NNTT∼7). In both settings, standard serum biochemistry failed to identify individuals at risk of monogenic KSD. Conclusions and clinical implications: Genetic testing for monogenic KSD has utility in specialist settings where there is clinical suspicion of an inherited disorder even in the absence of biochemical abnormalities.

Engaging with patients and the public is essential to design and deliver impactful research. Enhancing the relevance of research and tailoring treatments to align with patients' preferences can facilitate improved clinical care. We aimed to identify the research, support and treatment priorities of individuals with kidney stone disease (KSD) using a 25-question survey in inpatient and outpatient urology departments. Forty-four individuals with KSD responded to our survey; 28 (64%) had experienced multiple KSD episodes and 11 reported 5 or more episodes. Median self-rated quality-of-life (QoL) impact (0 = negligible; 10 = severe) was 7.00 out of 10.00 (interquartile range [IQR]: 5.00-9.00), equivalent in individuals with single and recurrent stone episodes. Pain (n = 34), haematuria (n = 28) and anxiety (n = 22) were the primary factors contributing to QoL impact. Participants prioritised research into preventing recurrence, alleviating pain and slowing stone growth. More than one-third desired more information about KSD. Most (n = 36) felt 'likely' or 'very likely' to take medication to reduce their risk of KSD and 25 would commit to life-long therapy. Daily dosing was acceptable to 13 participants if risk of KSD recurrence was reduced by 50%, rising to 34 respondents if risk of recurrence was reduced by 75%. Most respondents (n = 44) expressed willingness to have genetic testing to facilitate personalised medicine research. Our findings emphasise symptoms contributing to reduced physical and psychological wellbeing in patients with KSD. We highlight the need for research into developing therapies to prevent stone recurrence, alleviate pain and slow stone growth, and for educational materials. Responses indicate an appetite for personalised medicine and oral medications in KSD.

BACKGROUND: Kidney stone disease (KSD) affects approximately 10% of adults, is heritable, and is associated with mineral metabolic abnormalities. METHODS: Genetic variants and pathways increasing KSD risk via calcium and phosphate homeostasis were ascertained using GWAS, region-specific Mendelian randomization (MR), and genetic colocalization. The utility of pathway modulation was estimated via drug target MR, and the effects of variants on calcium-sensing receptor (CaSR) signaling were characterized. RESULTS: Seventy-nine independent KSD-associated genetic signals at 71 loci were identified. MR identified 3 loci affecting KSD risk via increased serum calcium or decreased serum phosphate concentrations (ORs for genomic regions = 4.30, 11.42, and 13.83 per 1 SD alteration; P < 5.6 × 10 ^–10 ). Colocalization analyses defined putative, noncoding KSD-causing variants estimated to account for 11%–19% of KSD cases in proximity to diacylglycerol kinase δ ( DGKD ), a CaSR signaling partner; solute carrier family 34 member 1 ( SLC34A1 ), a renal sodium-phosphate transporter; and cytochrome P450 family 24 subfamily A member 1 ( CYP24A1 ) , which degrades 1,25-dihydroxyvitamin D. Drug target MR indicated that reducing serum calcium by 0.08 mmol/L via CASR , DGKD , or CYP24A1 , or increasing serum phosphate by 0.16 mmol/L via SLC34A1 may reduce KSD relative risk by up to 90%. Furthermore, reduced DGKδ expression and KSD-associated DGKD missense variants impaired CaSR signal transduction in vitro, which was ameliorated by cinacalcet, a positive CaSR allosteric modulator. CONCLUSION: DGKD -, SLC34A1 -, and CYP24A1 -associated variants linked to reduced CaSR signal transduction, increased urinary phosphate excretion, and impaired 1,25-dihydroxyvitamin D inactivation, respectively, are common causes of KSD. Genotyping patients with KSD may facilitate personalized KSD risk stratification and targeted pharmacomodulation of associated pathways to prevent KSD. FUNDING: Oxfordshire Health Services Research Committee (OHSRC, part of Oxford Hospitals Charity); Kidney Research UK (RP_030_20180306); The Urology Foundation; National Institute for Health Research (NIHR) Oxford Biomedical Research Centre (NF-SI-0514–10091); Wellcome Trust (204826/z/16/z and 106995/z/15/z); Medical Research Council (MRC) Clinical Research Training Fellowships (MR/W03168X/1 and MR/S021329/1); Wellcome Trust Clinical Career Development Fellowship; Sir Henry Dale Fellowship, with joint funding by the Wellcome Trust and the Royal Society (224155/Z/21/Z); St. Peter’s Trust for Kidney Bladder and Prostate Research.

Purpose: To compare stone clearance and complications between a ‘wide’ (9 × 50 mm) and ‘narrow’ shockwave focus (6 × 28 mm) when undertaking shockwave lithotripsy (SWL) in patients with renal or ureteric stones. Methods: Data from patients undergoing SWL using the dual focus Storz Modulith SLX-F2 lithotripter at a single centre were prospectively collected between February 2018 and September 2020. Patients were matched by stone size, location, and number of treatments. Stone clearance, re-presentation within 31 days, symptoms, complications, and need for post SWL-interventions were compared using McNemar’s test. Results: Patients receiving wide focus SWL (WF-SWL, n = 152) were matched with patients receiving narrow focus SWL (NF-SWL, n = 152). Median stone size was 6 mm; energy delivered to WF-SWL and NF-SWL groups was comparable. Complete stone clearance was achieved in 55% of WF-SWL patients ( n = 84) and 41% ( n = 63) of NF-SWL patients ( p = 0.04). Treatment was considered successful in 74% ( n = 113) of WF-SWL cases and 66% ( n = 100) of NF-SWL ( p = 0.20). No difference in rates of readmission, post-procedural pain, haematuria, urinary tract infections, analgesia or antibiotic requirements were identified. Conclusion: This service evaluation demonstrates no differences in rates of overall treatment success nor complications on comparing WF-SWL and NF-SWL.

Gastroenteropancreatic neuroendocrine tumours (GEP‐NETs), which may be hormone secreting (e.g., gastrinomas and insulinomas) or non‐secreting (also known as non‐functioning NETs) are associated with severe morbidity and have a median overall survival of 75–124 months. Studies have highlighted the importance of epigenetic mechanisms in GEP‐NETs pathogenesis, with the most frequently mutated genes being the epigenetic regulators, MEN1, DAXX, and ATRX. However, the consequences of these aberrant epigenetic mechanisms are poorly understood. The calcium sensing receptor (CASR), a G protein coupled‐receptor, is epigenetically silenced in cancers, and therefore we examined its role in GEP‐NET subtypes. Using RNA‐Scope and quantitative PCR analyses in two independent tumour cohorts from Europe (n = 18 patients) and the USA (n = 46 patients) we showed that CASR mRNA is almost completely absent in gastrinomas, insulinomas and non‐functioning pancreatic NETs. Furthermore, immunohistochemical staining confirmed a significant reduction in CaSR protein expression in all GEP‐NET subtypes, compared to normal islets. DNA methylationEPIC and ATAC‐seq analyses in the pancreatic NET cell line QGP‐1 showed the CaSR promoter was both hypermethylated and in a region of closed chromatin. Furthermore, transfection of wild type CaSR into QGP‐1 cells decreased cell viability, in keeping with the CaSR having a role in cellular proliferation. In summary, our study reveals that CaSR expression is decreased in GEP‐NETs and that this reduced expression is likely due to DNA methylation and chromatin changes. Moreover, we demonstrate that transfection of the CaSR into a PNET cell line reduces cell viability, thereby indicating that the CaSR acts as a tumour suppressor in this tumour type.

The calcium-sensing receptor (CaSR) has a critical role in maintaining serum calcium concentrations within the normal physiological range, and mutations in the receptor, or components of its signaling and trafficking pathway, cause disorders of calcium homeostasis. Inactivating mutations cause neonatal severe hyperparathyroidism or familial hypocalciuric hypercalcemia (FHH), while gain-of-function mutations cause autosomal dominant hypocalcemia (ADH). Characterizing the functional impact of mutations of the CaSR, and components of the CaSR-signaling pathway, is clinically important to enable correct diagnoses of FHH and ADH, optimize management, and prevent inappropriate parathyroidectomy or vitamin D supplementation. CaSR signals predominantly by activating the G-alpha subunit-11 to mobilize calcium release from intracellular stores. Thus, measurement of CaSR-induced intracellular calcium (Ca²⁺_i) signaling is the gold standard method to investigate the pathogenicity of CaSR genetic variants. This protocol describes a method to assess CaSR-induced Ca²⁺_I signaling using the Indo-1 calcium indicator dye and flow cytometry. This method has been used to assess multiple genetic variants in CaSR and components of its signaling and trafficking pathway in HEK293 cells.

Mendelian randomization (MR) is a genetic epidemiological technique that uses genetic variation to infer causal relationships between modifiable exposures and outcome variables. Conventional observational epidemiological studies are subject to bias from a range of sources; MR analyses can offer an advantage in that they are less prone to bias as they use genetic variants inherited at conception as “instrumental variables”, which are proxies of an exposure. However, as with all research tools, MR studies must be carefully designed to yield valuable insights into causal relationships between exposures and outcomes, and to avoid biased or misleading results that undermine the validity of the causal inferences drawn from the study. In this review, we outline Mendel’s laws of inheritance, the assumptions and principles that underlie MR, MR study designs and methods, and how MR analyses can be applied and reported. Using the example of serum phosphate concentrations on liability to kidney stone disease we illustrate how MR estimates may be visualized and, finally, we contextualize MR in bone and mineral research including exemplifying how this technique could be employed to inform clinical studies and future guidelines concerning BMD and fracture risk. This review provides a framework to enhance understanding of how MR may be used to triangulate evidence and progress research in bone and mineral metabolism as we strive to infer causal effects in health and disease.

Kidney stones (KS) are common, heritable, and associated with mineral metabolism abnormalities. We used Mendelian randomization and colocalization to identify variants predicted to increase KS risk via increased serum calcium or decreased serum phosphate (odds ratios for genomic regions=4.30-13.83 per 1 standard deviation alteration) that account for 11-19% of KS due to reduced calcium-sensing receptor (CaSR)-signal transduction, increased urinary phosphate excretion, and impaired 1,25-dihydroxyvitamin D inactivation via diacylglycerol kinase delta ( DGKD ), solute carrier family 34 member 1 ( SLC34A1 ), and cytochrome P450 family 24 subfamily A member 1 ( CYP24A1 ), respectively. In silico analyses revealed that targeting CASR , DGKD , or CYP24A1 to decrease serum calcium, or SLC34A1 to increase serum phosphate may reduce KS risk, and in vitro studies demonstrated that positive CaSR-allosteric modulation ameliorates CaSR-signal transduction impaired by reduced DGKδ expression or KS-associated DGKD missense variants. These studies suggest that genotyping individuals with KS may facilitate personalized risk stratification and pharmacomodulation.