The management of patients with enteric hyperoxaluria

Metabolic Evaluation and Recurrence Prevention for Urinary Stone Patients: An EAU Guidelines Update

BACKGROUND AND OBJECTIVE

The aim of this review was to define patients who are at high risk of recurrence of urolithiasis, to delineate diagnostic and therapeutic algorithms for each type of stone, and to clarify general guidelines and recommendations for prevention of recurrence.

METHODS

A professional research librarian carried out literature searches for all sections of the urolithiasis guidelines, covering the timeframe between 1976 and June 2023.

KEY FINDINGS AND LIMITATIONS

For every patient with urolithiasis, an attempt should be made to analyse the stone. Patients should be given general instructions on how to prevent recurrence, including adequate fluid and calcium intake, and low consumption of sodium and protein. Identifying and correcting the causative factors is a cornerstone in preventing the recurrence of urolithiasis. Diagnostic and therapeutic algorithms by stone composition are available. Every patient should undergo baseline metabolic screening, while patients with calcium stones, who are at high risk of relapse and complications, should undergo extensive metabolic screening with two 24-h urine collections and should receive targeted therapy. Patients with uric acid, infection, or cystine stones are at high risk of relapse. All patients at high risk of recurrence should be closely monitored, especially those not complying with therapy in the long term.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Metabolic stone evaluation and patient follow-up are highly recommended to prevent urolithiasis recurrence.

Metabolic Profile of Calcium Oxalate Stone Patients with Enteric Hyperoxaluria and Impact of Dietary Intervention

This study investigated the risk profile and the impact of dietary intervention in calcium oxalate stone formers with enteric hyperoxaluria under controlled, standardized conditions. Thirty-seven patients were included in the study. Dietary and 24-h urinary parameters were obtained on the self-selected diet and a balanced, standardized diet. Tests for [13C2]oxalate absorption, calcium- and ammonium chloride-loading were performed. Mean [13C2]oxalate absorption was 18.8%. A significant positive association was observed between urinary oxalate excretion and intestinal oxalate absorption. In addition, urinary oxalate excretion was significantly correlated with dietary oxalate intake. Mean urinary oxalate excretion decreased from 0.841 mmol/24 h on the usual diet to 0.662 mmol/24 h on the balanced diet, corresponding to a reduction of 21.3%. Besides hyperoxaluria, hypocitraturia and hypomagnesuria were the most common urinary abnormalities at baseline, being present in 83.8% and 81.1% of patients, respectively. Urinary citrate increased by 50.9% and magnesium excretion increased by 25.2% on the balanced diet. As a result, the relative supersaturation of calcium oxalate declined significantly (by 36.2%) on the balanced diet. Since 41% of patients on the balanced diet still had a urine volume of less than 2.0 L/24 h, efforts should be made to increase urine volume by increasing fluid intake and reducing intestinal fluid losses. Dietary intervention proved to be effective in reducing urinary oxalate excretion and should be a cornerstone of the treatment of patients with enteric hyperoxaluria.

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.

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.

Higher Risk of Repeat Stone Surgery in Stone Formers With Concomitant Bowel Disease: Single-Center Long-Term Analysis

OBJECTIVE

To identify the need for repeat stone surgery in patients with and without bowel disease. Few studies have compared risks between different types of bowel disease and whether their need for repeat stone surgery differs.

METHODS

From our IRB-approved study, we identified patients with and without bowel disease. We categorized patients' bowel disease into 4 categories: inflammatory bowel disease (IBD), bypass procedures, bowel resection, and bowel disease not otherwise specified (eg, irritable bowel syndrome, celiac disease). Differences between patient demographics, stone disease, and recurrent stone events for patients with and without bowel disease were compared using univariate and multivariate survival analyses (SPSS 25).

RESULTS

Of all surgical stone patients (2011), 484 (24%) had some type of bowel disease. Compared to patients without bowel disease, patients with bowel disease presented with stones at an older age (62.2 ± 14.5 vs 58.4 ± 15.3 years; P <.001) and were more likely to be female (56 vs 46%; P <.001). Patients with bowel disease required more repeat stone surgery than those without bowel disease (31% vs 23%, P <.001). In multivariate analysis, patients with bypass and bowel resection were associated with more repeat surgery than patients without bowel disease (P <.001, P = .002, respectively). Patients with IBD and bowel disease not otherwise specified did not have higher risk for repeat surgery than patients without bowel disease.

CONCLUSION

Surgical stone patients with bowel disease, specifically those with prior bowel resection and bypass, had a higher risk of repeat stone surgery over time than stone formers without bowel disease.

DATA AVAILABILITY

The data sets generated and analyzed during the current study are available from the corresponding author on reasonable request.

Prevention, diagnosis, and treatment of urolithiasis in geriatric patients - differences, similarities and caveats in comparison to the general population

PURPOSE OF REVIEW

Purpose of the review is to address management and prevention of urolithiasis in elderly patients examining the dynamic interplay between general measures, dietary adjustments, lifestyle modifications, and targeted pharmacological and/ or surgical interventions. The goal is to provide understanding of the evolving strategies required for effective urolithiasis prevention in the geriatric population.

RECENT FINDINGS

Age-specific diagnostic considerations are necessary because urolithiasis in the elderly population is characterized by bigger stones, greater peri-operative risks, and heightened symptom severity. When comorbidities are present, conservative treatments - especially analgesia - provide difficulties. Surgical procedures prove to be safe and effective, with complication rates and practical application comparable to younger cohorts. Prevention approaches that include lifestyle changes and the investigation of novel pharmaceutical options such as sodium-dependent glucose co-transporter 2 (SGLT-2)-inhibitors are promising in the management of urolithiasis in the elderly population.

SUMMARY

Our review offers a thorough investigation of urolithiasis in the elderly population, elucidating distinct clinical manifestations, complex diagnostic issues, and treatment implications. The safety and effectiveness of ureteroscopy in older patients, as well as the possible prophylactic function of SGLT-2-I, offer crucial insights for clinicians. Subsequent studies are necessary to enhance age-specific therapies, addressing the distinct obstacles presented by urolithiasis in the elderly population within this rapidly growing demographic.

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.

Current Dietary and Medical Prevention of Renal Calcium Oxalate Stones

Kidney stones refer to abnormal crystal formation that occurs in the kidney. Among a variety of components of kidney stones, calcium oxalate (CaOx) is the most common type. Despite many efforts to investigate the pathogenesis of CaOx stones, the pathogenesis remains an issue of debate. With high occurrence and recurrence, individuals with stone formation are prone to frequently consult a doctor and to be hospitalized, and the treatment of kidney stones poses a heavy burden on the patients. Concerns should be focused not only on treatment but also on prevention. Herein, we reviewed the studies on prevention methods of CaOx stones through diet, lifestyle, and medication extending until the current time frame. As hyperoxaluria is the most common metabolic disorder among CaOx stone formations, we also included several studies on the treatment and prevention of hyperoxaluria. Our objective was to outline the effective methods to prevent renal CaOx stone formation.

Navigating the Evolving Landscape of Primary Hyperoxaluria: Traditional Management Defied by the Rise of Novel Molecular Drugs

Primary hyperoxalurias (PHs) are inherited metabolic disorders marked by enzymatic cascade disruption, leading to excessive oxalate production that is subsequently excreted in the urine. Calcium oxalate deposition in the renal tubules and interstitium triggers renal injury, precipitating systemic oxalate build-up and subsequent secondary organ impairment. Recent explorations of novel therapeutic strategies have challenged and necessitated the reassessment of established management frameworks. The execution of diverse clinical trials across various medication classes has provided new insights and knowledge. With the evolution of PH treatments reaching a new milestone, prompt and accurate diagnosis is increasingly critical. Developing early, effective management and treatment plans is essential to improve the long-term quality of life for PH patients.

The Anti-urolithiatic effect of the roots of Saussurea costus (falc) Lipsch agonist ethylene glycol and magnesium oxide induced urolithiasis in rats

Phytotherapy, which involves the use of plant extracts and natural compounds for medicinal purposes, is indeed a promising alternative for managing urinary lithiasis. Many plants have been studied for their potential to prevent and treat kidney stones, and they may offer a more natural and potentially less harmful approach compared to conventional treatments. Additionally, phytotherapy may be more cost-effective. The aim of the present study was to investigate the antilithic potential of extracts and essential oils of Saussurea costus (Falc) Lipsch in two in vivo models, one on ethylene glycol-induced calcium oxalate crystal formation and the other to assess the effects of these extracts on magnesium oxide-induced struvite crystal formation. The experiment involved the administration of different doses of aqueous and ethanolic extracts of S. costus (200 and 400 mg/kg) and essential oils (25 and 50 mg/kg) to male Wistar rats, followed by the evaluation of various physiological, biochemical and histopathological parameters. The results demonstrated that the administration of S. costus essential oils and extracts had significant effects on the rats, influencing body weight, urine volume, crystal deposition, cytobacteriological examination of urine, and serum biochemical parameters. Histopathological examinations revealed varying impacts on the kidneys and livers of the treated rats. The findings suggest that S. costus extracts and essential oils may hold promise in inhibiting calcium oxalate crystal formation in vivo and influencing various physiological and biochemical parameters in rats. Overall, the 200 mg/kg ethanolic extract of S. costus demonstrated antilithiatic efficacy, did not exhibit signs of toxicity and reduced the number of crystals in the kidneys. Furthermore, the study did not find a significant effect on reducing struvite crystals.

Intestinal Oxalate Absorption, Enteric Hyperoxaluria, and Risk of Urinary Stone Formation in Patients with Crohn's Disease

Nephrolithiasis is a common urologic manifestation of Crohn's disease. The purpose of this study was to investigate the clinical characteristics, intestinal oxalate absorption, and risk factors for urinary stone formation in these patients. In total, 27 patients with Crohn's disease and 27 healthy subjects were included in the present study. Anthropometric, clinical, and 24 h urinary parameters were determined, and the [13C2]oxalate absorption test was performed. Among all patients, 18 had undergone ileal resection, 9 of whom had a history of urinary stones. Compared to healthy controls, the urinary excretion values of calcium, magnesium, potassium, sulfate, creatinine, and citrate were significantly lower in patients with Crohn's disease. Intestinal oxalate absorption, the fractional and 24 h urinary oxalate excretion, and the risk of calcium oxalate stone formation were significantly higher in patients with urolithiasis than in patients without urolithiasis or in healthy controls. Regardless of the group, between 83% and 96% of the [13C2]oxalate was detected in the urine within the first 12 h after ingestion. The length of ileum resection correlated significantly with the intestinal absorption and urinary excretion of oxalate. These findings suggest that enteric hyperoxaluria can be attributed to the hyperabsorption of oxalate following extensive ileal resection. Oral supplementation of calcium and magnesium, as well as alkali citrate therapy, should be considered as treatment options for urolithiasis.

The Saudi urological association guidelines on urolithiasis

Aims

The Saudi Urolithiasis Guidelines are a set of recommendations for diagnosing, evaluating, and treating urolithiasis in the Saudi population. These guidelines are based on the latest evidence and expert consensus to improve patient outcomes and optimize care delivery. They cover the various aspects of urolithiasis, including risk factors, diagnosis, medical and surgical treatments, and prevention strategies. By following these guidelines, health-care professionals can improve care quality for individuals with urolithiasis in Saudi Arabia.

Panel

The Saudi Urolithiasis Guidelines Panel consists of urologists specialized in endourology with expertise in urolithiasis and consultation with a guideline methodologist. All panelists involved in this document have submitted statements disclosing any potential conflicts of interest.

Methods

The Saudi Guidelines on Urolithiasis were developed by relying primarily on established international guidelines to adopt or adapt the most appropriate guidance for the Saudi context. When necessary, the panel modified the phrasing of recommendations from different sources to ensure consistency within the document. To address areas less well covered in existing guidelines, the panel conducted a directed literature search for high quality evidence published in English, including meta analyses, randomized controlled trials, and prospective nonrandomized comparative studies. The panel also searched for locally relevant studies containing information unique to the Saudi Arabian population. The recommendations are formulated with a direction and strength of recommendation based on GRADE terminology and interpretation while relying on existing summaries of evidence from the existing guidelines.

The role of the general practictioner in the management of urinary calculi

BACKGROUND

The prevalence of kidney stones tends to increase worldwide due to dietary and climate changes. Disease management involves a high consumption of healthcare system resources which can be reduced with primary prevention measures and prophylaxis of recurrences. In this field, collaboration between general practitioners (GPs) and hospitals is crucial.

METHODS

a panel composed of general practitioners and academic and hospital clinicians expert in the treatment of urinary stones met with the aim of identifying the activities that require the participation of the GP in the management process of the kidney stone patient.

RESULTS

Collaboration between GP and hospital was found crucial in the treatment of renal colic and its infectious complications, expulsive treatment of ureteral stones, chemolysis of uric acid stones, long-term follow-up after active treatment of urinary stones, prevention of recurrence and primary prevention in the general population.

CONCLUSIONS

The role of the GP is crucial in the management and prevention of urinary stones. Community hospitals which are normally led by GPs in liaison with consultants and other health professional can have a role in assisting multidisciplinary working as extended primary care.

2022 Recommendations of the AFU Lithiasis Committee: Medical management - from diagnosis to treatment

The morphological-compositional analysis of urinary stones allows distinguishing schematically several situations: dietary, digestive, metabolic/hormonal, infectious and genetic problems. Blood and urine testing are recommended in the first instance to identify risk factors of urinary stone disease in order to avoid recurrence or progression. The other objective is to detect a potential underlying pathology associated with high risk of urinary stone disease (e.g. primary hyperparathyroidism, primary or enteric hyperoxaluria, cystinuria, distal renal tubular acidosis) that may require specific management. Lifestyle-diet measures are the basis of the management of all stone types, but pharmacological treatments may be required. METHODOLOGY: These recommendations were developed using two methods: the Clinical Practice Recommendation (CPR) method and the ADAPTE method, depending on whether the question was considered in the European Association of Urology (EAU) recommendations (https://uroweb.org/guidelines/urolithiasis) [EAU 2022] and their adaptability to the French context.

Frequency and impact of enteric hyperoxaluria in pediatric short bowel syndrome: a retrospective single centre study

Objectives

The survival of pediatric patients with short bowel syndrome has improved in recent years. Enteric hyperoxaluria as a pathophysiological consequence has been hardly addressed so far. It can be associated with nephrolithiasis, nephrocalcinosis or even renal insufficiency. We assessed the prevalence of hyperoxaluria and its pathogenic consequences in a retrospective single centre study over the last 12 years.

Methods

We conducted an internal database search for all pediatric patients suffering from short bowel syndrome treated from 2010 to 2022 in the department of pediatric gastroenterology as well as the pediatric nephrology and dialysis unit. Out of 56 patients identified, 26 patients were analysed for etiology of short bowel syndrome, renal excretion of oxalate (24/26), remaining short bowel and large intestinal length as well as further clinical parameters such as eGFR, nephrocalcinosis/urinary stone formation or stool frequency.

Results

Hyperoxaluria was detected in 14/26 patients (54%). Nephrocalcinosis was present in four patients. Out of these four patients, hyperoxaluria could be proven (21% of all hyperoxaluric patients) in three cases, one hyperoxaluric patient had nephrolithiasis (7%). In one patient hyperoxaluria lead to end stage renal disease. We found that 80% of patients with volvulus developed enteric hyperoxaluria. None of the investigated factors had an effect on oxalate excretion.

Conclusion

Enteric hyperoxaluria is a relevant pathophysiological finding in patients with short bowel syndrome occurring in about 50% of our cohort with multiple pathogenic complications. Regular screening for hyperoxaluria may be implemented in medical care for patients with short bowel syndrome. If necessary, prophylaxis, e.g., dietary advice or metaphylaxis should be initiated.

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.

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.

Delta weight loss unlike genetic variation associates with hyperoxaluria after malabsorptive bariatric surgery

The risk of enteric hyperoxaluria is significantly increased after malabsorptive bariatric surgery (MBS). However, its underlying determinants are only poorly characterized. In this case-control study, we aimed at identifying clinical and genetic factors to dissect their individual contributions to the development of post-surgical hyperoxaluria. We determined the prevalence of hyperoxaluria and nephrolithiasis after MBS by 24-h urine samples and clinical questionnaires at our obesity center. Both hyperoxaluric and non-hyperoxaluric patients were screened for sequence variations in known and candidate genes implicated in hyperoxaluria (AGXT, GRHPR, HOGA1, SLC26A1, SLC26A6, SLC26A7) by targeted next generation sequencing (tNGS). The cohort comprised 67 patients, 49 females (73%) and 18 males (27%). While hyperoxaluria was found in 29 patients (43%), only one patient reported postprocedural nephrolithiasis within 41 months of follow-up. Upon tNGS, we did not find a difference regarding the burden of (rare) variants between hyperoxaluric and non-hyperoxaluric patients. However, patients with hyperoxaluria showed significantly greater weight loss accompanied by markers of intestinal malabsorption compared to non-hyperoxaluric controls. While enteric hyperoxaluria is very common after MBS, genetic variation of known hyperoxaluria genes contributes little to its pathogenesis. In contrast, the degree of postsurgical weight loss and levels of malabsorption parameters may allow for predicting the risk of enteric hyperoxaluria and consecutive kidney stone formation.

A Case of Oxalate Nephropathy Associated With Prolonged Cholecystostomy Tube Placement

Oxalate nephropathy is a rare pathology that can be difficult to diagnose. It results from calcium oxalate crystals that are deposited in the renal interstitium or renal tubules. Once the deposition ensues, a multitude of complications can occur, including renal failure. One etiology for oxalate nephropathy is a lack of biliary acid. The diagnosis of oxalate nephropathy is typically based on visualization of oxalate crystals in the renal tubules on biopsy, and treatment based on the etiology can range from simple removal of the offending agent or a change in diet to liver/kidney transplant in the setting of primary hyperoxaluria. This report discusses a case of severe oxalate nephropathy related to long-term cholecystostomy tube placement resulting in a deficiency of biliary acid.

Untargeted and targeted metabolomics reveal bile acid profile changes in rats with ethylene glycol-induced calcium oxalate nephrolithiasis

Calcium oxalate (CaOx) nephrolithiasis is a prevalent disorder linked to metabolism. Examining metabolic alterations could potentially give an initial understanding of the origins of CaOx nephrolithiasis. This study aims to determine gut metabolic biomarkers differentiating CaOx nephrolithiasis utilizing untargeted and targeted metabolomics. CaOx nephrolithiasis model rats were built by 1% ethylene glycol administration. Histologic staining and renal function measurement revealed the presence of crystals in the lumen of the renal tubules, the renal injury and interstitial fibrosis in CaOx rats, demonstrating that the models of CaOx were established successfully. Hematoxylin & eosin (H&E) staining showed that CaOx group had inflammation and damage in the ileal tissue. Immunofluorescence and PCR results displayed that the tight junction proteins, ZO-1 and Occludin levels were decreased in the ileal tissues of the CaOx group. The untargeted metabolomic analysis revealed that 269 gut metabolites were differentially expressed between the CaOx group and the control group. Meanwhile, bile secretion, the main metabolic pathway in CaOx nephrolithiasis, was identified. Following, five significant bile acid metabolites were selected utilizing the targeted bile acid metabolomics, including Hyodeoxycholic acid (HDCA), Glycohyodeoxycholic acid (GHDCA), Nor-Deoxycholic Acid, omega-muricholic acid, and Taurolithocholic acid. Among these metabolites, HDCA and GHDCA presented the highest predictive accuracy with AUC = 1 to distinguish the CaOx group from the control group. As a result of network pharmacology, target genes of HDCA and GHDCA in CaOx nephrolithiasis were enriched in oxidative stress and apoptosis pathways. Conclusively, our study provides insight into bile acids metabolic changes related to CaOx nephrolithiasis. Although alterations in biochemical pathways indicate a complex pathology in CaOx rats, bile acid changes may serve as biomarkers of CaOx nephrolithiasis.

Secondary oxalate nephropathy and impact of high-dose vitamin C intake for COVID-19 prevention on a patient with Roux-en-Y gastric bypass: A case report

The current study is important in informing clinicians about the possibility of concurrent oxalate nephropathy caused by Roux-en-Y gastric bypass, high oxalate materials, and high-dose vitamin C intake for COVID-19 prevention.

Oxalate homeostasis

Oxalate homeostasis is maintained through a delicate balance between endogenous sources, exogenous supply and excretion from the body. Novel studies have shed light on the essential roles of metabolic pathways, the microbiome, epithelial oxalate transporters, and adequate oxalate excretion to maintain oxalate homeostasis. In patients with primary or secondary hyperoxaluria, nephrolithiasis, acute or chronic oxalate nephropathy, or chronic kidney disease irrespective of aetiology, one or more of these elements are disrupted. The consequent impairment in oxalate homeostasis can trigger localized and systemic inflammation, progressive kidney disease and cardiovascular complications, including sudden cardiac death. Although kidney replacement therapy is the standard method for controlling elevated plasma oxalate concentrations in patients with kidney failure requiring dialysis, more research is needed to define effective elimination strategies at earlier stages of kidney disease. Beyond well-known interventions (such as dietary modifications), novel therapeutics (such as small interfering RNA gene silencers, recombinant oxalate-degrading enzymes and oxalate-degrading bacterial strains) hold promise to improve the outlook of patients with oxalate-related diseases. In addition, experimental evidence suggests that anti-inflammatory medications might represent another approach to mitigating or resolving oxalate-induced conditions.

Role, importance and assessment of dietary habits in urolithiasis patient

Urolithiasis, which prevalence is increasing, poses a risk for chronic kidney disease in patients. Dietary habits play a significant role in stone formation, growth and recurrence. Also, comorbidities and lifestyle changes are among the factors affecting stone formation. The next step should be to detect metabolic disorders, if any, with analyzes to be made after a detailed anamnesis, and to arrange the necessary treatment. Insufficient fluid intake is considered to be the main dietary risk factor for urolithiasis. A daily fluid intake of 2.5-3.0 L/day or diuresis of 2.0-2.5 L/day is recommended to prevent recurrence of kidney stones. Not all beverages are beneficial, and some may even increase the risk of stone formation. Dietary management, vitamins and supplements, physical activity are important components in reducing the risk of recurrent urolithiasis. A detailed dietary assessment is recommended as dietary habits affect the faith of the disease. In this review we evaluated the dietary approach of urolithiasis patients with and without comorbidities, the recommended daily fluid intake, vitamin supplementation, and relation of the urolithiasis with physical activity.

Bone marrow oxalosis with pancytopenia in a patient with short bowel syndrome: Report of a case and review of the literature

Systemic oxalosis is a condition in which calcium oxalate crystals deposit into various bodily tissues. Although this may occur as the result of a rare primary syndrome in which an error of glyoxylate metabolism causes an overproduction of oxalate, it is more often seen as a secondary process characterized by increased enteric oxalate absorption. Here, we describe a patient with short bowel syndrome on long-term parenteral nutrition support who developed a unique manifestation of systemic oxalosis, leading to deposition of oxalate crystals within the bone marrow contributing to pancytopenia. In this report, in addition to reviewing the literature on this presumably rare manifestation of oxalosis, we also discuss its pathogenesis in the setting of short bowel syndrome and its management, including prevention.

Changes in patient perceptions regarding ChatGPT-written explanations on lifestyle modifications for preventing urolithiasis recurrence

Purpose

Artificial Intelligence (AI) imitating human-like language, such as ChatGPT, has impacted lives throughout various multidisciplinary fields. However, despite these innovations, it is unclear how well its implementation will assist patients in clinical situations. We evaluated changes in patient perceptions regarding AI before and after reading a ChatGPT-written explanation.

Materials and methods

In total, 24 South Korean patients receiving urolithiasis treatment were surveyed through questionnaires. The ChatGPT explanatory note was provided between the first and second questionnaires, detailing lifestyle modifications for preventing urolithiasis recurrence. The study questionnaire was the Korean version of the General Attitudes toward Artificial Intelligence Scale, including positive and negative attitude items. Wilcoxon signed-rank tests were accomplished to compare questionnaire scores before and after receiving the explanatory note. A linear regression analysis with stepwise elimination was used to assess variable (demographic data) accuracy in predicting outcomes.

Results

There were significant differences between total negative questionnaire scores pre- and post-surveys of ChatGPT, but not in the positive scores. Among variables, only education level significantly influenced mean score differences in the negative questionnaires.

Conclusions

The negative perception change among urolithiasis patients after receiving the explanatory note provided by the AI chatbot program was observed, evidencing that patients with lower education levels expressed a more negative response. The explanatory note provided by the AI chatbot program could provoke an adverse change in AI perception. Negative human responses must be considered to improve and adapt new technology in health care. Only through changing patient perspectives will upgraded AI technology integrate into medical healthcare.

Case report: Acute oxalate nephropathy due to traditional medicinal herbs

Acute oxalate nephropathy (AON), defined as the association between acute kidney injury (AKI) and the deposition of oxalate crystals in the renal parenchyma, is a rare complication of hyperoxaluria. We report a rare case of AON in an adult due to medicinal herbs intake leading to crystal-induced AKI. We recommend that a thorough medication history including the use of medicinal herbs, should be obtained for all patients with a rapid loss of kidney function, especially in the absence of known risk factors for AKI. The use of medicinal herbs with unknown oxalate contents would increase the risk of AON and should be avoided.

Chologene Diarrhö, Stiefkind der chronischen Diarrhö – Prävalenz, Diagnostik und Therapie

Die chologene Diarrhö ist eine der häufigsten nicht diagnostizierten Ursachen der chronischen Diarrhö, der zahlreiche verschiedene Pathophysiologien zugrunde liegen können. Auch nach Ausschlussdiagnostik der häufigeren Ursachen verbleiben bis zu 5% der Bevölkerung von einer ungeklärten chronischen Diarrhö betroffen. In diesem Kollektiv findet sich in bis zu 50% als Ursache eine chologene Diarrhö.

Dietary restriction and medical therapy drives PPARα-regulated improvements in early diabetic kidney disease in male rats

The attenuation of diabetic kidney disease (DKD) by metabolic surgery is enhanced by pharmacotherapy promoting renal fatty acid oxidation (FAO). Using the Zucker Diabetic Fatty and Zucker Diabetic Sprague Dawley rat models of DKD, we conducted studies to determine if these effects could be replicated with a non-invasive bariatric mimetic intervention. Metabolic control and renal injury were compared in rats undergoing a dietary restriction plus medical therapy protocol (DMT; fenofibrate, liraglutide, metformin, ramipril, and rosuvastatin) and ad libitum-fed controls. The global renal cortical transcriptome and urinary 1H-NMR metabolomic profiles were also compared. Kidney cell type-specific and medication-specific transcriptomic responses were explored through in silico deconvolution. Transcriptomic and metabolomic correlates of improvements in kidney structure were defined using a molecular morphometric approach. The DMT protocol led to ∼20% weight loss, normalized metabolic parameters and was associated with reductions in indices of glomerular and proximal tubular injury. The transcriptomic response to DMT was dominated by changes in fenofibrate- and peroxisome proliferator-activated receptor-α (PPARα)-governed peroxisomal and mitochondrial FAO transcripts localizing to the proximal tubule. DMT induced urinary excretion of PPARα-regulated metabolites involved in nicotinamide metabolism and reversed DKD-associated changes in the urinary excretion of tricarboxylic acid (TCA) cycle intermediates. FAO transcripts and urinary nicotinamide and TCA cycle metabolites were moderately to strongly correlated with improvements in glomerular and proximal tubular injury. Weight loss plus pharmacological PPARα agonism is a promising means of attenuating DKD.

Pathophysiology and Management of Hyperoxaluria and Oxalate Nephropathy: A Review

Hyperoxaluria results from either inherited disorders of glyoxylate metabolism leading to hepatic oxalate overproduction (primary hyperoxaluria), or increased intestinal oxalate absorption (secondary hyperoxaluria). Hyperoxaluria may lead to urinary supersaturation of calcium oxalate and crystal formation, causing urolithiasis and deposition of calcium oxalate crystals in the kidney parenchyma, a condition termed oxalate nephropathy. Considerable progress has been made in the understanding of pathophysiological mechanisms leading to hyperoxaluria and oxalate nephropathy, whose diagnosis is frequently delayed and prognosis too often poor. Fortunately, novel promising targeted therapeutic approaches are on the horizon in patients with primary hyperoxaluria. Patients with secondary hyperoxaluria frequently have long-standing hyperoxaluria-enabling conditions, a fact suggesting the role of triggers of acute kidney injury such as dehydration. Current standard of care in these patients includes management of the underlying cause, high fluid intake, and use of calcium supplements. Overall, prompt recognition of hyperoxaluria and associated oxalate nephropathy is crucial because optimal management may improve outcomes.

Portulaca Oleracea-associated oxalate nephropathy complicated with an ANCA-positive acute renal injury: A case report

Oxalate nephropathy is a rare disease that can lead to acute kidney injury (AKI). In clinical practice, as renal biopsy is required for diagnosis, physicians often do not have sufficient understanding of this disease. When AKI is associated with positive blood anti-neutrophil cytoplasmic antibodies (ANCA), a diagnosis of renal injury due to ANCA-associated vasculitis is likely to be made, leading to treatment with immunosuppressive therapy. A case of AKI after eating a large quantity of Portulaca oleracea is reported. While blood P-ANCA was positive, both urine proteinuria and urine occult blood were negative. Renal biopsy was performed and identified an acute tubulointerstitial injury: disc-shaped crystals were seen in the lumen of renal tubules that demonstrated birefringence under polarized light, and an oxalate nephropathy was therefore diagnosed. Typical histological changes of an ANCA-associated vasculitis with renal injury such as cellulose-like necrosis and crescent formation were not present. After the patient stopped eating P. oleracea, and following rehydration and hemodialysis, renal function returned to normal. In patients with AKI, the secondary causes of hyperoxalemia should be sought and attention paid to excluding an oxalate nephropathy. In patients with AKI who are ANCA-positive, it is prudent to complete the renal pathological diagnostic process before assuming that the renal injury is caused by an ANCA-associated vasculitis, and before starting hormone and immunosuppressive therapy.

Oxalate nephropathy: a review

This review describes the clinical and pathological features of oxalate nephropathy (ON), defined as a syndrome of decreased renal function associated with deposition of calcium oxalate crystals in kidney tubules. We review the different causes of hyperoxaluria, including primary hyperoxaluria, enteric hyperoxaluria and ingestion-related hyperoxaluria. Recent case series of biopsy-proven ON are reviewed in detail, as well as the implications of these series. The possibility of antibiotic use predisposing to ON is discussed. Therapies for hyperoxaluria and ON are reviewed with an emphasis on newer treatments available and in development. Promising research avenues to explore in this area are discussed.

Oxalate Flux Across the Intestine: Contributions from Membrane Transporters

Epithelial oxalate transport is fundamental to the role occupied by the gastrointestinal (GI) tract in oxalate homeostasis. The absorption of dietary oxalate, together with its secretion into the intestine, and degradation by the gut microbiota, can all influence the excretion of this nonfunctional terminal metabolite in the urine. Knowledge of the transport mechanisms is relevant to understanding the pathophysiology of hyperoxaluria, a risk factor in kidney stone formation, for which the intestine also offers a potential means of treatment. The following discussion presents an expansive review of intestinal oxalate transport. We begin with an overview of the fate of oxalate, focusing on the sources, rates, and locations of absorption and secretion along the GI tract. We then consider the mechanisms and pathways of transport across the epithelial barrier, discussing the transcellular, and paracellular components. There is an emphasis on the membrane-bound anion transporters, in particular, those belonging to the large multifunctional Slc26 gene family, many of which are expressed throughout the GI tract, and we summarize what is currently known about their participation in oxalate transport. In the final section, we examine the physiological stimuli proposed to be involved in regulating some of these pathways, encompassing intestinal adaptations in response to chronic kidney disease, metabolic acid-base disorders, obesity, and following gastric bypass surgery. There is also an update on research into the probiotic, Oxalobacter formigenes, and the basis of its unique interaction with the gut epithelium. © 2021 American Physiological Society. Compr Physiol 11:1-41, 2021.

Clinical Outcomes and Histological Patterns in Oxalate Nephropathy due to Enteric and Nonenteric Risk Factors

INTRODUCTION

Current knowledge of risk factors and renal histologic patterns of oxalate nephropathy (ON) not due to primary hyperoxaluria (PH) has been limited to small case series and case reports. Thus, we analyzed and compared clinical risk factors, histologic characteristics, and renal outcomes of patients with biopsy-confirmed ON among a cohort of patients with enteric and nonenteric risk factors.

METHODS

A clinical data repository of native kidney pathology reports from 2009 to 2020 at all Mayo Clinic sites was used to identify 421 ON cases.

RESULTS

After excluding cases in transplanted kidneys or due to PH, 64 cases remained. Enteric risk factors were present in 30 and nonenteric in 34. Roux-en-Y gastric bypass (17) and pancreatic insufficiency (6) were most common in the enteric hyperoxaluria group. In the nonenteric group, vitamin C (7) and dietary oxalate (7) were common, while no apparent risk was noted in 16. Acute kidney injury (AKI) stage III at the time of diagnosis was present in 60%, and 40.6% required dialysis. Patients in the nonenteric group had more interstitial inflammation (p = 0.01), and a greater number of tubules contained intratubular calcium oxalate (CaOx) crystals (p = 0.001) than the nonenteric group. Patients in the enteric group were more likely to have baseline chronic kidney disease (CKD) (p = 0.02) and moderate-to-severe tubulointerstitial fibrosis and atrophy (IFTA) (OR 3.49, p = 0.02). After a median follow-up of 10 months, 39% were dialysis dependent, 11% received a kidney transplant, and 32% died. On univariate analysis, >10 tubules with CaOx crystals, baseline CKD, and AKI requiring dialysis correlated with the risk of dialysis, transplant, or death. On multivariate analysis, only AKI requiring dialysis correlated with adverse renal outcomes.

CONCLUSION

This is the largest cohort study of ON not due to PH. Histologic features differ in patients with enteric versus nonenteric risks. Patients in the enteric group are more likely to have baseline CKD and significant IFTA, while patients in the nonenteric group were more likely to have a greater number of tubules with CaOx crystals and corresponding interstitial inflammation. AKI requiring dialysis at the time of diagnosis was the single most significant predictor of adverse renal outcome.

Chronic intestinal failure and short bowel syndrome in Crohn’s disease

Chronic intestinal failure (CIF) is a rare but feared complication of Crohn’s disease. Depending on the remaining length of the small intestine, the affected intestinal segment, and the residual bowel function, CIF can result in a wide spectrum of symptoms, from single micronutrient malabsorption to complete intestinal failure. Management of CIF has improved significantly in recent years. Advances in home-based parenteral nutrition, in particular, have translated into increased survival and improved quality of life. Nevertheless, 60% of patients are permanently reliant on parenteral nutrition. Encouraging results with new drugs such as teduglutide have added a new dimension to CIF therapy. The outcomes of patients with CIF could be greatly improved by more effective prevention, understanding, and treatment. In complex cases, the care of patients with CIF requires a multidisciplinary approach involving not only physicians but also dietitians and nurses to provide optimal intestinal rehabilitation, nutritional support, and an improved quality of life. Here, we summarize current literature on CIF and short bowel syndrome, encompassing epidemiology, pathophysiology, and advances in surgical and medical management, and elucidate advances in the understanding and therapy of CIF-related complications such as catheter-related bloodstream infections and intestinal failure-associated liver disease.

Nutrition and Kidney Stone Disease

The prevalence of kidney stone disease is increasing worldwide. The recurrence rate of urinary stones is estimated to be up to 50%. Nephrolithiasis is associated with increased risk of chronic and end stage kidney disease. Diet composition is considered to play a crucial role in urinary stone formation. There is strong evidence that an inadequate fluid intake is the major dietary risk factor for urolithiasis. While the benefit of high fluid intake has been confirmed, the effect of different beverages, such as tap water, mineral water, fruit juices, soft drinks, tea and coffee, are debated. Other nutritional factors, including dietary protein, carbohydrates, oxalate, calcium and sodium chloride can also modulate the urinary risk profile and contribute to the risk of kidney stone formation. The assessment of nutritional risk factors is an essential component in the specific dietary therapy of kidney stone patients. An appropriate dietary intervention can contribute to the effective prevention of recurrent stones and reduce the burden of invasive surgical procedures for the treatment of urinary stone disease. This narrative review has intended to provide a comprehensive and updated overview on the role of nutrition and diet in kidney stone disease.

Pathophysiology and Treatment of Enteric Hyperoxaluria

Enteric hyperoxaluria is a distinct entity that can occur as a result of a diverse set of gastrointestinal disorders that promote fat malabsorption. This, in turn, leads to excess absorption of dietary oxalate and increased urinary oxalate excretion. Hyperoxaluria increases the risk of kidney stones and, in more severe cases, CKD and even kidney failure. The prevalence of enteric hyperoxaluria has increased over recent decades, largely because of the increased use of malabsorptive bariatric surgical procedures for medically complicated obesity. This systematic review of enteric hyperoxaluria was completed as part of a Kidney Health Initiative-sponsored project to describe enteric hyperoxaluria pathophysiology, causes, outcomes, and therapies. Current therapeutic options are limited to correcting the underlying gastrointestinal disorder, intensive dietary modifications, and use of calcium salts to bind oxalate in the gut. Evidence for the effect of these treatments on clinically significant outcomes, including kidney stone events or CKD, is currently lacking. Thus, further research is needed to better define the precise factors that influence risk of adverse outcomes, the long-term efficacy of available treatment strategies, and to develop new therapeutic approaches.

[Bile acid diarrhea, stepchild of chronic diarrhea - prevalence, diagnosis and treatment. Update 2021]

Bile acid diarrhea is one of the most frequently undiagnosed causes of chronic diarrhea. A variety of different pathophysiologic causes can underlie chronic diarrhea. Even after exclusion of the more frequent causes, up to 5 % of the population remains affected by unexplained chronic diarrhea. In up to 50 % within this cohort, bile acid diarrhea is the underlying cause.The various pathophysiologies leading to bile acid diarrhea are well characterized. In this way, bile acid diarrhea can be divided into primary, secondary and tertiary subtypes. Common to all causes is the increased amount of bile acids in the colon and in the faeces and the resulting secretory-osmotic diarrhea, in more severe forms in combination with steatorrhea. The diagnosis of bile acid diarrhea follows a clear algorithm which, in addition to the search for the cause and possibly a therapeutic trial, recognizes the 75SeHCAT test as the reference method for the detection of an increased loss of bile acids. In view of the chronic nature of the symptoms and the need for permanent, lifelong therapy, the use of a one-time, reliable diagnostic test is justified, though the test is currently only available at a few centers. In addition to the treatment of identifiable underlying diseases, the current treatment includes the use of drugs that bind bile acids, with additional nutritional recommendations and vitamin substitutions.The present review article summarizes the pathophysiology and importance of bile acid diarrhea and discusses the current approach towards diagnosis and treatment.

Reversibility of oxalate nephropathy in a kidney transplant recipient with prior gastric bypass surgery

Bariatric surgery is an acknowledged treatment for obesity and related comorbidities with beneficial effects on kidney function. However, bariatric surgery can also lead to secondary hyperoxaluria and oxalate nephropathy, resulting in end-stage kidney disease in both native and transplanted kidneys. We present a 66-year-old man who was in need of dialysis 3 months after kidney transplantation due to recurrent oxalate nephropathy. Intensified haemodialysis together with increased liquid intake, dietary restrictions of oxalate and fat and supplementation with calcium citrate and a bile acid binder were applied. Graft function improved and the patient did not require dialysis during the following 8 months.

Risk Factors for Kidney Stone Formation following Bariatric Surgery

Kidney stones are painful, common, and increasing in incidence. Obesity and bariatric surgery rates are also on the rise in the United States. Although bariatric surgery is associated with improvements in metabolic outcomes, malabsorptive bariatric surgery procedures are also associated with increased risk of kidney stones. Restrictive bariatric surgeries have not been associated with kidney-stone risk. Higher risk of kidney stones after malabsorptive procedures is associated with postsurgical changes in urine composition, including high urine oxalate, low urine citrate, and low urine volume. Certain dietary recommendations after surgery may help mitigate these urine changes and reduce risk of kidney stones. Understanding risk of kidney stones after surgery is essential to improving patient outcomes after bariatric surgery.

Effect of Fat-Soluble Vitamins A, D, E and K on Vitamin Status and Metabolic Profile in Patients with Fat Malabsorption with and without Urolithiasis

Patients with intestinal fat malabsorption and urolithiasis are particularly at risk of acquiring fat-soluble vitamin deficiencies. The aim of the study was to evaluate the vitamin status and metabolic profile before and after the supplementation of fat-soluble vitamins A, D, E and K (ADEK) in 51 patients with fat malabsorption due to different intestinal diseases both with and without urolithiasis. Anthropometric, clinical, blood and 24-h urinary parameters and dietary intake were assessed at baseline and after ADEK supplementation for two weeks. At baseline, serum aspartate aminotransferase (AST) activity was higher in stone formers (SF; n = 10) than in non-stone formers (NSF; n = 41) but decreased significantly in SF patients after supplementation. Plasma vitamin D and E concentrations increased significantly and to a similar extent in both groups during intervention. While plasma vitamin D concentrations did not differ between the groups, vitamin E concentrations were significantly lower in the SF group than the NSF group before and after ADEK supplementation. Although vitamin D concentration increased significantly in both groups, urinary calcium excretion was not affected by ADEK supplementation. The decline in plasma AST activity in patients with urolithiasis might be attributed to the supplementation of ADEK. Patients with fat malabsorption may benefit from the supplementation of fat-soluble vitamins ADEK.

Simple dietary advice targeting five urinary parameters reduces urinary supersaturation in idiopathic calcium oxalate stone formers

Among 208 kidney stone patients referred within 2 years, 75 patients (66 men, nine women) with truly idiopathic calcium oxalate stones (ICSF) were recruited. Dietary advice (DA) aimed at (1) urine dilution, (2) reduced crystallization promotion (lowering oxalate), and (3) increased crystallization inhibition (increasing citrate). We recommended higher intakes of fluid and calcium with meals/snacks (reducing intestinal oxalate absorption) as well as increased alkali and reduced meat protein (acid) for increasing urinary citrate. The intended effects of DA were elevations in urine volume, calcium (U-Ca) and citrate (U-Cit) as well as reductions in oxalate (U-Ox) and uric acid (U-UA). We retrospectively calculated an adherence score (AS), awarding + 1 point for parameters altered in the intended direction and − 1 point for opposite changes. Calcium oxalate supersaturation (CaOx-SS) was calculated using Tiselius’ AP(CaOx) index EQ. DA induced changes (all p < 0.0001) in urine volume (2057 ± 79 vs. 2573 ± 71 ml/day) and U-Ca (5.49 ± 0.24 vs. 7.98 ± 0.38 mmol/day) as well as in U-Ox (0.34 ± 0.01 vs. 0.26 ± 0.01 mmol/day) and U-UA (3.48 ± 0.12 vs. 3.13 ± 0.10 mmol/day). U-Cit only tendentially increased (3.07 ± 0.17 vs. 3.36 ± 0.23 mmol/day, p = 0.06). DA induced a 21.5% drop in AP(CaOx) index, from 0.93 ± 0.05 to 0.73 ± 0.05 (p = 0.0005). Decreases in CaOx-SS correlated with AS (R = 0.448, p < 0.0005), and highest AS (+ 5) always indicated lowering of CaOx-SS. Thus, simple DA can reduce CaOx-SS which may be monitored by AS.

Metabolic Surgery to Treat Obesity in Diabetic Kidney Disease, Chronic Kidney Disease, and End-Stage Kidney Disease; What Are the Unanswered Questions?

Obesity is a major factor in contemporary clinical practice in nephrology. Obesity accelerates the progression of both diabetic and non-diabetic chronic kidney disease and, in renal transplantation, both recipient and donor obesity increase the risk of allograft complications. Obesity is thus a major driver of renal disease progression and a barrier to deceased and living donor kidney transplantation. Large observational studies have highlighted that metabolic surgery reduces the incidence of albuminuria, slows chronic kidney disease progression, and reduces the incidence of end-stage kidney disease over extended follow-up in people with and without type 2 diabetes. The surgical treatment of obesity and its metabolic sequelae has therefore the potential to improve management of diabetic and non-diabetic chronic kidney disease and aid in the slowing of renal decline toward end-stage kidney disease. In the context of patients with end-stage kidney disease, although complications of metabolic surgery are higher, absolute event rates are low and it remains a safe intervention in this population. Pre-transplant metabolic surgery increases access to kidney transplantation in people with obesity and end-stage kidney disease. Metabolic surgery also improves management of metabolic complications post-kidney transplantation, including new-onset diabetes. Procedure selection may be critical to mitigate the risks of oxalate nephropathy and disruption to immunosuppressant pharmacokinetics. Metabolic surgery may also have a role in the treatment of donor obesity, which could increase the living kidney donor pool with potential downstream impact on kidney paired exchange programmes. The present paper provides a comprehensive coverage of the literature concerning renal outcomes in clinical studies of metabolic surgery and integrates findings from relevant mechanistic pre-clinical studies. In so doing the key unanswered questions for the field are brought to the fore for discussion.

ALLN-177, oral enzyme therapy for hyperoxaluria

Purpose

To evaluate the potential of ALLN-177, an orally administered, oxalate-specific enzyme therapy to reduce urine oxalate (UOx) excretion in patients with secondary hyperoxaluria.

Methods

Sixteen male and female subjects with both hyperoxaluria and a kidney stone history were enrolled in an open-label study. Subjects continued their usual diets and therapies. During a 3-day baseline period, two 24-h (24-h) urines were collected, followed by a 4-day treatment period with ALLN-177 (7,500 units/meal, 3 × day) when three 24-h urines were collected. The primary endpoint was the change in mean 24-h UOx from baseline. Safety assessments and 24-h dietary recalls were performed throughout.

Results

The study enrolled 5 subjects with enteric hyperoxaluria and 11 with idiopathic hyperoxaluria. ALLN-177 was well tolerated. Overall mean (SD) UOx decreased from 77.7 (55.9) at baseline to 63.7 (40.1) mg/24 h while on ALLN-177 therapy, with the mean reduction of 14 mg/24 h, (95% CI − 23.71, − 4.13). The calcium oxalate-relative urinary supersaturation ratio in the overall population decreased from a mean of 11.3 (5.7) to 8.8 (3.8) (− 2.8; 95% CI − 4.9, − 0.79). This difference was driven by oxalate reduction alone, but not any other urinary parameters. Mean daily dietary oxalate, calcium, and fluid intake recorded by frequent diet recall did not differ by study periods.

Conclusion

ALLN-177 reduced 24-h UOx excretion, and was well tolerated. The results of this pilot study provided justification for further investigation of ALLN-177 in patients with secondary hyperoxaluria.

Trial registration: Clinicaltrials.gov NCT02289755.

The Effect of Calcium and Vitamin B6 Supplementation on Oxalate Excretion in a Rodent Gastric Bypass Model of Enteric Hyperoxaluria

OBJECTIVE

To test the effect of calcium and vitamin B6 therapies on urinary oxalate excretion in a rodent model of enteric hyperoxaluria after Roux-en Y gastric bypass (RYGB) surgery.

METHODS

Obese male Sprague-Dawley rats underwent sham (n = 7) or RYGB (n = 10). Animals were maintained on low oxalate (1.5%) and fat (10%; LOF), normal calcium (0.6 %) diet for 8 weeks and then completed a 2-phase crossover metabolic study. In the first 2-week phase, animals were fed a Low oxalate and fat (LOF), high calcium (2.4%; HC) diet. After a 2-week washout, rats were fed a LOF/normal calcium diet highly enriched with vitamin B6. Urine was collected before and after each intervention. Plasma pyridoxal 5'-phosphate (PLP) and metabolites were measured baseline and 11 weeks after sham or RYGB.

RESULTS

Compared to baseline, sham animals on LOF/HC diet doubled their urinary calcium excretion but not oxalate. RYGB animals on LOF/HC diet decreased urinary oxalate excretion 28% (P = .001) without a significant rise in urinary calcium. Vitamin B6 supplementation decreased RYGB urinary oxalate by approximately 15% (P = .06), and serum PLP explained 63% of urinary oxalate variability.

CONCLUSION

Based on the findings in this model, calcium supplementation appears to be a reasonable therapy to decrease urinary oxalate in RYGB patients who maintain a low fat and oxalate diet. Serum PLP had a fair correlation to urinary oxalate excretion and may be a useful screening tool in hyperoxaluric RYGB patients. Further experimental human studies after RYGB are necessary to determine whether these commonly employed supplements truly provide a benefit in enteric hyperoxaluria.

Modulatory effect of 4-phenyl butyric acid on hyperoxaluria-induced renal injury and inflammation

Hyperoxaluria-associated deposition of calcium oxalate crystals results from oxalate-induced renal injury and inflammation. The present study was designed to evaluate the effect of 4-Phenyl butyric acid (4-PBA), a chemical chaperone, in ethylene glycol-induced hyperoxaluria and compare its effect with antioxidant, N-acetyl cysteine (NAC). Male Sprague-Dawley rats were given ethylene glycol in drinking water for 28 days to induce hyperoxaluria. 4-PBA and NAC were given by oral gavage. Effect of 4-PBA was analyzed in both prophylactic and curative regimens. After every 7 days, 24-h urine samples were analyzed for kidney injury and inflammation markers. Increased amounts of kidney injury markers like Kidney injury molecule-1, Lactate dehydrogenase, and N-acetyl-β-glucoseaminidase were found in the urine of hyperoxaluric rats which were significantly reduced by 4-PBA treatment in both prophylactic and curative regimens. Inflammatory markers IL-1β, IL-6, and MCP-1 were also raised in the urine of hyperoxaluric rats which were significantly decreased by 4-PBA treatment. Hyperoxaluria was accompanied with renal oxidative stress as reflected by decreased glutathione redox status and increased reactive oxygen species which was significantly reduced by 4-PBA treatment. Histological study with H&E and Pizzolato staining showed numerous calcium oxalate crystal deposits in the renal tissues of hyperoxaluric rats. However, no significant crystal deposits were seen in the 4-PBA-treated hyperoxaluric rats. N-acetyl cysteine treatment effectively decreased renal oxidative stress but did not alter the production of inflammatory markers. Collectively, the present study suggested the potential protective effect of 4-PBA in hyperoxaluria-induced renal injury and inflammation.