Factors increasing the risk for stone formation in adult patients with cystic fibrosis

Evolving Nutritional Needs in Cystic Fibrosis

The course of cystic fibrosis (CF) as a nutritional illness is diverging since the introduction of highly effective modulator therapy, leading to more heterogeneous phenotypes of the disease despite CF genetic mutations that portend worse prognosis. This may become more evident as we follow the pediatric CF population into adulthood as some highly effective modulator therapies (HEMT) are approved for those as young as 1 year old. This review will outline the current research and knowledge available in the evolving nutritional health of people with CF as it relates to the impact of HEMT on anthropometrics, body composition, and energy expenditure, exocrine and endocrine pancreatic insufficiencies (the latter resulting in CF-related diabetes), vitamin and mineral deficiencies, and nutritional health in CF as it relates to pregnancy and lung transplantation.

Identification of Exhaled Metabolites in Children with Cystic Fibrosis

The early detection of inflammation and infection is important to prevent irreversible lung damage in cystic fibrosis. Novel and non-invasive monitoring tools would be of high benefit for the quality of life of patients. Our group previously detected over 100 exhaled mass-to-charge (m/z) features, using on-line secondary electrospray ionization high-resolution mass spectrometry (SESI-HRMS), which distinguish children with cystic fibrosis from healthy controls. The aim of this study was to annotate as many m/z features as possible with putative chemical structures. Compound identification was performed by applying a rigorous workflow, which included the analysis of on-line MS² spectra and a literature comparison. A total of 49 discriminatory exhaled compounds were putatively identified. A group of compounds including glycolic acid, glyceric acid and xanthine were elevated in the cystic fibrosis group. A large group of acylcarnitines and aldehydes were found to be decreased in cystic fibrosis. The proposed compound identification workflow was used to identify signatures of volatile organic compounds that discriminate children with cystic fibrosis from healthy controls, which is the first step for future non-invasive and personalized applications.

Recovery of ΔF508-CFTR Function by Citrate

Treatment of cystic fibrosis relies so far on expensive and sophisticated drugs. A logical approach to rescuing the defective ΔF508-CFTR protein has not yet been published. Therefore, virtual docking of ATP and CFTR activators to the open conformation of the CFTR protein was performed. A new ATP binding site outside of the two known locations was identified. It was located in the cleft between the nucleotide binding domains NBD1 and NBD2 and comprised six basic amino acids in close proximity. Citrate and isocitrate were also bound to this site. Citrate was evaluated for its action on epithelial cells with intact CFTR and defective ΔF508-CFTR. It activated hyaluronan export from human breast carcinoma cells and iodide efflux, and recovered ΔF508-CFTR from premature intracellular degradation. In conclusion, citrate is an activator for ΔF508-CFTR and increases export by defective ΔF508-CFTR into the extracellular matrix of epithelial cells.

Treatment of cystic fibrosis related bone disease

The advent of highly effective CFTR modulator therapies has slowed the progression of pulmonary complications in people with cystic fibrosis. There is increased interest in cystic fibrosis bone disease (CFBD) due to the increasing longevity of people with cystic fibrosis. CFBD is a complex and multifactorial disease. CFBD is a result of hypomineralized bone leading to poor strength, structure and quality leading to susceptibility to fractures. The development of CFBD spans different age groups. The management must be tailored to each group with nuance and based on available guidelines while balancing therapeutic benefits to risks of long-term use of bone-active medication. For now, the mainstay of treatment includes bisphosphonates. However, the long-term effects of bisphosphonate treatment in people with CF are not fully understood. We describe newer agents available for osteoporosis treatment. Still, the lack of data behooves trials of monoclonal antibodies treatments such as Denosumab and Romozosumab and anabolic bone therapy such as teriparatide and Abaloparatide. In this review, we also summarize screening and non-pharmacologic treatment of CFBD and describe the various options available for the pharmacotherapy of CFBD. We address the prospect of CFTR modulators on bone health while awaiting long-term trials to describe the effects of these medications on bone health.

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.

Systematic Review of the Prevalence of Kidney Stones in Cystic Fibrosis

Purpose: To investigate the prevalence of urolithiasis in cystic fibrosis (CF) and to summarize the available clinical features within this unique population. Methods: Studies reporting the prevalence of urolithiasis in CF patients were identified by a systematic search of the literature from inception to July 31, 2020 on three databases: Ovid Medline, Ovid Embase, and Web of Science. Data were extracted on a predetermined standardized form by two independent authors. Results: A total of 596 publications were retrieved and screened, 15 of which met the eligibility criteria. The publications were published between 1993 and 2019 and were all observational in design. There was a total of 2982 patients with CF included in this review. The overall prevalence of stone formation in the CF population was 4.6% (137/2982). The mean age of diagnosis was 25.1 ± 9.6 and ranged from 0.25 to 47. Ultrasound was the most common imaging modality for kidney stone diagnosis. There was no apparent sex difference, with a female to male ratio of 1:1. Surgical intervention was required in 37.8% (34/90) of cases. Stone recurrence was reported in 42.9% (33/77) of stone formers. Conclusions: This review provides the most recent update for the prevalence of urolithiasis in CF patients and summarizes the available clinical data. Our findings suggest that patients with CF could be at risk for developing stones at a younger age and require interventional management strategies at higher rates compared with the general population. Given the heterogeneity of the literature for urolithiasis in CF, larger population-based studies reporting the epidemiology, clinical features, and management strategies are required to further our understanding of urolithiasis in CF.

Cystic fibrosis in the kidney: new lessons from impaired renal HCO3- excretion

PURPOSE OF REVIEW

A key role of cystic fibrosis transmembrane conductance regulator (CFTR) in the kidney has recently been uncovered. This needs to be integrated into the understanding of the developed phenotypes in cystic fibrosis (CF) patients.

RECENT FINDINGS

In the beta-intercalated cells of the collecting duct , CFTR functions in very similar terms as established in the exocrine pancreatic duct and both CFTR and SLC26A4 (pendrin) orchestrate regulated HCO3- secretion. Like in the pancreas, the hormone secretin is a key agonist to activate renal HCO3- secretion. In mice lacking CFTR or pendrin, acute and chronic base challenges trigger marked metabolic alkalosis because collecting duct base secretion is defective. Also in CF patients, the ability to acutely increase renal HCO3- excretion is markedly reduced.

SUMMARY

The now much enlarged understanding of CFTR in the kidney may permit the measurement of challenged urine HCO3- excretion as a new biomarker for CF. We suggest a new explanation for the electrolyte disorder in CF termed Pseudo-Bartter Syndrome. The hallmark electrolyte disturbance features of this can be well explained by a reduced function of collecting duct Cl-/HCO3- exchange. Eventually, we suggest the diagnostic term distal renal tubular alkalosis to cover those disturbances that causes metabolic alkalosis by a reduced collecting duct base secretion.

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.

Comparative Study of Urinary Minerals and Their Effect on Stone Formation in Two Groups of Cystic Fibrosis (CF) and Healthy Children

Background: Cystic Fibrosis (CF) is a systemic autosomal disorder and the most important chronic lung disease in children. Oxalate is the end product of vitamin C metabolism, which increases the risk of kidney stones, urinary bladder stones, and calcium deposits in CF patients. Objectives: Considering the increased mineral excretion and the rate of stone formation in the urinary tract, examining the excretion of minerals will greatly help resolve clinical problems. Methods: This descriptive-analytical study was performed on CF and healthy children in Gorgan in 2018 - 19. In this study, 40 CF children and 40 healthy children were randomly selected. After obtaining informed consent from the parents of the children, a random urine sample was collected to evaluate urine minerals. Children with abnormal urinary mineral excretion underwent ultrasonography. The data were analyzed by SPSS 18 using descriptive indices (mean ± SD, frequency, and percentage) and statistical tests (independent t-test, chi-square test, and nonparametric tests). Results: Out of 80 CF and healthy children, 34 were girls, and the rest was boys. The mean age of the patients was 4.34 ± 3.38. The age difference was not significant between the groups (P > 0.05). The mean urinary levels of phosphorus, uric acid, magnesium, and citrate were 0.87 ± 1.01, 1.16 ± 0.68, 0.23 ± 0.18, 2.37 ± 3.13 mg/mg of creatinine. In the pediatric patient group, respectively (P < 0.001). The mean urinary calcium level in CF patients was 0.28 ± 0.39, which was lower than that in the healthy group. The mean urinary oxalate level was 0.13 ± 0.20 in CF patients, which was higher than that in the healthy group (P > 0.05). Hyperoxaluria, hyperuricosuria, hypomagnesiuria, and hypocitraturia occurred in 35, 30, 62, and 7.5% of the CF patients, respectively. Among the urinary minerals studied, hyperoxaluria was found to be a major determinant of stone formation risk in CF. No correlation was observed between the formation of stones and the rate of excretion of minerals (P > 0.05). Conclusions: In summary, CF patients are at an increased risk of developing citrate and calcium stones compared to the healthy group, which is associated with hyperuricosuria, hypocitraturia, and hyperoxaluria.

Acute and chronic non-pulmonary complications in adults with cystic fibrosis

INTRODUCTION

Cystic fibrosis (CF) is a genetic disease that primarily affects the respiratory system and often leads to respiratory failure and premature death. Although pulmonary complications contribute to 85% of deaths, non-pulmonary complications are responsible for significant morbidity and mortality in adults with CF. Areas covered: This review summarizes acute and chronic non-pulmonary complications in CF patients, with emphasis on emerging complications and in the context of the current growth and aging of the CF adult population. It also addresses the potential benefits of CF transmembrane conductance regulator modulator therapy. Complications that occur after solid organ (e.g. lung and/or liver) transplantation have been excluded. The review is based on an extensive search of the available literature, using PubMed and international guidelines, and on the authors' clinical experience. Expert commentary: Acute non-pulmonary complications have been well described but should be recognized and managed carefully. Managing chronic non-pulmonary complications is an important and changing aspect of CF patient care, particularly with the emergence of novel complications in adults. Early detection of non-pulmonary complications is essential to the development of prevention and treatment strategies that aim to further improve the survival and health status of adult CF patients.

[Acute pulmonary and non-pulmonary complications in adults with cystic fibrosis]

INTRODUCTION

Cystic fibrosis (CF) is a genetic disease primarily affecting the lungs, which could lead to chronic respiratory failure and premature death. CF patients are usually followed in specialized centers, but may present outside of these centers when they seek care for acute pulmonary and/or non-pulmonary complications. The aim of this paper is to provide appropriate knowledge necessary for managing respiratory and non-respiratory emergencies in CF adults.

METHODS

The review is based on international guidelines, extensive search of the available literature using Pubmed, and experience of the CF reference center at Cochin hospital (Paris, France). Complications occurring after solid organ transplantation (e.g., lung and/or liver) are excluded from this review.

RESULTS

Main acute respiratory complications are pulmonary exacerbations, hemoptysis, pneumothorax and allergic bronchopulmonary aspergillosis. Acute non-respiratory complications include hyponatremic dehydration, acute pancreatitis, acute complications of gallstones, distal intestinal obstruction syndrome, symptomatic nephrolithiasis, acute kidney injury, drug intolerances and catheter-related acute complications.

CONCLUSION

This review summarizes acute pulmonary and non-pulmonary complications occurring in adults with CF, focusing on diagnosis and principles of treatment, with the aim of providing a reference that can be used in clinical practice.

Cystic Fibrosis: A Risk Condition for Renal Disease

OBJECTIVE

Cystic fibrosis (CF) is the most common autosomal recessive disease affecting the Caucasian population, with a birth incidence ranging between 1:2,500 and 1:1,800. It is caused by mutations in the CF transmembrane regulator gene which is localized on 7 chromosomes. Renal disease is reported as a relatively rare complication in adult patient with CF. We evaluated proteinuria and chronic renal failure (CRF) in a population of patients with CF.

METHODS

A retrospective study was carried out in a referral center for CF at University of Messina in Italy. We identified all patients with renal disease, characterized by proteinuria and/or CRF, during the period 2007 to 2012 and reviewed their medical records to assess influence on renal disease of genotype, number of pulmonary exacerbation, pancreatic insufficiency, pulmonary function, CF-related diabetes, and antibiotics courses.

RESULTS

From a population of 77 adult patients with CF, we identified 9 patients with proteinuria (11.7%), and 11 patients (14.28%) with CRF. Mean age was 35.6 (+5.1 standard deviation) years, 55% were female and 33% had diabetes mellitus. Renal biopsy was performed in 3 patients because of nephrotic syndrome in 1 patient and proteinuria with renal failure in the other 2 patients. Renal amyloidosis was disclosed in 2, whereas IgA nephropathy in 1 patient. The ΔF508 mutation in homozygosis was present in 44% of patients with proteinuria (vs. 27% of our CF population, relative risk 2.07), whereas genotype ΔF508/N1303K in 22%. ΔF508 allele mutation was present in 77.7% of proteinuric patients.

CONCLUSIONS

Our study shows a higher prevalence of renal disease in patients with CF, than was previously described. The main reason may be related to increased life expectancy because of better management. Moreover, patients with ΔF508 homozygosis had higher risk of proteinuria.

Drug-Induced Kidney Stones and Crystalline Nephropathy: Pathophysiology, Prevention and Treatment

Drug-induced calculi represent 1-2% of all renal calculi. The drugs reported to produce calculi may be divided into two groups. The first one includes poorly soluble drugs with high urine excretion that favour crystallisation in the urine. Among them, drugs used for the treatment of patients with human immunodeficiency, namely atazanavir and other protease inhibitors, and sulphadiazine used for the treatment of cerebral toxoplasmosis, are the most frequent causes. Besides these drugs, about 20 other molecules may induce nephrolithiasis, such as ceftriaxone or ephedrine-containing preparations in subjects receiving high doses or long-term treatment. Calculi analysis by physical methods including infrared spectroscopy or X-ray diffraction is needed to demonstrate the presence of the drug or its metabolites within the calculi. Some drugs may also provoke heavy intra-tubular crystal precipitation causing acute renal failure. Here, the identification of crystalluria or crystals within the kidney tissue in the case of renal biopsy is of major diagnostic value. The second group includes drugs that provoke the formation of urinary calculi as a consequence of their metabolic effects on urinary pH and/or the excretion of calcium, phosphate, oxalate, citrate, uric acid or other purines. Among such metabolically induced calculi are those formed in patients taking uncontrolled calcium/vitamin D supplements, or being treated with carbonic anhydrase inhibitors such as acetazolamide or topiramate. Here, diagnosis relies on a careful clinical inquiry to differentiate between common calculi and metabolically induced calculi, of which the incidence is probably underestimated. Specific patient-dependent risk factors also exist in relation to urine pH, volume of diuresis and other factors, thus providing a basis for preventive or curative measures against stone formation.

Imaging the Abdominal Manifestations of Cystic Fibrosis

Cystic fibrosis (CF) is a multisystem disease with a range of abdominal manifestations including those involving the liver, pancreas, and kidneys. Recent advances in management of the respiratory complications of the disease has led to a greater life expectancy in patients with CF. Subsequently, there is increasing focus on the impact of abdominal disease on quality of life and survival. Liver cirrhosis is the most important extrapulmonary cause of death in CF, yet significant challenges remain in the diagnosis of CF related liver disease. The capacity to predict those patients at risk of developing cirrhosis remains a significant challenge. We review representative abdominal imaging findings in patients with CF selected from the records of two academic health centres, with a view to increasing familiarity with the abdominal manifestations of the disease. We review their presentation and expected imaging findings, with a focus on the challenges facing diagnosis of the hepatic manifestations of the disease. An increased familiarity with these abdominal manifestations will facilitate timely diagnosis and management, which is paramount to further improving outcomes for patients with cystic fibrosis.

Medical management of urinary calculi: up to date 2016

Nephrolithiasis (NL) is one of the most prevalent nontransmissible diseases in western countries. It is being associated with other frequent diseases, including osteoporosis, cardiovascular disease, hypertension, diabetes mellitus, through a putative common link with metabolic syndrome and insulin resistance or altered mineral metabolism. This review will focus on classification, physicochemical basis, risk factors, laboratory and imaging investigations, medical management.Classification as to stone composition includes calcium, uric acid (UA), cystine (Cys), infected, 2-8 dihydroxyadenine and rare NL. According to pathophysiology, NL is classified as primary, secondary to systemic diseases or drugs, caused by renal or metabolic hereditary disorders.A stone can only form in supersaturated environment, and this is sufficient in UA, Cys and infected NL, but not in Ca-NL, which results from the imbalance between supersaturation and inhibition. All types are characterized by derangements of peculiar risk factors. Laboratory investigations aim at identifying type of NL, underlying risk factors and state of saturation, and pathophysiology. This justifies a rationale therapy able to dissolve some types of stones and/or produce reduction in recurrence rate in others.Medical management includes alkali and allopurinol for UA nephrolithiasis (UA-NL), thiols and alkali in Cys-NL, dietary and pharmacological intervention for Ca-NL. Thiazides and alkaline citrate salts are the most widely used drugs in Ca-NL, where they proved efficient to prevent new stones. Other drugs have only been used in particular subsets.Proper medical management and modern urological approaches have already notably improved clinical outcomes. Future studies will further clarify mechanisms of NL with expected new and targeted therapeutic options.

Primary and secondary hyperoxaluria: Understanding the enigma

Hyperoxaluria is characterized by an increased urinary excretion of oxalate. Primary and secondary hyperoxaluria are two distinct clinical expressions of hyperoxaluria. Primary hyperoxaluria is an inherited error of metabolism due to defective enzyme activity. In contrast, secondary hyperoxaluria is caused by increased dietary ingestion of oxalate, precursors of oxalate or alteration in intestinal microflora. The disease spectrum extends from recurrent kidney stones, nephrocalcinosis and urinary tract infections to chronic kidney disease and end stage renal disease. When calcium oxalate burden exceeds the renal excretory ability, calcium oxalate starts to deposit in various organ systems in a process called systemic oxalosis. Increased urinary oxalate levels help to make the diagnosis while plasma oxalate levels are likely to be more accurate when patients develop chronic kidney disease. Definitive diagnosis of primary hyperoxaluria is achieved by genetic studies and if genetic studies prove inconclusive, liver biopsy is undertaken to establish diagnosis. Diagnostic clues pointing towards secondary hyperoxaluria are a supportive dietary history and tests to detect increased intestinal absorption of oxalate. Conservative treatment for both types of hyperoxaluria includes vigorous hydration and crystallization inhibitors to decrease calcium oxalate precipitation. Pyridoxine is also found to be helpful in approximately 30% patients with primary hyperoxaluria type 1. Liver-kidney and isolated kidney transplantation are the treatment of choice in primary hyperoxaluria type 1 and type 2 respectively. Data is scarce on role of transplantation in primary hyperoxaluria type 3 where there are no reports of end stage renal disease so far. There are ongoing investigations into newer modalities of diagnosis and treatment of hyperoxaluria. Clinical differentiation between primary and secondary hyperoxaluria and further between the types of primary hyperoxaluria is very important because of implications in treatment and diagnosis. Hyperoxaluria continues to be a challenging disease and a high index of clinical suspicion is often the first step on the path to accurate diagnosis and management.

Genetically engineered Lactobacillus plantarum WCFS1 constitutively secreting heterologous oxalate decarboxylase and degrading oxalate under in vitro

Hyperoxaluria is a major risk factor for urinary stone disease, where calcium oxalate (CaOx) is the most prevalent type of kidney stones. Systemic treatments of CaOx kidney stone patients are limited and comprise drawbacks including recurrence of stone formation and kidney damages. In the present work Lactobacillus plantarum (L. plantarum) was engineered to constitutively secrete oxalate decarboxylase (OxdC) for the degradation of intestinal oxalate. The homologous promoter PldhL and signal peptide Lp_0373 of L. plantarum were used for constructing recombinant vector pLdhl0373OxdC. Results showed that homologous promoter PldhL and signal peptide Lp_0373 facilitated the production, secretion, and functional expression of OxdC protein in L. plantarum. SDS-PAGE analysis revealed that 44 kDa protein OxdC was seen exceptionally in the culture supernatant of recombinant L. plantarum (WCFS1OxdC) harboring the plasmid pLdhl0373OxdC.The culture supernatant of L. plantarum WCFS1OxdC showed OxdC activity of 0.06 U/mg of protein, whereas no enzyme activity was observed in the supernatant of the wild type WCFS1 and the recombinant NC8OxdC strains. The purified recombinant OxdC from the WCFS1OxdC strain showed an activity of 19.1 U/mg protein. The recombinant L. plantarum strain secreted 25 % of OxdC protein in the supernatant. The recombinant strain degraded more than 70 % of soluble oxalate in the culture supernatant. Plasmid segregation analysis revealed that the recombinant strain lost almost 70-89 % of plasmid in 42nd and 84th generation, respectively. In conclusion, recombinant L. plantarum strain containing plasmid pLdhl0373OxdC showed constitutive secretion of bioactive OxdC and also capable of degrading externally available oxalate under in vitro conditions.

Abdominal pain in adults with cystic fibrosis

Abdominal pain is a common symptom in individuals with cystic fibrosis (CF). As prognosis has improved, CF has changed from a pediatric disease to the current situation wherein most people with CF are adults. With improved survival, the spectrum of pathologies causing abdominal pain in CF has shifted. Despite this, there have been relatively few previous publications focusing on gastrointestinal disease in CF adults. The aim of this review was to examine the characteristics, differential diagnosis, investigation, and optimal management of adults with CF presenting with abdominal pain.

The trigger-maintenance model of persistent mild to moderate hyperoxaluria induces oxalate accumulation in non-renal tissues

Persistent mild to moderate hyperoxaluria (PMMH) is a common side effect of bariatric surgery. However, PMMH's role in the progression to calcium oxalate (CaOx) urolithiasis and its potential effects on non-renal tissues are unknown. To address these points, a trigger + maintenance (T + Mt) model of PMMH was developed in rats (Experiment 1). The trigger was an i.p. injection of PBS (TPBS) or 288 μmol sodium oxalate (T288). Maintenance (Mt) was given via minipumps dispensing PBS or 7.5-30 μmol potassium oxalate/day for 28 days. Urinary oxalate ranged from 7.7 ± 0.8 μmol/day for TPBS + MtPBS to 18.2 ± 1.5 μmol/day for T288 + Mt30 (p ≤ 0.0005). All rats receiving T288 developed CaOx nephrocalcinosis, and many developed 'stones'. This was also true for Mt doses that did not elevate urinary oxalate above that of TPBS + MtPBS (p > 0.1) and for rats that did not have a detectable surge in urinary oxalate post T288. When TPBS was administered, CaOx nephrocalcinosis did not develop regardless of the Mt dose even if urinary oxalate was elevated compared to TPBS + MtPBS (p ≤ 0.0005). One of the risks associated with PMMH is oxalate accumulation within tissues. Hence, in a second set of experiments (Experiment 2) different doses of oxalate (Mt0.05, Mt15, Mt30) labeled with (14)C-oxalate ((14)C-Ox) were administered by minipump for 13 days. Tissues were harvested and (14)C-Ox accumulation assessed by scintillation counting. (14)C-Ox accumulated in a dose dependent manner (p ≤ 0.004) in bone, kidney, muscle, liver, heart, kidney, lungs, spleen, and testis. All these tissues exhibited (14)C-Ox concentrations higher (p ≤ 0.05) than the plasma. Extrapolation of our results to patients suggests that PMMH patients should take extra care to avoid dietary-induced spikes in oxalate excretion to help prevent CaOx nephrocalcinosis or stone development. Monitoring for oxalate accumulation within tissues susceptible to damage by oxalate or CaOx crystals may also be required.

Metastatic Bladder Cancer Presenting with Persistent Hematuria in Young Man with Cystic Fibrosis

We report a case of metastatic bladder cancer developing in a young man with cystic fibrosis (CF) that was initially diagnosed as ureterolithiasis and managed as renal colic. With the improved survival of patients with CF, an increasing burden of extrapulmonary disease manifestations is apparent. Renal colic is observed at an increased frequency in patients with CF relative to the general population and is a commonly recognized cause of hematuria. However, CF patients harboring a malignancy are recognized to be at increased risk of delayed identification owing to atypical symptoms and lack of demographic risk factors. This case illustrates how investigations to rule out malignancy are warranted in those CF patients not responding to therapies directed towards presumptive diagnoses.

Determinants of urolithiasis in patients with intestinal fat malabsorption

OBJECTIVE

To investigate the determinants of urinary stone formation in patients with fat malabsorption, because, although the prevalence of urolithiasis is greater in patients with intestinal diseases, the pathogenetic mechanisms and risk factors associated with urolithiasis in this population remain partially unsolved.

MATERIALS AND METHODS

The present study retrospectively analyzed the determinants of urolithiasis in 51 patients with fat malabsorption due to different intestinal diseases. Anthropometric, clinical, blood, 24-hour urinary parameters, and dietary intake were assessed.

RESULTS

The resection rate (ie, pancreatic and/or bowel resection) differed significantly between stone formers (SF; n=10) and nonstone formers (NSF; n=41; 70% vs 29%; P=.027). Urinary citrate was lower (1.606±1.824 vs 3.156±1.968 mmol/24 h; P=.027), while oxalate excretion (0.659±0.292 vs 0.378±0.168 mmol/24 h; P=.002) and the relative supersaturation of calcium oxalate were greater in SF than NSF (8.16±4.61 vs 3.94±2.93; P=.003). Total cholesterol and low-density lipoprotein cholesterol, but also high-density lipoprotein cholesterol, plasma β-carotene, and vitamin E concentrations, were significantly diminished, whereas serum aspartate aminotransferase activity was significantly greater in SF compared with NSF. Binary logistic regression analysis revealed resection status as a major extrarenal risk factor for stone formation (odds ratio 5.639).

CONCLUSION

Increased urinary oxalate and decreased citrate excretion, probably resulting from pancreatic and/or bowel resection with mainly preserved colon, were identified as the most crucial urinary risk factors for stone formation in patients with fat malabsorption. The findings suggest that hyperoxaluria predominantly results from increased colonic permeability for oxalate due to disturbed bile acid metabolism. The impaired status of fat-soluble antioxidants β-carotene and vitamin E indicates severe malabsorptive states associated with an enhanced stone-forming propensity.

Sensitivity of human strains of Oxalobacter formigenes to commonly prescribed antibiotics

OBJECTIVE

To determine the sensitivity of 4 strains of Oxalobacter formigenes (Oxf) found in humans--HC1, Va3, CC13, and OxK--to varying concentrations of commonly prescribed antibiotics. Oxf gut colonization has been associated with a decreased risk of forming recurrent calcium oxalate kidney stones.

METHODS

For each strain and each antibiotic concentration, 100 μL of an overnight culture and 100 μL of the appropriate antibiotic were added to a 7-mL vial of oxalate culture medium containing 20 mM oxalate. On the fourth day, vials were visually examined for growth, and a calcium oxalate precipitation test was performed to determine whether Oxf grew in the presence of the antibiotic.

RESULTS

All 4 Oxf strains were resistant to amoxicillin, amoxicillin/clavulanate, ceftriaxone, cephalexin, and vancomycin, and they were all sensitive to azithromycin, ciprofloxacin, clarithromycin, clindamycin, doxycycline, gentamicin, levofloxacin, metronidazole, and tetracycline. One strain, CC13, was resistant to nitrofurantoin, and the others were sensitive. Differences in minimum inhibitory concentration between strains were demonstrated.

CONCLUSION

Four human strains of Oxf are sensitive to a number of antibiotics commonly used in clinical practice; however, minimum inhibitory concentrations differ between strains.

Hyperoxaluria: a gut-kidney axis?

Hyperoxaluria leads to urinary calcium oxalate (CaOx) supersaturation, resulting in the formation and retention of CaOx crystals in renal tissue. CaOx crystals may contribute to the formation of diffuse renal calcifications (nephrocalcinosis) or stones (nephrolithiasis). When the innate renal defense mechanisms are suppressed, injury and progressive inflammation caused by these CaOx crystals, together with secondary complications such as tubular obstruction, may lead to decreased renal function and in severe cases to end-stage renal failure. For decades, research on nephrocalcinosis and nephrolithiasis mainly focused on both the physicochemistry of crystal formation and the cell biology of crystal retention. Although both have been characterized quite well, the mechanisms involved in establishing urinary supersaturation in vivo are insufficiently understood, particularly with respect to oxalate. Therefore, current therapeutic strategies often fail in their compliance or effectiveness, and CaOx stone recurrence is still common. As the etiology of hyperoxaluria is diverse, a good understanding of how oxalate is absorbed and transported throughout the body, together with a better insight in the regulatory mechanisms, is crucial in the setting of future treatment strategies of this disorder. In this review, the currently known mechanisms of oxalate handling in relevant organs will be discussed in relation to the different etiologies of hyperoxaluria. Furthermore, future directions in the treatment of hyperoxaluria will be covered.

Renal impairment in children with cystic fibrosis

BACKGROUND

Due to the improvement in life expectancy in cystic fibrosis (CF), co-morbidities such as renal function impairment may be more frequent.

AIM

To determine the prevalence of renal disease in children with CF and to identify associated risk factors.

METHODS

A single-center retrospective study analyzing the genetic, clinical and therapeutic characteristics of 112 children. The estimated glomerular filtration rate (GFR), microalbuminuria and lithiasic risk factors were assessed.

RESULTS

The median calculated GFR (Schwartz) was 123, 161 and 155ml/min/1.73m(2) in children aged 1, 6 and 15years, respectively. The cumulative dose of aminoglycosides was not correlated to GFR. Microalbuminuria was present in 22/38 patients. Hyperoxaluria was observed in 58/83 patients and was associated with a severe genotype, pancreas insufficiency and liver disease. Hypercalciuria, hyperuricuria and hypocitraturia were identified in 16/87, 15/83 and 57/76 patients, respectively.

CONCLUSION

Renal impairment in CF has various presentations. There appears to be low levels of renal impairment in children with CF. However, the risk of oxalocalcic urolithiasis is enhanced, and GFR may be underestimated by the Schwartz formula. Further studies using measured GFR techniques are thus warranted.

[Renal diseases in cystic fibrosis]

Patients with cystic fibrosis (CF) show a continuing improvement in their life expectancy thanks to advances in knowledge of this disorder, allowing better multidisciplinary routine monitoring and earlier therapeutic interventions. Likewise, more than of 40% of these patients are adults and CF is no more only a pediatric disease. Due to their higher life expectancy, CF patients present new and unusual complications that were not recorded before. Among them, some renal disorders have to be added to the CF-related renal diseases. They are due to frequent and prolonged exposure to various potentially nephrotoxic factors that need to be taken into account early enough in order to avoid renal failure : essentially risk factors for kidney stones formation, bacterial infections with their associated immune complexes diseases, nephrotoxic effects of antibiotics, diabetes mellitus. Because we observed a case of IgA glomerulonephritis in a 35-year-old patient with cystic fibrosis, we have searched about all these renal consequences due to this affection and here report them.

Oxalate in renal stone disease: the terminal metabolite that just won't go away

The incidence of calcium oxalate nephrolithiasis in the US has been increasing throughout the past three decades. Biopsy studies show that both calcium oxalate nephrolithiasis and nephrocalcinosis probably occur by different mechanisms in different subsets of patients. Before more-effective medical therapies can be developed for these conditions, we must understand the mechanisms governing the transport and excretion of oxalate and the interactions of the ion in general and renal physiology. Blood oxalate derives from diet, degradation of ascorbate, and production by the liver and erythrocytes. In mammals, oxalate is a terminal metabolite that must be excreted or sequestered. The kidneys are the primary route of excretion and the site of oxalate's only known function. Oxalate stimulates the uptake of chloride, water, and sodium by the proximal tubule through the exchange of oxalate for sulfate or chloride via the solute carrier SLC26A6. Fecal excretion of oxalate is stimulated by hyperoxalemia in rodents, but no similar phenomenon has been observed in humans. Studies in which rats were treated with (14)C-oxalate have shown that less than 2% of a chronic oxalate load accumulates in the internal organs, plasma, and skeleton. These studies have also demonstrated that there is interindividual variability in the accumulation of oxalate, especially by the kidney. This Review summarizes the transport and function of oxalate in mammalian physiology and the ion's potential roles in nephrolithiasis and nephrocalcinosis.

Hyperoxaluria and systemic oxalosis: current therapy and future directions

Excessive urinary oxalate excretion, termed hyperoxaluria, may arise from inherited or acquired diseases. The most severe forms are caused by increased endogenous production of oxalate related to one of several inborn errors of metabolism, termed primary hyperoxaluria. Recurrent kidney stones and progressive medullary nephrocalcinosis lead to the loss of kidney function, requiring dialysis or transplantation, accompanied by systemic oxalate deposition that is termed systemic oxalosis. For most primary hyperoxalurias, accurate diagnosis leads to the use of therapies that include pyridoxine supplementation, urinary crystallisation inhibitors, hydration with enteral fluids and, in the near future, probiotic supplementation or other innovative therapies. These therapies have varying degrees of success, and none represent a cure. Organ transplantation results in reduced patient and organ survival when compared with national statistics. Exciting new approaches under investigation include the restoration of defective enzymatic activity through the use of chemical chaperones and hepatocyte cell transplantation, or recombinant gene therapy for enzyme replacement. Such approaches give hope for a future therapeutic cure for primary hyperoxaluria that includes correction of the underlying genetic defect without exposure to the life-long dangers associated with organ transplantation.