Primary hyperoxaluria in Italy: the past 30 years and the near future of a (not so) rare disease.

BACKGROUND: Primary hyperoxalurias (PHs) are rare autosomal recessive diseases of the glyoxylate metabolism; PH1 is caused by mutations in the AGXT gene, PH2 in GRHPR and PH3 in HOGA1. METHODS: Here we report the first large multi-center cohort of Italian PH patients collected over 30 years (1992-2020 median follow-up time 8.5 years). Complete genotype was available for 94/95 PH1 patients and for all PH2 (n = 3) and PH3 (n = 5) patients. Symptoms at onset were mainly nephrolithiasis (46.3%) and nephrocalcinosis (33.7%). Median age at onset of symptoms and diagnosis were 4.0 years and 9.9 years, respectively. RESULTS: Fifty-four patients (56.8%) were diagnosed after chronic kidney disease. Sixty-three patients (66.3%) developed end stage kidney disease (median age 14.0 years). Twenty-one patients had a kidney-only transplant and, among them, seven had a second kidney transplant combined with liver transplant. A combined kidney-liver transplant was carried out in 29 patients and a sequential kidney-liver transplant was performed in two. In five cases a preemptive liver transplant was performed. Those receiving a liver-only transplant tended to have lower kidney function at last follow-up. CONCLUSION: Our study of PHs in Italy underlines a considerable diagnostic delay, which has only slightly decreased in recent years. Therefore, we suggest a more extensive use of both metabolic screening among patients with recurrent kidney stones and genotyping, including unambiguous assignment of minor/major allele status in order to promptly begin appropriate treatment. This will be fundamental in order to have access to the new therapies, which are mainly focused on substrate reduction for the oxalate-producing enzymes using RNA-interference.

Estimating 24-hour urinary excretion using spot urine measurements in kidney stone formers.

BACKGROUND: One limitation of the use of 24-hour collection is impracticality. We analysed the performance of spot urine measurements to estimate 24-hour excretion in patients with kidney stones. METHODS: A total of 74 adult patients from two centres performed a 24-hour urine collection. A sample of the last micturition was sent for spot urine analysis. Twenty patients were asked to collect two additional spot urine samples, one before dinner and the other after dinner. Urinary concentrations of creatinine, calcium, oxalate, uric acid, citrate and magnesium were measured in the 24-hour and each of the spot urine samples. Four approaches were used to estimate 24-hour urinary excretion, multiplying the ratio of the spot urinary analyte to creatinine concentration by (i) measured 24-hour urinary creatinine excretion (Prediction 1), (ii) estimated 24-hour urinary creatinine excretion (Prediction 2), (iii) assumed 1-g 24-hour urinary creatinine excretion (Prediction 3) or (iv) assumed 1.5-g 24-hour urinary creatinine excretion (Prediction 4). For each parameter we computed Lin's concordance correlation coefficients (CCCs), Bland-Altman plots and 95% limits of agreement. RESULTS: The performance of estimates obtained with Prediction 1 and Prediction 2 was similar, except for citrate and uric acid, for which Prediction 2 performed worse. Both approaches performed moderately well: citrate CCC {0.82 [95% confidence interval (CI) 0.75-0.90]}, oxalate [0.66 (95% CI 0.55-0.78)], magnesium [0.66 (95% CI 0.54-0.77)], calcium [0.63 (95% CI 0.50-0.75)] and uric acid [0.52 (95% CI 0.36-0.68)]. The performance of Predictions 3 and 4 was worse. CONCLUSIONS: Although spot urine samples may hold promise for clinical and population-based research, at present they have limited utility in clinical practice. Measuring or estimating 24-hour creatinine, rather than assuming a given creatinine excretion, will be necessary in future studies of spot urine samples.

[A comparison between 24h urine collection and overnight spot urines in evaluating the risk of stone disease].

Despite being recommended by most guidelines, the metabolic evaluation of patients with nephrolithiasis has limited diffusion due to difficulties relating both to the access to laboratory investigations and to urine collection modalities. Consequently, in addition to the classical 24-h collection, alternative and simplified collection modes have been proposed. We report here on the comparison between metabolic evaluation carried out on 24-h double collection (Lithotest) and overnight spot urines (RF test). Fifty-four patients with stone disease were enrolled, excluding patients with infection or cystine stones. For Lithotest, we measured all analytes necessary to calculate state of saturation (ß) with calcium oxalate, brushite and uric acid, by means of Lithorisk.com. For RF, we measured calcium, magnesium, oxalate, citrate, sulphate, phosphate, pH and creatinine. The comparison was made with creatinine ratios. An estimate of ßCaOx, ßbrushite and ßAU was obtained also on RF urines by using simplified algorithms. We found highly significant correlations between all parameters, despite quite different means. There was a nice correspondence between the two sets of measurements, assessed by the Bland-Altmann test, for calcium, oxalate, citrate, sulphate, urate and pH. Overnight urine had higher saturations compared to 24-h one owing to higher concentration of the former. In conclusion, RF test on overnight urine cannot completely replace Lithotest on 24-hr urine. However, it can represent a simplified tool for either preliminary evaluation or follow-up of patients with stone disease.

LITHORISK.COM: the novel version of a software for calculating and visualizing the risk of renal stone.

Estimation of state of saturation with stone-forming salt represents a reliable tool to assess the overall risk. The available methods are based on computer-assisted ab initio calculations. Our earlier method URSUS was subsequently substituted by Lithorisk®, a software including visualization of risk profiles. Unfortunately, Lithorisk does not adapt to new versions of Windows® and Macintosh® Apple, neither runs on smartphones or tablets. We propose a novel version of the software which can be directly used online on any device equipped by different operating systems. Upon online connection and after registration, the software is ready for unlimited accesses, in either Italian, English or French. After digiting input variables (urea and creatinine also included) in a fixed dashboard, state of saturation is promptly given. In addition to state of saturation (ß) with calcium oxalate, brushite and uric acid, ß struvite and cystine are available. Both input variables and ß results are graphically depicted as green or red horizontal bars to indicate recommended values. The software was implemented with equations allowing to omit sulphate and ammonium excretion for users with difficult access to these measurements. This simplified version, tested for ßCaOx and ßBsh on 100 urine samples showed close correlation with the full version. The software gives a list of total and free concentrations and soluble complex species distribution. Results can be printed or saved as PDF. So, we propose an easily accessible software to estimate state of saturation usable on any operating system and personal device.

Urine and stone analysis for the investigation of the renal stone former: a consensus conference.

The Consensus Group deliberated on a number of questions concerning urine and stone analysis over a period of months, and then met to develop consensus. The Group concluded that analyses of urine and stones should be routine in the diagnosis and treatment of urinary stone diseases. At present, the 24-h urine is the most useful type of urine collection, and accepted methods for analysis are described. Patient education is also important for obtaining a proper urine sample. Graphical methods for reporting urine analysis results can be helpful both for the physician and for educating the patient as to proper dietary changes that could be beneficial. Proper analysis of stones is also essential for diagnosis and management of patients. The Consensus Group also agreed that research has shown that evaluation of urinary crystals could be very valuable, but the Group also recognizes that existing methods for assessment of crystalluria do not allow this to be part of stone treatment in many places.

A diagnostic-therapeutic pathway for patients with kidney stone disease: 2020 update / Percorso diagnostico-terapeutico per il paziente con calcolosi renale: update 2020

The natural history of urinary kidney stone disease includes the risk of relapses and can be associated with the risk of chronic kidney disease, bone and cardiovascular disease. For this reason, a wide clinical-metabolic assessment of the kidney stone patient is of great importance since the first presentation of the stone, to set an appropriate preventive treatment. The proposed diagnostic-therapeutic pathway includes a careful medical history, in order to highlight a secondary kidney stone disease and the main risk factors for kidney stones, chronic renal disease, or cardiovascular and bone disease; a metabolic evaluation on multiple levels, according to the severity of the disease, and the presence or absence of risk factors, and appropriate instrumental investigations. Thus, the information collected makes it possible to set a preventive treatment consisting of general rules and, if necessary, specific pharmacological or nutritional interventions. This paper has been prepared by the Italian Multidisciplinary Study Group for Kidney Stone Disease, and it is addressed to the several professional figures involved in the management of patients suffering from nephrolithiasis, from the emergency doctor to the general practitioner, urologist, nephrologist, radiologist, and dietician. A diagnostic-therapeutic pathway for patients with kidney stone disease was first published on this Journal in 2010. The present contribution aims at amending and updating the article published exactly ten years ago, to serve as an easy-to-use reference and to guide good clinical practice in this field.

A multiregional Italian cohort of 24-hour urine metabolic evaluation in renal stone formers.

BACKGROUND: Nephrolithiasis is a common condition with several studies documenting an increased prevalence over the past four decades. EAU and AUA guidelines recommend 24-hour urine metabolic evaluation in high-risk stone formers. Aim of this study is to retrospectively evaluate the first three years of experience with LithoTest® (Biohealth Italia Srl, Turin, Italy) through the analysis of demographic, clinical and biochemical data collected from a large cohort of patients with kidney stones. METHODS: We retrospectively analyzed data from the LithoCenter database, including data from outpatient consultations, between January 2007 and December 2009 from all over Italy. LithoTest® was performed through a 24-hour urine collection and included measurements of urine volume and pH, 24-hour excretion of creatinine as well as main cations and anions, including calcium, magnesium sodium potassium, ammonium, uric acid, oxalate, citrate, phosphate, inorganic sulphate and chloride. Urine state of saturation for calcium oxalate (ßCaOx), calcium hydrogen phosphate or brushite (ßbsh) and uric acid (ßUA) were also calculated by means of the computer program LithoRisk. Brand's test for cystinuria was also carried out. Statistical analysis was performed using the S-PSS software v. 22.0. RESULTS: The number of patients with data available for analysis was 435, of whom 236 were male (54%) and 199 female (46%). Complete 24-hour urine measurements were available for all 435 patients. Compared to men, women had significantly lower values for creatinine, urate, oxalate, phosphate, sodium, potassium, magnesium and chloride excretion, whereas 24-hour pH and citrate excretion were higher. No significant differences were found for the other examined variables. ßCaOx and ßUA were significantly higher in men than women, whereas no significant difference was found for ßbsh. There was a direct relationship between calcium and sodium urine excretion. Excessive sodium excretion was recorded in 191 patients (44%) and low urine volumes in 201 (46.2%). Hyperoxaluria was observed in 118 patients (27.3%), hypercalciuria in 115 (26.6%), hyperuricosuria in 153 (35.4%), hypomagnesuria in 96 (22.2%), and hypocitraturia in 134 patients (31%). Hyperexcretion of sodium, hypocitraturia and hyperoxaluria were most frequent in males. ßCaOx was significantly higher in the setting of hypercalciuria, hypocitraturia, hyperoxaluria and urine pH below 5.5. CONCLUSIONS: Our findings in a large cohort of high-risk stone-forming patients show significant differences in urinary metabolic profiles between men and women. Carrying on the collection and analysis of data by LithoTest® from 2009 to 2015 and matching urinary and dietary data could eventually improve our understanding on the metabolic profile of stone-formers in Italy.

Updated genetic testing of Italian patients referred with a clinical diagnosis of primary hyperoxaluria.

BACKGROUND: Primary hyperoxaluria (PH) is a rare autosomal recessive disease commonly arising in childhood and presenting with nephrolithiasis, nephrocalcinosis and/or chronic renal failure. Three genes are currently known as responsible: alanine-glyoxylate aminotransferase (AGXT, PH type 1), glyoxylate reductase/hydroxypyruvate reductase (GRHPR, PH type 2), and 4-hydroxy-2-oxoglutarate aldolase (HOGA1, PH type 3). In our Centre, at the end of 2014 molecular diagnosis of PH1 had been performed in 80 patients, while one patient received a PH2 diagnosis. MATERIALS AND METHODS: Fifteen patients referred to our Centre and suspected to have PH on clinical grounds were negative for pathogenic variants in the entire coding sequence and exon-intron boundaries of the AGXT gene. Therefore, we extended the analysis to the AGXT promoter region and the GRHPR and HOGA1 genes. RESULTS: Two patients were heterozygous for two novel AGXT-promoter variants (c.-647C > T, c.-424C > T) that were probably non pathogenic. One patient was homozygous for a novel HOGA1 variant of intron 2 (c.341-81delT), whose pathogenicity predicted by in silico splicing tools was not confirmed by a minigene splicing assay in COS-7 and HEK293T cells. CONCLUSION: New genetic subtypes of PH can be hypothesized in our patients, that may be caused by mutations in other gene encoding proteins of glyoxylate metabolism. Alternatively, some kind of mutations (e.g., deletions/duplications, deep intronic splicing regulatory variants) could be missed in a few cases, similarly to other genetic diseases.

[The Hyperoxalurias]. / Le iperossalurie.

Oxalate (Ox) is an end-product of metabolism, important for poor solubility of its calcium salt in biological fluids. Ox can therefore be found in about 70% of urinary calculi. Hyperoxaluria (HOx) defined as Ox exceeding 0.5 mmol)/day, may cause nephrolithiasis/nephrocalcinosis and may be classified as dietary (DH), enteric (EH) or primary (PH). Fractional intestinal absorption of Ox is less than 10%, but increases to over 20% at calcium intakes below 200 mg/day. DH is often related to low-calcium diets. EH is caused by non-absorbed fatty acids which bind to calcium and lower its concentration in the intestinal lumen. Ox forms more soluble complexes with other cations and results in HOx. Similar mechanisms may cause HOx following bariatric surgery. PHs are the most severe causes of HOx. Three types have so far been described, all being autosomic recessive. PH1 is due to mutations of AGXT gene encoding liver alanine-glyoxylate aminotransferase, PH2 is caused by mutations of GR-HPR gene encoding glyoxylate reductase and PH3 by mutations of HOGA1 encoding for hydroxyl-oxoglutarate aldolase. HOx results from deficient detoxification from glyoxylate, which is oxidized to Ox. The three PHs have different severity, though not always clinically distinguishable. They are identified through genetics and, in PH1, good genotype/phenotype correlations have been established. Thanks to early biochemical and genetic diagnosis, which are crucial to either prevent progression to ESRF or choose adequate transplantation strategies, the outlook of PH patients has dramatically improved in the last decades and will furtherly do in view of new therapeutic strategies.

Toxicological findings in a fatal multidrug intoxication involving mephedrone.

The distribution of mephedrone in the body fluids and tissues of a subject found dead after the concomitant intake of cocaine and mephedrone is reported. Mephedrone (4-methylmethcathinone) is a designer drug of the phenethylamine family that is able to cause central nervous system stimulation, psychoactivity and hallucinations and that is becoming popular among youth as a recreational drug. Mephedrone has been available in Europe since 2007, and it is sold through the internet and by local shops as bath salt or plant food. In the case reported here, a 25-year-old man was found dead in the apartment of a friend after a night spent in several local clubs. A fragment of a blue diamond-shaped pill was found in the pocket of the trousers worn by the decedent. During the autopsy, no evidence of natural disease or trauma was found to account for this death. Blood, urine and gastric content samples were collected and submitted for toxicological analysis. Moreover, bile, brain, lung and hair samples were collected as additional matrices. The content of the pill was submitted to a general screening analysis in order to determine its composition. Mephedrone was detected in the blood, urine, gastric contents and in the additional matrices using an expressly validated GC/MS method. The blood and urine concentrations were 1.33mg/L and 144mg/L, respectively. Contextually, cocaine and cocaethylene were found in the blood and urine specimens. The distribution of mephedrone in the body organs was evaluated by analyzing the brain, bile and lung specimens. Hair analysis revealed a past exposure to mephedrone, ketamine, MDMA and cocaine. Sildenafil was identified as the main component of the blue, diamond-shaped pill. The quantitative determination of mephedrone in several body fluids and tissues provides significant knowledge about the distribution of this new drug of abuse in the human body after massive ingestion.

Fast screening of 88 pharmaceutical drugs and metabolites in whole blood by ultrahigh-performance liquid chromatography-tandem mass spectrometry.

Forensic investigations involving acute or lethal intoxication, drug-facilitated sexual assault, driving or workplace impairment frequently require the analysis of fresh or postmortem blood samples to check out a wide variety of pharmaceutical and illicit drugs, even after single-dose consumption. A sensitive and selective ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) screening method was developed for fast screening of 88 psychoactive drugs and metabolites in blood samples, including the ones most frequently involved in acute intoxications and forensic investigations in Italy. The new method allows short sample processing and analysis time (the whole procedure can be accomplished in less than 30 min) together with the simultaneous monitoring of a large number of pharmaceutical substances. These features represent crucial factors in the approach of acute intoxications, when the patient requires urgent and appropriate therapy. Blood sample treatment was limited to protein precipitation. Two UHPLC-MS/MS runs in positive and negative electrospray ionization modes were performed. The data were acquired at unit mass resolution in the selected reaction monitoring mode. According to international guidelines, linearity range, precision, trueness, detection and quantification limits, recovery, selectivity, specificity, carryover, and matrix effect phenomena were determined. Despite the limited sample purification and the inherent decreased chance of eliminating any potential interference, the present multiresidue screening method proved extremely effective and sensitive, allowing the detection of all tested drugs, even those belonging to structurally different classes of substances. Moreover, the developed method is easily susceptible to further expansion to encompass more drugs, either new or those becoming important for criminal investigation. This protocol was also applied to the analysis of authentic blood samples collected from victims of various crimes in routine casework, whose relevance in forensic investigations is presented in five cases.

Hair analysis of drugs involved in drug-facilitated sexual assault and detection of zolpidem in a suspected case.

In drug-facilitated crimes, victims are subjected to nonconsensual acts while they are incapacitated by the effects of a drug. A specific LC-MS/MS protocol for determining benzodiazepines and hypnotics at low concentration in hair specimens was developed and validated in order to target the allegedly administered drugs on a chronological basis. In the case hereby reported, a 26-year-old woman claimed to have been sexually assaulted after being administered an allegedly drugged coffee, but toxicological analysis of urine and blood provided no evidence of any drug intake. Subsequently, a second woman accused the same man of sexual abuse. Hence, the suspect was prosecuted. Specimens were collected from four subjects (two alleged victims, the suspect and his wife) and segmental hair analysis was performed. The results revealed that zolpidem was present at low picogram per milligram concentration in three out of eleven segments of hair specimen obtained from the first of the alleged victims, offering plain evidence of single or sporadic exposure, whereas the agent was detected in the high picogram per milligram range in the hair collected from suspect's wife, coherently with therapeutic administration. The presence of interfering signals typical of the keratin-containing matrix was found and possible hair degradation by cosmetic treatments was investigated by electron microscopy, so as to obtain a judicious interpretation of the analytical findings.

The increase in exhaled NO following allergen challenge is not associated with airway acidification.

BACKGROUND: Exhaled nitric oxide (NO), commonly accepted marker of airways inflammation, may be generated both by specific enzymes, NO synthases, as well as by nonenzymatic reduction in its metabolites. During asthma exacerbations, owing to lower airways pH, it has been reported that nitrite reduction may contribute to the increase in exhaled NO. Allergen exposure, an important cause of asthma exacerbations, is also known to increase exhaled NO. DESIGN: To investigate whether cat allergen exposure of cat-sensitized asthmatics leads to airway acidification, which could explain the expected increase in exhaled NO. Twelve nonsmoking, cat-sensitized patients (nine women) aged 33·5 (22-54) years with mild intermittent asthma performed a cat allergen challenge. Exhaled NO at 50-200 mL s(-1), nasal NO, exhaled breath condensate (EBC) pH, nitrite and nitrate were measured before, 8 and 24 h after allergen challenge. RESULTS: A significant increase in FE(NO 50) was observed 24 h after allergen challenge compared to baseline: 110 ppb (34, 143) vs. 60 ppb (19, 122), P = 0·006. This was mainly explained by an increase in bronchial NO flux (P = 0·02), while no changes in EBC pH were observed (P = 0·35). CONCLUSIONS: Allergen exposure is not associated with airways acidification, implying that the observed increase in exhaled NO is probably because of enzymatic NO production.

Time-related changes of metabolic and physicochemical profiles in patients with mechanical ileal neobladders.

OBJECTIVE: To investigate metabolic disturbances, possibly leading to stone disease, in the Camey II technique for creating a urinary reservoir from an intestinal segment. PATIENTS, SUBJECTS AND METHODS: Thirty patients with a Camey II ileal neobladder and 26 controls had metabolic investigations of blood samples, and 24-h and fasting urine samples, to assess renal function, the risk of stone formation, and bone turnover. The state of saturation with calcium oxalate, uric acid and brushite were calculated using a computer program. RESULTS: The patients had lower renal clearances than the controls (P < 0.001), with a slight tendency to decrease with time from surgery. Metabolic hyperchloraemic acidosis occurred in 57% of the patients and tended to be worse at lower glomerular filtration rates (P < 0.05). Severe hypocitraturia in both daily and fasting urine was the most striking urinary feature. There was no difference in the other variables. The state of saturation with brushite was slightly higher in patients due to the slightly higher urinary pH. There was a trend to lower bone turnover, involving markers of both resorption and formation, in the patients. CONCLUSIONS: The Camey II technique led to only minor functional or metabolic changes; renal function tended to deteriorate and mild metabolic acidosis was the main feature. Fasting and 24-h hypocitraturia occurred in most patients, representing a potential threat for calcium stone formation.

Use of drugs for nephrolithiasis.

Renal stone disease often begins by renal colic. In order to manage this event adequately, several goals should be pursued: first, attenuate pain; second, favour progression and spontaneous expulsion of stones; third, prevent from obstructive and infectious complications. All of the aforementioned points pertain to medical management of this disease. Concerning prevention, it is widely agreed that pathogenesis of kidney stones is a consequence of abnormalities in urine environment, leading to a disequilibrium between promoters and inhibitors of crystallization. Therefore, the rationale for therapy is to make urine less conductive to stone formation, by both decreasing state of saturation and increasing inhibitory potential. In only some types of stone-forming salts it is possible to obtain undersaturation with the solid phase. Indeed, uric acid stones can be chemically dissolved by using alkali and allopurinol. To a lesser extent, this also applies to cystine stones, with the use of thiols and alkali. In these subsets, the aforementioned tools are also effective to prevent new stone formation. Much more challenging appears the treatment of calcium containing stones. About 10% of such stones is caused by systemic disorders and, in these cases, the prevention of new stones is successfully accomplished by curing the underlying disease. For instance, parathyroidectomy cures calcium nephrolithiasis in case of hyperparathyroidism. However, the majority of patients with calcium stones are idiopathic stone-formers, in whom metabolic abnormalities often occur, namely, hypercalciuria, hyperoxaluria, hypocitraturia. The correction of these abnormalities by using thiazide diuretics, alkaline citrates, potassium phosphate and bisphosphonates is based on the prevailing metabolic defect. Among the most recent available tools, Oxalobacter Formigenes and probiotics have been proposed to treat primary or secondary hyperoxalurias. In general, the treatment of stone disease reduces its recurrence rate, but only seldom results in stable remission. Anyway, less stones mean reduction of the need for urological procedures and the associated infective or obstructive complications. Of course, medical prevention implies financial efforts, but a careful cost to benefit analysis demonstrates that these are well justified.

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

BACKGROUND: Patients with cystic fibrosis (CF) are at high risk of nephrolithiasis (NL), but controversy still exists in terms of causes, including low urine output, hypercalciuria, hyperoxaluria, hyperuricosuria and hypocitraturia. Moreover, heterozygotes (H-CF), which may exhibit altered renal concentrating and diluting ability, have never studied so far. We, therefore, evaluated the metabolic and physicochemical data of adult CF and H-CF patients, comparing them to controls (C). METHODS: Twenty-nine CF patients (16 females, aged 28.4 +/- 7.1 years), 20 H-CF (12 females, aged 58.6 +/- 6.3 years) and 30 C (19 females, aged 39.1 +/- 11.5 years) underwent kidney ultrasound and metabolic evaluation to assess stone risk profile. RESULTS: There was a 21% prevalence of NL in CF vs 15% in H-CF. The CF group had elevated uric acid, but no other serological differences compared with the H-CF and C group. Conversely, the citrate and oxalate content in the urine differed significantly, being lower and higher, respectively. These changes held after correction for urine creatinine. Consequently, urine specimens were more supersaturated with calcium oxalate, despite exhibiting no differences for other relevant constituents. Uric acid increased only after normalization for the body weight and urine creatinine. Lower urine volume and more acidic pH produced mild supersaturation with uric acid in samples from CF, while urine from both H-CF and C remained undersaturated. H-CF had only minor increases in both urine oxalate and calcium oxalate supersaturation. CONCLUSIONS: This study confirms a high prevalence of kidney stones among CF patients associated with supersaturated urine. Their longer survival justifies diets and/or medications aimed at reducing the risk of forming stones.

Severe course of primary hyperoxaluria and renal failure after domino hepatic transplantation.

We report herein a domino orthotopic liver transplantation (LT), from a 38-year-old woman undergoing liver-kidney transplantation (LKT) for primary hyperoxaluria type I (PH1) to a recipient with cirrhosis and hepatocellular carcinoma. Delayed onset of PH1 and renal failure and 10% residual alanine-glyoxylate aminotransferase (AGT) activity in domino liver justified its use for domino procedure. The clinical course after LKT was similar to that described in other series, including ours. Renal function started promptly and maintained despite sustained hyperoxaluria from dissolution of oxalotic deposits. Conversely, the domino recipient manifested severe hyperoxaluria and developed nephrolithiasis and renal insufficiency with rapid progression over 2 months. A new LT resulted in slow decrease of oxaluria and improvement of renal function. Therefore, PH1 behaved quite differently in these two patients, leading us to conclude that domino LT using livers from PH1 patients should be considered very carefully, only as a bridge to definitive LT in recipients with critical clinical conditions.

Long-term, low-dose, intravenous vitamin C leads to plasma calcium oxalate supersaturation in hemodialysis patients.

BACKGROUND: Ascorbate supplementation for patients on regular dialysis treatment (RDT) is advised to obviate deficiency and improve epoetin response in those with functional iron deficiency. However, clear-cut safety concerns regarding hyperoxalemia are still poorly understood. This study tries to establish safety/efficacy profiles of ascorbate and oxalate during long-term intravenous ascorbate supplementation. METHODS: A prospective study was performed in 30 patients on RDT showing ascorbate deficiency (plasma ascorbate < 2.6 mg/L [<15 micromol/L]): 18 patients were administered intravenous ascorbate during 18 months (250 mg/wk, subsequently increased to 500 mg), and 12 patients were taken as reference untreated cases. Plasma ascorbate and oxalate assays and dialytic balance determinations were performed (ion chromatography and reverse-phase high-performance liquid chromatography, respectively) at baseline, during treatment, and 12 months after withdrawal. RESULTS: Plasma ascorbate levels increased dose dependently with supplementation (1.6 +/- 0.8 mg/L [9.1 +/- 4.6 mumol/L] at baseline, 2.8 +/- 1.8 mg/L [15.9 +/- 10.1 micromol/L]) with 250 mg of ascorbate, and 6.6 +/- 2.8 mg/L [37.5 +/- 16.0 micromol/L] with 500 mg/wk of ascorbate), but only normalized with greater dosages for several months in 94% of patients. Baseline plasma oxalate levels increased from 3.2 +/- 0.8 mg/L (35.8 +/- 8.8 micromol/L) to 3.6 +/- 0.8 mg/L (39.5 +/- 9.1 micromol/L) and 4.5 +/- 0.9 mg/L (50.3 +/- 10.4 micromol/L) with 250 and 500 mg, respectively ( P < 0.001). The calcium oxalate saturation threshold was exceeded by 7 of 18 patients (40%) during 6 months therapy with 500 mg/wk. Ascorbate dialysis removal increased from 37.8 +/- 23.2 mg (215 +/- 132 micromol) to 99.6 +/- 51.7 mg (566 +/- 294 micromol) during supplementation (P < 0.001), with corresponding increases in oxalate removal from 82.5 +/- 33.2 mg (917 +/- 369 micromol) to 111.2 +/- 32.6 mg/L (1,236 +/- 362 micromol; P < 0.01). Withdrawal reverted plasma levels and dialysis removal to initial values. Values for untreated patients did not change during 1 year of follow-up. CONCLUSION: Patients on RDT may resolve ascorbate deficiency with intravenous supplementation of 500 mg/wk, but this implies a significant risk for oxalate supersaturation. Oxalate measurements are strongly recommended during long-term ascorbate therapy.

Crystallization inhibitors in the pathophysiology and treatment of nephrolithiasis.

It is currently agreed that stone formation in the urinary tract requires supersaturation with respect to a given solid phase. However, this principle fully applies only to stones other than calcium-containing stones, in which case compounds acting as inhibitors are postulated to naturally occur in urine. Stone formation would therefore ensue from an imbalance between promoters and inhibitors. The saturation state can be estimated by means of computer model systems based on ab initio calculations, which account for the main soluble complexes formed in urine between relevant cations and anions. This estimates the overall promoting potential of urine. However, in the case of calcium nephrolithiasis, supersaturation does not make a clear-cut separation between normal subjects and patients. Several studies in the last two decades have identified many inhibitors of calcium oxalate and calcium phosphate crystallization, which are classified into the ionic and macromolecular. They have been shown to act on kinetics by interfering with nucleation, growth and aggregation of crystals. Unfortunately, except for citrate, none of the newly discovered substances has been definitely characterized in its molecular composition and structure, type and potency of inhibition, differences in concentration and structure between stone-forming and non stone-forming subjects. Citrate exhibits a dual action in urine, opposing crystal formation by both thermodynamic and kinetic mechanisms. At present it is the only natural inhibitor which can be measured in urine, quantitated as to inhibitory activity and used in medical treatment.