Validation of Surrogates of Urine Osmolality in Population Studies.

BACKGROUND: The importance of vasopressin and/or urine concentration in various kidney, cardiovascular, and metabolic diseases has been emphasized recently. Due to technical constraints, urine osmolality (Uosm), a direct reflect of urinary concentrating activity, is rarely measured in epidemiologic studies. METHODS: We analyzed 2 possible surrogates of Uosm in 4 large population-based cohorts (total n = 4,247) and in patients with chronic kidney disease (CKD, n = 146). An estimated Uosm (eUosm) based on the concentrations of sodium, potassium, and urea, and a urine concentrating index (UCI) based on the ratio of creatinine concentrations in urine and plasma were compared to the measured Uosm (mUosm). RESULTS: eUosm is an excellent surrogate of mUosm, with a highly significant linear relationship and values within 5% of mUosm (r = 0.99 or 0.98 in each population cohort). Bland-Altman plots show a good agreement between eUosm and mUosm with mean differences between the 2 variables within ±24 mmol/L. This was verified in men and women, in day and night urine samples, and in CKD patients. The relationship of UCI with mUosm is also significant but is not linear and exhibits more dispersed values. Moreover, the latter index is no longer representative of mUosm in patients with CKD as it declines much more quickly with declining glomerular filtration rate than mUosm. CONCLUSION: The eUosm is a valid marker of urine concentration in population-based and CKD cohorts. The UCI can provide an estimate of urine concentration when no other measurement is available, but should be used only in subjects with normal renal function.

The pathogenesis of Randall's plaque: a papilla cartography of Ca compounds through an ex vivo investigation based on XANES spectroscopy.

At the surface of attached kidney stones, a particular deposit termed Randall's plaque (RP) serves as a nucleus. This structural particularity as well as other major public health problems such as diabetes type-2 may explain the dramatic increase in urolithiasis now affecting up to 20% of the population in the industrialized countries. Regarding the chemical composition, even if other phosphate phases such as whitlockite or brushite can be found as minor components (less than 5%), calcium phosphate apatite as well as amorphous carbonated calcium phosphate (ACCP) are the major components of most RPs. Through X-ray absorption spectroscopy performed at the Ca K-absorption edge, a technique specific to synchrotron radiation, the presence and crystallinity of the Ca phosphate phases present in RP were determined ex vivo. The sensitivity of the technique was used as well as the fact that the measurements can be performed directly on the papilla. The sample was stored in formol. Moreover, a first mapping of the chemical phase from the top of the papilla to the deep medulla is obtained. Direct structural evidence of the presence of ACCP as a major constituent is given for the first time. This set of data, coherent with previous studies, shows that this chemical phase can be considered as one precursor in the genesis of RP.

Stone formation and pregnancy: pathophysiological insights gained from morphoconstitutional stone analysis.

PURPOSE: We examined whether stone composition in pregnant women reflects peculiar pathophysiological conditions. MATERIALS AND METHODS: We analyzed in detail the composition of stones from 244 pregnant women 17 to 44 years old and from 5,712 nonpregnant women in the same age range, as recorded between January 1991 and December 2007. Clinical features were also recorded. All stones were analyzed by morphological examination coupled with infrared spectroscopy. The 2 patient groups were compared by clinical and biochemical characteristics. RESULTS: Stone episodes in pregnant women manifested mainly in trimesters 2 and 3 (39% and 46%, respectively). Spontaneous passage was noted in 81% of pregnant vs 47% of nonpregnant women (p <0.0001). Calcium phosphate, mainly in the form of carbapatite, was the main stone component in 65.6% of pregnant vs 31.4% of nonpregnant women (p <0.0001). Octacalcium phosphate pentahydrate, a transition phase in calcium phosphate stone formation, was found in a 5-fold higher proportion in carbapatite stones in pregnant than in nonpregnant women, a finding also suggesting recent stone formation during pregnancy. CONCLUSIONS: The composition of stones manifesting during pregnancy clearly differs from that of stones formed in nonpregnant women of childbearing age, suggesting a different pathophysiology specific to the pregnant state. In view of the pH dependency of calcium phosphate stones factors that increase the physiological elevation in maternal urinary calcium excretion and pH are likely to have a role in the preferential formation of calcium phosphate stones during pregnancy.

[Encrusted pyelitis: early diagnosis facilitates conservative management]. / Pyélite incrustante: un diagnostic précoce facilite la prise en charge conservatrice.

Diagnosis of encrusted pyelitis in predisposed patients is difficult. The bacteriology laboratory must be specifically asked to perform the appropriate tests. Computed tomography without injection is very important for diagnosis and follow-up. Conservative treatment is essential insofar as possible. Long-term follow-up is also necessary.

[Inherited monogenic kidney stone diseases: recent diagnostic and therapeutic advances]. / Lithiases rénales héréditaires monogéniques : récents acquis diagnostiques et thérapeutiques.

Hereditary monogenic kidney stone diseases are rare diseases, since they account for nearly 2% of nephrolithiasis cases in adults and 10% in children. Most of them are severe, because they frequently are associated with nephrocalcinosis and lead to progressive impairment of renal function unless an early and appropriate etiologic treatment is instituted. Unfortunately, treatment is often lacking or started too late since they are often misdiagnosed or overlooked. The present review reports the genotypic and phenotypic characteristics of monogenic nephrolithiases, with special emphasis on the recent advances in the field of diagnosis and therapeutics. Monogenic stone diseases will be classified into three groups according to their mechanism: (1) inborn errors of the metabolism of oxalate (primary hyperoxalurias), uric acid (hereditary hyperuricemias) or other purines (2,8-dihydroxyadeninuria), which, in addition to stone formation, result in crystal deposition in the renal parenchyma; (2) congenital tubulopathies affecting the convoluted proximal tubule (such as Dent's disease, Lowe syndrome or hypophosphatemic rickets), the thick ascending limb of Henlé's loop (such as familial hypomagnesemia and Bartter's syndromes) or the distal past of the nephron (congenital distal tubular acidosis with or without hearing loss), which are frequently associated with nephrocalcinosis, phosphatic stones and extensive tubulointerstitial fibrosis; (3) cystinuria, an isolated defect in tubular reabsorption of cystine and dibasic aminoacids, which results only in the formation of stones but requires a cumbersome treatment. Analysis of stones appears of crucial value for the early diagnosis of these diseases, as in several of them the morphology and composition of stones is specific. In other cases, especially if nephrocalcinosis, phosphatic stones or proteinuria are present, the evaluation of blood and urine chemistry, especially with regard to calcium, phosphate and magnesium, is the key of diagnosis. Search for mutations is now increasingly performed in as much as genetic counselling is important for the detection of heterozygotes in autosomic recessive diseases and of carrier women in X-linked diseases. In conclusion, better awareness to the rare monogenic forms of nephrolithiasis and/or nephrocalcinosis should allow early diagnosis and treatment which are needed to prevent or substantially delay progression of end-stage renal disease. Analysis of every first stone both in children and in adults should never be neglected, in order to early detect unusual forms of nephrolithiasis requiring laboratory evaluation and deep etiologic treatment.

[Difference in urine concentration according to gender and ethnicity: possible involvement in the different susceptibility to various renal and cardiovascular diseases]. / Différence de concentration urinaire selon le sexe ou l'origine ethnique: implications possibles dans la susceptibilité variable à différentes pathologies rénales et cardiovasculaires.

Men and African-Americans are known to be at greater risk of urolithiasis and cardiovascular and renal diseases than women and Caucasians. Previous studies suggest that the antidiuretic effects of vasopressin and/or a greater urine concentration are associated with the rate of progression of these diseases. The present review addresses possible sex and ethnic-related differences in urine volume and osmolality which could participate in this male and black higher predominance. We reanalyzed 24h-urine data collected previously by different investigators for other purposes. In studies concerning healthy subjects (six studies) or patients with chronic kidney disease or Diabetes mellitus (three studies), men excreted a larger osmolar load than women, with a 15 to 30% higher urinary osmolality (or another index of urine concentration based on the urine/plasma creatinine concentration ratio) and a similar 24h urine volume than in women. In two American studies, African-Americans showed a significantly higher urinary concentration than Caucasians and a lower 24h-urine volume. Sex and ethnic differences in thirst threshold, vasopressin level, or other regulatory mediators may contribute to the higher urinary concentration of men and of African Americans. These differences could play a role in the greater susceptibility of these subjects to these pathologies. New prospective studies should take into account the antidiuretic effects of vasopressin as a potential risk factor in the initiation and progression of cardiovascular and renal diseases.

Recurrence rates of urinary calculi according to stone composition and morphology.

Few studies have examined the relative risk of recurrence of different stone types. The object of the present study was to evaluate the tendency for stone recurrence as a function of major mineral composition of the stones and morphological characteristics of the stones. This study was carried out using 38,274 stones for which we had data available to specify if the stone was from the first or a subsequent urinary stone episode. Stones were analyzed for morphology by stereomicroscope and for composition by infrared spectroscopy. Overall, 42.7% of stones were from patients who had had a previous stone event, with these being more frequent in men (44.4%) than in women (38.9%, p < 0.0001). Age of first stone occurrence was lowest for dihydroxyadenine (15.7 ± 16.6 years) and highest for anhydrous uric acid (62.5 ± 14.9 years), with the average age of first stones of calcium oxalate falling in the middle (40.7 ± 14.6 years for calcium oxalate dihydrate, and 48.4 ± 15.1 years for calcium oxalate monohydrate, COM). By composition alone, COM was among the least recurrent of stones, with only 38.0% of COM stones coming from patients who had had a previous episode; however, when the different morphological types of COM were considered, type Ic-which displays a light color, budding surface and unorganized section-had a significantly greater rate of recurrence, at 82.4% (p < 0.0001), than did other morphologies of COM. Similarly, for stones composed of apatite, morphological type IVa2-a unique form with cracks visible beneath a glossy surface-had a higher rate of recurrence than other apatite morphologies (78.8 vs. 39-42%, p < 0.0001). Stone mineral type alone is insufficient for identifying the potential of recurrence of the stones. Instead, the addition of stone morphology may allow the diagnosis of highly recurrent stones, even among common mineral types (e.g., COM) that in general are less recurrent.

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.

[Continued late referral of patients with chronic kidney disease. Causes, consequences, and approaches to improvement]. / Retard persistant au suivi néphrologique de l'insuffisance rénale chronique. Causes, conséquences et moyens d'amélioration.

OBJECTIVES: Efforts in recent years have aimed at increasing physicians' awareness of the frequent and harmful consequences of late referral to nephrologists of patients with chronic kidney disease (CKD), shown in repeated concordant studies. We sought to determine whether these efforts have led to improved predialysis care of these patients. METHODS: This study included all 1391 consecutive patients who began maintenance dialysis at Necker Hospital between January 1989 and December 2000. We examined baseline data and outcomes and determined for four three-year periods the percentage of patients who received early specialized care (at least 6 months before onset of dialysis). RESULTS: Late referral (<6 months before dialysis) did not change significantly over the four periods, remaining around 30%, even during the most recent period (1998-2000). Clinical condition and laboratory indicators of patients referred early but not those referred late improved in the latest period, compared with the initial period (1989-1991). Overall, prevalence of major cardiovascular events (myocardial or cerebral infarction, peripheral arteriopathy, or heart failure) was more than twice as high in patients who received nephrologic care for less than 6 months and nearly twice as high even in those followed 6-35 months than in patients followed for at least 36 months before beginning dialysis. Subsequent mortality after maintenance dialysis was also significantly higher in patients with late referral than in those followed at least 3 years before dialysis. Multivariate Cox proportional model analysis identified graded duration of predialysis nephrologic care as a significant independent factor predictive of risk of mortality while on dialysis. CONCLUSION: Late referral of CKD patients for specialist care remains frequent, around 30%, although it is most often unjustified. Late referral deprives the patient of early implementation of a reno- and cardioprotective therapeutic strategy that reduces cardiovascular comorbidity and mortality. Better coordinated cooperation between family doctors and nephrologists, through the implementation of regional healthcare networks, now appears as the most effective way to improve the care of CKD patients.

Advanced oxidation protein products as risk factors for atherosclerotic cardiovascular events in nondiabetic predialysis patients.

BACKGROUND: Inflammation and oxidative stress are established risk factors for atherosclerosis, but whether they contribute to the accelerated atherogenesis associated with chronic kidney disease (CKD) remains to be assessed at the predialysis stage. METHODS: We prospectively examined the relationship between plasma levels of C-reactive protein (CRP), fibrinogen, and advanced oxidation protein products (AOPPs), as selected markers of inflammation and oxidative stress, and incident first occlusive atherosclerotic cardiovascular (CV) events (ASCVEs) in a single-center cohort of 80 uremic predialysis patients without diabetes with a creatinine clearance ranging from 20 to 40 mL/min/1.73 m2 . RESULTS: During follow-up (median, 7 years), 21 patients developed coronary, cerebral, or peripheral artery occlusive accidents, an incidence of 44/1,000 patient-years. Except for older age, their conventional risk factors did not differ compared with the 59 patients who remained free of such accidents. Conversely, plasma levels of CRP (4.3 +/- 2.7 versus 2.3 +/- 2 mg/L; P = 0.005), fibrinogen (5.6 +/- 1.4 versus 4.4 +/- 1.2 mg/L; P = 0.0009), and AOPPs (58 +/- 20 versus 42 +/- 14 micromol/L; P = 0.0002) were significantly greater at baseline, although serum creatinine levels did not differ between the 2 groups. By multivariate Cox regression analysis, age and CRP, fibrinogen, and AOPP levels were significant independent predictors of ASCVEs. Risk factor-adjusted hazard ratios were as follows: age, 1.13 (95% confidence interval, 1.04 to 1.22; P = 0.002); CRP level, 1.37 (95% confidence interval, 1.05 to 1.79; P = 0.02); fibrinogen level, 2.23 (95% confidence interval, 1.20 to 4.13; P = 0.011); and AOPP level, 1.68 (95% confidence interval, 1.12 to 2.51; P = 0.011). CONCLUSION: CRP, fibrinogen, and AOPP levels independently predict ASCVEs in patients with CKD in the predialysis phase and might directly contribute to the uremia-associated accelerated atherogenesis.

[Nephrolithiasis-induced ESRD: frequency, causes and prevention]. / Insuffisance rénale terminale d'origine lithiasique : fréquence, causes et prévention.

Nephrolithiasis still remains a too frequent - and under-appreciated - cause of end-stage renal disease (ESRD), and this is all the most unfortunate since such an untoward course is now preventable in most cases. Among 1391 patients who started maintenance dialysis at Necker hospital between 1989 and 2000, nephrolithiasis was identified as the cause of ESRD in 45 of them, an overall prevalence of 3.2%. Infection stones accounted for 42.2% of cases, calcium stones for 26.7%, uric acid stones for 17.8% and hereditary diseases for 13.3%. The proportion of nephrolithiasis-associated ESRD declined from 4.7% to 2.2% from the 1989-1991 to the 1998-2000 period, as a result of the decreased incidence of ESRD in patients with infection and calcium nephrolithiasis. Based on our observations and on published reports, it emerges that most cases of nephrolithiasis-associated ESRD were due to sub-optimal management (especially in the case of infection or cystine stones) or to late (or erroneous) etiologic diagnosis, precluding early institution of appropriate therapeutic measures. In particular, several patients with primary hyperoxaluria or 2,8-dihydroxyadeninuria were diagnosed while already on dialysis or after unsuccessful kidney transplantation, due to wrong initial diagnosis. In conclusion, thanks to recent advances in diagnosis and management of stone formers, ESRD should now be prevented in the great majority of patients, at the condition of early etiologic diagnosis based on accurate morphoconstitutional analysis of calculi and metabolic evaluation, and early implementation of appropriate preventive medical treatment.

Drug-induced renal calculi: epidemiology, prevention and management.

Drug-induced calculi represent 1-2% of all renal calculi. The drugs reported to produce calculi formation may be divided into two groups. The first one includes poorly soluble drugs with high urine excretion that favours crystallisation in the urine. Among poorly soluble molecules, triamterene was the leading cause of drug-containing urinary calculi in the 1970s, and it is still currently responsible for a significant number of calculi. In the last decade, drugs used for the treatment of HIV-infected patients, namely indinavir and sulfadiazine, have become the most frequent cause of drug-containing urinary calculi. Besides these drugs, about twenty other molecules may induce nephrolithiasis in patients receiving long-term treatment or high doses. 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. The second group includes drugs that provoke urinary calculi as a consequence of their metabolic effects. Here, diagnosis relies on careful clinical inquiry because physical methods are ineffective to differentiate between urinary calculi induced by the metabolic effects of a drug and common metabolic calculi. The incidence of such calculi, especially those resulting from calcium/vitamin D supplementation, is probably underestimated. Although drug-induced urinary calculi most often complicate high-dose, long-duration drug treatments, there also exist specific patient risk factors in relation to urine pH, urine output and other parameters, which provide a basis for preventive or curative treatment of calculi. Better awareness of the possible occurrence of lithogenic complications, preventive measures based on drug solubility characteristics and close surveillance of patients on long-term treatment with drugs with lithogenic potential, especially those with a history of urolithiasis, should reduce the incidence of drug-induced nephrolithiasis.

ESRD caused by nephrolithiasis: prevalence, mechanisms, and prevention.

BACKGROUND: The contribution of nephrolithiasis-related end-stage renal disease (ESRD) to patients requiring renal replacement therapy has never been specifically evaluated. METHODS: Of the entire cohort of 1,391 consecutive patients who started maintenance dialysis therapy at our nephrology department between January 1989 and December 2000, a total of 45 patients (21 men) had renal stone disease as the cause of ESRD and constitute the study material. Type and cause of renal stone disease was determined in the 45 patients, as well as the change in prevalence of nephrolithiasis-related ESRD with time during this 12-year period. RESULTS: The overall proportion of nephrolithiasis-related ESRD was 3.2%. Infection (struvite) stones accounted for 42.2%; calcium stones, 26.7%; uric acid nephrolithiasis, 17.8%; and hereditary diseases (including primary hyperoxaluria type 1 and cystinuria), 13.3% of cases. Women were predominant among patients with infection and calcium stones, whereas men were predominant among patients with uric acid or hereditary stone disease. The proportion of patients with nephrolithiasis-related ESRD decreased from 4.7% in the triennial period 1989 to 1991 to 2.2% in the most recent period, 1998 to 2000 ( P = 0.07). This tendency to a decreasing prevalence mainly was caused by a rarefaction of infection and calcium stones with time, whereas frequencies of uric acid and hereditary stone disease remained essentially unchanged. CONCLUSION: Severe forms of nephrolithiasis remain an underestimated cause of potentially avoidable ESRD and need for renal replacement therapy. These findings highlight the crucial importance of accurate stone analysis and metabolic evaluation to provide early diagnosis and proper therapy for conditions that may lead to ESRD through recurrent stone formation and/or parenchymal crystal infiltration.

Clinical value of crystalluria and quantitative morphoconstitutional analysis of urinary calculi.

Morphoconstitutional analysis of urinary calculi, i.e. morphologic examination combined with Fourier transform infrared spectroscopy (FTIR), is of decisive interest for the diagnosis of rare but severe inherited or acquired stone diseases such as cystine, 2,8-dihydroxyadenine, xanthine, struvite, ammonium urate or drug-containing calculi as well as primary hyperoxalurias. In the absence of early diagnosis and proper management, these diseases may lead to progressive loss of renal function. Among common forms of calcium oxalate (CaOx) stones, predominant CaOx monohydrate (whewellite) is mainly associated with hyperoxaluric conditions whereas predominant CaOx dihydrate (weddellite) is mainly associated with hypercalciuria, and this distinction is of interest to orient metabolic evaluation and preventive measures. Crystalluria examination, also based on morphology and FTIR, is a valuable diagnostic method when no stone is available for analysis. Presence of specific crystals (cystine, 2,8-dihydroxyadenine, struvite, ammonium urate) is diagnostic by itself. In all types of nephrolithiasis, serial crystalluria determination appears as a simple, cheap and reliable method to evaluate the risk of stone formation and assess the effectiveness of preventive measures. Determination of urinary crystal volume was in our experience a useful tool in the management of patients with cystinuria or primary hyperoxaluria in the post-transplantation period. In conclusion, both accurate morphologic and FTIR analysis of stones and serial crystalluria determination should be more largely used, in view of their value in the diagnosis and management of renal stone formers.

[Frequency of anaemia and indications for treatment with epoetin in chronic renal failure at the pre-dialysis stage]. / Fréquence de l'anémie et indications du traitement par époétine chez l'insuffisant rénal chronique au stade prédialytique.

OBJECTIVES: To determine the degree of anaemia corresponding to the decreasing levels of renal function in patients with chronic renal failure (CRF) and not yet on dialysis, and to assess the indications for treatment with recombinant erythropoeitin (epoetin). METHODS: We studied the relationship between haemoglobin (Hb) concentration and creatinine clearance (Ccr) in 403 consecutive patients with CRF regularly monitored in nephrology consultations between January 1 and June 30, 1999, and who received appropriate iron and vitamin supplementation. These patients were then followed-up until June 30, 2000 or until maintenance dialysis was initiated. RESULTS: There was a significant and close correlation between the degree of anaemia and renal dysfunction. An Hb value<11 g/dl (corresponding to the present threshold for the indication of epoetin) was observed in 62% of patients with creatinine levels>400 micromol/l and in 58% when Ccr was<20 ml/mn/1.73 m2. Whatever the level of CRF, the degree of anaemia was higher in the women than in the men. Among the 123 patients who had to start maintenance dialysis during the observation period, 85 (69%) were treated with epoetin before dialysis was started. CONCLUSION: In patients with CRF, clinically symptomatic anaemia is more frequent than imagined, and early treatment is required. Regular monitoring of Hb and iron levels is mandatory in order to allow patients to benefit from timely initiation of epoetin and thus prevent the development of disabling asthenia and other deleterious consequences of anaemia.

[Urinary stones and urinary tract abnormalities. Is the stone composition independent of the anatomical abnormality?]. / Lithiases et anomalies des voies urinaires: la composition des calculs est-elle indépendante de l'anomalie anatomique?

INTRODUCTION: More than ten per cent of stones are associated with a urinary tract abnormality. To verify whether the malformation influences stone composition, we studied the composition of stones observed in fifteen urological abnormalities. MATERIAL AND METHOD: This study is based on 1,461 stones associated with a clearly defined malformation analysed by infrared spectroscopy plus 402 bladder stones in men with benign prostatic hyperplasia. RESULTS: In this series of 1,863 abnormalities, 732 (39.3%) involved the kidney, 561 (30.1%) involved the ureter and 570 (30.6%) involved the lower tract. Whewellite stones were predominant in all renal abnormalities with the exception of cysts, which were mainly associated with uric acid. The main differences concerned the second constituent: weddellite in horseshoe kidneys, carbapatite in Cacchi-Ricci disease and caliceal abnormalities. Struvite was uncommon (<10%). Whewellite was the main component in ureteric abnormalities except for megaureter and reflux in which carbapatite was predominant. Struvite was present in 10% to 30% of stones. Vesicourethral abnormalities were accompanied by calcium and magnesium phosphate stones (90% of cases), and struvite was present in 58% to 90% of cases. The exception to this general rule was bladder stones associated with benign prostatic hyperplasia, in which the main component was uric acid. CONCLUSION: Significant differences in stone composition were observed as a function of anatomical abnormalities reflecting the fact that some abnormalities add infectious or metabolic risk factors to anatomical factors.

[Drinking water and urinary stones. Which drinking water and which modalities of diuresis?]. / Eaux de boisson et lithiase calcique urinaire idiopathique. Quelles eaux de boisson et quelle cure de diurèse?

Urologists frequently advise a high fluid intake to their patients with calcium stones, but apart from this simple advice, they often have few convincing arguments. This article describes the various types of drinking water available in France (mineral water, spring water, tap water), the legislation concerning drinking water, and the ions that must be taken into account for long-term forced diuresis. After studying their composition and adapting the dietary advice (particularly concerning dairy foods) to this ionic composition, various types of water can be advised to patients, including tap water, most types of spring water, but not all mineral waters.

Comparison between copeptin and vasopressin in a population from the community and in people with chronic kidney disease.

CONTEXT: Vasopressin plays a central role in water homeostasis but it has also been recognized to be associated with adverse effects in several chronic diseases. Recently, copeptin has been increasingly used as a surrogate for vasopressin, as they are co-secreted, and copeptin is easier to measure. However, the relationship between plasma concentrations of copeptin (P(cop)) and vasopressin (P(vp)) has only been studied in relatively small numbers of selected people. OBJECTIVE: This study sought to evaluate the relationship between P(vp) and P(cop) in a community-based population and in people with chronic kidney disease (CKD). DESIGN, SETTING, AND PARTICIPANTS: P(vp), P(cop), and urinary osmolarity (Uosm) were compared in 500 participants of the DESIR study, and in 83 ambulatory people with CKD. RESULTS: Median [interquartile range] of P(cop) and P(vp) in the DESIR study were 4.13 [3.58] pmol/L and 0.92 [1.93] pmol/L, respectively. Log-transformed P(cop) and P(vp) concentrations correlated significantly and positively (r = 0.686, P < .001) and they correlated inversely with estimated U(osm) (P < .001). Copeptin explained only approximately half of the vasopressin variation. In CKD, P(cop) and P(vp) both increased with decreasing estimated glomerular filtration rate (eGFR), but P(cop) increased much faster than P(vp). The P(cop)/P(vp) ratios in the lower and upper quintile groups of eGFR were 14.3 [18.3] and 5.3 [4.5], P < .001, respectively. CONCLUSIONS: This study in a normal population, the largest ever with measurements of both peptides, shows that copeptin and vasopressin concentrations correlated well. But their relationship is distorted in CKD, suggesting that the peptide clearances differ when the renal function is impaired.