The identification of hyperoxaluria in very low-birthweight infants – which urine sampling method?

The present study was performed to determine the best method of urine collection for measurement of oxalate excretion in very low-birthweight (VLBW) infants and to verify the utility of the oxalate/creatinine ratio in VLBW infants. This has not been investigated in this group with developing renal function. In a prospective study of 30 VLBW infants, we compared oxalate excretion in urine collected over 24 h and in a spot urine sample. The urinary oxalate concentration was measured by the oxalate oxidase method. The correlation coefficient between the amount of oxalate per kilogram body weight excreted daily and the oxalate/creatinine ratio in spot urine sample was 0.80 (P<0.0001) and with the oxalate/creatinine ratio in a 24-h urine collection 0.82 (P<0.0001). The two highest levels of oxalate excretion (>100 μmol/kg per day) were detected with both oxalate/creatinine ratios (>1 mmol/mmol). No circadian rhythm of oxalate excretion was found. The measurement of the oxalate/creatinine ratio in spot urine samples is suitable for screening VLBW infants for hyperoxaluria. Received October 23, 1995; received in revised form and accepted July 29, 1996     

Effect of dietary control of urinary uric acid excretion in calcium oxalate stone formers and non-stone-forming controls

BACKGROUND AND PURPOSE: Hyperuricosuria is a well-recognized risk factor for calcium oxalate urolithiasis. Some studies have demonstrated elevated urinary uric acid excretion in stone formers compared with non-stone-forming controls; nevertheless, these studies were limited by patient consumption of self-selected diets. With the recognition that dietary differences may induce variations in urinary uric acid excretion, we evaluated excretion of this compound in stone formers and controls consuming a standardized diet. SUBJECTS AND METHODS: A standardized formula diet was administered to 65 calcium oxalate stone formers and 61 age-matched non-stone-forming controls. During the 3 days of dietary intervention, 24-hour urine collections were obtained. Mean urinary uric acid excretion indexed to urinary creatinine was calculated for each subject, and the results in the two groups were compared. RESULTS: Stone-forming subjects did not have an elevation in urinary uric excretion compared with control subjects, with mean indexed urinary uric acid excretions of 337 +/- 64 mg/g of creatinine and 379 +/- 76 mg/g of creatinine, respectively. CONCLUSIONS: With dietary standardization, there was no observed increase in urinary uric acid excretion in our sampled populations. These findings emphasize the role of dietary factors in urinary uric acid excretion and highlight the potential value of dietary interventions.     

Prophylactic and therapeutic properties of a sodium citrate preparation in the management of calcium oxalate urolithiasis: randomized, placebo-controlled trial

The purpose of this study was to investigate the prophylactic and therapeutic effects of a hitherto untested preparation containing sodium citrate in the management of calcium oxalate urolithiasis. In this study, a host of calcium oxalate kidney stone risk factors was investigated using a randomised, placebo controlled, within-patient clinical trial. The trial involved four groups of subjects: healthy male controls, healthy female controls , calcium oxalate stone-forming males and calcium oxalate stone-forming females. There were 30 subjects in each group. Twenty subjects in each group ingested the preparation containing sodium citrate and ten subjects in each group ingested a placebo for 7 days. Collection of 24 h urines were carried out at baseline, at day 7 and day 10 (i.e. 3 days after suspension of drug/placebo ingestion). These were analysed for biochemical and physicochemical risk factors. They were also tested for their inhibitory properties in crystallization experiments. Data were statistically analyzed using analysis of variance (ANOVA). Key risk factors were significantly and beneficially altered across all groups after ingestion of the preparation. The pH and urinary citrate excretion increased while urinary oxalate and calcium excretions decreased, as did relative supersaturations of calcium oxalate and uric acid. In addition, inhibition of calcium oxalate crystallization increased. Beneficial carryover effects were observed for some risk factors. The results of this study have demonstrated, for the first time, that a sodium citrate-containing preparation favourably alters the risk factors for calcium oxalate urolithiasis.     

Effect of vitamin C supplements on urinary oxalate and pH in calcium stone-forming patients

BACKGROUND: The contribution of ascorbate to urinary oxalate is controversial. The present study aimed to determine whether urinary oxalate and pH may be affected by vitamin C supplementation in calcium stone-forming patients. METHODS: Forty-seven adult calcium stone-forming patients received either 1 g (N=23) or 2 g (N=24) of vitamin C supplement for 3 days and 20 healthy subjects received 1 g. A 24-hour urine sample was obtained both before and after vitamin C for calcium, oxalate, magnesium, citrate, sodium, potassium, and creatinine determination. The Tiselius index was used as a calcium oxalate crystallization index. A spot fasting morning urine sample was also obtained to determine the urinary pH before and after vitamin C. RESULTS: Fasting urinary pH did not change after 1 g (5.8 +/- 0.6 vs. 5.8 +/- 0.7) or 2 g vitamin C (5.8 +/- 0.8 vs. 5.8 +/- 0.7). A significant increase in mean urinary oxalate was observed in calcium stone-forming patients receiving either 1 g (50 +/- 16 vs. 31 +/- 12 mg/24 hours) or 2 g (48 +/- 21 vs. 34 +/- 12 mg/24 hours) of vitamin C and in healthy subjects (25 +/- 12 vs. 39 +/- 13 mg/24 hours). A significant increase in mean Tiselius index was observed in calcium stone-forming patients after 1 g (1.43 +/- 0.70 vs. 0.92 +/- 0.65) or 2 g vitamin C (1.61 +/- 1.05 vs. 0.99 +/- 0.55) and in healthy subjects (1.50 +/- 0.69 vs. 0.91 +/- 0.46). Ancillary analyses of spot urine obtained after vitamin C were performed in 15 control subjects in vessels with or without ethylenediaminetetraacetic acid (EDTA) with no difference in urinary oxalate between them (28 +/- 23 vs. 26 +/- 21 mg/L), suggesting that the in vitro conversion of ascorbate to oxalate did not occur. CONCLUSION: These data suggest that vitamin C supplementation may increase urinary oxalate excretion and the risk of calcium oxalate crystallization in calcium stone-forming patients.     

Urolithiasis in the first year of life

Data on urolithiasis (UL) in infancy are limited. The objective of this study was to increase awareness of infant UL and to investigate the influence of possible risk factors in this very specific age group. Nonfasting, second-voiding urine samples were obtained to test for urinary excretions of calcium, oxalate, citrate, magnesium, uric acid, and creatinine. Blood analysis included calcium, phosphate, magnesium, uric acid, creatinine, sodium, potassium, chloride, and alkaline phosphatase. Patients received follow-up testing every 1–2 months; serial ultrasonography was used to track UL status. Fifty infants with a median age of 5 months were enrolled in the study. Hypercalciuria was detected in 9/47, hyperoxaluria in 5/39, hypocitraturia in 4/31, and cystinuria in 2/50 infants. We identified at least one metabolic abnormality in 46% of our patients; no metabolic abnormality was identified in 27 infants. Within a mean follow-up period of 14 months, 17 infants became stone free, stones increased in number in ten patients and decreased in number in 16, and recurrence was detected in seven. This study showed that UL could be detected in very early life, even in the newborn period, and could be the source of late childhood/adulthood UL. Infants with nonspecific symptoms such as restlessness may have UL and should undergo ultrasonographic examination. Metabolic evaluation of UL in this specific age group carries some diagnostic challenges, e.g. unsatisfactory data regarding normal ranges of urinary mineral excretion, and collection of 24-h urine samples.     

Comparison of renal function and metabolic abnormalities of cystine stone patients and calcium oxalate stone patients in China

Purpose

To compare renal function and metabolic abnormalities of cystine stone patients and calcium oxalate stone patients in China.

Methods

Between 2008 and 2011, thirty cystine stone patients were involved in our study, and an equal number of age- and gender pair-matched patients with calcium oxalate stones. Non-stone forming individuals were elected as controls. The evaluation included blood chemistry studies and 24-h urine collection in both groups of patients.

Results

The cystine stone patients had higher mean values of serum blood urea nitrogen, urate and creatinine levels than patients in other two groups. With respect to urine risk factors, cystine stone patients had higher urinary citrate and lower urinary oxalate and creatinine than calcium oxalate stone patients. When compared to non-stone forming individuals, cystine stone patients had higher urinary urate excretion and lower urinary creatinine excretion. Metabolic abnormalities could be demonstrated in 80 % of the cystine stone patients and in 100 % of the calcium oxalate stone patients. We also compared urine risk factors among cystine stone patients with different urine cystine excretion (<1 mmol/24 h, 1–2 mmol/24 h and >2 mmol/24 h). No significant difference was found in urine risk factors among three groups.

Conclusions

This study suggested that cystine stone patients were at greater risk for the loss of renal function than calcium oxalate stone patients, but the risk of the formation of calcium oxalate stones was lower. Our results also indicated that urinary cystine had little or no impact on the excretion of urine chemistries in cystine stone patients.     

The influence of sex hormones on renal osteopontin expression and urinary constituents in experimental urolithiasis

PURPOSE: To our knowledge the influence of sex hormones on urinary stone formation remains undetermined. We investigated the effect of castration on urinary lithogenic factors and renal osteopontin expression in rats previously treated with ethylene glycol. MATERIALS AND METHODS: Sprague-Dawley rats were divided normal males, castrated males, males with 2 weeks of 0.75% ethylene glycol treatment, castrated males with 2 weeks of 0.75% ethylene glycol treatment, normal females, castrated females, females with 2 weeks of 0.75% ethylene glycol treatment and castrated females with 2 weeks of 0.75% ethylene glycol treatment. We analyzed 24-hour urine samples for urinary constituents, such as calcium, oxalate, citrate, uric acid, phosphate, magnesium, sodium, potassium and creatinine. The kidneys were examined for osteopontin expression by Northern blot analysis and for crystal deposition by histological examination. RESULTS: In intact male rats calcium and citrate excretion decreased and oxalate excretion increased significantly after ethylene glycol treatment. Castrated male rats with ethylene glycol had greater calcium and less oxalate excretion than male intact rats with ethylene glycol. In intact female rats uric acid excretion decreased and only calcium excretion increased significantly after ethylene glycol treatment. Castrated female rats with ethylene glycol excreted significantly more oxalate and less calcium than intact female rats with ethylene glycol. Renal osteopontin expression was the same in male intact and castrated rats, and in female intact and castrated rats. In males with ethylene glycol expression was stronger in castrated than in intact rats. In females with ethylene glycol expression was weaker in castrated than in intact rats. No crystal deposits were found in the kidneys in any group. CONCLUSIONS: Testosterone appears to promote stone formation by suppressing osteopontin expression in the kidneys and increasing urinary oxalate excretion. Estrogen appears to inhibit stone formation by increasing osteopontin expression in the kidneys and decreasing urinary oxalate excretion.     

Gestational hypercalciuria causes pathological urine calcium oxalate supersaturations

Although normal pregnant women are more hypercalciuric than women with calcium oxalate nephrolithiasis (243 +/- 23 mg/day vs. 194 +/- 5 mg/day), pregnancy is not an established stone-forming state and pregnant women do not exhibit pathological crystalluria. One hypothesis to explain their lack of overt stone formation and pathological crystalluria is that pregnancy does not raise urine supersaturation with respect to stone forming salts such as calcium oxalate or calcium monohydrogen phosphate (brushite) to levels as high as in stone forming women. To test this hypothesis, we studied eleven normal women during each trimester of pregnancy, and between six and eight weeks post-partum. During pregnancy, hypercalciuria occurs with unchanged urine volume, citrate and magnesium excretions do not increase proportionally with calcium excretion, and urine pH increases. Supersaturations with respect to calcium oxalate (CaOx) and brushite (Br) are as high as those of women with calcium nephrolithiasis. The lack of pathological crystalluria and stones during pregnancy is not due to a failure of supersaturations to increase; urinary potential for crystallization is as high as in patients with established stone disease.     

Urinary vitamin A excretion in very low birth weight infants

Vitamin A (VA) deficiency in very low birth weight (VLBW) infants is associated with an increased risk for disorders related to kidney and lung maturation and function. VA losses through increased urinary retinol (ROH) excretion might contribute to this deficiency risk. The mechanism accounting for ROH loss in the urine has not yet been clarified. The aim of this study was to assess the excretion of ROH, retinol-binding protein 4 (RBP4) and transthyretin (TTR) in urine from VLBW infants in comparison with that in term infants in relation to kidney function. Urine specimens were collected from 15 VLBW infants (birth weight < 1,500 g) as well as from 20 term infants during the first 2 days after birth. ROH in urine was detectable in 14 of the 15 VLBW infants at a median concentration of 234 nmol/g creatinine. In the group of term infants, 17 of the 20 excreted ROH, but at an approximately five-times lower concentration (P < 0.001). Excretion of RBP4 and TTR was also much higher in VLBW infants (both P< 0.001). The urinary ROH excretion in VLBW infants may be related to the impaired tubular handling of its carrier proteins RBP4 and TTR. Thus, ROH excretion might contribute to an increased risk of VA deficiency, especially in VLBW infants.     

Citrate (CG-120) therapy in urolithiasis. 2. Effect on urinary and serum biochemistry

The long-term effects of citrate therapy (CG-120, 3 g/day or 4 g/day) were examined in 398 patients with upper urinary tract calculi. We studied the influence of citrate therapy on urinary and blood biochemistry in 353 of them. CG-120 caused a sustained increase in urinary citrate, urinary pH and potassium, but no substantial or significant changes in other urinary parameters (uric acid, phosphate, oxalate, sodium, chloride and urine volume). Although urinary calcium decreased significantly up to the 24th week, it did not change significantly there after and it tended to increase at the 54th week. Urinary creatinine excretion decreased after 34 weeks of administration, but this phenomenon could not be explained, because the level of blood urea nitrogen and serum creatinine was not elevated in any case before administration. There were no changes in the serum calcium, magnesium, phosphate, uric acid, sodium, potassium or chloride level.     

月见草油抑制草酸钙结晶形成的实验研究

目的了解月见草油在草酸钙结石形成中的作用,为临床治疗提供新的方法与思路。方法雄性SD大鼠60只,随机分为4组,各组15只。C组和D组以月见草油（含γ-亚麻酸9.2%）或葵花籽油（含亚油酸70%）10g/kg灌胃4周后,用诱石剂1%乙二醇（EG）加2%氯化氨喂饮,同时继续以月见草油或葵花籽油灌胃4周,8周后检测各组大鼠肾功能、24h血尿生化指标和肾草酸钙结晶情况;仅饲普通饲料（A组,空白组）和普通饲料加1%乙二醇（EG）加2%氯化氨喂饮（B组,成石组）大鼠作为对照。结果月见草油组肾组织水肿较轻,肾内草酸钙结晶数及肾成石率低于成石组（P〈0.05）,尿枸橼酸较成石组高（P〈0.01）,24h尿钙、尿草酸排泄均低于成石组（P〈0.01）,血尿素氮（P〈0.01）、血肌酐（P〈0.05）低于成石组。结论γ-亚麻酸能有效改善肾功能,减少尿钙及草酸的排泄,抑制实验鼠肾草酸钙结晶形成,在尿石症防治方面可能有一定应用价值。     

Increased protein intake on controlled oxalate diets does not increase urinary oxalate excretion

High animal protein intake is a risk factor for calcium oxalate stone disease. The effect of dietary protein on the urinary excretion of calcium, acid and citrate is well established. However, its effect on oxalate excretion is unclear, due in part to an inadequate control of dietary oxalate intake in previous studies. This relationship warrants clarification due to the proposed important role of the metabolism of amino acids in endogenous oxalate synthesis. In this study, 11 normal subjects consumed controlled oxalate diets containing 0.6, 1.2 and 1.8 g protein/kg body weight/day. The analysis of 24 h urine collections confirmed that as protein intake increased, urinary calcium and glycolate increased and urinary pH and citrate decreased. The increased glycolate excretion was due in part to an increased hydroxyproline, but not glycolate consumption. Total daily urinary oxalate excretion did not change. When indexed to creatinine there was a small but significant decrease in oxalate excretion. This is most likely due to hyperfiltration. These results indicate that as dietary protein intake increases, the catabolism of diet-derived amino acids is not associated with an increased endogenous oxalate synthesis in normal subjects.     

Etiology of nephrocalcinosis in preterm neonates: association of nutritional intake and urinary parameters

BACKGROUND: Nephrocalcinosis (NC) in preterm neonates has been described frequently, and small-scale studies suggest an unfavorable effect on renal function. The etiologic factors have not yet been fully clarified. We performed a prospective observational study to identify factors that influence the development of NC. METHODS: The study population consisted of 215 preterm neonates with a gestational age <32 weeks. Clinical characteristics and intake in the first four weeks of calcium, phosphorus, vitamin D, protein, and ascorbic acid were noted. Serum calcium, phosphate, vitamin D, magnesium, uric acid, creatinine, urea and urinary calcium, phosphate, oxalate, citrate, magnesium, uric acid, and creatinine were assessed at four weeks of age and at term. Renal ultrasonography (US) was performed at four weeks and at term. At term was defined as a postconceptional age of 38 to 42 weeks. RESULTS: NC was diagnosed by means of US in 33% at four weeks and in 41% at term. Patients with NC at four weeks had a significantly higher mean intake of calcium (P < 0.05), phosphorus (P < 0.05), and ascorbic acid (P < 0.01) than patients without NC. They had a higher mean serum calcium (2.55 vs. 2.46 mmol/L, P < 0.01) and a higher mean urinary calcium/creatinine ratio (2.6 vs. 2.1 mmol/mmol, P < 0.05). Patients with NC at term had a lower birth weight (1142 vs. 1260 g, P < 0.05) and a lower gestational age (28.8 vs. 29.4 weeks, P < 0.05), were treated significantly longer with furosemide, dexamethasone, theophylline, and thiazides, developed chronic lung disease more frequently (40 vs. 16%, P < 0.001), and had a higher mean urinary calcium/creatinine ratio (2.7 vs. 2.3 mmol/mmol, P < 0.05) and a lower mean urinary citrate/calcium ratio (1.1 vs. 1.7 mmol/mmol, P = 0.005). CONCLUSIONS: NC develops as a result of an imbalance between stone-inhibiting and stone-promoting factors. A high intake of calcium, phosphorus, and ascorbic acid, a low urinary citrate/calcium ratio, a high urinary calcium/creatinine ratio, immaturity, and medication to prevent or treat chronic lung disease with hypercalciuric side effects appear to contribute to the high incidence of NC in preterm neonates.     

The effect of different diets on urine composition and the risk of calcium oxalate crystallisation in healthy subjects

OBJECTIVE: The aim of the study was to determine the impact of defined diet modifications on urine composition and the risk of calcium oxalate crystallisation. METHODS: Ten healthy male volunteers consumed a self-selected diet (SD) for 14 days, and three different standard diets for a period of 5 days each. Whereas the western-type diet (WD) is representative of the usual dietary habits, the normal mixed diet (ND) and the ovo-lacto-vegetarian diet (VD) were calculated according to the requirements. RESULTS: The risk of calcium oxalate crystallisation, calculated as relative supersaturation (EQUIL2) from urine composition, was highest during ingestion of diets SD and WD. The intake of diet ND resulted in a significant decrease in relative supersaturation with calcium oxalate by 58% (p<0.05) compared with diet WD, due to a significant decline in urinary calcium and uric acid excretion and a significant increase in urinary volume, pH-value and citrate excretion. In spite of an increase in urinary pH, citrate and magnesium excretion and a decline in calcium excretion, no further significant decrease in the risk of calcium oxalate crystallisation was observed on diet VD, due to a significant increase in urinary oxalate by 30% (p<0.05) on average. CONCLUSIONS: The change of usual dietary habits for a normal mixed diet significantly reduces the risk of calcium oxalate crystallisation. With a vegetarian diet a similar decline in urinary supersaturation with calcium oxalate can be achieved compared to a normal mixed diet. Since urinary oxalate excretion increased significantly, a vegetarian diet without adequate intake of calcium may not be recommended to patients with mild hyperoxaluria.     

Estimation of the concentration of urinary ionic calcium and its clinical role in urolithiasis

The concentration of urinary ionic calcium was estimated using an ion-selective electrode and ion analyzer for healthy controls and patients with calcium urolithiasis. The following results were obtained: 1) After calculating the ionic strength and calibrating the standard solutions of ionic calcium in each urine, the urinary ionic calcium was estimated using an ion-selective electrode and ion analyzer. The reproducibility and accuracy of the value of urinary ionic calcium were satisfactory. 2) There was a significant correlation between the concentration of urinary ionic calcium and the total calcium excretion. Although the percentage of ionic calcium did not show any correlations among the total calcium, oxalate and urinary pH, it had an inverse relation to urinary citrate and phosphate. 3) In calcium stone formers, the excretion of ionic calcium was higher than in healthy controls significantly. 4) In hypercalciuric calcium stone formers, the concentrations and excretions of total and ionic calcium were significantly higher than in normocalciuric calcium stone formers. However, the percentage of ionic calcium was not different. 5) When the patients were treated with citrate orally, the excretion of urinary citrate was increased, and the excretion of ionic calcium and the percentage for total calcium were decreased significantly. There were significant reductions of ionic calcium in the urine after oral administration of rice-bran. 6) The estimation of urinary ionic calcium might be important to evaluate the urinary risk in recurrent calcium stone, and to estimate the effects of the preventive treatments for its recurrence.     

Genetic and dietary factors in urinary citrate excretion

BACKGROUND AND PURPOSE: Hypocitraturia, an important risk factor for calcium oxalate nephrolithiasis, is the result of numerous factors. We studied citrate excretion by patients with and without stones consuming normal and controlled formula diets. SUBJECTS AND METHODS: Subjects with and without a history of calcium oxalate stones (N = 101 per group) provided two or three 24-hour urine specimens during consumption of self-selected diets. Data also were collected on subsets of subjects consuming formula (Ensure) diets. Citrate was determined using the citrate lyase method of Petrarulo and associates, and values for multiple specimens were averaged. The data were adjusted for creatinine excretion and examined on a per-day basis. RESULTS: The mean citrate excretion of the non-stone formers was slightly but not significantly higher than that of the stone formers (442 +/- 217 versus 378 +/- 153 mg/g of creatinine). All statistical analyses revealed highly significant differences between, but not within, individuals, a result compatible with a genetic influence. In the normal population, 5% of subjects had a citrate excretion <200 mg/g of creatinine, whereas this result was seen in 34% of the stone-forming subjects. When the subjects consumed a formula diet, women in both groups had much higher citrate excretion than when on a self-selected diet, but little difference was seen in the men. The patterns of citrate recovery suggest low, intermediate, and high excretors. In the normal population, 15% of subjects excreted <340 mg/g of creatinine, whereas this was true of 43% of the stone-forming subjects. Analysis of six families suggested three excretor phenotypes, with a codominant pattern of inheritance. CONCLUSION: These findings imply a genetic influence on citrate excretion, as has already been demonstrated for calcium excretion. Further studies of genetic influences on calcium oxalate stone formation are warranted.     

Role of overweight and obesity on the urinary excretion of promoters and inhibitors of stone formation in stone formers

In recent decades there has been an increasing prevalence of urolitithiasis in many western countries and at the same time there has been an increasing progression of obesity that has reached epidemic proportions. The aim of the present study was to assess the influence of overweight/obesity on the metabolic risk factors for renal stone formation. We studied 799 renal stone formers (462 men and 337 women) who came to the clinic for metabolic risk factors evaluation. They were all studied with a standard protocol (two 24-h urine collections and serum parameters). They were divided according to their BMI in normal (BMI < 25) overweight (BMI 25–29.9) and obese (BMI > 30). Low-weight individuals were excluded. Overall, 487 of 799 (60.9%) patients had a BMI > 25, including 40.6% overweight and 20.3% obese. Among women 55.2% had normal weight, 25.5 were overweight, and 19.3% were Obese; among men 27.3% had normal weight, 51.7 were overweight, and 21% were obese. Age increased significantly with increasing BMI both in men and women. In women there was a significant increase in the excretion of oxalate, uric acid, phosphorus, creatinine, and sodium with increasing BMI, but no change was observed in calcium, magnesium, citrate, and urine pH. In men there was a significant increase in the excretion of oxalate, uric acid, creatinine, phosphorus, sodium, magnesium, and citrate with increasing BMI, no change in urinary calcium and significant progressive decrease in urinary pH. In this population of stone formers there was a high prevalence of overweight/obesity (60.9%). Both in men and women we found a significant increase in the urinary excretion of two promoters of stone formation, oxalate, and uric acid but no change in urinary calcium. There was either no change or increase in magnesium and citrate, inhibitors of crystallization, and a significant decrease in urine pH only in men. This article directly relates to material presented at the 11th International Urolithiasis Symposium, Nice, September 2008, from which the abstracts were published in the following issue of Urological Research: Urological Research (2008) 36:157–232. doi: .     

The efficacy of dietary intervention on urinary risk factors for stone formation in recurrent calcium oxalate stone patients

PURPOSE: Nutrition is suggested to be the major environmental risk factor in idiopathic calcium oxalate stone disease. The study was designed to evaluate the effect of dietary intervention on urinary risk factors for recurrence in calcium oxalate stone formers. MATERIALS AND METHODS: A total of 76 men and 31 women with idiopathic calcium oxalate stone disease collected 24-hour urine on their habitual, self-selected diets and after 7 days on a balanced standardized diet according to the recommendations for calcium oxalate stone formers. RESULTS: On the usual diet, a urine volume of less than 2.0 l per 24 hours was present in 57.9%, hypercalciuria in 25.2%, hypomagnesuria in 18.7%, hyperoxaluria in 14.0%, hyperuricosuria in 41.3% and hypocitraturia in 57.0% of patients. The frequency of metabolic abnormalities and the risk of calcium oxalate stone formation decreased significantly on the ingestion of the balanced diet, due to the significant increase in urinary volume, pH and citrate excretion and the significant decrease in urinary calcium and uric acid excretion. No change occurred in urinary oxalate and magnesium excretion. CONCLUSIONS: The evaluation of urinary risk profiles of the patients on their usual dietary habits revealed a high risk for calcium oxalate stone formation. A low fluid intake and an increased intake of protein and alcohol were identified as the most important dietary risk factors. The shift to a nutritionally balanced diet according to the recommendations for calcium oxalate stone formers significantly reduced the stone forming potential.     

Influence of magnesium on the absorption and excretion of calcium and oxalate ions

In two test series additional oxalic acid excretion in urine was induced in healthy test persons by administering a spinach diet. This additional excretion could be markedly reduced by magnesium administration. Calcium and citrate excretions are largely unaffected by magnesium administration. Magnesium excretions, however, are clearly increased. The calcium oxalate crystallization rates in the 5-or 7-hour urines reveal a behavior parallel to that of the oxalic acid excretion profile. In the control urines, the crystal picture is characterized by numerous medium-sized whewellite crystals. In contrast, in the test series weddellite crystals are reduced in size and frequency after magnesium administration. New aspects of magnesium effects must be discussed; above all the possible absorption changes resulting from gastrointestinal diseases.     

瘦猪肉餐对草酸钙结石患者尿生化的影响

目的研究瘦猪肉餐对一水草酸钙（calciumoxalate monohydrate,COM）与二水草酸钙（calciumoxalate dehydrate,COD）结石患者尿生化的影响,探讨草酸钙结石形成的机制。方法正常人、COM与COD结石患者各6例,共18例同予以煮瘦猪肉350g食用,收集实验日晨5-7时2h尿为样本,餐后各留3次2h尿标本,测定尿pH值和尿晶体成分浓度;采用SPSS软件对检测结果进行方差分析。结果三组受试者瘦猪肉餐后尿钙、尿酸和尿草酸排泄逐渐增加,而尿量、尿pH值和尿枸橼酸降低;瘦肉餐前后比较,COM与COD结石患者尿pH值、尿枸橼酸、尿钙和尿草酸有显著性差异（P〈0.05）,尿酸排泄有极显著性差异（P〈0.01）;对照组,尿钙、尿酸排泄均有显著性差异（P〈0.05,P〈0.01）。结论大量饮食猪瘦肉可导致尿pH值和尿晶体成分变化,可能是尿结石形成的重要原因之一。