Effects of an intravenous bolus calcium injection on glomerular filtration rate and electrolyte excretion in the kidney in conscious pigs

This paper reports the changes observed in the concentration of various constituents of plasma and in their excretion in the urine after a bolus intravenous injection of 2,2 mM calcium gluconate into conscious pigs weighing 20 kg. In the plasma, both ionic and total calcium concentrations increased but returned to normal within 35 minutes, while sodium, potassium and inorganic phosphate did not change significantly. In the kidney, the urine volume, glomerular filtration rate (GFR) and fractional sodium excretion increased slightly during the first 10 minutes but became significantly depressed later. Potassium and phosphate levels decreased, the latter significantly, while the calcium concentration increased significantly and only returned to normal after 70 minutes. These results suggest that since the disturbances in urinary volume, GFR and fractional phosphate excretion persist after both the plasma calcium and urinary calcium levels have returned to normal, factors other than these calcium values may be responsible for changes in the former measurements.     

Renal calcium and magnesium handling in water immersion in nephrotic patients

The effect of water immersion to the neck on renal calcium and magnesium handling was studied in 11 nephrotic patients. There was an increase in the urinary excretion of both calcium and magnesium on immersion, and a return towards preimmersion control values in the hour following immersion. Clearances of calcium and magnesium, and fractional excretion of calcium and of magnesium all increased significantly during water immersion, and decreased in the postimmersion hour. However, magnesium excretion was 10-50 times greater than calcium excretion. Fractional excretion of sodium was highly significantly related to fractional excretion of calcium (p less than 0.001) and magnesium (p less than 0.001). The relationship between fractional excretion of phosphate and fractional excretion of calcium was statistically significant (p less than 0.05), as was that between fractional excretion of phosphate and that of magnesium (p less than 0.01). Magnesium and calcium fractional excretions were significantly correlated (p less than 0.01). It was concluded that the increase in calcium and magnesium excretion on immersion is likely to be related to the sodium diuresis caused by central hypervolemia due to immersion.     

HYPERNATRIURIA AND KALIURESIS IN ENURETIC CHILDREN AND THE DIURNAL VARIATION

Purpose

We investigate the underlying pathophysiological cause of primary nocturnal enuresis by comparing electrolyte alterations in urine samples of enuretics during the daytime and nighttime compared with those of nonenuretic subjects.

Materials and Methods

Urine output, urine specific gravity and urinary electrolytes in 15 enuretic and 12 nonenuretic children were measured. We collected daytime serum and urine samples of children fed a similar diet between 7 a.m. and 7 p.m., and nighttime between samples 7 p.m. and 7 a.m. Urinary calcium/creatinine ratio, tubular reabsorption of phosphorus and excretions of fractional sodium and potassium were calculated.

Results

There was no significant difference between the calcium/creatinine ratio ratios. There was a significant increase in fractional sodium and fractional potassium values in enuretics compared to nonenuretics during the day and at night. Daytime and nighttime fractional sodium and fractional potassium values in enuretics were similar. In contrast to nonenuretics, enuretic patients had no diurnal variation of fractional sodium. There was significant positive correlation between bedwetting status, and fractional sodium and fractional potassium.

Conclusions

Since sodium and potassium excretions were higher in enuretic patients than nonenuretic children, and no significant diurnal variation in urinary excretion of these ions there might be a difference in the mechanism of reabsorption of sodium and potassium between enuretic and nonenuretic children.     

The relationship of the urinary cations, Calcium, Magnesium, Sodium and Potassium, in patients with Renal Calculi.

Calcium, magnesium, sodium and potassium were estimated in the 24-hour urine collections of 101 idiopathic male stone-formers, 89 male patient controls and 59 young male adult controls. The results were calculated in terms of 24-hour volume and 1 g of creatinine. The concentrations of the 4 cations, relative to a gram of creatinine, were also determined in the early-morning urines of 41 male stone-formers and 13 young male adult controls. No difference was observed in the 24-hour excretion of calcium, magnesium and sodium between the stone-formers and controls. The mean daily potassium excretion, however, was significantly reduced in the urine of stone-formers. The linear regression equations were calculated for calcium on magnesium, calcium on sodium, and calcium on potassium, using the 24-hour excretion values of these cations. Only the calcium on potassium line of stone-formers was significantly different from that of the normal subjects. A significant increase by stone-formers in the urinary calcium concentration of their early-morning specimens was found. The high concentration of urinary calcium in overnight urines of stone-formers combined with a low magnesium concentration might possibly contribute to the development of renal stone disease.     

Urinary inhibitors of calcium phosphate formation: the inhibitory activity of normal and artificial urines.

Eelven urine samples from normal subjects inhibited the formation of calcium phosphate. In all cases the activity of the urine was identical with that of an artificial urine having the same concentration of urea, creatinine, sodium, potassium, magnesium, calcium, ammonia, sulphate, chloride, inorganic phosphate, citrate, isocitrate and pyrophosphate, and the same pH.     

Urinary nitrite excretion and urinary variables in patients with primary nocturnal frequency of micturition: effects of indomethacin suppositories

Urinary nitrite excretion was measured in patients with primary nocturnal frequency of micturition (PNFM) and in normal individuals. Effects of indomethacin suppository on urine volume and other urinary variables were evaluated. The study comprised seven patients with PNFM and seven healthy control (age range 30–45 years). Nitrite was assayed in spot morning urine samples; urine volume, urine osmolality and electrolytes, serum osmolality and electrolytes and functional bladder capacity (FBC) were assayed. Both groups were then given 100 mg of indomethacin suppository daily for a maximum of 10 days and urinary variables were re-evaluated during day 10. Results showed that urinary nitrite excretion of patients with PNFM was greater than that of the normal subjects (230±62 umol/l vs. 42±30 umol/l, P<0.05). The mean (SD) 24 h urine volume and osmolality, the night urine volume and osmolality, serum osmolality, FBC, creatinine clearance, fractional excretion of sodium (FENa), fractional excretion of potassium (FEK), and urinary excretion of glucose and potassium were lower in patients with PNFM as compared with normal individuals, although not statistically significantly so, except for FBC that was significantly lower in the patients. Urinary excretion of sodium, calcium, chloride, phosphorus, magnesium, day-night urinary volume ratio, spot morning osmolality, nocturnal index, and nocturnal polyuria index were higher in patients with PNFM. Indomethacin decreased the 24 h urinary volume by 21%, creatinine clearance by 12%, osmolar clearance by 14% and urinary protein excretion by 38% in the patients. These variables decreased by 26, 45, 17 and 12% respectively in the healthy subjects, whereas 24 h urinary protein excretion increased mildly by 9%. Indomethacin increased day-night urinary volume ratio by 73% in the healthy subjects. It might be concluded that urinary nitrite excretion, urinary excretion of sodium, chloride, phosphorus, calcium, and magnesium increased and FBC decreased in patients with PNFM; Indomethacin decreased urinary volume, FENa, FEK, osmolar clearance, and free water clearance in the healthy subjects and the patients. These might explain the mechanism of action of indomethacin to reduce frequency of voiding. The possible interaction of prostaglandin and NO in the pathogenesis of PNFM is discussed.     

Acute effects of gentamicin on urinary electrolyte excretion in neonates

It has recently been shown that a single dose of gentamicin causes immediate and transient calcium and magnesium renal wasting in adults. The aim of this study was to determine the acute effect of gentamicin administration on renal electrolyte handling in preterm and full-term neonates. Twenty-three neonates treated with gentamicin for suspected infection were enrolled in the study. Serum and 3-h urine electrolytes were measured before and immediately after gentamicin infusion on the 1st, 3rd, 4th, and 7th day of treatment. Serum gentamicin levels were monitored. Gentamicin caused a statistically significant post-infusion increase in fractional excretion of sodium and magnesium and in the urine calcium to urine creatinine ratio. Potassium and phosphate fractional excretion remained unchanged. The disturbances in electrolyte excretion were observed in full-term as well as in preterm neonates. Serum electrolyte levels remained unchanged. In conclusion, therapeutic doses of gentamicin result in urinary loss of sodium, calcium, and magnesium in neonates immediately after the infusion of the drug. These electrolyte changes may be of clinical importance, especially for sick preterm neonates.     

Urinary mineral excretion among normal Taiwanese children

Prompted by a large population of children with renal stones seen in 20 of our country's teaching hospitals over the past 10 years, this study of urinary mineral excretion in normal children was performed. Fasting urine from 1,072 normal Taiwanese school children and 24-h urine collections from 125 children separated into three age groups were analysed for calcium (Ca), phosphate, magnesium (Mg), uric acid, sodium (Na) and creatinine (Cr). Fasting Ca/Cr ratios were not different between the sexes. Ca/Cr ratios were higher in the 17- to 18-year age group as were 24-h urinary Ca excretions. Urinary Mg/Cr ratios were higher in girls than boys and 24-h urinary Mg excretion was highest in the younger age groups. Urinary Mg excretion in Taiwanese children is 54%–86% lower than previously reported in Caucasian children. Both uric acid/Cr ratios and 24-h urinary uric acid excretion were highest in the youngest children. Urinary Na/Cr ratios and 24-h urinary Na excretion were higher in the two younger age groups. There was no correlation between 24-h urinary Ca and Na excretion.     

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.     

Litiasis en pediatría: correlación de métodos que dependen de la recogida de orina de 24 horas con otros más sencillos que no requieren orina minutada

IntroductionDaily practice requires quick, simple and accessible methods to appropriately assess the urinary excretion of solutes in diagnostic or follow-up evaluations of children with renal lithiasis.ObjectivesThe objective of this study was to correlate urine elimination of substances related to renal lithiasis that depend on the volume of excreted urine in a unit of time with other parameters that are calculated by measuring the concentration of these substances in blood and urine, such as urinary ratios, fractional excretions and excretion rates.Materials and methodsThe study included 401 healthy children aged 3-14 years (187 boys and 214 girls), mean age 8.78±3.40 years. The analysis was carried out by Pearson's correlation coefficient.ResultsThere was significant correlation between the elimination of sodium, potassium and chlorine in 24-hour urine sample and the urinary ratios and fractional excretions of these ions.Urinary ratios and rates of excretion of calcium, uric acid, phosphate, magnesium, citrate and oxalate were highly correlated with the determinations of these substances in 24-hour collections.ConclusionsThese equations provide relevant information for the study of the etiology of renal lithiasis in children, as well as about compliance to dietary treatment. They also assess the effectiveness of the various treatments used in these patients, without having to resort to 24-hour collections, which pose a considerable challenge in the pediatric age group.     

Renal tubular cell damage and oxidative stress in renal stone patients and the effect of potassium citrate treatment

Our objective was to evaluate the oxidative stress and renal tubular cell damage in patients who have renal stones compared to normal subjects. The patients were re-evaluated after 1-months supplementation with potassium citrate. We recruited 30 patients (11 males and 19 females) diagnosed with kidney stones and scheduled for surgical stone removal the following month, and 30 healthy non-stone formers (14 males and 16 females). Two 24-h urine samples and one heparinized blood sample were collected from each subject. Plasma was separated from the erythrocytes and assayed for creatinine, potassium, sodium, calcium, magnesium, phosphate, malondialdehyde (MDA, a lipid peroxidation product) (P-MDA), protein thiol as an indicator of protein oxidation, and vitamin E. Erythrocytes were analysed for MDA (E-MDA), reduced glutathione (GSH) and cellular glutathione peroxidase (cGPx) activity. The urine was analyzed for pH, creatinine, potassium, sodium, calcium, magnesium, phosphate, oxalate, citrate, MDA (U-MDA), total protein (U-protein) and N-acetyl--glucosaminidase (NAG) activity. For the stone patients, urine and blood samples were re-evaluated after supplementation with potassium citrate (60 mEq/day) for 1 month. Renal stone patients had higher plasma creatinine and lower plasma potassium, urinary pH, potassium, magnesium, phosphate and citrate than the controls. The patients had higher P-MDA, E-MDA, U-MDA, U-protein and NAG activity, but lower GSH, cGPx activity, protein thiol and vitamin E, when compared with controls. After potassium citrate supplementation, P-MDA and E-MDA decreased while plasma vitamin E, urinary NAG activity and citrate increased. Renal stone disease is associated with high oxidative stress and damage to renal tubular cells. These abnormalities are coincident with an increase in blood lipid peroxidation products and a decrease in antioxidant status. Although supplementation with potassium citrate improved urinary citrate levels and oxidative stress, it neither reduced urinary lipid peroxidation products nor remedied the damage to renal tubular cells, probably due to the existence of kidney stones.     

Effects of intravenously infused magnesium on renal calcium metabolism and plasma parathyroid hormone in patients with essential hypertension]

This study aimed to elucidate the effects of intravenously infused magnesium on renal calcium and sodium metabolism in patients with essential hypertension. Mean arterial pressure (MAP), heart rate (HR), urine volume (UV), endogenous creatinine clearance (Ccr), urinary excretion of calcium (UCaV) and sodium (UNaV), fractional excretion of calcium (FECa) and sodium (FENa), plasma ionized calcium (pCa2+) and parathyroid hormone(PTH) were measured before and after intravenous infusion of 10% magnesium sulfate (initial dose: Mg 13.5mg/m2.BSA/15 min.: maintenance dose: Mg 2.7mg/m2.BSA/105min) in 6 normotensive subjects (NT) and 13 mild-to-moderate essential hypertensives (EHT). After the magnesium infusion, significant increases of UV, UCaV, UNaV, FECa and FENa, and a significant decrease of PTH were observed in both NT and EHT while MAP and HR did not change in either group. PCa2+ significantly decreased and Ccr tended to increase only in EHT. Although no significant difference was found in the change in Ccr (delta Ccr) or PTH (delta PTH) between NT and EHT, the changes of UCaV (delta UCaV), UNaV (delta UNaV), FECa (delta FECa) and FENa (delta FENa) were greater in EHT than each in NT. A positive correlation was found between delta UCaV and delta FECa, as well as delta UCaV and delta Ccr, but the former was more remarkable in both groups. In addition, delta UCaV was positively correlated with delta FENa in EHT, but not in NT. No significant relationship was observed between delta UCaV and delta PTH in either group.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Urine anion gap in patients with chronic renal insufficiency.

We investigated the urinary acid excretion and urine anion gap (AG) (Na+ + K(+)-Cl-) during NH4Cl-induced metabolic acidosis in 38 normal subjects and 53 patients with chronic renal diseases in order to clarify the significance of the urine AG as a useful marker of the ammonium (NH4+) excretion even in a state of chronic renal insufficiency. The urine pH became higher, and the urinary excretions of titratable acid (TA) and NH4+ decreased significantly, in parallel with a reduction of the creatinine clearance (Ccr). The urinary electrolyte excretion, especially the chloride excretion, also decreased significantly as Ccr fell. As a result, the urine AG increased from negative to positive values, in proportion to the decrease in Ccr with statistical significance. The urine AG showed the most significant correlation with the urine NH4+ excretion (r = -0.707, p less than 0.001). We conclude that the urine AG provides a significant marker of the urine NH4+ excretion even in a state of moderate to severe renal insufficiency.     

The loss of circadian rhythmicity of urinary solute excretion in idiopathic stone formers

Circadian rhythmicity in urinary volume and excretion of creatinine, calcium, oxalate, uric acid and phosphate was studied in 15 idiopathic stone formers and in 17 control subjects who were age-matched, related adult males, living in the same house and engaged in similar occupations to those of the stone patients, but who had no clinically obvious stone disease. Three-hourly urine samples were collected and creatinine, calcium, oxalate, uric acid and inorganic phosphate were estimated. The time series of data were analysed by cosinor rhythmometry. Circadian rhythmicity has been described in urinary volume and urinary excretion of creatinine, calcium, oxalate, uric acid and inorganic phosphate in normal subjects, but it was not detected in the stone formers. The control subjects exhibited a circadian rhythmicity only in urinary volume and creatinine excretion. Thus they occupied a position midway between healthy adults, who exhibit circadian rhythmicity in all of the above parameters, and the stone formers, who appear to have lost it altogether.     

Uninephrectomy enhances urolithiasis in ethylene glycol treated rats.

Uninephrectomy (uNX) usually induces compensatory hyperfunction of the remaining kidney in an attempt to preserve the homeostasis of body fluid composition. The present study used uninephrectomized Sprague-Dawley rats on a lithogenic diet (0.5% ethylene glycol, EG) to evaluate the influence on urinary stone formation and calcium oxalate crystal deposition of compensatory excretion of lithogenic substances in the remnant kidney. The results showed that there were no urinary stones or calcium oxalate crystal deposits in the intact or uNX rats fed a normal diet. In the EG feeding groups, the incidence of massive (grade 3) crystal deposits was significantly higher in the uNX rats (87.5%) than that in the intact rats (37.5%; P less than 0.05). The incidence of urinary stone formation was also higher in the uNX rats as compared to that of the intact rats, although the difference did not achieve statistical significance. The serum magnesium, phosphorus and creatinine increased significantly, whereas creatinine clearance (CCr), 24-hour urinary excretions of citrate, sodium, potassium and chloride decreased significantly in the uNX rats fed EG. These data indicate that uninephrectomy increases the vulnerability of the contralateral remnant kidney to urolithiasis and crystal deposition when the lithogenic risk factors are present. Furthermore, once the remnant kidney forms urolithiasis or massive calcium oxalate crystal deposits, the renal function is severely compromised.     

Differences in 24-hour urine composition between black and white women

Black women are less likely to develop kidney stones and have greater bone mass than white women. However, little is known about racial differences in urine composition. Urine pH, volume, and 24-h urinary excretion of calcium, citrate, oxalate, uric acid, sodium, potassium, magnesium, phosphate, sulfate, and creatinine of 146 black women were compared with 330 white women in the Nurses' Health Study. All participants were postmenopausal non-stone formers. ANOVA was used to compare mean urinary values. Linear regression models were adjusted for age, body mass index, dietary intake, and urinary factors. On average, black women excreted 65 mg less urinary calcium (P < 0.001), 4 mg more oxalate (P < 0.001), 9 mEq less potassium (P < 0.001), 11 mg less magnesium (P = 0.003), 120 mg less phosphate (P < 0.001), and 3 mmol less sulfate (P < 0.001) per day than did white women. The urine pH of black women was 0.11 units higher (P = 0.03) and urine volume was 0.24 L less (P = 0.001). The urinary relative supersaturations of calcium oxalate (P = 0.03) and brushite (P = 0.002) were lower in black women. No other significant differences were observed. Differences in urinary calcium and pH persisted after multivariate adjustment and after exclusion of participants who were taking thiazide diuretics or those with diabetes. In conclusion, black women excrete less urinary calcium and have a higher urinary pH than do white women. These differences are not explained by differences in age, body mass index, or diet and may account for the lower incidence of both nephrolithiasis and osteoporosis in black women.     

Seasonal and geographic variations in urinary composition in England,Scotland and Wales

Summary Aliquots of 24 hour urine samples were collected from a series of normal doctors in various areas of England, Scotland and Wales. The total volume was recorded and aliquots sent in for analysis for sodium, potassium, urea, creatinine, calcium, phosphate, urate, magnesium and oxalate. Geographical variations in urinary composition were small except for a raised oxalate content in Scotland. Likewise, seasonal variations were small and not systematic with the notable exception of a summer rise in oxalate content in all areas.     

Urinary supersaturation with calcium oxalate before and during orthophosphate therapy.

The concentrations of sodium, potassium, calcium, magnesium, phosphorus, sulfate, citrate and oxalate in the urine of normal subjects were compared to the concentrations in urine of calcium oxalate stone-forming patients. Because of the large volume excreted by stone-forming patients the urine contained less concentrations of sodium, potassium, magnesium, phosphorus, sulfate and citrate than did the urine from normal subjects. The urinary concentrations of calcium and oxalate were similar in the 2 groups and, thus, the calculated supersaturation of calcium oxalate was greater in the urine of stone-forming patients than in the urine of normal subjects. Orthophosphate therapy increased the urinary concentration of alkali ions and phosphate but reduced urinary calcium concentration, thereby causing a reduction in urine supersaturation with calcium oxalate. There was no discernible correlation between the phosphate-induced changes in urine supersaturation and the presence or absence of continued calculus formation.     

Silicon metabolism. I. Some aspects of renal silicon handling in normal man

Renal silicon handling was investigated in 23 healthy adults using electrothermal atomic absorption techniques. The mean urinary silicon excretion was 33.1 +/- 3.85 mg/day; the mean renal silicon clearance was 88.6 +/- 7.94 ml/min; the mean fractional excretion of silicon was 86.35 +/- 8.1%, and the mean urine silicon concentration was 0.265 micrograms/ml. Using multiple correlation analysis, the urinary silicon was found to be highly significantly correlated with the urine magnesium concentration (p less than 0.001) and also with urinary sodium and urinary osmolality (p less than 0.01). 24-hour urinary silicon excretion was highly significantly correlated with fractional excretion of silicon (p less than 0.001), sodium (p less than 0.001), phosphorus (p less than 0.001), magnesium (p less than 0.001), and osmolar load. In split urine studies in 7 subjects urinary silicon was correlated highly significantly with urinary magnesium in all 7 and with urinary osmolality, urine calcium, and urine creatine concentration in 6 of 7. There was a highly significant correlation between renal silicon clearance and fractional excretion of silicon (p less than 0.0005), with magnesium excretion (p less than 0.01), and with sodium excretion. It is suggested that ion pairing of orthosilicate and magnesium may explain some of these urinary findings.