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Nephrocalcinosis in siblings--familial hypomagnesemia, hypercalciuria with nephrocalcinosis (FHHNC syndrome).

Familial Hypomagnesemia, Hypercalciuria with Nephrocalcinosis is a rare autosomal recessive inherited disease associated with renal failure. Two girls born of consanguineous parentage aged 16 and 17 presented to us with renal failure, nephrocalcinosis and bone deformities. On evaluation they were found to have hypomagnesemia, hypercalciuria, increased fractional excretion of magnesium, hypocitraturia, renal failure and elevated PTH. Their parental screening was normal. There were no extra-renal features in them. One sibling had nephrolithiasis and the stone analysis revealed calcium phosphate stones. Both were treated with sodium bicarbonate, thiazides, calcitriol and calcium carbonate. They did not require dialysis during hospital stay. Both of them were treated conservatively. They are on regular outpatient follow up. The primary defect in this syndrome is impaired paracellular reabsorption of magnesium and calcium in the medullary thick ascending limb. Mutations in the PCLN-1gene which encodes for the tight junction protein paracellin -1 is identified as the underlying genetic defect. Ocular abnormalities and deafness are the commonly reported associations. End stage renal failure usually occurs in second to third decade. Renal transplantation is the definite treatment.

Acid-Base Equilibrium↗

X-ray microanalysis of uremic nephrocalcinosis: cellular distribution of calcium, aluminium and silicon in uremic nephrocalcinosis.

Nephrocalcinosis with a deposition of aluminum and silicon has been previously reported in uremic rats. To clarify the origin of these elements thin sections of renal cortex were examined by means of electron microscopy and energy dispersive x-ray microanalysis. Studies were performed on subtotally nephrectomized rats (SNX) and sham-operated control animals. Electron microscopy of proximal tubular epithelial cells in SNX rats unlike control rats revealed severe mitochondrial disorganization; irregularity of the tubular basement membrane which exhibited various inclusions; and lamellar bodies within the brush border membrane. On x-ray microanalysis disorganized mitochondria contained calcium and silicon, while secondary lysosomes displayed aluminum and silicon. The tubular basement membrane of SNX rats, as well as lamellar body-like inclusions within the brush border contained calcium, aluminum and silicon together. It is suggested that lysosomal and mitochondrial interaction in proximal tubular cells of uremic rats may contribute to the deposition of calcium together with aluminum and silicon in the renal parenchyma, resulting in nephrocalcinosis.

Aluminum↗

Nephrocalcinosis is associated with renal tubular acidosis in children with X-linked hypophosphatemia.

BACKGROUND: X-linked hypophosphatemia is characterized clinically by rickets and growth retardation. Therapy of this disorder with phosphate and vitamin D often produces nephrocalcinosis. The long-term effects of nephrocalcinosis on renal function in patients with X-linked hypophosphatemia are unknown. The purpose of this study was to evaluate the prevalence of glomerular and tubular disorders in patients with X-linked hypophosphatemia who developed nephrocalcinosis. METHODS: The creatinine clearance and the prevalence of renal tubular acidosis were compared in 19 patients with X-linked hypophosphatemia and nephrocalcinosis with 15 patients with X-linked hypophosphatemia without nephrocalcinosis. RESULTS: Sixteen of the 19 patients (84%) with nephrocalcinosis had a hyperchloremic metabolic acidosis compared with one of the 13 patients without nephrocalcinosis (P < .01). The serum bicarbonate of patients with nephrocalcinosis was 20.0 +/- 0.7 as compared to 24.5 +/- 0.6 mmol/L in patients without nephrocalcinosis (P < .01). The urinary anion gap was positive in all patients with acidosis (+62.1 +/- 13.3 mmol/L). The creatinine clearance was 125 +/- 6 mL/min/1.73 m2 in patients with nephrocalcinosis and 124 +/- 7 mL/min/1.73 m2 in those without nephrocalcinosis. CONCLUSION: Therapy of X-linked hypophosphatemia is often associated with nephrocalcinosis. Nephrocalcinosis is associated with renal tubular acidosis in patients with X-linked hypophosphatemia.

Acidosis, Renal Tubular↗

Medullary nephrocalcinosis in nephropathic cystinosis.

Children with nephropathic cystinosis excrete large amounts of calcium and phosphate due to renal tubular Fanconi syndrome, and also receive substantial supplements of phosphate and alkalinizing agents. Since these constitute risk factors for nephrocalcinosis, we evaluated 41 children age 2 months to 15 years with nephropathic cystinosis and good renal function by performing retroperitoneal ultrasound examinations in a blinded fashion. We also retrospectively analyzed parameters of calcium and phosphate metabolism representing 216 person-years of data on these children. Fifteen children had no evidence of medullary nephrocalcinosis, while 18 had mild nephrocalcinosis, and 8 severe nephrocalcinosis; 5 had renal stones. Mean urine calcium and phosphate concentrations increased from 1.47 mM and 5.30 mM, respectively, in children without nephrocalcinosis to 1.60 mM and 5.69 mM in children with mild nephrocalcinosis to 1.66 mM and 6.19 mM in children with severe nephrocalcinosis. Mean urine pH ranged from 7.5 to 8.1. The mean (+/- SD) age of the 26 patients with nephrocalcinosis was 9.4 +/- 3.8 years compared with 5.1 +/- 3.8 years for those without nephrocalcinosis (P < 0.005). Serum calcium, phosphate, vitamin D, and parathyroid hormone did not correlate with frequency or degree of nephrocalcinosis. We conclude that nephrocalcinosis frequently accompanies nephropathic cystinosis, can be detected by ultrasound examination, and might be managed by reducing oral replacement of phosphate, calcium, vitamin D, and citrate. Consideration should be given to truncating phosphate replacement once bone growth ceases.

Adolescent↗

Development of nephrocalcinosis in very low birth weight infants.

Premature infants undergo intensive growth during the postnatal period. Adequate mineralization is dependent on sufficient intake of calcium (Ca) and phosphorus (P). However, Ca and P supplementation can be associated with some risks, for example development of nephrocalcinosis. We investigated pathophysiological risk factors in premature very low birth weight (VLBW) infants associated with the development of nephrocalcinosis. From June 1994 to September 1995 all preterm neonates with a birth weight below 1,500 g were screened prospectively. At regular intervals of 2 weeks, ultrasonography (US) of the kidneys was performed and parameters of mineral metabolism were assessed in blood and spot urine samples. For analysis, premature infants with nephrocalcinosis (group N) were compared with infants without nephrocalcinosis (group R) and with a retrospectively pair-matched subgroup of premature infants without nephrocalcinosis (control group C) taken from the same study. Nephrocalcinosis was detected in 20 of 114 preterm neonates (group N, 17.5%). Of these 20 infants with nephrocalcinosis, 16 presented with a tendency towards systemic acidosis (pH<7.25) on day 2-7, compared with only 4 of 20 premature infants of the control group. Premature infants of group N had a lower serum P at 2 weeks of life and 5 (versus 0 patients of the control group C) had transient hypophosphatemia (serum P<1.6 mmol/l). Moreover, the Ca/creatinine ratio in spot urine specimens tended to be higher (P<0.1) in patients developing nephrocalcinosis. There were no significant differences in the duration of ventilation, the length of stay in the intensive care unit, and duration and frequency of furosemide and steroid treatment between the groups N and C. VLBW premature infants developing nephrocalcinosis frequently presented with slightly impaired acid-base homoeostasis within the 1st week, followed by signs of impaired mineralization (and immature or impaired renal function) within 2 weeks. In VLBW premature infants, close observation of acid-base status and regular analysis of spot urine specimens (Ca, P, creatinine) during the first weeks of life may help to identify those premature infants at risk for nephrocalcinosis.

Acidosis, Renal Tubular↗

High incidence of nephrocalcinosis in extremely preterm infants treated with dexamethasone.

BACKGROUND: The use of postnatal corticosteroids to treat or prevent chronic lung disease is common in very preterm infants. Medullary nephrocalcinosis has been noted as a possible side effect. OBJECTIVE: This prospective study was designed to assess the incidence of nephrocalcinosis in extremely preterm infants exposed to dexamethasone. PATIENTS AND METHODS: A prospective study of extremely preterm infants, recruited to a randomized trial of dexamethasone treatment for chronic lung disease, was initiated. Infants had US of the renal tract scheduled on entry into the study, at day 28 and at discharge or at the corrected gestational age of 36 weeks. RESULTS: Thirty-three infants were enrolled in the study. Birth weight ranged between 440 and 990 g and gestation between 24 and 28 weeks. Nine infants died and six had incomplete data. Because there was no difference in incidence of calcification between those on the short course and those on the long course of dexamethasone, analysis was made on the entire cohort. One infant had nephrocalcinosis at the time of the initial US examination on day 26 of life. By day 28, nephrocalcinosis was present in 31% of those with complete data. By discharge, or corrected gestational age of 36 weeks, US evidence of nephrocalcinosis was present in 15 (83%) of 18 infants. All infants had at least one course of an aminoglycoside antibiotic during the study. All infants had parenteral nutrition. Only four infants received furosemide more regularly than single doses. The longest course was 10 days, received by an infant who did not develop nephrocalcinosis. CONCLUSION: The incidence of nephrocalcinosis is high in this group of sick, extremely preterm infants. Dexamethasone may be a factor in the development of nephrocalcinosis. Future research should focus on the natural history of nephrocalcinosis in extremely preterm infants.

Aminoglycosides↗

Incidence, ultrasonic patterns and resolution of nephrocalcinosis in very low birthweight infants.

This longitudinal study was undertaken in order to elucidate the incidence and natural course of nephrocalcinosis in preterm infants and to evaluate whether the ultrasonic classification for nephrocalcinosis used here is suitable for predicting subsequent resolution of the condition. A total of 129 very low birthweight infants were screened for nephrocalcinosis by renal ultrasonography at 2 wk, 6 wk and 3 mo. The pyramidal changes were classified as peripheral, scattered or extensive. Follow-up renal ultrasonography was performed on the infants with nephrocalcinosis at 6, 12, 18 and 24 mo, and thereafter annually up to 6 y of age, or until ultrasonic resolution. The overall incidence of nephrocalcinosis was 20% (26/129). Nephrocalcinotic changes were peripheral in 14 out of the 26 infants (54%), scattered in 7 (27%) and extensive in 5 (19%). Ultrasonic resolution had taken place in all the cases with peripheral nephrocalcinosis by 12 mo, but 3 of the 7 infants with the scattered pattern and 3 of the 4 with the extensive pattern (1 died) were still affected at 24 mo. In two cases with extensive nephrocalcinosis the condition still persisted at 5-6 y of age. We conclude that about 20% of very low birthweight infants develop nephrocalcinosis during the first 3 mo of life. In about half of the affected infants renal changes are restricted and transient, but more extensive forms may last several years. The classification of nephrocalcinosis used here is appropriate for predicting later ultrasonic resolution.

Anti-Inflammatory Agents↗

Medullary nephrocalcinosis associated with long-term furosemide abuse in adults.

BACKGROUND: The use of furosemide is well recognized as a predisposing factor of nephrocalcinosis in infants. Although furosemide is widely used for various medical conditions in adults, its association with nephrocalcinosis in adults is not well established. METHODS: We studied 18 consecutive adult patients (male:female ratio 1:17, age range 21-59 years) who habitually took furosemide to control weight or oedema for long periods of time (range 3-25 years). The daily dose of continuous intake of furosemide ranged from 40 to 2800 mg. Nephrocalcinosis was evaluated using renal ultrasonography (US), computed tomography (CT), or kidney biopsies. RESULTS: Renal US and CT revealed bilateral nephrocalcinosis of the medullary pyramids in 15 (83.3%) out of 18 patients. The duration of furosemide abuse was similar between nephrocalcinosis positive (NC(+)) and nephrocalcinosis negative (NC(-)) groups. The daily dose of furosemide was nearly 10 times higher in the NC(+) group (range 120-2800 mg, mean 538 mg) than the NC(-) group (range 40-80 mg, mean 67 mg). All patients showed variable degrees of renal insufficiency and there was no difference in creatinine clearance between the NC(+) and NC(-) groups (P>0.05). Kidney biopsies performed in three patients showed focal tubulo-interstitial fibrosis and atrophy and calcifications were observed in outer medullary tubulo-interstitium. CONCLUSIONS: Long-term furosemide abuse can cause medullary nephrocalcinosis in adults, and the risk of developing of nephrocalcinosis seems to be correlated with the daily dose of furosemide. We suggest that long-term furosemide abuse should be suspected in adult patients when medullary nephrocalcinosis is incidentally detected by US or CT.

Adult↗

Thiazide diuretics arrest the progression of nephrocalcinosis in children with X-linked hypophosphatemia.

OBJECTIVE: X-linked hypophosphatemia (XLH) is characterized clinically by rickets, hypophosphatemia, and hyperphosphaturia. Conventional treatment of XLH with oral phosphate and vitamin D is associated with increased urinary calcium excretion and nephrocalcinosis. Thiazide diuretics decrease urinary calcium excretion. The objective of this study was to determine the effect of thiazide diuretics on the clinical and radiologic course of nephrocalcinosis in children with XLH. METHODS: The effect of hydrochlorothiazide (HCTZ) on clinical and radiologic progression of nephrocalcinosis was evaluated in 11 children with XLH. All patients had been treated previously with vitamin D and oral phosphate and had radiologic evidence of nephrocalcinosis. The average age of the patients at the start of HCTZ was 6.6 +/- 1.0 years. The effect of oral HCTZ at 0.8 +/- 0.1 mg/kg body weight per day given for 3.3 +/- 0.6 years on the progression of nephrocalcinosis and urinary calcium excretion was evaluated. RESULTS: There was no change in serum phosphorous, calcium, potassium, and chloride after HCTZ therapy. HCTZ therapy increased serum bicarbonate and decreased urinary calcium excretion. The grade of nephrocalcinosis increased from 0.4 +/- 0.2 to 1.5 +/- 0.3 in the 2.3 +/- 0.3 years before initiation of HCTZ therapy, whereas the degree of nephrocalcinosis was stable after 3.3 +/- 0.6 years of HCTZ therapy (1.5 +/- 0.3 vs 3.0 +/- 0.3). CONCLUSION: HCTZ decreased urinary calcium excretion but did not result in the resolution of nephrocalcinosis. However, when compared with the control period, HCTZ prevented the progression of nephrocalcinosis in children with XLH.

Calcium↗

Nephrocalcinosis in X-linked hypophosphatemia: effect of treatment versus disease.

While the literature has suggested that vitamin D and phosphate therapy benefits children, and possibly adults, with X-linked hypophosphatemia (XLH), there have been increasing reports of nephrocalcinosis by renal ultrasound examination in treated patients. Although it has been assumed that nephrocalcinosis is the result of treatment, there has been no systematic comparison of treated and untreated XLH patients with long-term follow-up. Therefore, we studied 10 adults and 4 children by renal ultrasound examination with no history of medical therapy and 10 adults and 8 children with a history of medical therapy. None of the untreated patients had nephrocalcinosis; 5 treated adults and 5 treated children had nephrocalcinosis. In 3 of 4 treated children, serial renal ultrasounds did not show progression of the nephrocalcinosis. One patient progressed from baseline to year 1 only. Comparisons of means between treated patients without and with nephrocalcinosis showed statistically significant differences for urine calcium/creatinine ratios and urine phosphorus/creatinine ratios, differences not seen between untreated patients and treated patients without nephrocalcinosis. Phosphate dose, but not vitamin D dose, was statistically significantly different between the two treated groups. Our studies point to a convincing role for the association between nephrocalcinosis, as diagnosed by renal ultrasound examination, and medical therapy.

Child↗

Nephrocalcinosis in full-term infants receiving furosemide treatment for congestive heart failure: a study of the incidence and 2-year follow up.

UNLABELLED: In order to study the incidence and course of nephrocalcinosis in full-term infants with congestive heart failure receiving long-term furosemide treatment, 36 such infants (median age 2.9 months, range 1.2-8.0) and 36 full-term control infants not receiving any diuretics (median age 3.4 months, range 1.1-8.4) were studied by renal ultrasonography and random urine calcium variables. The infants with nephrocalcinosis were followed at 3-6 month intervals up to 2 years of age, or until ultrasonic resolution. Nephrocalcinosis was found in 5 out of the 36 (14%) treated infants, but in none of the controls (P = 0.03). The dose of furosemide was higher in the infants with nephrocalcinosis than in those without (1.9+/-0.6 vs. 1.3+/-0.4 mg/kg per day; P = 0.01). The urinary calcium concentration was higher in the infants receiving furosemide than in controls and a similar trend was observed in the urinary calcium/creatinine ratio, but these variables did not differ between the study infants with and without nephrocalcinosis. Ultrasonic resolution of nephrocalcinosis was observed in 3 of the 5 infants at 12 months, but in the other 2 the condition still persisted at 24 months. CONCLUSIONS: Long-term furosemide treatment in full-term infants with congestive heart failure entails a considerable risk of developing nephrocalcinosis. Renal ultrasonography is warranted in these patients within a few months after initiation of the treatment and in the case of nephrocalcinosis alteration of the diuretic regimen is to be considered.

Calcium↗

Nephrocalcinosis in preterm infants: a single center experience.

The risk of nephrocalcinosis in preterm infants is considerable, but conflicting numbers are given for the actual incidence (10-65%). Furosemide induced hypercalciuria is said to be the main risk factor. We examined retrospectively the incidence, causes and outcome of nephrocalcinosis in preterm infants born in our hospital from 1988 to 1998 ( n=2190). An abnormal renal echogenicity or nephrocalcinosis was seen in 31 infants (29.7+/-3.3 weeks gestational age; 1307+/-690 g birth weight). Nephrocalcinosis was diagnosed in 16, hyperechoic kidneys (HK) in 10 and Tamm-Horsfall kidneys in 5 infants. Main risk factors were low gestation age and birth weight, length of hospitalization, variations in acid-base status, length of assistant ventilation and hypercalciuria at diagnosis. The incidence of nephrocalcinosis was 0.73% [1.7% for low birth weight infants (VLBW)]. Taking the cases of nephrocalcinosis and HK together, incidence was calculated to be 1.2% overall and 2.5% for VLBW infants, but increased to 7% in 1998. The follow-up showed persisting nephrocalcinosis or hyperechoic kidneys in 8/26 preterm infants. In conclusion, the incidence of nephrocalcinosis was lower in our population than is usually reported. The numbers have, however, increased over the past few years. From the follow-up it was obvious that long-term observation of preterm infants is necessary and that complications might arise in the long run.

Follow-Up Studies↗

Prematurity-associated nephrocalcinosis and kidney function in early childhood.

To assess the impact of prematurity-associated nephrocalcinosis on kidney function later in life, 20 premature children with neonatal nephrocalcinosis and 20 controls, matched for birth weight and postnatal age but without nephrocalcinosis, were examined (birth weight 905+/-209 vs. 957+/-226 g; study age 4.7+/-1.1 vs. 4.6+/-0.9 years). Distal tubular acidification capacity was measured with the oral acetazolamide test, in which the response was abnormal in 1 out of the 20 children with a history of nephrocalcinosis, but in none of the controls. Urinary calcium and beta(2)-microglobulin excretion were higher in the children with nephrocalcinosis, but no differences were found in fractional excretion of sodium and potassium or tubular reabsorption of phosphate. Estimated creatinine clearance was not different between the groups. Of the 6 children with nephrocalcinosis lasting beyond 2 years of age, 5 had had chronic lung disease neonatally and exhibited a tendency for compensated respiratory acidosis at the time of the examination. Neonatal nephrocalcinosis seems to lead to some signs of renal tubular dysfunction in early childhood of preterm infants. Glomerular function, however, appears not to be specifically disturbed by nephrocalcinosis.

Calcium↗

Nephrocalcinosis and diets containing alkali- and non-alkali-treated soy protein.

Diets containing alkali-treated soy protein have been shown to cause nephrocalcinosis in rats. In order to determine if alkali-treated soy protein is the dietary component that induces nephrocalcinosis, the effects of a purified diet containing 20% alpha-protein (an alkali-treated soy protein) were compared with the effects of the same diet containing 20% promine-D (a non-alkali-treated soy protein) on renal morphology and renal calcium and phosphorus metabolism. After a 9-week feeding trial, light and transmission electron microscopy revealed that the animals fed either the alpha-protein or promine-D diet developed nephrocalcinosis. In fact, the type of nephrocalcinosis was the same in both groups of animals. Moreover, quantitative determinations of total renal calcium and phosphorus showed that the severity of nephrocalcinosis was also the same in the two groups. No signs of nephrocalcinosis were detected in rats fed a standard commercial laboratory diet. Since nephrocalcinosis was present in the animals fed the promine-D diet, and that it was identical to that found in the animals fed the alpha-protein diet, it appears that alkali-treated soy protein is not the factor responsible for nephrocalcinosis in rats fed a diet containing the protein.

Alkalies↗

The natural history of nephrocalcinosis in premature infants treated with loop diuretics.

PURPOSE: We investigated the natural history of nephrocalcinosis in premature infants treated with furosemide and attempted to identify factors to predict infants most at risk. MATERIALS AND METHODS: We evaluated 13 preterm infants in this longitudinal pilot study. During hospitalization and while receiving a loop diuretic nephrocalcinosis developed in each patient. Patients were divided into groups based on resolution (6) and nonresolution (7) according to spontaneous resolution of nephrocalcinosis at any point during followup. The 2 groups were compared to each other and to a control group. RESULTS: Mean followup after discontinuation of furosemide in the resolution versus nonresolution groups was 10.3 and 7.7 months, respectively. Between the 2 groups there was no significant difference in average gestational age, birth weight, number of days hospitalized or on furosemide, or total furosemide dose. Mean calcium-to-creatinine ratio while receiving furosemide at the time nephrocalcinosis developed was 0.38 in the resolution group but 2.23 in the nonresolution group (p < 0.005). Initial calcium-to-creatinine ratio in age matched infants who did not have nephrocalcinosis was 0.4. Frank renal stones developed in 2 of the 7 patients without resolution and 0 of the 6 with resolution. When nephrocalcinosis resolved, it was at a mean of 5.2 months following discontinuation of the diuretic. CONCLUSIONS: Early data indicate that nephrocalcinosis resolves in approximately 50% of premature infants 5 to 6 months after discontinuation of furosemide. The only factor that appears to be predictive of the infants who will have resolution is the calcium-to-creatinine ratio when nephrocalcinosis is diagnosed. In patients without resolution this ratio is much higher than in age adjusted normal controls, while in those with resolution it appears normal for age.

Diuretics↗