Usefulness of basic renal function tests in the management of hydronephrosis. / Utilidad de las pruebas básicas de función renal en el manejo de la hidronefrosis.

OBJECTIVE: Nowadays, the algorithms for the study of hydronephrosis in children include voiding cystourethrogram (VCUG) and diuretic renogram (DR) in all patients. Both are invasive, distressing, and associated with radiation risk. However, basic renal function tests (bRFTs) are not included. This study was designed to determine whether bRFTs may help avoid VCUG and/or DR in some children. METHODS: Retrospective review of hydronephrosis (≥20 mm renal pelvis) patient records over one year (n = 38) (pyeloureteral stenosis (PUS) n = 12; high-grade vesicoureteral reflux (VUR) n = 8; non-obstructive hydronephrosis (NOH) n = 18. Data from the three protocolized bRFTs (maximum urine osmolality after DDAVP (UOsm), albumin/creatinine ratio (Alb/Cr), and NAG/creatinine ratio (NAG/Cr), together with VCUG and DR, were analyzed. RESULTS: 38 hydronephrosis patients (pyeloureteral stenosis (PUS) n = 12; high grade vesicoureteral reflux (VUR) n = 8; non-obstructive hydronephrosis (NOH) n = 18. UOsm was decreased in 100% of VUR patients, 75% of PUS patients, and 16.7% of NOH patients. Alb/Cr ratio was increased in 62.5% of VUR patients, 8.3% of PUS patients, and 11.1% of NOH patients. NAG/Cr ratio was increased in 42.8% of VUR patients, 25% of PUS patients, and 6.7% of NOH patients. UOsm was decreased in most patients who required surgery (100% of VUR patients and 74% of PUS patients), but only in 11.1% of patients who did not (NOH group). CONCLUSIONS: These results suggest that bRFTs may be useful in delaying or avoiding VCUG in some hydronephrosis cases. UOsm is the most sensitive test. No child with (high grade) VUR had a normal UOsm. VCUG could have been avoided in 43% of our patients -with a normal UOsm- without missing any high grade VUR.

OBJETIVO: Actualmente, los algoritmos para estudiar hidronefrosis en niños, incluyen realizar cistografía miccional (CUMS) y renograma diurético (RD) a todos. Ambos son invasivos, molestos, y con riesgo de radiación. Contrariamente, las pruebas básicas de función renal (PFRb), no están incluidas. Este estudio se realizó para saber si las PFRb, pueden ayudarnos a evitar alguna CUMS y/o RD. METODOS: Análisis retrospectivo de todas las historias de niños con hidronefrosis (pelvis renal ≥20 mm) atendidos durante un año (n=38), [estenosis pieloureteral (EPU) n = 12; reflujo vesicoureteral (RVU) de alto grado n = 8; hidronefrosis no obstructiva (HNO) n = 18]. Analizamos las tres PFRb protocolizadas [osmolalidad urinaria máxima tras DDAVP (UOsm), albúmina/creatinina (Alb/Cr) y NAG/creatinina (NAG/Cr)], junto con CUMS y RD. RESULTADOS: UOsm estaba disminuida en 100% RVU, 75% EPU, 16,7% HNO. Alb/Cr estaba aumentado en 62,5% RVU, 8,3% EPU, 11,1% HNO. NAG/Cr estaba aumentado en 42,8% RVU, 25% EPU, 6,7% HNO. En relación a la necesidad de cirugía, UOsm estaba disminuida en la mayoría de pacientes intervenidos (100% con RVU y 74% con EPU), mientras solo en el 11% de pacientes sin cirugía (HNO). CONCLUSION: Estos resultados sugieren que las PFRb pueden ser útiles para retrasar o evitar CUMS en algunos niños con hidronefrosis. La UOsm es la PFRb más sensible. Ningún niño con RVU (de alto grado) mostró una UOsm normal. Se podrían haber evitado CUMS en el 43% de nuestros pacientes, con UOsm normal, sin haber perdido ningún diagnóstico de VUR (de alto grado).

Discípulos y maestros. Lo que aprendimos de Juan Rodríguez Soriano / Disciples and teachers. What we learn from Juan Rodríguez Soriano

Juan Rodríguez Soriano (1933-2010) fue un eminente nefrólogo pediátrico español, formador de varias generaciones de pediatras y nefrólogos pediátricos. Estaba considerado internacionalmente como uno de los pioneros de la nefrología pediátrica y, referente, en el de las tubolopatías. Su prestigio en esa especialidad fue unánimemente reconocido. Realizó sus estudios de Medicina en la Universidad de Barcelona. En 1959, obtuvo, una beca para ampliar su formación en el Hópital des Enfants Malades de Paris. En 1963 fue admitido en el Albert Einstein College of Medicine de Nueva York, en el que identificó la acidosis tubular proximal renal como una entidad fisopatológica independiente. En 1970, se hizo cargo del Departamento de Pediatría del Hospital Universitario de Cruces, cerca de Bilbao. Alklí, junto a Alfredo Vallo, siguió investigando y publicando sobre muchos temas pediátricos pero, especialmente sobre diversos aspectos de sus dos grandes temas de interés, las pruebas de función renal y las grandes temas de interés, las pruebas de función renal y la tubulopatías. A lo largo de 30 años, ambos desarrollaron las bases para la creación de una auténtica “escuela científica” nefrológica pediátrica (AU)

Juan Rodríguez Soriano (1933-2010) was an eminent Spanish nephrologist, forming several generations of paediatricians and paediatric nephrologist. He was internationally regarded as one of the pioneers of paediatric nephrology, and reference in tubolopathies. His reputation in that field was unanimously recognized. He studied medicine at the University of Barcelona. In 1959, he won a scholarship to further their training in the Hospital des Enfants Malades in Paris. In 1963 he was admitted to the Albert Einstein College of Medicine in New York where identified the proximal renal tubular acidosis as an independent physiopathological entity. In 1970, he took charge of the Department of Pediatrics, University Hospital of Cruces, Bilbao. There, nex to to Alfredo Vallo, continued its research and publications on many paediatric topics, but especially on various aspects of its two main topics of interest: renal function test and tubulopathies. Over 30 years, both developed the basis for creating a true “scientific school” of the paediatric nephrology (AU)

[Should a cystography be performed on all breastfeeding infants with mild to moderate dilatation of the urinary tract? Renal function tests can help to answer this question]. / ¿Debe realizarse una cistografía a todos los lactantes con dilatación leve y moderada de las vías urinarias? Las pruebas de función renal pueden ayudar a responder a esta pregunta.

INTRODUCTION: Pyelectasis can be defined as mild to moderate dilatation of the urinary tract and is diagnosed by means of an ultrasound scan (0.5-2cm transverse diameter in the initial ultrasound performed after birth). There is some disagreement about whether cystography should be indicated as standard practice. The aim of this study was to establish if renal function tests are useful in determining which cases of mild to moderate dilatation of the urinary tract do not require an initial cystography. PATIENTS AND METHODS: The study was conducted on 79 infants (57 males, 22 females) with pyelectasis. Seventy-three were diagnosed in utero and 6 after birth. All infants underwent at least one cystography and one desmopressin urine concentration test before one year of age. RESULTS: Compared to infants without vesicoureteral reflux (VUR) (n=68), infants with VUR (n=11; two with Grade I, three with Grade II, five with Grade III, two with Grade IV) showed a significantly lower (P=.006) maximum urine osmolality and a significantly higher microalbumin/creatinine ratio (P<.001) and NAG/creatinine ratio (P=.003). The negative predictive value of the first two tests was 93%. Sensitivity of the maximum urine osmolality to detect VUR was 72.7% (specificity 63.2%). Sensitivity of the microalbumin/creatinine ratio to detect VUR was 62.5% (specificity 75%). The positive probability ratio (PR) was 1.29 for the NAG/creatinine ratio, 2.03 for the maximum urine osmolality and 2.5 for the microalbumin/creatinine ratio. The negative PR was 0.95 for the NAG/creatinine ratio, 0.43 for the maximum urine osmolality and 0.5 for the microalbumin/creatinine ratio. CONCLUSIONS: Pyelectasis is a benign condition. Only 2 patients required pharmacological intervention (prophylactic treatment for VUR Grade IV patients). Initially at least, cystography should not be indicated in cases of microalbuminuria and/or normal urine concentrations.

[Are simple renal cysts another manifestation of prelithiasis in infancy?]. / ¿Los quistes renales simples son otra forma de manifestación de prelitiasis en la infancia?

Simple renal cysts are uncommon lesions in paediatric patients. In the absence of hypokalaemia or an increase in the production of NH+, the cause of simple renal cysts is unknown. Hepler, in 1930, suggested that they may be caused by a tubular obstruction. We prospectively studied the presence of hypercalciuria or hypocitraturia as well as the family history of urolithiasis in a group of children diagnosed sonographically with simple renal cysts. The average age of the 22 patients (12M, 10F) was 6.04 +/- 2.9 years at the time of diagnosis. The ultrasound examination had been requested due to urinary tract infection, abdominal pain, haematuria or other disorders. The cysts were slightly more frequent on the left side (54.5%). All were located in the upper kidney pole. 14 patients were found to have hypercalciuria and/or hypocitraturia (hypercalciuria n = 11, 50%). Thirteen families had history of renal stones. The metabolic abnormalities associated with calculi in children and/or family history of stones were present in 19 families (86.3%). Our hypothesis is that both entities, renal cysts, and genetic predisposition to kidney stones, are related.

¿Los quistes renales simples son otra forma de manifestación de prelitiasis en la infancia? / Are simple renal cysts another manifestation of prelithiasis in infancy?

Los quistes renales simples son lesiones poco frecuentes en pacientes pediátricos. En ausencia de hipopotasemia o de un incremento en la producción de NH4+, se desconoce el origen de los mismos. Hepler, en 1930, propuso que su causa podría ser una obstrucción tubular. Hemos estudiado de forma prospectiva la presencia de hipercalciuria o de hipocitraturia, así como los antecedentes familiares de litiasis en un grupo de niños diagnosticados ecográficamente de quistes renales simples. Al diagnóstico, la edad media de los 22 pacientes (12 varones y10 mujeres) fue de 6,04 ± 2,9 años. El estudio ecográfico se había solicitado por infección de vías urinarias, dolor abdominal, hematuria u otros. Los quistes fueron ligeramente más frecuentes en el lado izquierdo (54,5%). Todos estaban ubicados en el polo renal superior. En 14 pacientes (63,6%) se demostró que eran portadores de hipercalciuria o hipocitraturia (hipercalciuria n = 11, 50%). En 13 familias existían antecedentes de litiasis renal. En conjunto, las anomalías metabólicas estudiadas causantes de cálculos en los niños o los antecedentes familiares de litiasis estaban presentes en 19 familias (86,3%).Nuestra hipótesis es que ambas entidades, quistes renales y predisposición genética a padecer cálculos renales, están relacionadas (AU)

Simple renal cysts are uncommon lesions in paediatric patients. In the absence of hypokalaemia or an increase in the production of NH+, the cause of simple renal cysts is unknown. Hepler, in 1930, suggested that they may becaused by a tubular obstruction. We prospectively studied the presence of hypercalciuria or hypocitraturia as well as the family history of urolithiasis in a group of children diagnosed sonographically with simple renal cysts. The average age of the22 patients (12M, 10F) was 6.04 ± 2.9 years at the time of diagnosis. The ultrasound examination had been requested due to urinary tract infection, abdominal pain, haematuria or other disorders. The cysts were slightly more frequent on the left side(54.5%). All were located in the upper kidney pole. 14 patients were found to have hypercalciuria and/or hypocitraturia (hypercalciuria n = 11, 50%). Thirteen families had history of renal stones. The metabolic abnormalities associated with calculiin children and/or family history of stones were present in 19families (86.3%). Our hypothesis is that both entities, renal cysts, and genetic predisposition to kidney stones, are related (AU)

[Celebrating fifty years of percutaneous renal biopsies in Spain]. / En el cincuentenario de las primeras biopsias renales percutáneas realizadas en España.

The first renal biopsies, made as much in adults as in children, were surgical. They were made to patients who were under renal decapsulation with the intention to reduce the kidney pressure, especially in cases of nephrotic syndrome. In 1944, Nils Alwall initiated the accomplishment of percutaneous kidney biopsies by means of a needle and aspiration at the University of Lund (Sweden), although his experience was published in 1952. The first article that had by subject the practice of a percutaneous renal biopsy was written in 1950 by a Cuban doctor, Antonino Pérez Ara, and published in a local journal with little diffusion. The first work that appeared in a Spanish journal (1953) about the practice of the percutaneus renal biopsies was not signed by any Spanish group but by members of the Hospital "Calixto García" of the University of The Havana, Cuba. The first article published in Spain regarding to this subject, saw the light in 1958, now 50 years ago, in the Revista Clínica Española. The two first signers were Alfonso de la Peña Pineda and Vicente Gilsanz García, professors of the Medicine Faculty of Madrid. Later, the practice of the percutaneous renal biopsy became general in other Spanish hospitals.

[Multicystic kidney disease in a segment of horseshoe kidney: an uncommon combination of malformations]. / Displasia renal multiquística en un segmento de un riñón ''en herradura'': una asociación de malformaciones poco usual.

Multicystic dysplasia is the most common type of renal cystic disease, and it is one of the most common causes of an abdominal mass in infants. The contralateral system is also frequently abnormal. The most commonly associated anomalies are contralateral ureteropelvic junction obstruction and contralateral vesicoureteral reflux. In a few cases, multicystic dysplasia involves a horseshoe kidney or one pole of a duplex kidney. We present a female patient diagnosed with this condition at 9 years old, when she was being studied due to recurrent abdominal pain. The renal function was normal.

Displasia renal multiquística en un segmento de un riñón "en herradura": una asociación de malformaciones poco usual / Multicystic kidney disease in a segment of horseshoe kidney: an uncommon combination of malformations

La displasia renal multiquística es la variedad más frecuente de enfermedad quística renal y una de las causas más comunes de masa abdominal en recién nacidos y lactantes. Las anomalías contralaterales que se asocian con más frecuencia son la estenosis de la unión pieloureteral y el reflujo vesicoureteral. En muy pocos casos, la displasia renal multiquística está presente en uno de los segmentos de un riñón "en herradura" o en uno de los polos, en el caso de un doble sistema. Presentamos el caso de una paciente portadora de esta asociación de malformaciones diagnosticada a los 9 años de edad al ser estudiada por tener dolor abdominal recurrente. La función renal fue normal (AU)

Multicystic dysplasia is the most common type of renal cystic disease, and it is one of the most common causes of an abdominal mass in infants. The contralateral system is also frequently abnormal. The most commonly associated anomalies are contralateral ureteropelvic junction obstruction and contralateral vesicoureteral reflux. In a few cases, multicystic dysplasia involves a horseshoe kidney or one pole of a duplex kidney. We present a female patient diagnosed with this condition at 9 years old, when she was being studied due to recurrent abdominal pain. The renal function was normal (AU)

[Study of renal morphology and function in children with nocturnal enuresis. Relationship with sensitivity or resistance to desmopressin]. / Estudio de la morfología y la función renal en niños diagnosticados de enuresis nocturna. Su relación con la sensibilidad o la resistencia a la desmopresina.

BACKGROUND: In the last few years, there have been reports that children with nocturnal enuresis frequently have hypercalciuria. Likewise, children with desmopressin-resistant enuresis have recently been reported to have a higher renal concentration capacity than patients with desmopressin-sensitive enuresis. OBJECTIVES: To study renal function and urinary calcium excretion and to register familial history of enuresis and urolithiasis in a group of children with enuresis, whether responders or nonresponders to desmopressin, followed-up in our hospital. MATERIAL AND METHODS: A cohort of 60 patients (42 boys and 18 girls) who were referred to the hospital because of nocturnal enuresis. RESULTS: Hypercalciuria was detected in 26 children (43.3 %) and hypocitraturia in eight (13.3 %). The frequency of hypercalciuria was higher in desmopressin-resistant patients than in desmopressin-sensitive patients, but this difference was not statistically significant. Sonographic renal morphological anomalies were detected in 11 children (18.3 %). No differences in renal handling of water were detected when the patients were distributed according to the grade of sensitivity to desmopressin. CONCLUSIONS: In our cohort we found a high frequency of hypercalciuria in children with nocturnal enuresis. No differences were observed in maximal urinary osmolality among desmopressin-resistant and desmopressin-sensitive children.

Estudio de la morfología y la función renal en niños diagnosticados de enuresis nocturna. Su relación con la sensibilidad o la resistencia a la desmopresina / Study of renal morphology and function in children with nocturnal enuresis. Relationship with sensitivity or resistance to desmopressin

Antecedentes: En los últimos años, se ha descrito que, con frecuencia, los niños con enuresis nocturna presentan hipercalciuria. Así mismo, se acaba de comunicar que los niños con enuresis nocturna resistente a desmopresina tienen una capacidad de concentración renal superior a la de aquellos pacientes con enuresis sensible a ese fármaco. Objetivos: Estudiar la función renal y la eliminación urinaria de calcio y registrar los antecedentes familiares de enuresis y de litiasis en un grupo de niños enuréticos respondedores y resistentes a desmopresina controlados en nuestro hospital. Material y métodos: Cohorte de 60 pacientes, 42 varones y 18 mujeres, que fueron remitidos al hospital por padecer enuresis nocturna. Resultados: Se detectó hipercalciuria en 26 niños (43,3 %) e hipocitraturia en ocho (13,3 %). La frecuencia de hipercalciuria fue superior en los pacientes resistentes con respecto a los sensibles a desmopresina, sin diferencias estadísticamente significativas. En 11 niños se detectaron anomalías morfológicas ecográficas renales. No se comprobaron diferencias en el manejo renal del agua al distribuir a los pacientes según el grado de sensibilidad a la desmopresina. Conclusiones: En nuestra serie se demuestra la elevada frecuencia de hipercalciuria en niños con enuresis nocturna. No observamos diferencias en la osmolalidad urinaria máxima entre los niños sensibles y los resistentes a la desmopresina

Background: In the last few years, there have been reports that children with nocturnal enuresis frequently have hypercalciuria. Likewise, children with desmopressin-resistant enuresis have recently been reported to have a higher renal concentration capacity than patients with desmopressin-sensitive enuresis. Objectives: To study renal function and urinary calcium excretion and to register familial history of enuresis and urolithiasis in a group of children with enuresis, whether responders or nonresponders to desmopressin, followed-up in our hospital. Material and methods: A cohort of 60 patients (42 boys and 18 girls) who were referred to the hospital because of nocturnal enuresis. Results: Hypercalciuria was detected in 26 children (43.3 %) and hypocitraturia in eight (13.3 %). The frequency of hypercalciuria was higher in desmopressin-resistant patients than in desmopressin-sensitive patients, but this difference was not statistically significant. Sonographic renal morphological anomalies were detected in 11 children (18.3 %). No differences in renal handling of water were detected when the patients were distributed according to the grade of sensitivity to desmopressin. Conclusions: In our cohort we found a high frequency of hypercalciuria in children with nocturnal enuresis. No differences were observed in maximal urinary osmolality among desmopressin-resistant and desmopressin-sensitive children

Comparación de la desmopresina intranasal y oral en la determinación de la capacidad de concentración renal en la infancia / Determination of the renal concentrating ability in childhood: intranasal desmopressin versus oral desmopressin

Antecedentes: En los últimos años, se ha descrito que uno de los parámetros más sensibles para estimar la función renal es la prueba de concentración urinaria realizada con estímulo de desmopresina (DDAVP). Objetivo: Estudiar la capacidad de concentración urinaria en un grupo de pacientes controlados en nuestro hospital comparando los resultados de la osmolalidad urinaria máxima obtenida con desmopresina administrada tanto por vía oral como nasal. Material y métodos: Cohorte de 53 pacientes (30 niños y 32 niñas) que están en seguimiento en las consultas externas de Nefrología Pediátrica. Resultados: La osmolalidad urinaria máxima obtenida con desmopresina intranasal fue 726,4 ± 163,8 mOsm/kg y con desmopresina oral 782,1 ± 198,5 mOsm/kg (p = 0,003). Se comprobó una correlación directa entre ambas variables (r = 0,75; p < 0,001). En 40 niños (75,5%) coincidían los valores de osmolalidad urinaria máxima, es decir, el que concentraba con un método lo hacía con el otro y a la inversa. 32 de ellos (80%) presentaban defecto de concentración urinaria. En 13 pacientes (24,5%) los valores no fueron coincidentes; todos ellos concentraban adecuadamente con uno u otro método, pero en 12 (92,3%) el valor máximo se alcanzó con desmopresina vía oral. Conclusiones: Los hallazgos más significativos de este estudio radican en el hecho de que si existe defecto de concentración urinaria, éste se constata independientemente de la vía de administración de la desmopresina. En aquellos casos en los que no existió coincidencia entre ambas determinaciones, la vía oral es la que valida la prueba

Background: In the last few years, it has been described that one of the best renal function parameters is the renal concentrating test with desmopressin. Objective: The aim of the present study was the evaluation of the renal function comparing the results of the urine concentration test with desmopressin administrated by oral or intranasal way in a group of children followed up in our hospital. Material and methods:Aseries of 53 patients (30 males and 23 females) who consulted at the hospital. Results: The maximum urinary osmolality was 726,4 ± 163,8 mOsm/kg with desmopressin administrated by intranasal way and 782,1 ± 198,5 mOsm/kg (p = 0,003) with desmopressin administrated by oral way. It was observed a direct correlation between both parameters (r = 0,75; p < 0,001). In 40 children (75,5%) were coinciding the maximum urinary osmolality, that is, the one that he was concentrating with a method did it with the other and the other way around. 32 of them (80%) had a defect in the urinary concentration test. In 13 patients (24,5%) the values were not coincident; all of them presented a normal urinary concentration test but in 12 the maximum value was obtained with oral desmopressin. Conclusions: The most meaning results of this study are that if there is a defect in the renal concentrating capacity, this will be present independently of the desmopressin administration method. On the other hand, in those cases where there are not coincidence between both determinations, the oral way is the reference method

Estudio de la capacidad de acidificación renal en niños diagnosticados de hipercalciuria idiopática / Study of renal acidification capacity in children diagnosed of idiopathic hypercalciuria

Objetivo: Estudiar la capacidad de acidificación renal en un grupo de niños diagnosticados de hipercalciuria idiopática. Pacientes y Métodos: Se estudiaron 36 niños, a los que se les determinó la pCO2 (UpCO2) urinaria máxima con dos estímulos diferentes, acetazolamida y bicarbonato sódico (CO3HNa). A 33 de ellos, se les realizó una prueba de acidificación con estímulo de furosemida. Se estudiaron 13 controles tanto para la primera como la segunda pruebas y otros 14 para la prueba de acidificación con furosemida. Resultados: En la pruebas realizadas tanto con CO3HNa como con acetazolamida, no se comprobaron diferencias en los valores de UpCO2 ni en la concentración urinaria de CO3H- (UCO3H-) con respecto al grupo control. No obstante, la UpCO2 y la concentración de UCO3H- en los pacientes fueron significativamente inferiores con acetazolamida con respecto al estímulo de CO3HNa. En la prueba de acidificación con furosemida, se alcanzaron valores significativamente inferiores de acidez titulable y de amonio en relación al grupo control. Conclusiones: En niños diagnosticados de hipercalciuria idiopática, la capacidad de secreción de H+ es normal lo que se evidencia, especialmente, al estudiar la UpCO2 máxima con estímulo de CO3HNa. Cuando se utilizan diuréticos como estímulos, existen más resultados negativos, que pueden deberse a una cierta resistencia parcial a la acción de los mismos o a que son menos potentes para inducir la secreción de H+

Objective: To study the capacity of renal acidification in a group of children diagnosed of idiopathic hypercalciuria. Patient and Methods: 36 children were studied, to those that were determined the pCO2 (UpCO2) maximum urinary with two different stimuli, acetazolamide and sodium bicarbonate (NaHCO3). At 33 of them, was performed an acidification test with frusemide stimulus. We studied a control group of 13 healthy children so much for the first one as the second tests and other 14 healthy children for the acidification test with frusemide. Results: In the tests performed with NaHCO3 and acetazolamide stimulus, they were not proven differences in the values of UpCO2 neither in the urinary concentration of HCO3 - (UHCO3 -) than control children. Nevertheless, the UpCO2 and the concentration of UHCO3 - in the patients were significantly lower with acetazolamide with regard to the NaHCO3 stimulus. In the acidification test with frusemide, significantly lower values of titratable acid and ammonium were obtained than control children. Conclusions: In children with idiopathic hypercalciuria, the capacity of secretion of H+ is normal, what is evidenced, especially, when studying the maximum UpCO2 after stimulus with NaHCO3. When diuretics are used as stimuli, exists more negative results that can be due to a certain partial resistance to the action of the same ones or to that are less potent to induce the secretion of H+

Tratornos del metabolismo óseo en las enfermedades renales de la infancia / Bone metabolism disorders in renal diseases in childhood

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