Background
Fractional tubular reabsorption of phosphate (TRP) has been used for over 60 years to establish the existence of renal phosphate loss. It is a parameter of corrected volume per decilitre ...of glomerular filtration rate (GFR). Later, a mass parameter per dl GFR called TP/GFR (tubular PO
4
reabsorption per dl GFR) was devised which some authors have sought to substitute for TRP. The aim of the present work is to attempt to demonstrate that TRP and TP/GFR are similar parameters and, in certain aspects, TRP is more effective for diagnosis.
Methods
Data were gathered on the metabolism of phosphate corresponding to a group of healthy children without hypophosphatemia (
n
= 47), a group of patients with idiopathic hypercalciuria (
n
= 27), and ten patients diagnosed with X-linked hypophosphatemia (XLH). The TRP, the TP/GFR, and the percent tubular reabsorption of phosphate were calculated.
Results
All the patients with XLH presented TRP values lower than 95 ml/dl GFR and of TP/GFR equal to or lower than 2.8 mg/dl GFR. In the total sample, a direct correlation was observed between TRP and TP/GFR (
r
= 0.65;
p
= 0.01). The TRP and the percent tubular reabsorption of phosphate values were the same in the three groups (
r
= 1;
p
= 0.01).
Conclusions
TRP and TP/GFR are similar parameters. TRP is more effective than TP/GFR given that in renal hypophosphatemia it is always below 95% and above 95% in reduced phosphatemia and normal kidney proximal tubular function. There is no solid reason for using TP/GFR rather than TRP.
Graphical abstract
A higher resolution version of the Graphical abstract is available as
Supplementary information
.
Renal hypouricemia (RHUC) is a rare inherited disorder characterized by impaired urate reabsorption in the proximal tubule resulting in low urate serum levels and increased urate excretion. Some ...patients may present severe complications such as exercise-induced acute renal failure and nephrolithiasis. RHUC is caused by inactivating mutations in the
(RHUC type 1) or
(RHUC type 2) genes, which encode urate transporters URAT1 and GLUT9, respectively. In this study, our goal was to identify mutations associated with twenty-one new cases with RHUC through direct sequencing of
and
coding exons. Additionally, we carried out an SNPs-haplotype analysis to determine whether the rare
variant c.374C>T; p.(T125M), which is recurrent in Spanish families with RHUC type 2, had a common-linked haplotype. Six intragenic informative SNPs were analyzed using PCR amplification from genomic DNA and direct sequencing. Our results showed that ten patients carried the
mutation c.1400C>T; p.(T467M), ten presented the
mutation c.374C>T, and one carried a new
heterozygous mutation, c.593G>A; p.(R198H). Patients carrying the
mutation c.374C>T share a common-linked haplotype, confirming that it emerged due to a founder effect.
To determine the effect of thiazide treatment on bone mineral density (BMD) in children with idiopathic hypercalciuria (IH) and osteopenia, we reviewed the case notes of 22 children aged 11.7 ± 2.7 ...years diagnosed with IH and osteopenia who had received thiazides for 2.4 years. The data on this group were compared with those of 32 IH children with osteopenia aged 11.2 ± 2.7 years who had not received thiazide treatment. By the end of the follow-up period, the
z
-BMD had improved spontaneously in 23 of the 32 control children (72%) and in 12 of the 22 patients on thiazides (54%). Although treated patients had a higher body mass index (BMI) and a higher BMD following treatment, the differences became statistically negligible when these parameters were expressed as
z
-BMD or as bone mineral apparent density (BMAD). In contrast, within the control group, there were significant differences in BMAD and
z
-BMD at the end of the follow-up. Patients who had an improved
z
-BMD at the end of the treatment also showed an increase in their BMI. Based on these results, we conclude that thiazide treatment does not improve the
z
-BMD in children with IH. More than half of the children suffering from IH enrolled in our study showed a spontaneous improvement in their
z
-BMD, which was more evident when the initial BMAD was not low and when their BMI increased during the follow-up period.
Severe (grades IV and V) vesicoureteral reflux (VUR) is a risk factor for acute pyelonephritis, renal scars, and renal failure. This study evaluates albumin and
N
-acetylglucosaminidase (NAG) urinary ...excretion, and renal concentrating ability as screening tools to select patients for voiding cystourethrogram (VCUG). Children (111 M, 52 F) aged 10.97 ± 21.17 months (mean + SD), diagnosed with UTI, and who had undergone renal ultrasound and a VCUG, underwent a desmopressin test and had albumin/creatinine and NAG/creatinine urinary excretion measured. Urine osmolality was significantly lower in 27 children with severe VUR (375.3 ± 171.8 mOsm/kg; mean + SD) compared to 100 patients with normal VCUG (611.5 ± 175.8 mOsm/kg),
p
< 0.001, and to 36 patients with VUR grades I to III (636.2 ± 180.2 mOsm/kg),
p
< 0.001. NAG/creatinine ratio was significantly elevated in 20 children with severe VUR (26.4 (28.3) U/g); median and interquartile range compared to 67 children with normal VCUG (10.8 (17.9) U/g),
p
= 0.003, and to 20 patients with VUR grades I to III (7.6 (21.1) U/g),
p
= 0.009.
Conclusions:
Urinary osmolality is significantly decreased and urinary excretion of NAG is significantly increased in patients with severe VUR. These tests could select patients for VCUG to assess for severe VUR.
What is Known:
•
Severe vesicoureteral reflux (SVUR) may contribute to renal damage. Severe vesicoureteral reflux is diagnosed by voiding cystourethrogram and represents about 10% of all patients with VUR. Currently, there are no reliable tests used prior to VCUG to help on the decision of obtaining a VCUG to diagnose SVUR
.
What is New:
•
This study shows that renal tubular markers (concentrating ability and N-acetylglucosaminidase (NAG) excretion) are useful tests prior to voiding cystourethrogram to screen for severe vesicoureteral reflux.
•
This study suggests the use of renal concentrating ability and urinary N-acetylglucosaminidase (NAG) excretion to screen for severe vesicoureteral reflux before requesting a voiding cystourethrogram.
Kidney function tests at the crossroads García Nieto, Víctor M; Luis Yanes, María Isabel; Tejera Carreño, Patricia ...
Anales de Pediatría
92, Številka:
2
Journal Article
Resumen Introducción Las infecciones de la vía urinaria (IVU) causadas por Escherichia coli ( E. coli ) son frecuentes en pacientes con hipercalciuria idiopática. Al ser tanto IVU como hipercalciuria ...(prelitiasis) de origen genético, planteamos si la historia familiar de urolitiasis es más frecuente en niños con IVU causada por E. coli . Secundariamente, planteamos si las cicatrices renales son más frecuentes en niños con prelitiasis. Material y métodos Estudio ambispectivo con datos de 104 pacientes (40 masculinos y 64 femeninos) seguidos tras haber sido diagnosticados, al menos una vez, de IVU por E. coli . Se preguntó por la existencia de urolitiasis en familiares (primer y segundo grado). En 80 pacientes se determinó la eliminación urinaria de calcio y citrato. Resultados En toda la muestra, la historia familiar de urolitiasis fue positiva en una frecuencia significativamente mayor de estos niños (n = 71; 68,3%) que en la población de control del mismo área (el 29,7% según datos previos publicados). La frecuencia de prelitiasis en niños con IVU fue del 47,5% (38/80). Se observó asociación entre prelitiasis tanto con la historia familiar de urolitiasis (p = 0,030) como con el reflujo vesicoureteral (p = 0,034). Además, los pacientes que desarrollaron cicatrices renales tenían más prelitiasis (OR 5,3; p = 0,033). Conclusiones La frecuencia de historia familiar de urolitiasis en niños con IVU causada por E. coli es muy alta. Basándonos en nuestros resultados, sugerimos la hipótesis de que la predisposición a litiasis involucra una defensa alterada contra E. coli y, consecuentemente, una mayor posibilidad de cicatrices renales.
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