| Abstract|| |
Urinary reflux can cause irreversible complications such as reflux nephropathy and ESRD. Diagnostic imaging such as voiding cystourethrogram (VCUG) is invasive and causes irradiation. Several studies have shown that markers such as urine IL-8 or serum Procalcitonin might be useful for the diagnosis of vesico-ureteral reflux (VUR) as a substitution for invasive methods. The aim of this study was to determine and compare the mean urine Ca/Cr ratio and hypercalciuria between two groups of children aged 2-10 years affected by VUR. This is a cross-sectional study in which 32 children having the following entrance criteria were included: children 2-10 years old not affected by urinary tract infection during the last three months and their reflux or recovery having been diagnosed by VCUG or direct radionuclide cystography, divided into two groups of affected by reflux and recovered from reflux. Then, the point urine specimens were collected with permission of their parents in a single laboratory and urine Ca and Cr for each specimen were measured. The Ca/Cr ratio was calculated for each child to evaluate Ca excretion from the urine, which was possible without collecting the 24-hours urine. The Ca/Cr ratio mean and the hypercalciuria were compared between the groups. To analyze our data, the Mann-Whiney test and the Chi-square test were used, using SPSS V.15. Thirty-two children, including 18 children recovered from reflux and 14 affected by reflux, were entered in our study. The Ca/Cr ratio mean was 0.692 ± 1.874 for the affected and 0.118 ± 0.187 for the recovered group. The Ca/Cr ratio mean for the affected male and female groups was 0.012 ± 0.008 and 0.805 ± 1.0913, respectively. This amount was 0.0175 ± 0.01767 for the recovered male and 0.131 ± 0.195 for the recovered female group. There was no significant statistical difference between the groups with respect to the Ca/Cr ratio mean, but there was a significant statistical difference between the two groups of females (P-value = 0.026). Also, there was no significant statistical difference between the two groups of males relative frequency of hypercalciuria was significantly higher in the group affected by reflux than in the recovered from reflux group (P-value = 0.017). Urine Ca excretion is elevated in children with reflux, and may be more useful as an appropriate marker for the diagnosis of VUR than other invasive methods.
|How to cite this article:|
Badeli H, Sadeghi M, Shafe O, Khoshnevis T, Heidarzadeh A. Determination and comparison of mean random urine calcium between children with vesicoureteral reflux and those with improved vesicoureteral reflux. Saudi J Kidney Dis Transpl 2011;22:79-82
|How to cite this URL:|
Badeli H, Sadeghi M, Shafe O, Khoshnevis T, Heidarzadeh A. Determination and comparison of mean random urine calcium between children with vesicoureteral reflux and those with improved vesicoureteral reflux. Saudi J Kidney Dis Transpl [serial online] 2011 [cited 2013 May 24];22:79-82. Available from: http://www.sjkdt.org/text.asp?2011/22/1/79/74357
| Introduction|| |
Vesico-ureteral reflux (VUR) is the backward flow of urine from the bladder into the ureter, with an incidence of 1-2% during childhood.  Thirty percent to 60% of children with VUR have some degrees of renal injury.  The most common chronic complication of VUR is HTN, whose incidence is around 10-20% in longterm studies. Also, 15% the of patients with reflux nephropathy become ESRD ultimately. , Therefore, all of the children below eight years of age with urinary tract infections (UTI) should undergo voiding cystourethrogram (VCUG). VCUG is the best measure for the diagnosis of VUR.  But, it is technically difficult  and can cause exposure to irradiation and result in UTI.  Because of these complications, easier and less-invasive methods seem to be beneficial and useful. Data in recent years have proposed that VUR by itself and without urinary tract infection is an inflammatory process. Galanakis and colleagues suggest that the inflammatory process in VUR is ongoing even after the UTI has resolved.  Procalcitonin (PCT) is the prohormone of calcitonin and is cleaved by proteolytic enzyme into active hormone. Circulating levels of PCT in healthy subjects are below the detection limit. But, the serum level of PCT is elevated during inflammatory states.  Calcitonin can reduce the Ca level of serum by excreting Ca from renal tubules and the gastrointestinal tract. Leory et al reported that the serum PCT level would be elevated during VUR.  Garcia-Nieto and colleagues found that children with VUR had a higher incidence of hypercalciuria compared with those without VUR.  With the above-mentioned information about PCT, if vesicoureteral reflux can continue kidney inflammation, then comparing its effect on Ca handling (such as increased urinary calcium content) may help in the diagnosis of possible reflux. The aim of our study is to compare the mean urine Ca and the relative frequency of hypercalciuria between two groups of children: children with urinary reflux and children with improved urinary reflux, to find an easier and non-invasive method for the diagnosis and follow-up of VUR in children.
| Subjects and Methods|| |
In this cross-sectional study, we compared the mean non-fasting single-spot urine Ca and creatinine ratio of 32 children with VUR (group A) and improved VUR (group B). All children were between two to ten years old, without UTI during the last three months, no urologic abnormalities and VUR or their improvement was documented by direct radionuclide cystography (DRNC) or VCUG.
A single laboratory measured all urine Ca and Cr levels. They used special kits for Ca and Cr. The measuring machine was a "Hitachi auto analyzer". The "Alcion" technique was used for Ca with (precision) CV = 1.3% and the "Jaffe" technique was used for Cr with (precision) CV = 2.3%.
Information such as age, sex and unilateral or bilateral reflux was extracted from the files of children. To analyze the data, SPSS version 15 software was used. Also, for comparing the mean urine Ca between the two groups, Mann- Whitney test, and for comparing the relative frequency of hypercalciuria between the groups, Chi-square test, were used.
Hypercalciuria was considered as a Ca/Cr (mg/mg) ratio higher than 0.2 for children over two years old. The ethics committees of our university approved this study.
| Results|| |
Thirty-two children were evaluated. The mean age was 5.8 ± 2.13 years (four males and 28 females). Fourteen children had reflux (group A), with a mean age of 4.85 ± 1.79 years (two males and 12 females), and the remaining children had improved reflux (group B; 18), with a mean age of 5.9 ± 2.29 years (two males and 16 females). In group A, the mean age of the first UTI was 31.7 ± 2.4 months and the mean duration between diagnosis of reflux and entering into this study was 30 ± 9.1 months. In group B, the mean age of the first UTI was 27 ± 2.04 months and the mean duration between diagnosis of reflux and recovery from reflux was 19.9 ± 1.3 months.
The severity of reflux was defined by VCUG or DRNC and then divided into three stages: mild, moderate and severe (grades 1 and 2 were considered as mild, grade 3 was considered as moderate and grades 4 and 5 were considered as severe stage).
In group A, seven children (50%) had mild, four children (28.6%) had moderate and three children (21.4%) had severe reflux; six of the children in this group (42.9%) had bilateral reflux and eight of them (57.1%) had unilateral reflux according to the last radiological assessments.
In group B, eight children (44.4%) had mild, three children (16.6%) had moderate and seven children (38.8%) had severe reflux. Thirteen children of group B (72.2%) had bilateral reflux and the rest of them had unilateral reflux according to radiological assessments that were done before recovery.
Renal scars were evaluated by DMSA scan for all the children. There were four children with renal scars diagnosed by DMSA scan, and three of them belonged to group A. The Ca/Cr ratio was 0.692 ± 1.847 for group A and 0.118 ± 0.187 for group B [Figure 1].
|Figure 1: Distribution of urine Ca/Cr ratio and the limitation of mean of the urine Ca/Cr ratio for the two|
groups. The horizontal line shows that the urine Ca/Cr level equals 0.2 to define hypercalciuria.
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Because the data did not have a normal distribution, non-parametric tests (Mann-Whitney test) was used for comparison of the urine Ca mean between the two groups.
The statistical analysis has shown that there is no significant statistical difference for the Ca/Cr ratio between the two groups. The Ca/Cr ratio mean among males of group A was 0.012 ± 0.008 and of group B was 0.0175 ± 0.0176. Also, this amount among females of group A was 0.805 ± 1.913 and of group B was 0.131 ± 0.195.
After statistical comparison of the Ca/Cr ratio between males and females of each group, we did not find a significant statistical difference between males of the two groups, but there was a significant statistical difference between the two groups of females (P = 0.026).
Despite there being no significant difference between the Ca/Cr ratio mean between the two groups, the relative frequency of hypercalciuria was significantly greater for group A than for group B (P = 0.017). Comparing the relative frequency of hypercalciuria between females of each group, we found that it was significantly greater in females of group A than those of group B (P = 0.01).
| Discussion|| |
VUR occurs during childhood, with a prevalence of 1-2%, and can lead to reflux nephropathy, HTN and ESRD. The most important presentation of VUR is UTI and, therefore, radiological surveillance (VCUG or DRNC) of children below five years of age after the first febrile UTI is mandated. These diagnostic methods are invasive and can cause irradiation and UTI. To date, several attempts were made to replace the non-invasive method with VCUG or DRNC. Different substances have been followed in urine for this aim, such as IL-6 and soluble TNF receptor-1.  Although researchers such as Smellie  believe that sterile reflux cannot harm the kidneys, Galanakis and colleagues suggest that inflammatory processes in the VUR is ongoing even after the UTI has resolved. Their supporting evidence was that urine IL-8 levels remain elevated in infants with VUR even in the absence of a UTI. 
The serum PCT level can increase during the inflammatory states, which causes increased excretion of Ca from the renal tubules. Garcia Nieto et al reported that the prevalence of hypercalciuria in children with reflux was 58.6%, which is significantly greater than that in the general pediatric population.
The prevalence of hypercalciuria in different studies in the general pediatric population was reported at 3.8%,  2.2% and 3%. 
With this background, we performed our study to elucidate the calcium excretion difference in the group with VUR and in the group with improved from VUR. The mean Ca/Cr ratio has had no significant difference between the two groups, but the relative frequency of hypercalciuria in group A (57.143%) was significantly greater than that group B (16.67%) (P = 0.017). Our finding was similar to that of the Garcia Nieto et al study. Our study similarly demonstrated that hypercalciuria is more common in patients with VUR, which decreased with recovery of VUR.
In conclusion, elevated urine Ca might be an appropriate marker for the diagnosis of VUR if there was no simultaneous UTI. To determine the exact mechanism of hypercalciuria in VUR, more studies need to evaluate hormones or mediators that can cause hypercalciuria in patients with VUR thus providing a non-invasive approach to diagnose VUR.
| Acknowledgment|| |
The authors wish to acknowledge and thank their patients and their parents because without them they could not have been able to perform this study. Also, the authors would like to thank Ms. L.M. Nabizadeh and the staff of Guilan Reference Laboratory for their excellent logistic support for this study.
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Department of Pediatric, Guilan University of Medical Science, Rasht