Can Fractional Urea Excretion Be A Marker in Pediatric Urinary Stone Disease?

Year 2023, , 382 - 385, 31.12.2023

Özlem Yüksel Aksoy , Mihriban İnözü , Begüm Avcı , Zehra Aydın , Fatma Şemsa Çaycı , Umut Selda Bayrakçı

https://doi.org/10.36516/jocass.1345117

Abstract

Introduction: In the setting of pediatric urolithiasis, it is important to determine the presence of any metabolic disorder to prevent new stone formation and to treat the existing stone. With this aim, the urinary excretions of electrolytes and uric acid are usually obtained. Fractional excretion of urea (FeU) has been demonstrated to be useful in the setting of acute renal injury. However it has not been studied in the setting of pediatric stone disease. The objective of this study is to search the importance of FeU in pediatric stone disease and to compare FeU with other urine electrolyte excretions and uric acid excretion.

Materials and Methods: We retrospectively evaluated the laboratory and medical records of 41 pediatric urolithiasis patients whose FeU percentages were studied together with the etiologic work-up. Patients were divided into two groups as microlithiasis and macrolithiasis. Demographic and laboratory data as well as FeU were compared between the two groups.
Results: Twenty-four patients (59%) had stone size less than 3 mms, seventeen patients (41%) had stones larger than 5 mms. Among all patients 20 of them were boys, 21 of them were girls. M/F ratio was 13/11 in microlithiasis and 7/10 in macrolithiasis group. Mean age was 55.8 months in microlithiasis group, wheras 39 months in macrolithiasis group. Mean serum urea, creatinine, sodium, potassium, phosphorus levels and FeNa, FeU and TRP percentages were similar between the two groups. (p>0.05).
We divided the patients according to their FeU percentages as FeU<35% and FeU ≥35%, and compared the microlithiasis and macrolithiasis groups. Among 24 patients with microlithiasis, 20 patients had FeU greater than 35%, and 4 patient had FeU less than 35%. To differentiate microlithiasis from macrolithiasis the sensitivity and spesificity of FeU≥35 is 83% and 6% respectively. For FeU<35%, sensitivity and spesificity of the test to differentiate microlithiasis from macrolithiasis is 17% and 94% respectively (p>0.05).
When we analyze FeNa, among the two groups, For FeNa<1%, sensitivity and spesificity of the test to differentiate microlithiasis from macrolithiasis is 53% and 25% respectively. And for FeNa ≥1% the sensitivity and the spesificity of the test is 47% and 75% respectively. (p>0.05).
The urinary calcium excretion of the patients (random urine calcium/creatinine ratios) are correlated with random urine uric acid/creatinine ratios in both microlithiasis and macrolithiasis groups (p=0.001). Random urine calcium/creatinine ratio also correlates with the tubular phosphorus reabsorption (p=0.023), as well as random urine uric acid excretion correlates with tubular phosphorus reabsorption (p=0.024).

Conclusion:
Fractional excretion of urea is not affected from the size of the stone. However, urinary urea excretion is associated with urinary sodium and uric acid excretion. Further studies with larger groups and comparison of the urolithiasis patients with healthy children without urinary stones in the controlled studies will reveal the exact results.

Keywords

urea excretion, nephrolithiasis, children

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