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

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