Fractional excretion of magnesium (FEMg), a marker for tubular dysfunction in children with clinically recovered ischemic acute tubular necrosis

Abstract

Among the different etiologies of acute renal failure (ARF), acute tubular necrosis (ATN) is one of the most common causes. There is no consensus on the duration of follow-up needed among these patients and also on choosing a reliable screening test to recognize early signs of chronic kidney injury that may ensue. The aim of this study was to evaluate the clinical and biochemical findings in children with a history of clinically recovered ischemic ATN, to detect the patients who may be at risk of ensuing chronic kidney disease. A cross-sectional study was carried out on 20 children between six months and 10 years of age, admitted at St. Al Zahra Hospital and Amin Children′s Hospital, Isfahan, Iran, with a past history of ischemic ATN. Eighteen patients were evaluated between 12 and 24 months, and two patients were evaluated at 30 months. The second sample of urine while still fasting was used for assessing urinary sodium, creatinine and magnesium. The mean ages for study and control groups were 3.4 ± 1.3 years and 4.5 ± 1.1 years, respectively. Glomerular filtration rate, urinary magnesium, fractional excretion of magnesium (FEMg), urinary sodium and fractional excretion of sodium (FENa) were significantly higher in the study group compared to those in the control group. No significant differences were demonstrated in systolic and diastolic blood pressures between the two groups. Since FEMg can reflect tubular function for both the ability of tubules for reabsorption of the filtered magnesium and for retaining the intracellular magnesium, FEMg can be used as a marker to detect early stages of chronic renal injury. However, further studies with larger number of cases are needed to evaluate the sensitivity of this test.