Hypomagnesemia and Fractional Excretion of Magnesium (FeMg) in Children with Nephrotic Syndrome

Background- Hypomagnesemia and increased FeMg have been identified in patients with tubular damage; we explore the possibility of using these parameters to identify tubular damage in children with nephrotic syndrome especially those with steroid resistant disease. Methods: This cross-sectional study was done from July 2021-July 2022 (n= 50); itsprimary objective was to estimate FeMg and serum magnesium levels in children and adolescents (2-18 years) with nephrotic syndrome (both steroid sensitive and steroid resistant), currently in remission. Those with CKD stage 3 or more, receiving drugs like diuretics, aminoglycosides, proton pump inhibitors, secondary and congenital nephrotic syndrome were excluded. Clinical details were elicited and biochemical investigations including urinary estimations of magnesium and creatinine were done. Results - 50 (31M: 19F) children (25 SSNS and25 SRNS) with median (IQR) age 10 years (7;11) were enrolled. Hypomagnesemia (S. magnesium<1.8 mg/dl)was seen in 36% and 52% (p=0.45) and FeMg was 1.76% and 1.39% in the SSNS and SRNS groups respectively (p= 0.25); none of the patients had symptoms of hypomagnesemia and increased FeMg (>2.2%) was similar (28%) in both groups. Conclusion- Hypomagnesemia appears to be a common electrolyte abnormality in children with nephrotic syndrome in disease remission especially in SRNS and underlying tubular damage may be contributory both in SSNS and SRNS.