Background: Acute kidney injury (AKI) is a known complication of idiopathic nephrotic syndrome (INS), though the exact mechanism still unclear, correlates and risk factors for the development and outcome of this problem is being studied in recent decades. Objective: to determine the correlation of urinary alpha 2 macroglobulin (α2M) with the development and progression of AKI in children with INS Methods: A cohort study of children 2-16 years with INS, admitted to Cairo University Children Hospital. AKI was diagnosed and categorized using pRIFLE criteria. Urinary (α2M) was measured for all admitted children using Human Alpha 2 macroglobulin ELISA kit Results: of 90 hospitalisations, AKI was diagnosed in 48.9% of them. AKI detected in a total of 44 (48.9%) hospitalizations of 36 patients. The gender specific prevalence was in favor of males 27 (61.4%) against 17 (38.6%) for females but the difference was not statistically significant, P = 0.296. eGFR had significant negative correlation with α2M level (r = - 0.390, P < 0.05), while no significant correlation found with eGFR and Albumin/Cr ratio. Conclusion: AKI of varying severity is a more common complication in hospitalized children with INS, representing 48.9% of studied sample. The high molecular weight protein α2M was associated with reduced eGFR in the hospitalized children with AKI