Introduction: Acute Kidney Injury (AKI) following surgery for congenital heart disease with cardiopulmonary bypass (CPB-AKI) is fairly common. Limited studies have compared newer definitions of AKI in relation to early non-invasive urinary biomarkers for prediction of post CPB AKI. We sought to evaluate a) incidence using pediatric RIFLE, AKIN and KDIGO criteria, b) utility of urinary protein creatinine ratio (UPCR), modified urine microscopy score and NGAL as predictive early AKI biomarkers and c) risk factors for post CPB-AKI in children with CHD. Material & Methods: Serial blood and urine samples were collected for all children (2 mo18 y) undergoing congenital heart surgery with cardiopulmonary bypass between Nov 2017 to Apr 2019 at pre surgery,6,24, 48 hrs and day 7, day 30. Incidence of AKI was calculated as per standard definitions. Urine samples were analysed for UPCR and NGAL in the supernatant and the sediments were microscopically analysed to derive a modified urine microscopy score. Risk factors predisposing to AKI were analysed by multivariate analysis. ROC analysis was done for urinary biomarkers taking KDIGO as gold standard definition of AKI. Results: Amongst 76 children with CHD, incidence of AKI was 51% with AKIN/KDIGO criteria and 55% with pRIFLE criteria. Urinary NGAL rose within 6 hrs of CPB. A cut-off >84 ng/ml had 95% specificity with only 45% sensitivity (AUC-ROC 0.71). At 24 hrs, urine PCR was significantly high (AUC-ROC 0.7686) while urine microscopy score was similar in cases who developed AKI. Ventilation >48 hrs, exposure to multiple antibiotics and sepsis were significantly associated with AKI. Conclusion: Combination of pRIFLE with AKIN/KDIGO increased detection of post CPB AKI by 4%. In our cohort urinary NGAL at 6 hours and UPCR at 24 hours had a moderate predictive value.