Renal Restrictive Index (RRI) Versus Urinary Neutrophil Gelatinase-Associated Lipocalin (uNGAL) for early prediction of acute kidney injury (AKI) in adults undergoing elective cardiac surgeries with cardiopulmonary bypass: A prospective randomized observational study

Background Acute kidney injury (AKI) complicates most cardiac surgery patients. This study assessed the accuracy of urine neutrophil gelatinase-associated lipocalin (uNGAL) and Renal Resistive Index (RRI) to early predict (AKI) after cardiopulmonary bypass (CPB). Methods This work enrolled 57 cases of elective cardiac surgery with CPB. Urinary NGAL and RRI were measured preoperatively and at 1, 6 and 24 h postoperatively. The primary outcome was AKI, defined by Acute Kidney Injury Network Classification (AKIN) System. The secondary aim was to assess the diagnostic accuracy, cut-off point of uNGAL and RRI, and their relation with AKI severity. AKI developed in 22 patients (38.5%), with 2 cases required dialysis. Mean uNGAL significantly increased by 10 folds at 1h and 15 folds at 6h postoperatively. Results As regard uNGAL,the 1 h diagnostic accuracy was 94.8%, The area under the curve (AUC) was 0.888, using a cut-off value of 194.3 ng/ml. The 6 h diagnostic accuracy was 96.5%, AUC was 0.995 at a cut-off value 67.1 ng/ml. The 1 and 6 h uNGAL were unrelated to AKI severity. As regard RRI, AKI patients had significantly higher 1 h and 6 h RRI. The diagnostic accuracy at 1 h was 93.0%, AUC was 0.991, using a cut-off value of 0.72. The diagnostic accuracy at 6 h was 94.8%, AUC 0.995 at a cut-off value of 0.71. Values of RRI were significantly related only to severe cases requiring dialysis. Conclusion Urinary NGAL and RRI are early accurate indicators of AKI. High RRI can predict dialysis-requirement.