Study of abnormalities in urine evaluation, biochemical investigations, imaging and clinical course among patients with pre-renal and acute tubular necrosis-related acute kidney injury

Abstract Background: In patients presenting with acute kidney injury (AKI), the available literature is sparse with regard to differentiation between pre-renal AKI and acute tubular necrosis (ATN) based on clinical, biochemical and imaging studies. Methods: We prospectively studied 50 consecutive adult patients presenting with AKI from March 2021 to June 2022. Fresh urine and blood samples were subjected to clinicopathological, biochemical and imaging testing to differentiate between pre-renal AKI and ATN. Results: Both pre-renal AKI and ATN groups were comparable in terms of age ( P = 0.339) and gender ( P = 0.339). The proportion of patients with scores based on the number of casts and renal tubular epithelial cells of 3 were significantly lower in pre-renal AKI compared to ATN (16% vs. 68%; P = 0.0002). Urine specific gravity ( P < 0.007) and urine creatinine ( P < 0.001) were significantly higher in pre-renal AKI compared to ATN. Urine sodium ( P < 0.0001), fractional excretion of sodium (FENa) ( P < 0.0001) and renal failure index (RFI) ( P < 0.0001) in ATN were significantly higher compared to pre-renal AKI. The proportion of patients with bilateral grade 2 renal parenchymal disease changes on abdominal ultrasonography was significantly higher in ATN compared to pre-renal AKI (8% vs. 0%; P = 0.007). Conclusions: Urine sediment scoring system, urine specific gravity, urine sodium, urine creatinine, FENa and RFI were found to be significantly different between pre-renal AKI and ATN, suggesting their potential utility as differentiating tests between these two entities.