LCN2 and acute kidney injury: The limitations of the present study were as follows: i) The samples of AKI were small, with no extremely serious cases requiring renal replacement therapy and no classification of AKI; ii) the renal biopsy cases were small, which affected NGAL and KIM-1 protein expression following tubular injury; iii) the study was a single center study, and therefore a further large-scale multi-center clinical study is required to confirm the results.