SLC9A3 and acute kidney injury: Due to the limited urine volume in AKI, we did not compare the urinary exosomal NHE3 with other new biomarkers, such as kidney injury molecule-1, N-acetyl-beta-D-glucosaminidase, neutrophil gelatinase-associated lipocalin, liver fatty acid-binding protein, or the urinary products of tissue inhibitor metalloproteinase and insulin growth factor binding protein-7.