The calculation of various indices is a time-honored strategy performed in virtually every patient with suspected acute kidney injury. Examples include FeNa, FeUrea, urine/plasma creatinine ratio, and urine/plasma urea ratio. However, these tests have not lived up to the hype and the diagnostic accuracy is many studies is quite poor. The use of urine microscopy for the detection of tubular casts might add some value in a few smaller prospective cohort studies.