Precision nosology versus precision nephrology: defining acute kidney injury, again

Consensus definitions for acute kidney injury (AKI) use change in serum creatinine or urine output as the basis for diagnosis and risk stratification. Consensus definitions have been validated largely by prospective associations with in-hospital mortality. Applying this same approach, Sparrow and colleagues propose a further subclassification of stage 1 AKI into 2 subgroups. Although they are informative for epidemiology, AKI definitions have largely failed to focus on the most interesting and clinically relevant issues: etiology and pathogenesis.