A “Troponin” for the Kidney?

Elevated creatinine levels in patients who present to an emergency department can result from three distinct types of pathophysiology: acute renal injury (previously termed acute renal failure), preexisting renal disease, or prerenal azotemia. Distinguishing among these etiologies is difficult but important, because questions about whether to initiate treatment and which treatment is indicated are crucial.

Neutrophil gelatinase–associated lipocalin (NGAL), one of several renal proteins excreted when a kidney is injured, is secreted into urine in the thick ascending loop of Henle, where it chelates iron compounds. NGAL is not expressed in prerenal azotemia and is not elevated in nonprogressive chronic renal failure. In a prospective study, th…