Which laboratory finding is indicative of acute tubular necrosis?

Granular casts are indicative of acute tubular necrosis (ATN) because they represent renal tubular damage and are formed when there is cellular necrosis and sloughing of renal tubular epithelium. In ATN, the tubules become injured due to various causes such as ischemia or nephrotoxins, leading to the disintegration of the renal tubular cells. As these cells die and shed, their remnants aggregate to form granular casts, which can be seen on urine microscopy.

Maltese crosses are typically associated with lipiduria, often seen in conditions such as nephrotic syndrome, rather than ATN. Waxy casts, on the other hand, generally indicate chronic kidney disease or advanced renal failure, reflecting longstanding damage rather than the acute processes seen in ATN. Neutrophils in urine may indicate an infectious process, such as pyelonephritis, rather than tubular necrosis. Thus, the presence of granular casts is a classic finding that aligns with the cellular and pathological changes occurring in acute tubular necrosis.