What urinalysis finding is most characteristic of acute tubular necrosis?

What urinalysis finding is most characteristic of acute tubular necrosis?

• A. Muddy brown granular casts
• B. White blood cell casts
• C. Eosinophiluria
• D. Erythrocyte casts

Answer: (A)

Muddy brown granular casts are the hallmark finding in the urine with acute tubular necrosis. They arise from sloughed tubular epithelial cells and granular debris formed within the damaged tubules, reflecting tubular injury from ischemia or nephrotoxins. This granular, pigmented cast pattern is characteristic of ATN and often accompanies some degree of tubular dysfunction such as impaired concentrating ability and increased fractional excretion of sodium. White blood cell casts point more toward tubulointerstitial inflammation or infection. Eosinophiluria is classically seen with drug-induced interstitial nephritis. Erythrocyte casts suggest glomerular disease with bleeding into the nephron, such as glomerulonephritis. So the muddy brown granular casts best fit the pathology of ATN.

Muddy brown granular casts are the hallmark finding in the urine with acute tubular necrosis. They arise from sloughed tubular epithelial cells and granular debris formed within the damaged tubules, reflecting tubular injury from ischemia or nephrotoxins. This granular, pigmented cast pattern is characteristic of ATN and often accompanies some degree of tubular dysfunction such as impaired concentrating ability and increased fractional excretion of sodium.

White blood cell casts point more toward tubulointerstitial inflammation or infection. Eosinophiluria is classically seen with drug-induced interstitial nephritis. Erythrocyte casts suggest glomerular disease with bleeding into the nephron, such as glomerulonephritis. So the muddy brown granular casts best fit the pathology of ATN.