This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Medicine
Pigmented "muddy brown" granular cast is characteristic of 
Select and explain. 
A. Prerenal ARF, B. Ischemic or nephrotoxic ATN, C. Postrenal ARF, D. Chronic renal failure
B: Ischemic or nephrotoxic ATN
Answer: B: Ischemic or nephrotoxic ATN 
Explanation: AKI from ATN due to ischemic injury, sepsis, or ceain nephrotoxins has characteristic urine sediment findings: pigmented "muddy brown" granular casts and tubular epithelial cell casts. These findings may be absent in more than 20% of cases Ref: Harrison 19e pg: 1805