<prompt> Investigations in a patient of oliguria revealed: Urine osmolality: 800 mOsmkg. Urinary sodium 10 mmolL.BUN: creatinine20:1. What is the most likely diagnosis?Pre-renal acute renal failureAcute tubular necrosisAcute coical necrosisUrinary tract obstruction  <response>: Pre renal Renal ATN Post renal Urine osmolality 500 mOsm 300 mOsm 400 mOsm Urine sodium 20 mmoldl 20 mmoldl Variable FeNa 1 1 Variable Urine microscopic findings Hyaline casts Muddy brown casts Normal or RBCWBC BUN: creatinine ratio 20:1 normal 10:1 20:1 20:1 