<prompt> Iso osmolar urine is seen in -ATNSevere dehydrationDiabetes insipidusPCKD  <response>: Acute tubular necrosis ATN is a medical condition involving the death of tubular epithelial cells that form the renal tubules of the kidneys. ATN presents with acute kidney injury AKI and is one of the most common causes of AKI. Common causes of ATN include low blood pressure and use of nephrotoxic drugs Acute tubular necrosis is classified as a renal i.e. not pre-renal or post-renal cause of acute kidney injury. Diagnosis is made by a FENa fractional excretion of sodium 3 and presence of muddy casts a type of granular cast in urinalysis. On histopathology, there is usually tubulorrhexis, that is, localized necrosis of the epithelial lining in renal tubules, with focal rupture or loss of basement membrane. Proximal tubule cells can shed with variable bility and not be purely necrotic.isosmolar urine is seen Ref Harrison20th edition pg 234 