Acute tubular necrosis or (ATN) is a meical condition involving the death of tubular cells that form the tubule that transports urine to the ureters while reabsorbing 99% of the water (and highly concentrating the salts and metabolic byproducts). Tubular cells continually replace themselves and if the cause of ATN is removed then recovery is likely. ATN presents with acute renal failure and is one of the most common causes of ARF. The presence of "muddy brown casts" of epithelial cells found in the urine during urinalysis is pathognomonic for ATN.