These diagrams illustrate acute tubular necrosis (ATN). The distribution of the areas of necrosis is more segmental with ischemic injuries, while toxic injuries result in more diffuse proximal tubular injury. Urine output will drop precipitously. If life-threatening uremia can be treated, then recovery of the tubular epithelium can occur. As the tubular epithelium is regenerating, urine concentrating ability is impaired, and polyuria occurs.