Acute tubular necrosis (ATN) is a type of renal azotemia caused by damage to the kidney tubules, leading to cell death. Ischemia, sepsis, heavy metals, and medications can trigger ATN. Symptoms include fatigue, anorexia, nausea, vomiting, and uremic signs such as skin frosting and a pericardial friction rub. Diagnosis involves identifying muddy brown granular casts in urine. Management includes removing the offending agents and possibly dialysis. ATN progresses through initiation, maintenance, and recovery stages, with recovery marked by improved GFR and increased urine output.