Acute Tubular Necrosis

A 42-year-old woman with severe sepsis from urosepsis is admitted to the ICU. She has been oliguric (urine output 0.3 mL/kg/hr) for 18 hours despite aggressive fluid resuscitation. Serum creatinine has risen from 1.2 to 4.1 mg/dL. Urinalysis shows muddy brown casts, and fractional excretion of sodium (FENa) is 3.2%. Serum potassium is 6.8 mEq/L. What is the most appropriate next step in management?

Which of the following is the PRIMARY pathological hallmark of acute tubular necrosis (ATN)?

In acute tubular necrosis, which segment of the nephron is MOST commonly affected in ischemic injury?

A 58-year-old man with diabetes mellitus type 2 undergoes elective coronary angiography for stable angina. Six hours post-procedure, he develops oliguria (urine output 200 mL/24 h). Serum creatinine rises from 1.2 mg/dL (baseline) to 3.8 mg/dL within 48 hours. Urinalysis shows muddy brown casts and epithelial cell casts. Urine sodium is 60 mEq/L and fractional excretion of sodium (FENa) is 3.2%. Which of the following is the most likely diagnosis?

A 42-year-old woman with sepsis secondary to urosepsis is admitted to the ICU. She receives aggressive fluid resuscitation and broad-spectrum antibiotics. On day 3, despite fluid resuscitation and vasopressor support, she develops oliguria with urine output of 150 mL/24 h. Serum creatinine is 4.2 mg/dL (baseline 0.9 mg/dL). Urinalysis shows granular casts and occasional epithelial cells. Renal biopsy shows focal necrosis of proximal and distal tubular epithelium with preservation of basement membrane. Which of the following best explains the mechanism of kidney injury in this patient?