A 72-year-old man with hypertension develops oliguria after prolonged hypotension (BP 78/52 mmHg) during septic shock. Over 48 hours, serum creatinine rises from 1.2 to 4.8 mg/dL, and urine output decreases to 180 mL daily. Urinalysis reveals muddy brown granular casts and fractional excretion of sodium of 3%. Urine microscopy shows no proteinuria. He takes lisinopril chronically. Which nephron segment is most vulnerable to this ischemic injury?
- A)Distal convoluted tubule and glomerulus
- B)Podocytes and mesangial cells
- C)Collecting duct and macula densa
- D)Afferent arteriole and proximal convoluted tubule only
- E)Proximal tubule and thick ascending limbGABARITO
Explicação
Ischemic acute tubular necrosis most severely affects metabolically active tubular cells in the proximal tubule and thick ascending limb, especially in the outer medulla where oxygen tension is low. Muddy brown casts after hypotension are classic for ATN. Ver explicação completa e trilha adaptativa →