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Discussion Starter · #1 ·
A 72-year-old woman undergoes three-vessel coronary artery bypass graft for coronary artery disease. Her postoperative course is complicated by wound infection leading to sepsis with multidrug-resistant Klebsiella. Her sepsis is difficult to manage, and she is on pressors, fluids, and antibiotics for several days before becoming afebrile and hemodynamically stable. Her creatinine rises postoperatively, and on postoperative day 4 electrolytes show blood urea nitrogen (BUN) of 34 mg/dL and creatinine of 2.6 mg/dL. Urine Na is 46 mEq/L, fractional excretion of sodium is calculated as 2.1%, and urine osmolarity is 310 mOsm/kg. Urinalysis shows muddy brown granular casts. Over the next week, her creatinine continues to rise despite aggressive fluid management; however, she continues to make small amounts of urine, and BUN and creatinine gradually return to normal over the next few weeks. What is the most likely pathogenesis of this woman’s acute renal failure?
(A) Allergic reaction to dobutamine
(B) Autoimmune glomerular destruction
(C) Hypovolemic shock
(D) Ischemic tubular injury
(E) Klebsiella infection of the kidney
 

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Discussion Starter · #3 ·
Correct answer is D

Yes Idaho you are right.
This woman most likely has acute tubular necrosis (ATN), which presents with a picture of acute renal failure, often following sepsis, hypotension, or other ischemic insult. Although prerenal failure can also result from these, it resolves more rapidly with fluid administration, and presents with a prerenal picture, including BUN:creatinine ratio > 20:1 and FeNa < 1%. ATN, in ontrast, lasts longer, with creatinine elevation often persisting for several weeks, and presents with signs of renal failure such as elevated BUN and creatinine, FeNa > 2%, and low urine osmolarity due to impaired urine concentrating ability despite hypovolemia. Muddy brown casts on urinalysis are characteristic of ATN.
 
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