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Chapter 38: Acute Kidney Injury

Which of the following findings is consistent with the diagnosis of prerenal AKI?

a. Specific gravity 1.029, FeNa 0.72%, uOsmol 550 mOsm/kg

b. Specific gravity 1.013, FeNa 1.72%, uOsmol 350 mOsm/L

c. Specific gravity 1.009, FeNa 2.02%, uOsmol 213 mOsm/L

d. Urinalysis: 1+ protein, 10 to 15 RBC, 10 to 15 WBC

e. Urinalysis: 3+ protein, no RBC, no WBC

Answer a is correct. A high specific gravity, low FeNa, and high urine osmolality are indicative of a prerenal AKI, a state in which the kidneys will avidly reabsorb sodium and water in an attempt to increase the perfusion to the kidneys and increase the intraglomerular pressure.

Answer b is incorrect. The specific gravity suggests normal urine density. The FeNa is within the normal range of 1% to 2%. The urine osmolality is also normal. These urine findings are not suggestive of any specific kidney damage.

Answer c is incorrect. In this situation the specific gravity is low, suggesting a diluted urine. The FeNa is possibly a little elevated, suggesting excess sodium loss. The urine osmolality is a bit low. These findings are the opposite of what might be seen in a prerenal AKI.

Answer d is incorrect. The protein and cellular matter in this urinalysis are suggestive of some type of intrinsic AKI. Typically, in prerenal AKI there will not be any particulate matter in the urine.

Answer e is incorrect. This urinalysis shows isolated, significant, proteinuria. Proteinuria suggests a defect within the glomerulus and intrinsic damage, not prerenal AKI.

A patient in the intensive care unit develops AKI. You review the medications the patient has been taking to evaluate for drug-induced AKI. Which of the following agents would be most likely to cause AIN?

a. Labetalol

b. Diltiazem

c. Oxacillin

d. Fentanyl

e. Propofol

Answer c is correct. Acute interstitial nephritis is a hypersensitivity reaction and was most commonly associated with nafcillin and penicillin derivatives.

Answer a is incorrect. Labetolol is a nonselective β1- and α2-antagonist as well as an α1-antagonist. Although it is possible to mount an allergic response to any foreign substance, labetolol is not a common cause of AIN. This agent would more likely contribute to a prerenal AKI through its ability to lower blood pressure and decrease renal perfusion.

Answer b is incorrect....

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