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Chapter 38: Acute Kidney Injury
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Which of the following findings is consistent with the diagnosis of prerenal AKI?
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a. Specific gravity 1.029, FeNa 0.72%, uOsmol 550 mOsm/kg
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b. Specific gravity 1.013, FeNa 1.72%, uOsmol 350 mOsm/L
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c. Specific gravity 1.009, FeNa 2.02%, uOsmol 213 mOsm/L
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d. Urinalysis: 1+ protein, 10 to 15 RBC, 10 to 15 WBC
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e. Urinalysis: 3+ protein, no RBC, no WBC
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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.
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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.
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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.
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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.
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Answer e is incorrect. This urinalysis shows isolated, significant, proteinuria. Proteinuria suggests a defect within the glomerulus and intrinsic damage, not prerenal AKI.
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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?
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Answer c is correct. Acute interstitial nephritis is a hypersensitivity reaction and was most commonly associated with nafcillin and penicillin derivatives.
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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.
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Answer b is incorrect....