Q&A Medicine>>>>>Nephrology
Question 33#

A 49-year-old woman is hospitalized for pneumonia. She is managed appropriately and laboratory values are drawn. She has no past medical history, and a complete blood count and chemistry panel from 1 year ago were normal. Her laboratory values from this hospitalization are shown below.

What is the most likely cause of this patient’s renal disease?

A. Pyelonephritis
B. Renal ischemia
C. Acute interstitial nephritis
D. Embolic phenomenon
E. Acute tubular necrosis

Correct Answer is E

Comment:

 Acute tubular necrosis. This question tests the reader’s knowledge of the most common cause of intrinsic renal AKI. Because the details in the vignette are quite limited, many of the answers could be the true diagnosis. However, on the shelf examination there are often similar questions that require the reader to “play the odds” and pick the most common cause. In this case, it is important to know that prerenal causes and ATN make up the majority of AKI cases in hospitalized patients. The FENa >2% indicates that this is intrinsic renal disease, and therefore the correct answer is ATN. (A, C) Pyelonephritis is a cause of AIN; however, AIN is not the most common cause of intrinsic renal AKI. AIN might have been selected since the patient likely took antibiotics for pneumonia; however, many antibiotics cause ATN as well. (B) Prerenal AKI from renal ischemia would be the correct answer if the FENa was <1%. (D) Cholesterol emboli syndrome usually occurs after catheterization procedures involving the aorta and would be suggested by a rash and urine eosinophils. (Goodpasture syndrome) presents with hemoptysis and/or hematuria, causing a nephritic syndrome. (Urinary tract obstruction) Postrenal AKI is not as common as prerenal AKI or ATN, and can be ruled out with a renal ultrasound. (Fibromuscular dysplasia) Fibromuscular dysplasia is most common in middle-aged women and is a cause of secondary hypertension. It may cause renal failure, but is not the most likely answer.