QBDOTW: A 25-year-old Male is Beginning Chemotherapy
Welcome back to MedSmarter’s USMLE Style Question of the Week. Here’s the breakdown of another high-yield Renal question for those preparing for your USMLE Step 1 or just to gain some knowledge. As always you want to begin with reading the last sentence of the vignette first to get an understanding of what the question is asking for.
Question Break Down of the Week:
A 25-year-old man is beginning chemotherapy for leukemia when he develops severe intermittent left flank pain that later migrates to the pelvis. Three days later, the patient’s creatinine level rises and he is diagnosed with acute renal failure. His FENa (Fractional Excretion of Sodium) is >4% with a urine osmolality of <350 mOsm kg. Blood and urine cultures are negative for bacteria and eosinophilia. An abdominal radiograph fails to locate any pathology. Which of the following is the most likely location of the lesion causing this patient’s renal failure?
C) Kidney tubules
D) Interstitium of the kidney
The correct answer choice is A: The history of being started on chemotherapy for leukemia is strongly suggestive of tumor lysis syndrome, which occurs when leukemic cells are lysed, releasing potentially toxic contents including potassium, phosphate, and uric acid. The FENa >4% is consistent with postrenal failure. It is likely that this patient’s presentation has been caused by a kidney stone that has passed into the left ureter and now into the urethra, causing postrenal failure. Uric acid stones are radiolucent, so they may not appear on x-ray films.
Did you think the answer was different?
Did you think that the correct answer choice was other than A? You can view this video for a deeper discussion of why B, C, D, and E were not the correct answer choices.
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