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Calcium oxalate nephrolithiasis — USMLE Step 2 CK MCQ

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EasyInternal MedicineCalcium oxalate nephrolithiasisUSMLE Step 2 CK

A 35-year-old White woman comes to the clinic because of progressive symptoms. History and focused examination are notable for colicky flank pain radiating to the groin with hematuria. Temperature is 98.6°F (37.0°C), blood pressure is 126/78 mmHg, pulse is 84/min, respirations are 16/min, and oxygen saturation is 98% on room air. Physical examination confirms the key finding and shows no unrelated abnormality that would better explain the presentation. Laboratory studies show creatinine 2.1 mg/dL, BUN 34 mg/dL, and urinalysis findings consistent with the presentation. Which of the following is the most appropriate initial diagnostic study?

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Correct answer: D — Noncontrast CT scan of the abdomen and pelvis

The vignette describes Calcium oxalate nephrolithiasis, supported by colicky flank pain radiating to the groin with hematuria. Noncontrast CT scan of the abdomen and pelvis is the single best answer because it matches the diagnostic or management priority in this clinical setting. The other choices are plausible alternatives in related presentations, but they do not best fit the timing, findings, and guideline-directed approach described here.

Reference: American Urological Association Kidney Stones Guideline