Chronic Kidney Disease USMLE Step 1 Practice Question
A 23-year-old woman presents with fatigue and recurrent nephrolithiasis. Vital signs show BP 128/82 mmHg, HR 88/min, RR 16/min, temperature 37°C. Laboratory studies reveal normal anion gap metabolic acidosis with pH 7.32, serum potassium 3.1 mEq/L, and urine pH 6.0 despite systemic acidosis. Serum calcium is elevated at 10.8 mg/dL. Urinalysis shows no hematuria. Which of the following is the most likely underlying defect?
Answer choices
- ADecreased aldosterone effect in the collecting duct
- BIncreased chloride reabsorption in the thick ascending limb
- CExcess ammonia generation in the proximal tubule
- DImpaired hydrogen ion secretion in alpha intercalated cellsCorrect answer
- EImpaired bicarbonate reabsorption in the proximal tubule
- FIncreased aquaporin-2 water channel expression in collecting duct principal cells
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