Chronic Kidney Disease USMLE Step 1 Practice Question
A 12-year-old boy presents with progressive muscle weakness and poor growth. Vital signs show BP 118/76 mmHg, HR 94/min, RR 18/min, temperature 37°C, and SpO2 98% on room air. Laboratory studies reveal serum potassium 2.8 mEq/L, pH 7.48, HCO3− 32 mEq/L, and urine chloride 65 mEq/L with elevated urinary calcium excretion. Serum creatinine and BUN are normal. Which renal tubular transporter is most likely defective?
Answer choices
- AEpithelial sodium channel in collecting duct
- BNa K 2Cl cotransporter in thick ascending limbCorrect answer
- CNa Cl cotransporter in distal convoluted tubule
- DSodium bicarbonate cotransporter in proximal tubule
- EAquaporin 2 water channel in collecting duct
- FNa/H exchanger in proximal tubule
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