Chronic Kidney Disease USMLE Step 1 Practice Question
A 14-year-old boy presents with progressive muscle cramps and lightheadedness. Vital signs show BP 96/58 mmHg, HR 102/min, RR 18/min. Labs reveal hypokalemic metabolic alkalosis with elevated plasma renin (8.5 ng/mL/hr) and aldosterone (28 ng/dL). Urine calcium is markedly elevated at 450 mg/day. Serum creatinine is normal at 0.8 mg/dL. He denies vomiting or diarrhea. A defect in which of the following transporters is most likely responsible?
Answer choices
- ANa bicarbonate cotransporter in the proximal tubule
- BAquaporin 2 channel in collecting duct cells
- CEpithelial sodium channel in principal cells
- DNa Cl cotransporter in the distal convoluted tubule
- ENa K 2Cl cotransporter in the thick ascending limbCorrect answer
- FBarttin subunit deficiency causing Bartter type 4 with deafness
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